[Application of classical isothermal adsorption models in heavy metal ions/ diatomite system and related problems].

Science.gov (United States)

Zhu, Jian; Wu, Qing-Ding; Wang, Ping; Li, Ke-Lin; Lei, Ming-Jing; Zhang, Wei-Li

2013-11-01

In order to fully understand adsorption nature of Cu2+, Zn2+, Pb2+, Cd2+, Mn2+, Fe3+ onto natural diatomite, and to find problems of classical isothermal adsorption models' application in liquid/solid system, a series of isothermal adsorption tests were conducted. As results indicate, the most suitable isotherm models for describing adsorption of Pb2+, Cd2+, Cu2+, Zn2+, Mn2+, Fe3+ onto natural diatomite are Tenkin, Tenkin, Langmuir, Tenkin, Freundlich and Freundlich, respectively, the adsorption of each ion onto natural diatomite is mainly a physical process, and the adsorption reaction is favorable. It also can be found that, when using classical isothermal adsorption models to fit the experimental data in liquid/solid system, the equilibrium adsorption amount q(e) is not a single function of ion equilibrium concentration c(e), while is a function of two variables, namely c(e) and the adsorbent concentration W0, q(e) only depends on c(e)/W(0). Results also show that the classical isothermal adsorption models have a significant adsorbent effect, and their parameter values are unstable, the simulation values of parameter differ greatly from the measured values, which is unhelpful for practical use. The tests prove that four-adsorption-components model can be used for describing adsorption behavior of single ion in nature diatomite-liquid system, its parameters k and q(m) have constant values, which is favorable for practical quantitative calculation in a given system.

Monolayer and multilayer adsorption isotherm models for sorption from aqueous media

Energy Technology Data Exchange (ETDEWEB)

Saadi, Reyhaneh; Saadi, Zahra; Fazaeli, Reza; Fard, Narges Elmi [Islamic Azad University, Tehran (Iran, Islamic Republic of)

2015-05-15

Industrial wastewater polluted with various contaminants, including heavy metals, dyes, etc., endangers human health and the environment. Various separation techniques have been developed for the removal of pollutants from aqueous solutions. Adsorption process has drawn considerable attention due to its simplicity of design, high removal efficiency, even at dilute concentration, and economical aspect. We reviewed the most common two, three, four, and five parameter adsorption isotherm models corresponding to monolayer and multilayer adsorption on the basis of parameters that can be used for exploring novel adsorbents. Thermodynamic assumptions of the models give information about the surface properties, capacity of the adsorbent and adsorption mechanism. Seven error functions were investigated to evaluate the fitness quality of isotherm models with the experimental equilibrium data.

Determination of adsorption isotherms of chlorinated hydrocarbons on halloysite adsorbent by inverse gas chromatography.

Science.gov (United States)

Czech, K; Słomkiewicz, P M

2013-05-03

Inverse gas chromatographic methods of isotherm determination peak maximum (PM) and peak division (PD) were compared. These methods were applied to determine adsorption isotherms of dichloroethylene, trichloroethylene and tetrachloroethylene on acid-activated halloysite and adsorption enthalpy. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of hydrophobicity of pharmaceuticals and personal care products for adsorption on activated carbon: Adsorption isotherms, kinetics and mechanism.

Science.gov (United States)

Kaur, Harkirat; Bansiwal, Amit; Hippargi, Girivyankatesh; Pophali, Girish R

2017-09-11

Adsorption of three pharmaceuticals and personal care products (PPCPs), namely caffeine, ibuprofen and triclosan on commercial powdered activated carbon was examined in aqueous medium. The contaminants were chosen based on their diverse log K ow (octanol-water partition coefficient) viz. - 0.07 for caffeine, 3.97 for ibuprofen and 4.76 for triclosan to examine the role of hydrophobicity on adsorption process. The adsorbent characterisation was achieved using BET surface area, SEM, pore size distribution studies and FTIR. Influence of mass of PAC, contact time, solution pH and initial concentration on adsorption capacity of PAC was studied. Adsorption isotherms and kinetics were applied to establish the mechanism of adsorption. The kinetics followed pseudo-second order with physisorption occurring through particle diffusion. The Freundlich model fitted best among the isotherm models. The adsorption capacity increased in the order CFN activated carbon.

A new apparatus for the determination of adsorption isotherms and adsorption enthalpies on microporous and meso-porous media

International Nuclear Information System (INIS)

Mouahid, A.

2010-01-01

A specific thermostated experimental device comprising a differential heat flow calorimeter coupled with a home built manometric system has been built for the simultaneous determination of adsorption isotherms and adsorption enthalpies. The differential heat flow calorimeter is a Tian Calvet Setaram C80 model which measures the heat flux of a gas and can be operated isothermally, the manometric system is a stainless steel homemade apparatus. This coupled apparatus allows measurements for pressure up to 2.5 MPa and temperature up to 423.15 K. On the one hand, the apparatus and the experimental procedures are described. On the second hand the reliability and reproducibility were established by measuring adsorption isotherms on a benchmark (Filtrasorb F400) at 318.15 K. The gravimetric method has been used at higher pressure at various temperatures. These devices allowed us to study the adsorption of supercritical fluid (nitrogen N 2 , methane CH 4 , carbon dioxide CO 2 ) in activated carbons and microporous or meso-porous silica. The adsorption of methane on a rock of type (TGR) was also studied. These experimental results are used for the study of the interactions fluid / solid that must be taken into account in molecular simulations or DFT theory. (author)

Adsorption Isotherms of CH 4 on Activated Carbon from Indonesian Low Grade Coal

KAUST Repository

Martin, Awaludin

2011-03-10

This article presents an experimental approach for the determination of the adsorption isotherms of methane on activated carbon that is essential for methane storage purposes. The experiments incorporated a constant-volume- variable-pressure (CVVP) apparatus, and two types of activated carbon have been investigated, namely, activated carbon derived from the low rank coal of the East of Kalimantan, Indonesia, and a Carbotech activated carbon. The isotherm results which cover temperatures from (300 to 318) K and pressures up to 3.5 MPa are analyzed using the Langmuir, Tóth, and Dubinin-Astakhov (D-A) isotherm models. The heat of adsorption for the single component methane-activated carbon system, which is concentration- and temperature-dependent, is determined from the measured isotherm data. © 2011 American Chemical Society.

Kinetics and adsorption isotherm of lactic acid from fermentation broth onto activated charcoal

Directory of Open Access Journals (Sweden)

Seankham Soraya

2017-01-01

Full Text Available Activated charcoal was applied for the recovery of lactic acid in undissociated form from fermentation broth. Lactic acid was obtained from the fermentation of Lactobacillus casei TISTR 1340 using acid hydrolyzed Jerusalem artichoke as a carbon source. The equilibrium adsorption isotherm and kinetics for the lactic acid separation were investigated. The experimental data for lactic acid adsorption from fermentation broth were best described by the Freundlich isotherm and the pseudo-second order kinetics with R2 values of 0.99. The initial adsorption rate was 41.32 mg/g⋅min at the initial lactic acid concentration of 40 g/L.

A hygroscopic method to measure the adsorption isotherm of porous construction materials

NARCIS (Netherlands)

Taher, A.; Zanden, van der A.J.J.; Brouwers, H.J.H.; Stephan, D.; Daake, von H.; Markl, V.; Land, G.

2013-01-01

A sorption isotherm is the relationship between the moisture content in a material and the relative humidity of the surrounding atmosphere in an equilibrium situation. Most often, the sorption isotherm is measured with a gravitational method. This work presents a method to measure the adsorption

Resorcinol adsorption from aqueous solution on activated carbon: Relation adsorption isotherm and immersion enthalpy

International Nuclear Information System (INIS)

Blanco, Diago A; Giraldo, Liliana; Moreno, Juan C.

2008-01-01

The resorcinol adsorption on a modified activated carbon, obtained from an activated commercial carbon Carbochem T M - PS30, CAG, modified by means of chemical treatment with HNO 3 7M oxidized activated carbon (CAO) and heat treatment under H 2 flow, reduced activated carbon (CAR) are studied. The influence of solution pH, the reduction and oxidation of the activated surface carbons in resorcinol aqueous solutions is determined. The interaction solid solution is characterized by adsorption isotherms analysis at 298 K and at pHs of 7.9 and 11 in order to evaluate the system on and below the value of resorcinol pKa. The adsorption capacity of carbons increases with diminishing solution pH. The amount retained increases in the reduced carbon at maximum adsorption pH and diminishes in the oxidized carbon. the experimental results of the adsorption isotherms are adjusted to the Freundlich and Langmuir models, obtaining values for the Q m ax parameter Langmuir model in the CAG of 179, 156 and 44 mgg - 1 For pH values of 7,9 and 11 respectively. In this case of modified carbons values of 233, 179 and 164 mgg - 1 Are obtained for CAR, CAG and CAO to pH 7 respectively, as general tendency the resorcinol adsorption increases in the following order CAR > CAG > CAO. Similar conclusions from immersion enthalpies are obtained, their values increase with the amount of solute retained. In the case of the CAG, immersion enthalpies between 25.8 to 40.9 Jg - 1, are obtained for resorcinol aqueous solutions in a range from 20 to 1500 mgL - 1

Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds

Energy Technology Data Exchange (ETDEWEB)

Ramos-Ramirez, Esthela, E-mail: ramosre@quijote.ugto.mx [Centro de Investigaciones en Quimica Inorganica de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto. (Mexico); Gutierrez Ortega, Norma L.; Conteras Soto, Cesar A. [Centro de Investigaciones en Quimica Inorganica de la Universidad de Guanajuato, Noria Alta s/n, Col. Noria Alta, C.P. 36050, Guanajuato, Gto. (Mexico); Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca s/n, km 36.5, La Marquesa, Coyoacan Mexico, C.P. 52750 (Mexico); Olguin Gutierrez, Maria T. [Instituto Nacional de Investigaciones Nucleares, Carretera Mexico-Toluca s/n, km 36.5, La Marquesa, Coyoacan Mexico, C.P. 52750 (Mexico)

2009-12-30

In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio = 2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N{sub 2} adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.

Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds

International Nuclear Information System (INIS)

Ramos-Ramirez, Esthela; Gutierrez Ortega, Norma L.; Conteras Soto, Cesar A.; Olguin Gutierrez, Maria T.

2009-01-01

In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio = 2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N 2 adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.

Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol-gel hydrotalcite-like compounds.

Science.gov (United States)

Ramos-Ramírez, Esthela; Ortega, Norma L Gutiérrez; Soto, Cesar A Contreras; Gutiérrez, Maria T Olguín

2009-12-30

In under-developed countries, industries such as paint and pigment manufacturing, leather tanning, chrome plating and textile processing, usually discharge effluents containing Cr(VI) and Cr(III) into municipal sanitary sewers. It has been reported that Cr(VI) acts as a powerful epithelial irritant and as a human carcinogen. In the present work, hydrotalcite-like compounds with a Mg/Al ratio=2 were synthesized by the sol-gel method. The hydrotalcite-like compounds and their corresponding thermally treated products were characterized by powder X-ray diffraction, infrared spectroscopy and N(2) adsorption. The hydrotalcite-like compounds and the heated solids were used as adsorbents for Cr(VI) in aqueous solutions. Adsorption isotherm studies of Cr(VI) from aqueous solution are described. The adsorbent capacity was determined using the Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherm models. The Cr(VI) adsorption isotherm data fit best to the Langmuir isotherm model. The maximum Cr(VI) uptake by hydrotalcite and the heated solids was determined using the Langmuir equation and was found to range between 26 and 29 mg Cr(VI)/g adsorbent.

Suitability of adsorption isotherms for predicting the retention capacity of active slag filters removing phosphorus from wastewater.

Science.gov (United States)

Pratt, C; Shilton, A

2009-01-01

Active slag filters are an emerging technology for removing phosphorus (P) from wastewater. A number of researchers have suggested that adsorption isotherms are a useful tool for predicting P retention capacity. However, to date the appropriateness of using isotherms for slag filter design remains unverified due to the absence of benchmark data from a full-scale, field filter operated to exhaustion. This investigation compared the isotherm-predicted P retention capacity of a melter slag with the P adsorption capacity determined from a full-scale, melter slag filter which had reached exhaustion after five years of successfully removing P from waste stabilization pond effluent. Results from the standard laboratory batch test showed that P adsorption correlated more strongly with the Freundlich Isotherm (R(2)=0.97, Pretention capacity of 0.014 gP/kg slag; markedly lower than the 1.23 gP/kg slag adsorbed by the field filter. Clearly, the result generated by the isotherm bears no resemblance to actual field capacity. Scanning electron microscopy analysis revealed porous, reactive secondary minerals on the slag granule surfaces from the field filter which were likely created by weathering. This slow weathering effect, which generates substantial new adsorption sites, is not accounted for by adsorption isotherms rendering them ineffective in slag filter design.

Isotherms of Capillary Condensation Influenced by Formation of Adsorption Films.

Science.gov (United States)

Churaev; Starke; Adolphs

2000-01-15

Isotherms of capillary condensation are often used to determine the vapor sorption capacity of porous adsorbents as well as the pore size distribution by radii. In this paper, for calculating the volume of capillary condensate and of adsorption films in a porous body, an approach based on the theory of surface forces is used. Adsorption isotherms and disjoining pressure isotherms of wetting films are presented here in an exponential form discussed earlier. The calculations were made for straight cylindrical capillaries of different radii and slit pores of different width. The mechanisms of capillary condensation differ in cylindrical and slit pores. In cylindrical pores capillary condensation occurs due to capillary instability of curved wetting films on a capillary surface, when film thickness grows. In the case of slit pores, coalescence of wetting films formed on opposite slit surfaces proceeds under the action of attractive dispersion forces. Partial volumes of liquid in the state of both capillary condensate and adsorbed films are calculated dependent on the relative vapor pressure in a surrounding media. Copyright 2000 Academic Press.

A Universal Isotherm Model to Capture Adsorption Uptake and Energy Distribution of Porous Heterogeneous Surface

KAUST Repository

Ng, Kim Choon; Burhan, Muhammad; Shahzad, Muhammad Wakil; Ismail, Azahar Bin

2017-01-01

The adsorbate-adsorbent thermodynamics are complex as it is influenced by the pore size distributions, surface heterogeneity and site energy distribution, as well as the adsorbate properties. Together, these parameters defined the adsorbate uptake forming the state diagrams, known as the adsorption isotherms, when the sorption site energy on the pore surfaces are favorable. The available adsorption models for describing the vapor uptake or isotherms, hitherto, are individually defined to correlate to a certain type of isotherm patterns. There is yet a universal approach in developing these isotherm models. In this paper, we demonstrate that the characteristics of all sorption isotherm types can be succinctly unified by a revised Langmuir model when merged with the concepts of Homotattic Patch Approximation (HPA) and the availability of multiple sets of site energy accompanied by their respective fractional probability factors. The total uptake (q/q*) at assorted pressure ratios (P/P s ) are inextricably traced to the manner the site energies are spread, either naturally or engineered by scientists, over and across the heterogeneous surfaces. An insight to the porous heterogeneous surface characteristics, in terms of adsorption site availability has been presented, describing the unique behavior of each isotherm type.

A Universal Isotherm Model to Capture Adsorption Uptake and Energy Distribution of Porous Heterogeneous Surface

KAUST Repository

Ng, Kim Choon

2017-08-31

The adsorbate-adsorbent thermodynamics are complex as it is influenced by the pore size distributions, surface heterogeneity and site energy distribution, as well as the adsorbate properties. Together, these parameters defined the adsorbate uptake forming the state diagrams, known as the adsorption isotherms, when the sorption site energy on the pore surfaces are favorable. The available adsorption models for describing the vapor uptake or isotherms, hitherto, are individually defined to correlate to a certain type of isotherm patterns. There is yet a universal approach in developing these isotherm models. In this paper, we demonstrate that the characteristics of all sorption isotherm types can be succinctly unified by a revised Langmuir model when merged with the concepts of Homotattic Patch Approximation (HPA) and the availability of multiple sets of site energy accompanied by their respective fractional probability factors. The total uptake (q/q*) at assorted pressure ratios (P/P s ) are inextricably traced to the manner the site energies are spread, either naturally or engineered by scientists, over and across the heterogeneous surfaces. An insight to the porous heterogeneous surface characteristics, in terms of adsorption site availability has been presented, describing the unique behavior of each isotherm type.

Adsorption isotherms of pear at several temperatures

Directory of Open Access Journals (Sweden)

Mitrevski Vangelče

2015-01-01

Full Text Available The moisture adsorption isotherms of pear were determined at 15ºC, 30ºC and 45ºC using the standard static gravimetric method over a range of water activity from 0.112 to 0.920. The experimental data were fitted with isotherm equations recommended in ASAE Standard D245.5. In order to find which equation gives the best results, large number of numerical experiments were performed. After that, several statistical criteria proposed in scientific literature for estimation and selection of the best sorption isotherm equations were used. For each equation and experimental data set, the average performance index was calculated and models were ranked afterwards. After that, some statistical rejection criteria were checked (D’Agostino-Pearson test of normality, single-sample run test and significance and precision of the model parameters. The performed statistical analysis shows that the Guggenheim-Anderson-de Boer (GAB equation has the highest value of average performance index, but higher correlation between pair of parameters leads to lower precision of estimated parameters.[Projekat Ministarstva nauke Republike Srbije, br. TR 31058

Experimental Adsorption Isotherm of Methane onto Activated Carbon at Sub- and Supercritical Temperatures

KAUST Repository

Rahman, Kazi Afzalur

2010-11-11

This paper presents the experimentally measured adsorption isotherm data for methane onto the pitch-based activated carbon type Maxsorb III for temperatures ranging from (120 to 220) K and pressures up to 1.4 MPa. These data are useful to study adsorbed natural gas (ANG) storage systems when the low temperature natural gas regasified from the liquid phase is considered to charge in the storage chamber. Adsorption parameters were evaluated from the isotherm data using the Tóth and Dubinin-Astakhov models. The isosteric heat of adsorption, which is concentration- and temperature-dependent, is extracted from the data. The Henry\\'s law coefficients for the methane/Maxsorb III pairs are evaluated at various temperatures. © 2010 American Chemical Society.

Improved Isotherm Data for Adsorption of Methane on Activated Carbons

KAUST Repository

Loh, Wai Soong; Rahman, Kazi Afzalur; Chakraborty, Anutosh; Saha, Bidyut Baran; Choo, Yoo Sang; Khoo, Boo Cheong; Ng, Kim Choon

2010-01-01

This article presents the adsorption isotherms of methane onto two different types of activated carbons, namely, Maxsorb III and ACF (A-20) at temperatures from (5 to 75) °C and pressures up to 2.5 MPa. The volumetric technique has been employed

Adsorption isotherm special study. Final report

International Nuclear Information System (INIS)

1993-05-01

The study was designed to identify methods to determine adsorption applicable to Uranium Mill Tailings Remedial Action (UMTRA) Project sites, and to determine how changes in aquifer conditions affect metal adsorption, resulting retardation factors, and estimated contaminant migration rates. EPA and ASTM procedures were used to estimate sediment sorption of U, As, and Mo under varying groundwater geochemical conditions. Aquifer matrix materials from three distinct locations at the DOE UMTRA Project site in Rifle, CO, were used as the adsorbents under different pH conditions; these conditions stimulated geochemical environments under the tailings, near the tailings, and downgradient from the tailings. Grain size, total surface area, bulk and clay mineralogy, and petrography of the sediments were characterized. U and Mo yielded linear isotherms, while As had nonlinear ones. U and Mo were adsorbed strongly on sediments acidified to levels similar to tailings leachate. Changes in pH had much less effect on As adsorption. Mo was adsorbed very little at pH 7-7.3, U was weakly sorbed, and As was moderately sorbed. Velocities were estimated for metal transport at different pHs. Results show that the aquifer materials must be characterized to estimate metal transport velocities in aquifers and to develop groundwater restoration strategies for the UMTRA project

Adsorption of 4-chlorophenol from aqueous solutions by xad-4 resin: Isotherm, kinetic, and thermodynamic analysis

International Nuclear Information System (INIS)

Bilgili, M. Sinan

2006-01-01

Removal of 4-chlorophenol (4-CP) from synthetic aqueous solutions through adsorption on Amberlite XAD-4 resin, a non-ionic macroreticular resins, under batch equilibrium experimental conditions at 298, 308 and 318 K was investigated. It is necessary to propose a suitable model to a better understanding on the mechanism of 4-CP adsorption. For this purpose, Langmiur, Freundlich, Toth, and Redlich-Peterson (RP) isotherm models were compared. The two and three parameters in the adopted adsorption isotherm models were determined by the help of MATLAB package program. It was determined that best fitted adsorption isotherm models were obtained to be in the order: Redlich-Peterson > Langmuir > Toth > Freundlich isotherms. The pseudo-second-order kinetic model provided the best correlation to the experimental results. Results of the intra-particle diffusion model show that the pore diffusion is not the only rate limiting step. The lower correlation of the data to the Bangham's equation also represents that the diffusion of the adsorbate into pores of the sorbent is not the only rate-controlling step. The thermodynamic constants of adsorption phenomena; ΔG o , ΔH o , and ΔS o were found as -4.17 (at 298 K) kJ/mol, -42.01 kJ/mol, and -0.127 kJ/(mol K), respectively. The results showed that adsorption of 4-CP on Amberlite XAD-4, a nonionic polymeric resin was exothermic and spontaneous

Experimental aspects of buoyancy correction in measuring reliable highpressure excess adsorption isotherms using the gravimetric method.

Science.gov (United States)

Nguyen, Huong Giang T; Horn, Jarod C; Thommes, Matthias; van Zee, Roger D; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO 2 and supercritical N 2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Kinetics Modeling and Isotherms for Adsorption of Phosphate from Aqueous Solution by Modified Clinoptilolit

Directory of Open Access Journals (Sweden)

Mohammad Malakootian

2012-01-01

Full Text Available The Phosphorous discharge into the surface water led to excessive growth of algae and eutrophication in lakes and rivers. Therefore the phosphorus removal is important due to negative effect on water resources. The aim of this study was to investigat the modification of clinoptilolite and application of modified clinoptilolite for phosphorous adsorption from aqueous solution and isotherms and kinetics modeling. Hexadecyl Trimethyl Ammonium bromide (HDTMA-Br, Hexadecyl trimethyl Ammonium Chloride (HDTMA-Cl, Sodium Decyl Sulphate (SDS and Cetrimide-C were used for modification of clinoptilolite. Experiments were conducted using jar apparatus and batch system. The effect of pH, adsorbent doses, contact time, phosphate initial concentration and particle size were studied surveyed on phosphate adsorption by modified clinoptilolite. The most common isotherms and the kinetics adsorption equations were used for determination of adsorption rate and dynamic reaction. The results showed that maximum phosphate adsorption was obtained in the pH of 7 and contact time 90min. Also it was found with the increasing of phosphate initial concentration, phosphate removal efficiency decreased significantly. Langmuir No 2 showed a good correlation compared to other isotherms (R2=0.997. Maximum adsorption capacity was obtained in 20g/L adsorbent dose (22.73mg/g. Also Interaparticle diffusion kinetics well fits with experimental data (R2=0.999 with constant rate of 3.84mg/g min0.5. The result showed that modified clinoptilolite can be used successfully as low cost and effective absorbent for phosphate removal.

WATER ADSORPTION AND DESORPTION ISOTHERMS ON MILK POWDER: II. WHOLE MILK

OpenAIRE

Edgar M. Soteras; Julio Gil; Paola Yacanto; Silvana Muratona; Clidia Abaca; María G. Sustersic

2014-01-01

The aim of this research was the determination of adsorption and desorption isotherms of cow whole milk powder. The experiments have been carried out at 15, 25 and 40 ºC, in ranges of moisture and water activity characteristic of normal conditions in which the processes of drying, packaging and storage are developed. By studying the influence of the temperature on the experimental plots, the isosteric adsorption heat was determined. Experimental data were correlated to the referential model ...

Adsorption isotherme de l'acide acétique par des charbons d'origine ...

African Journals Online (AJOL)

The adsorption properties of six samples of carbons of which two are obtained from AYOUS (Triplochiton Scléroxylon), two from AKOM (Terminalia Superba) and two obtained commercially were studied from their adsorption isotherms of acetic acid at 30° and 45°C. This study has resulted in the determination of the two ...

The adsorption characteristics and porous structure of bentonite adsorbents as determined from the adsorption isotherms of benzene vapor

Directory of Open Access Journals (Sweden)

LEPA STOJANOVSKA

2004-02-01

Full Text Available The adsorption of benzene vapor on natural and acid activated bentonites was treated by the theory of volume filling of micropores. The micropore volume and characteristic values of the free energy of adsorption were determined from the adsorption isotherms. The Dubinin–Radushkevish–Stoeckli and Dubinin–Astakhov equations were used for this purpose. The results showed that natural bentonite has a more homogeneous micropore structure than the acid activated ones. The characteristic values of the free energy of adsorption for the natural bentonite were higher than those of the acid activated bentonite. This is due to differences in its structure and the pore size.

Study on Shale Adsorption Equation Based on Monolayer Adsorption, Multilayer Adsorption, and Capillary Condensation

Directory of Open Access Journals (Sweden)

Qing Chen

2017-01-01

Full Text Available Shale gas is an effective gas resource all over the world. The evaluation of pore structure plays a critical role in exploring shale gas efficiently. Nitrogen adsorption experiment is one of the significant approaches to analyze pore size structure of shale. Shale is extremely heterogeneous due to component diversity and structure complexity. Therefore, adsorption isotherms for homogeneous adsorbents and empirical isotherms may not apply to shale. The shape of adsorption-desorption curve indicates that nitrogen adsorption on shale includes monolayer adsorption, multilayer adsorption, and capillary condensation. Usually, Langmuir isotherm is a monolayer adsorption model for ideal interfaces; BET (Brunauer, Emmett, Teller adsorption isotherm is a multilayer adsorption model based on specific assumptions; Freundlich isotherm is an empirical equation widely applied in liquid phase adsorption. In this study, a new nitrogen adsorption isotherm is applied to simultaneously depict monolayer adsorption, multilayer adsorption, and capillary condensation, which provides more real and accurate representation of nitrogen adsorption on shale. In addition, parameters are discussed in relation to heat of adsorption which is relevant to the shape of the adsorption isotherm curve. The curve fitting results indicate that our new nitrogen adsorption isotherm can appropriately describe the whole process of nitrogen adsorption on shale.

Rapid adsorption of copper(II) and lead(II) by rice straw/Fe₃O₄ nanocomposite: optimization, equilibrium isotherms, and adsorption kinetics study.

Science.gov (United States)

Khandanlou, Roshanak; Ahmad, Mansor B; Fard Masoumi, Hamid Reza; Shameli, Kamyar; Basri, Mahiran; Kalantari, Katayoon

2015-01-01

Rice straw/magnetic nanocomposites (RS/Fe3O4-NCs) were prepared via co-precipitation method for removal of Pb(II) and Cu(II) from aqueous solutions. Response surface methodology (RSM) was utilized to find the optimum conditions for removal of ions. The effects of three independent variables including initial ion concentration, removal time, and adsorbent dosage were investigated on the maximum adsorption of Pb (II) and Cu (II). The optimum conditions for the adsorption of Pb(II) and Cu(II) were obtained (100 and 60 mg/L) of initial ion concentration, (41.96 and 59.35 s) of removal time and 0.13 g of adsorbent for both ions, respectively. The maximum removal efficiencies of Pb(II) and Cu(II) were obtained 96.25% and 75.54%, respectively. In the equilibrium isotherm study, the adsorption data fitted well with the Langmuir isotherm model. The adsorption kinetics was best depicted by the pseudo-second order model. Desorption experiments showed adsorbent can be reused successfully for three adsorption-desorption cycles.

Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: Kinetic, isotherm and thermodynamic studies

International Nuclear Information System (INIS)

Kara, Ali; Demirbel, Emel; Tekin, Nalan; Osman, Bilgen; Beşirli, Necati

2015-01-01

Highlights: • Cr(VI) can oxidize biological molecules and be one of the most harmful substance. • Magnetic seperation techniques are used on different applications in many fields. • Magnetic systems can be used for rapid and selective removal as a magnetic processor. • We investigate properties of both new material and other magnetic adsorbents reported in the literatures on the adsorption of Cr(VI) ions. • No researchments were reported on adsorption of Cr(VI) with magnetic vinylphenyl boronic acid microparticles. - Abstract: Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)–vinylphenyl boronic acid(VPBA)) [m-poly(EG–VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG–VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG–VPBA) microparticles were characterized by N 2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG–VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin–Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG–VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic

Simultaneous removal of potent cyanotoxins from water using magnetophoretic nanoparticle of polypyrrole: adsorption kinetic and isotherm study.

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Hena, S; Rozi, R; Tabassum, S; Huda, A

2016-08-01

Cyanotoxins, microcystins and cylindrospermopsin, are potent toxins produced by cyanobacteria in potable water supplies. This study investigated the removal of cyanotoxins from aqueous media by magnetophoretic nanoparticle of polypyrrole adsorbent. The adsorption process was pH dependent with maximum adsorption occurring at pH 7 for microcystin-LA, LR, and YR and at pH 9 for microcystin-RR and cylindrospermopsin (CYN). Kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. Thermodynamic calculations showed that the cyanotoxin adsorption process is endothermic and spontaneous in nature. The regenerated adsorbent can be successfully reused without appreciable loss of its original capacity.

Experimental aspects of buoyancy correction in measuring reliable high-pressure excess adsorption isotherms using the gravimetric method

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Nguyen, Huong Giang T.; Horn, Jarod C.; Thommes, Matthias; van Zee, Roger D.; Espinal, Laura

2017-12-01

Addressing reproducibility issues in adsorption measurements is critical to accelerating the path to discovery of new industrial adsorbents and to understanding adsorption processes. A National Institute of Standards and Technology Reference Material, RM 8852 (ammonium ZSM-5 zeolite), and two gravimetric instruments with asymmetric two-beam balances were used to measure high-pressure adsorption isotherms. This work demonstrates how common approaches to buoyancy correction, a key factor in obtaining the mass change due to surface excess gas uptake from the apparent mass change, can impact the adsorption isotherm data. Three different approaches to buoyancy correction were investigated and applied to the subcritical CO2 and supercritical N2 adsorption isotherms at 293 K. It was observed that measuring a collective volume for all balance components for the buoyancy correction (helium method) introduces an inherent bias in temperature partition when there is a temperature gradient (i.e. analysis temperature is not equal to instrument air bath temperature). We demonstrate that a blank subtraction is effective in mitigating the biases associated with temperature partitioning, instrument calibration, and the determined volumes of the balance components. In general, the manual and subtraction methods allow for better treatment of the temperature gradient during buoyancy correction. From the study, best practices specific to asymmetric two-beam balances and more general recommendations for measuring isotherms far from critical temperatures using gravimetric instruments are offered.

Reliable prediction of adsorption isotherms via genetic algorithm molecular simulation.

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LoftiKatooli, L; Shahsavand, A

2017-01-01

Conventional molecular simulation techniques such as grand canonical Monte Carlo (GCMC) strictly rely on purely random search inside the simulation box for predicting the adsorption isotherms. This blind search is usually extremely time demanding for providing a faithful approximation of the real isotherm and in some cases may lead to non-optimal solutions. A novel approach is presented in this article which does not use any of the classical steps of the standard GCMC method, such as displacement, insertation, and removal. The new approach is based on the well-known genetic algorithm to find the optimal configuration for adsorption of any adsorbate on a structured adsorbent under prevailing pressure and temperature. The proposed approach considers the molecular simulation problem as a global optimization challenge. A detailed flow chart of our so-called genetic algorithm molecular simulation (GAMS) method is presented, which is entirely different from traditions molecular simulation approaches. Three real case studies (for adsorption of CO 2 and H 2 over various zeolites) are borrowed from literature to clearly illustrate the superior performances of the proposed method over the standard GCMC technique. For the present method, the average absolute values of percentage errors are around 11% (RHO-H 2 ), 5% (CHA-CO 2 ), and 16% (BEA-CO 2 ), while they were about 70%, 15%, and 40% for the standard GCMC technique, respectively.

Removal Rate of Organic Matter Using Natural Cellulose via Adsorption Isotherm and Kinetic Studies.

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Din, Mohd Fadhil Md; Ponraj, Mohanadoss; Low, Wen-Pei; Fulazzaky, Mohamad Ali; Iwao, Kenzo; Songip, Ahmad Rahman; Chelliapan, Shreeshivadasan; Ismail, Zulhilmi; Jamal, Mohamad Hidayat

2016-02-01

In this study, the removal of natural organic matter (NOM) using coconut fiber (CF) and palm oil fiber (POF) was investigated. Preliminary analysis was performed using a jar test for the selection of optimal medium before the fabricated column model experiment. The equilibrium studies on isotherms and kinetic models for NOM adsorption were analyzed using linearized correlation coefficient. Results showed that the equilibrium data were fitted to Langmuir isotherm model for both CF and POF. The most suitable adsorption model was the pseudo-first-order kinetic model for POF and pseudo-second-order kinetic model for CF. The adsorption capacities achieved by the CF and POF were 15.67 and 30.8 mg/g respectively. Based on this investigation, it can be concluded that the POF is the most suitable material for the removal of NOM in semi polluted river water.

Molecular simulation of excess isotherm and excess enthalpy change in gas-phase adsorption.

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Do, D D; Do, H D; Nicholson, D

2009-01-29

We present a new approach to calculating excess isotherm and differential enthalpy of adsorption on surfaces or in confined spaces by the Monte Carlo molecular simulation method. The approach is very general and, most importantly, is unambiguous in its application to any configuration of solid structure (crystalline, graphite layer or disordered porous glass), to any type of fluid (simple or complex molecule), and to any operating conditions (subcritical or supercritical). The behavior of the adsorbed phase is studied using the partial molar energy of the simulation box. However, to characterize adsorption for comparison with experimental data, the isotherm is best described by the excess amount, and the enthalpy of adsorption is defined as the change in the total enthalpy of the simulation box with the change in the excess amount, keeping the total number (gas + adsorbed phases) constant. The excess quantities (capacity and energy) require a choice of a reference gaseous phase, which is defined as the adsorptive gas phase occupying the accessible volume and having a density equal to the bulk gas density. The accessible volume is defined as the mean volume space accessible to the center of mass of the adsorbate under consideration. With this choice, the excess isotherm passes through a maximum but always remains positive. This is in stark contrast to the literature where helium void volume is used (which is always greater than the accessible volume) and the resulting excess can be negative. Our definition of enthalpy change is equivalent to the difference between the partial molar enthalpy of the gas phase and the partial molar enthalpy of the adsorbed phase. There is no need to assume ideal gas or negligible molar volume of the adsorbed phase as is traditionally done in the literature. We illustrate this new approach with adsorption of argon, nitrogen, and carbon dioxide under subcritical and supercritical conditions.

Adsorption of ammonium ion by coconut shell-activated carbon from aqueous solution: kinetic, isotherm, and thermodynamic studies.

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Boopathy, Ramasamy; Karthikeyan, Sekar; Mandal, Asit Baran; Sekaran, Ganesan

2013-01-01

Ammonium ions are one of the most encountered nitrogen species in polluted water bodies. High level of ammonium ion in aqueous solution imparts unpleasant taste and odor problems, which can interfere with the life of aquatics and human population when discharged. Many chemical methods are developed and being used for removal of ammonium ion from aqueous solution. Among various techniques, adsorption was found to be the most feasible and environmentally friendly with the use of natural-activated adsorbents. Hence, in this study, coconut shell-activated carbon (CSAC) was prepared and used for the removal of ammonium ion by adsorption techniques. Ammonium chloride (analytical grade) was purchased from Merck Chemicals for adsorption studies. The CSAC was used to adsorb ammonium ions under stirring at 100 rpm, using orbital shaker in batch experiments. The concentration of ammonium ion was estimated by ammonia distillate, using a Buchi distillation unit. The influence of process parameters such as pH, temperature, and contact time was studied for adsorption of ammonium ion, and kinetic, isotherm models were validated to understand the mechanism of adsorption of ammonium ion by CSAC. Thermodynamic properties such as ∆G, ∆H, and ∆S were determined for the ammonium adsorption, using van't Hoff equation. Further, the adsorption of ammonium ion was confirmed through instrumental analyses such as SEM, XRD, and FTIR. The optimum conditions for the effective adsorption of ammonium ion onto CSAC were found to be pH 9.0, temperature 283 K, and contact time 120 min. The experimental data was best followed by pseudosecond order equation, and the adsorption isotherm model obeyed the Freundlich isotherm. This explains the ammonium ion adsorption onto CSAC which was a multilayer adsorption with intraparticle diffusion. Negative enthalpy confirmed that this adsorption process was exothermic. The instrumental analyses confirmed the adsorption of ammonium ion onto CSAC.

Adsorption Isotherms of Phenol and 4-Chlorophenol on Petroleum Asphaltenes Adsorption du phénol et du 4-chlorophénol sur les asphaltènes pétroliers

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Jaoui M.

2006-11-01

Full Text Available The adsorption isotherms for phenol and 4-chlorophenol from water onto asphaltenes flocculated in bulk and asphaltenes deposited on silica were established by frontal analysis chromatography at 293, 298, 303, and 308 K. The adsorption was more important with asphaltenes flocculated in bulk and corresponded to a Freundlich isotherm mechanism. The high adsorbed amount of phenols suggests possible migration of phenols through the loose asphaltene structure. Isotherms observed with the silica coated by asphaltenes showed that adsorption occurs in two stages corresponding probably to two different organizations of solute molecules at the surface. Les isothermes d'adsorption du phénol et du 4-chlorophénol en solution dans l'eau sur des asphaltènes floculés en masse et sur des asphaltènes déposés sur de la silice ont été déterminés par analyse chromatographique frontale à 293, 298, 303 et 308 K. L'adsorption sur des asphaltènes floculés en masse était la plus importante avec des isothermes correspondant à un mécanisme de Freundlich. La quantité élevée de phénols adsorbés suggère une migration possible des molécules du phénol à travers la structure peu compacte des asphaltènes. Les isothermes observés dans le cas de silice tapissée d'asphaltènes ont montré que l'adsorption se produit en deux étapes correspondant probablement à deux organisations différentes des molécules de soluté à la surface.

Gas adsorption on commercial magnesium stearate: Effects of degassing conditions on nitrogen BET surface area and isotherm characteristics.

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Lapham, Darren P; Lapham, Julie L

2017-09-15

Commercial grades of magnesium stearate have been analysed by nitrogen adsorption having been pre-treated at temperatures between 30°C and 110°C and in the as-received state. Characteristics of nitrogen adsorption/desorption isotherms are assessed through the linearity of low relative pressure isotherm data and the BET transform plot together with the extent of isotherm hysteresis. Comparison is made between thermal gravimetric analysis and mass loss on drying. Features of gas adsorption isotherms considered atypical are identified and possible causes presented. It is shown that atypical isotherm features and issues of applying BET theory to the calculation of S BET are linked to the presence of hydrated water and that these depend on the hydration state: being more pronounced for the di-hydrate than the mono-hydrate. Dehydration reduces the extent of atypical features. S BET of a mono-hydrate sample is 5.6m 2 g -1 and 3.2m 2 g -1 at 40°C and 100°C degassing respectively but 23.9m 2 g 1 and 5.9m 2 g -1 for di-hydrate containing samples under comparable degassing. Di-hydrated samples also show S BET >15m 2 g 1 , BET C-values adsorption data. Copyright © 2017 Elsevier B.V. All rights reserved.

Adsorption Isotherm of Chromium (Vi) into Zncl2 Impregnated Activated Carbon Derived by Jatropha Curcas Seed Hull

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Mohammad, M.; Yakub, I.; Yaakob, Z.; Asim, N.; Sopian, K.

2017-12-01

Hexavalent chromium is carcinogenic and should be removed from industrial wastewater before discharged into water resources. Adsorption by using activated carbon from biomass is an economic and conventional way on removing the heavy metal ions from wastewater. In this research, activated carbon is synthesized from Jatropha curcas L. seed hull through chemical activation with ZnCl2 and carbonized at 800 °C (JAC/ZnCl2). The activated carbon has been characterized using FTIR, SEM-EDX, BET and CHNS-O analyzer. Adsorption isotherms have been analysed using Langmuir and Freundlich models to determine its removal mechanism. The maximum adsorption capacity of Cr (VI) metal ions onto JAC/ZnCl2 activated carbon is 25.189 mg/g and following Langmuir isotherm model which is monolayer adsorption.

Water adsorption isotherms of carboxymethyl cellulose, guar, locust bean, tragacanth and xanthan gums.

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Torres, María D; Moreira, Ramón; Chenlo, Francisco; Vázquez, María J

2012-06-20

Water adsorption isotherms of carboxymethyl cellulose (CMC), guar gum (GG), locust bean gum (LBG), tragacanth gum (TG) and xanthan gum (XG) were determined at different temperatures (20, 35, 50, and 65°C) using a gravimetric method. Several saturated salt solutions were selected to obtain different water activities in the range from 0.09 to 0.91. Water adsorption isotherms of tested hydrocolloids were classified like type II isotherms. In all cases, equilibrium moisture content decreased with increasing temperature at each water activity value. Three-parameter Guggenheim-Anderson-de Boer (GAB) model was employed to fit the experimental data in the water activity range and statistical analysis indicated that this model gave satisfactory results. CMC and GG were the most and the least hygroscopic gums, respectively. Sorption heats decreased with increasing moisture content. Monolayer moisture content evaluated with GAB model was consistent with equilibrium conditions of maximum stability calculated from thermodynamic analysis of net integral entropy. Values of equilibrium relative humidity at 20°C are proposed to storage adequately the tested gums. Copyright © 2012 Elsevier Ltd. All rights reserved.

Modeling of adsorption isotherms of phenol and chlorophenols onto granular activated carbon. Part I. Two-parameter models and equations allowing determination of thermodynamic parameters.

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Hamdaoui, Oualid; Naffrechoux, Emmanuel

2007-08-17

The adsorption equilibrium isotherms of five phenolic compounds from aqueous solutions onto granular activated carbon (GAC) were studied and modeled. Phenol (Ph), 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,4-dichlorophenol (DCP), and 2,4,6-trichlorophenol (TCP) were chosen for the adsorption tests. To predict the adsorption isotherms and to determine the characteristic parameters for process design, seven isotherm models: Langmuir (five linear forms), Freundlich, Elovich, Temkin, Fowler-Guggenheim, Kiselev, and Hill-de Boer models were applied to experimental data. The results reveal that the adsorption isotherm models fitted the data in the order: Fowler-Guggenheim>Hill-de Boer>Temkin>Freundlich>Kiselev>Langmuir isotherms. Adsorption isotherms modeling shows that the interaction of phenolic compounds with activated carbon surface is localized monolayer adsorption, that is adsorbed molecules are adsorbed at definite, localized sites. Each site can accommodate only one molecule. The interaction among adsorbed molecules is repulsive and there is no association between them, adsorption is carried out on energetically different sites and is an exothermic process. Uptake of phenols increases in the order Ph<2-CP<4-CPadsorption is directly proportional to their degree of chlorination.

Water Adsorption Isotherms on Fly Ash from Several Sources.

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Navea, Juan G; Richmond, Emily; Stortini, Talia; Greenspan, Jillian

2017-10-03

In this study, horizontal attenuated total reflection (HATR) Fourier-transform infrared (FT-IR) spectroscopy was combined with quartz crystal microbalance (QCM) gravimetry to investigate the adsorption isotherms of water on fly ash, a byproduct of coal combustion in power plants. Because of composition variability with the source region, water uptake was studied at room temperature as a function of relative humidity (RH) on fly ash from several regions: United States, India, The Netherlands, and Germany. The FT-IR spectra show water features growth as a function of RH, with water absorbing on the particle surface in both an ordered (ice-like) and a disordered (liquid-like) structure. The QCM data was modeled using the Brunauer, Emmett, and Teller (BET) adsorption isotherm model. The BET model was found to describe the data well over the entire range of RH, showing that water uptake on fly ash takes place mostly on the surface of the particle, even for poorly combusted samples. In addition, the source region and power-plant efficiency play important roles in the water uptake and ice nucleation (IN) ability of fly ash. The difference in the observed water uptake and IN behavior between the four samples and mullite (3Al 2 O 3 ·2SiO 2 ), the aluminosilicate main component of fly ash, is attributed to differences in composition and the density of OH binding sites on the surface of each sample. A discussion is presented on the RH required to reach monolayer coverage on each sample as well as a comparison between surface sites of fly ash samples and enthalpies of adsorption of water between the samples and mullite.

Adsorption of an anionic dye on a novel low-cost mesoporous adsorbent: kinetic, thermodynamic and isotherm studies

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Msaad, Asmaa; Belbahloul, Mounir; Zouhri, Abdeljalil

2018-05-01

Our activated carbon was prepared successfully using phosphoric acid as an activated agent. The activated carbon was characterized by Scanning Electron Micrograph (SEM), Brunauer-Emmett- Teller (BET), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The aim of our study is to evaluate the adsorption capacity of Methyl Orange (MO) on Ziziphus lotus activated carbon. Adsorption isotherms were studied according to Langmuir and Freundlich Model, and adsorption kinetics according to pseudo-first and second-order. Results show that the maximum adsorption was reached in the first 10min at ambient temperature with a yield of 96.31%. The Langmuir isotherm shows a correlation coefficient of 99.4 % higher than Freundlich model and the adsorption kinetic model follow a pseudo-second-order with a maximum adsorption capacity of 769.23 mg/g. FTIR and X-Ray spectroscopy indicate that our activated carbon has an amorphous structure with the presence of functional groups, where BET analysis revealed a high surface area of 553 mg/g, which facilitate the adsorption process

High Pressure Adsorption Isotherm of CO2 on Activated Carbon using Volumetric Method

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Awaludin Martin

2011-05-01

Full Text Available Adsorption system is ones of the most effective methods for CO2 separating with other substances that produced from the burning of fossil fuels. In the design for that application, beside of characteristics of porous material (adsorbent data, CO2 adsorption data on the adsorbent (kinetic and thermodynamic are also needed. The aim of this research is resulting isothermal adsorption data at pressures up to 3.5 MPa by indirect methods (volumetric method at isothermal temperature of 300, 308, 318 and 338 K. Adsorbent that used in this research is activated carbon made from East of Kalimantan coals by physical activation method (CO2 which is the surface area of activated carbon is 668 m2/g and pore volume is 0.47 mL/g. Carbon dioxide (CO2 that used in this research is high purity carbon dioxide with a purity of 99.9%. Data from the experiment results then correlated using the Langmuir and Toth equations model. The results showed that the maximum adsorption capacity is 0.314 kg/kg at 300 K and 3384.69 kPa. The results of regression of experiment data using Langmuir and Toth models were 3.4% and 1.7%.

Analysis of nitrogen and carbon tetrachloride adsorption isotherms and pore size distribution for siliceous MCM-41 synthesized from rice husk silica

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Siriluk Chiarakorn

2004-02-01

Full Text Available RH-MCM-41 particles were synthesized using sodium silicate prepared from rice husk as a silica source and hexadecyltrimethylammonium bromide (CTAB as a surfactant. The molar compositions were 1.0SiO2: 1.1NaOH: 0.13CTAB: 0.12H2O. This material was used for adsorption isotherm studies of carbon tetrachloride (CT at 25 oC using a magnetically coupled microbalance, and compared with adsorption isotherms using nitrogen at 77 K. The CT isotherms were classified as reversible Type V isotherms, and the nitrogen adsorption isotherm was Type IVc. Capillary condensation was found in a very narrow pressure range, indicating the presence of nearly uniform pores in the RH-MCM-41 particles, which agrees very well with TEM results. The surface area estimated by using the BET method was (800 ± 8 m2 g-1. Pore size distributions (PSD of nitrogen and CT adsorption isotherms for a series of MCM-41 were calculated by using method recommended by Naono and Hakuman (1997. The pore size distributions from the nitrogen isotherm using the BJH and Naono methods showed quite narrow pore diameter distributions, centered around 27 and 29 Å, respectively. Similarly, the peak pore diameters calculated from CT isotherms using the BJH and Naono methods were 24 and 28 Å. It was found that the PSDs analyzed by the BJH method were underestimated compared to that from Naono method.

Isotherm, Kinetic and Thermodynamic Characteristics for Adsorption of Congo Red by Activated Carbon

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Lee, Jong Jib [Kongju National University, Cheonan (Korea, Republic of)

2015-02-15

Batch experiment studies were carried out for adsorption of congo red using granular activated carbon with various parameters such as activated carbon dose, pH, initial dye concentration, temperature and contact time. Equilibrium experimental data are fitted to the Langmuir, Freundlich, Temkin and Dubin-Radushkevich isotherm equations. From Freundlich's separation factor (1/n) estimated, adsorption could be employed as effective treatment method for adsorption of congo red from aqueous solution. Base on Temkin constant (B) and Dubinin-Radushkevich constant (E), this adsorption process is physical adsorption. Adsorption kinetics has been tested using pseudo-first order and pseudo second order models. The results followed pseudo second order model with good correlation. Adsorption process of congo red on granular activated carbon was endothermic (ΔH=42.036 kJ/mol) and was accompanied by decrease in Gibbs free energy (ΔG=-2.414 to -4.596 kJ/mol) with increasing adsorption temperature.

Isotherm, Kinetic and Thermodynamic Characteristics for Adsorption of Congo Red by Activated Carbon

International Nuclear Information System (INIS)

Lee, Jong Jib

2015-01-01

Batch experiment studies were carried out for adsorption of congo red using granular activated carbon with various parameters such as activated carbon dose, pH, initial dye concentration, temperature and contact time. Equilibrium experimental data are fitted to the Langmuir, Freundlich, Temkin and Dubin-Radushkevich isotherm equations. From Freundlich's separation factor (1/n) estimated, adsorption could be employed as effective treatment method for adsorption of congo red from aqueous solution. Base on Temkin constant (B) and Dubinin-Radushkevich constant (E), this adsorption process is physical adsorption. Adsorption kinetics has been tested using pseudo-first order and pseudo second order models. The results followed pseudo second order model with good correlation. Adsorption process of congo red on granular activated carbon was endothermic (ΔH=42.036 kJ/mol) and was accompanied by decrease in Gibbs free energy (ΔG=-2.414 to -4.596 kJ/mol) with increasing adsorption temperature

Adsorption of hazardous cationic dye onto the combustion derived SrTiO3 nanoparticles: Kinetic and isotherm studies

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N.P. Bhagya

2016-03-01

Full Text Available In this article we report on solution combustion method to synthesize SrTiO3 nanoparticles (ST-NPs and the removal of malachite green (MG azo dye from the aqueous solution. The synthesized ST-NPs were calcined at 600 °C for 2 h. Powder X-ray diffraction (PXRD, field emission scanning electron microscopy (FE-SEM, transmission electron microscopy (TEM, Fourier transform infrared spectroscopy (FT-IR, and Brunauer–Emmett–Teller (BET were used to characterize the product. Adsorption experiments were performed with cationic malachite green (MG dye. ∼98% dye was adsorbed onto the ST-NPs at pH 10 for 30 min of the contact time. The optimum adsorbent dose was found to be 0.015 g/L of the dye. To study the adsorption kinetics Langmuir Hinshelwood model was used and the first order kinetic best describes the MG adsorption onto the ST-NPs. The adsorption isotherms data of MG onto ST-NPs obtained were analyzed by Langmuir and Freundlich isotherm models and the results describe the best representation of the Langmuir isotherm model.

Adsorption of a cationic dye (Yellow Basic 28 ontothe calcined mussel shells: Kinetics, Isotherm and Thermodynamic Parameters

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Imane EL Ouahabi

2015-11-01

Full Text Available The aim of this study is to valorise the mussel shells and evaluate the adsorption capacity of calcined mussel shells for the cationic dyes.  The adsorbent was characterized by DRX, FTIR, BET and SEM, respectively. The adsorption of Yellow Basic28 on calcined mussel shells was investigated using the parameters such as concentrations (10-50mg/L, pH (3-10, ionic strength (0-2 mol / L and temperature (288 - 318 °C.  The adsorption rate data were analysed according to the first and second-order kinetic models.  The adsorption kinetics was found to be best represented by the pseudo-second-order kinetic model.  The experimental isotherm data were analyzed using Langmuir, Freundlich, Temkin, Elovich and Dubinin–Radushkevich isotherm equations on the dye-adsorbent system. The experimental data yielded excellent fits with Freundlich isotherm equation (R² = 0.966. It was indicative of the heterogeneity of the adsorption sites on the CMS particles.  Various thermodynamic parameters such as enthalpy of adsorption ΔH°, free energy change ΔG°and entropy ΔS° were estimated.  The positive value of ΔH°(30.321 kJ/mol and negative values of ΔG° (from -5.392 to -2.873 kJ/mol show the process is endothermic and spontaneous.  The negative value of entropy ΔS° (-87.172 J/mol K suggest the decreased randomness at the solid-liquid interface during the adsorption of dyes onto calcined mussel shells.

Experimental Adsorption Isotherm of Methane onto Activated Carbon at Sub- and Supercritical Temperatures

KAUST Repository

Rahman, Kazi Afzalur; Loh, Wai Soong; Yanagi, Hideharu; Chakraborty, Anutosh; Saha, Bidyut Baran; Chun, Won Gee; Ng, Kim Choon

2010-01-01

This paper presents the experimentally measured adsorption isotherm data for methane onto the pitch-based activated carbon type Maxsorb III for temperatures ranging from (120 to 220) K and pressures up to 1.4 MPa. These data are useful to study

Simple and Efficient Synthesis of Iron Oxide-Coated Silica Gel Adsorbents for Arsenic Removal: Adsorption Isotherms and Kinetic Study

Energy Technology Data Exchange (ETDEWEB)

Arifin, Eric; Lee, Jiukyu [Interdisciplinary Program in Nanoscience and Technology, Virginia (United States); Cha, Jinmyung [Seoul National Univ., Seoul (Korea, Republic of)

2013-08-15

Iron oxide (ferrihydrite, hematite, and magnetite) coated silica gels were prepared using a low-cost, easily-scalable and straightforward method as the adsorbent material for arsenic removal application. Adsorption of the anionic form of arsenic oxyacids, arsenite (AsO{sup 2-}) and arsenate (AsO{sub 4}{sup -3}), onto hematite coated silica gel was fitted against non-linear 3-parameter-model Sips isotherm and 2-parameter-model Langmuir and Freundlich isotherm. Adsorption kinetics of arsenic could be well described by pseudo-second-order kinetic model and value of adsorption energy derived from non-linear Dubinin-Radushkevich isotherm suggests chemical adsorption. Although arsenic adsorption process was not affected by the presence of sulfate, chloride, and nitrate anions, as expected, bicarbonate and silicate gave moderate negative effects while the presence of phosphate anions significantly inhibited adsorption process of both arsenite and arsenate. When the actual efficiency to remove arsenic was tested against 1 L of artificial arsenic-contaminated groundwater (0.6 mg/L) in the presence competing anions, the reasonable amount (20 g) of hematite coated silica gel could reduce arsenic concentration to below the WHO permissible safety limit of drinking water of 10 μg/L without adjusting pH and temperature, which would be highly advantageous for practical field application.

Adsorption of surfactants on sand surface in enhanced oil recovery: Isotherms, kinetics and thermodynamic studies

Energy Technology Data Exchange (ETDEWEB)

Bera, Achinta; Kumar, T.; Ojha, Keka; Mandal, Ajay, E-mail: mandal_ajay@hotmail.com

2013-11-01

Adsorption of surfactants onto reservoir rock surface may result in the loss and reduction of their concentrations in surfactant flooding, which may render them less efficient or ineffective in practical applications of enhanced oil recovery (EOR) techniques. Surfactant flooding for EOR received attraction due to its ability to increase the displacement efficiency by lowering the interfacial tension between oil and water and mobilizing the residual oil. This article highlights the adsorption of surfactants onto sand surface with variation of different influencing factors. It has been experimentally found that adsorption of cationic surfactant on sand surface is more and less for anionic surfactant, while non-ionic surfactant shows intermediate behaviour. X-ray diffraction (XRD) study of clean sand particles has been made to determine the main component present in the sand particles. The interaction between sand particles and surfactant has been studied by Fourier Transform Infrared (FTIR) Spectroscopy of the sand particles before and after aging with surfactant. Salinity plays an important role in adsorption of anionic surfactant. Batch experiments were also performed to understand the effects of pH and adsorbent dose on the sorption efficiency. The sand particles exhibited high adsorption efficiency at low pH for anionic and nonionic surfactants. But opposite trend was found for cationic surfactant. Adsorption data were analyzed by fitting with Langmuir, Freundlich, Redlich-Peterson, and Sips isotherm models. Results show that the Langmuir isotherm and pseudo-second order kinetics models suit the equilibrium and kinetics of adsorption on sand surface. Thermodynamics feasibility of the adsorption process was also studied to verify the spontaneity of the process.

Adsorption of selected emerging contaminants onto PAC and GAC: Equilibrium isotherms, kinetics, and effect of the water matrix.

Science.gov (United States)

Real, Francisco J; Benitez, F Javier; Acero, Juan L; Casas, Francisco

2017-07-03

The removal of three emerging contaminants (ECs) (amitriptyline hydrochloride (AH), methyl salicylate (MS) and 2-phenoxyethanol (PE)) dissolved in several water matrices by means of their adsorption onto powdered activated carbon (PAC) and granular activated carbon (GAC) has been investigated. When dissolved in ultrapure water, adsorption of the ECs followed the trend of AH > MS > PE, with a positive effect of the adsorbent dose. According to the analysis of the adsorption isotherms and adsorption kinetics, PAC showed strongly higher adsorption efficiency in both capacity and velocity of the adsorption, in agreement with its higher mesoporosity. Equilibrium isotherm data were fitted by Langmuir and Freundlich models. Pseudo-second order kinetics modeled very successfully the adsorption process. Finally, the effect of the presence of dissolved organic matter (DOM) in the water matrices (ultrapure water, surface water and two effluents from wastewater treatment plants) on the adsorption of the selected ECs onto PAC was established, as well as its performance on the removal of water quality parameters. Results show a negative effect of the DOM content on the adsorption efficiency. Over 50% of organic matter was removed with high PAC doses, revealing that adsorption onto PAC is an effective technology to remove both micro-pollutants and DOM from water matrices.

Optimizing Available Phosphorus in Calcareous Soils Fertilized with Diammonium Phosphate and Phosphoric Acid Using Freundlich Adsorption Isotherm

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Asif Naeem

2013-01-01

Full Text Available In calcareous soils, phosphorus (P retention and immobilization take place due to precipitation and adsorption. Since soil pH is considered a major soil variable affecting the P sorption, an acidic P fertilizer could result in low P adsorption compared to alkaline one. Therefore, P adsorption from DAP and phosphoric acid (PA required to produce desired soil solution P concentration was estimated using Freundlich sorption isotherms. Two soils from Faisalabad and T. T. Singh districts were spiked with 0, 10, and 20 % for 15 days. Freundlich adsorption isotherms ( were constructed, and theoretical doses of PA and DAP to develop a desired soil solution P level (i.e., 0.20 mg L−1 were calculated. It was observed that P adsorption in soil increased with . Moreover, at all the levels of , P adsorption from PA was lower compared to that from DAP in both the soils. Consequently, lesser quantity of PA was required to produce desired solution P, 0.2 mg L−1, compared to DAP. However, extrapolating the developed relationship between soil contents and quantity of fertilizer to other similar textured soils needs confirmation.

Molar volume and adsorption isotherm dependence of capillary forces in nanoasperity contacts.

Science.gov (United States)

Asay, David B; Kim, Seong H

2007-11-20

The magnitude of the capillary force at any given temperature and adsorbate partial pressure depends primarily on four factors: the surface tension of the adsorbate, its liquid molar volume, its isothermal behavior, and the contact geometry. At large contacting radii, the adsorbate surface tension and the contact geometry are dominating. This is the case of surface force apparatus measurements and atomic force microscopy (AFM) experiments with micrometer-size spheres. However, as the size of contacting asperities decreases to the nanoscale as in AFM experiments with sharp tips, the molar volume and isotherm of the adsorbate become very important to capillary formation as well as capillary adhesion. This effect is experimentally and theoretically explored with simple alcohol molecules (ethanol, 1-butanol, and 1-pentanol) which have comparable surface tensions but differing liquid molar volumes. Adsorption isotherms for these alcohols on silicon oxide are also reported.

Investigation of Acorn fruit Ash Efficiency in Cadmium Removal from Aqueous Solutions: Adsorption Isotherm and Kinetic Studies

Directory of Open Access Journals (Sweden)

Salman Zarei

2014-12-01

Full Text Available Background: Heavy metals are known as significant pollutants because of toxicity and nonbiodegradable characteristics. Cadmium is one of the heavy metals that have carcinogen potential. So, this study carried out in order to investigate the acorn fruit ash efficiency in cadmium removal from aqueous solutions. Methods: This study was done in the batch laboratory conditions. In this study, the effect of different parameters including pH, contact time, adsorbent dose, and initial cadmium concentration were evaluated. The Langmuir, Freundlich and Temkin isotherm models were used for analysis of the equilibrium isotherm. Adsorption kinetics of cadmium by different models were also investigated. The measurement of residual cadmium in the samples was determined by atomic absorption spectrophotometry at 228.8 nm. The SPSS-16 software was used for analysis of data. Results: According to the results, the maximum adsorption capacity of cadmium was 9.29 mg/g at pH=7 and 8 g/L adsorbent dose. The removal efficiency was increased with increasing contact time and decreased with increasing of cadmium initial concentration. Investigation of achieving data showed that the adsorption process followed better by Freundlich isotherm and the pseudo-second order kinetic. Conclusions: According to the results of this study, it could be concluded that the acorn fruit ash had high ability in cadmium adsorption and could be used as a cheap adsorbent in the removal of cadmium.

Equilibrium arsenic adsorption onto metallic oxides : Isotherm models, error analysis and removal mechanism

Energy Technology Data Exchange (ETDEWEB)

Simsek, Esra Bilgin [Yalova University, Yalova (Turkmenistan); Beker, Ulker [Yldz Technical University, Istanbul (Turkmenistan)

2014-11-15

Arsenic adsorption properties of mono- (Fe or Al) and binary (Fe-Al) metal oxides supported on natural zeolite were investigated at three levels of temperature (298, 318 and 338 K). All data obtained from equilibrium experiments were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich, Sips, Toth and Redlich-Peterson isotherms, and error functions were used to predict the best fitting model. The error analysis demonstrated that the As(Ⅴ) adsorption processes were best described by the Dubinin-Raduskevich model with the lowest sum of normalized error values. According to results, the presence of iron and aluminum oxides in the zeolite network improved the As(Ⅴ) adsorption capacity of the raw zeolite (ZNa). The X-ray photoelectron spectroscopy (XPS) analyses of ZNa-Fe and ZNa-AlFe samples suggested that the redox reactions are the postulated mechanisms for the adsorption onto them while the adsorption process is followed by surface complexation reactions for ZNa-Al.

Optimizing Available Phosphorus in Calcareous Soils Fertilized with Diammonium Phosphate and Phosphoric Acid Using Freundlich Adsorption Isotherm

Science.gov (United States)

Akhtar, Muhammad

2013-01-01

In calcareous soils, phosphorus (P) retention and immobilization take place due to precipitation and adsorption. Since soil pH is considered a major soil variable affecting the P sorption, an acidic P fertilizer could result in low P adsorption compared to alkaline one. Therefore, P adsorption from DAP and phosphoric acid (PA) required to produce desired soil solution P concentration was estimated using Freundlich sorption isotherms. Two soils from Faisalabad and T. T. Singh districts were spiked with 0, 10, and 20 % CaCO3 for 15 days. Freundlich adsorption isotherms (P = aC b/a) were constructed, and theoretical doses of PA and DAP to develop a desired soil solution P level (i.e., 0.20 mg L−1) were calculated. It was observed that P adsorption in soil increased with CaCO3. Moreover, at all the levels of CaCO3, P adsorption from PA was lower compared to that from DAP in both the soils. Consequently, lesser quantity of PA was required to produce desired solution P, 0.2 mg L−1, compared to DAP. However, extrapolating the developed relationship between soil CaCO3 contents and quantity of fertilizer to other similar textured soils needs confirmation. PMID:24307878

Freundlich and Langmuir adsorption isotherms and kinetics for the removal of Tartrazine from aqueous solutions using hen feathers

International Nuclear Information System (INIS)

Mittal, Alok; Kurup, Lisha; Mittal, Jyoti

2007-01-01

Tartrazine, a yellow menace, is widely being used in cosmetics, foodstuffs, medicines and textile. It is carcinogenic and also catalyzes allergic problems. In the present work the ability to remove Tartrazine from aqueous solutions has been studied using waste material-hen feathers, as adsorbent. Effects of pH, concentration of the dye, temperature and adsorbent dosage have been studied. Equilibrium isotherms for the adsorption of the dye were measured experimentally. Results were analyzed by the Freundlich and Langmuir equation at different temperatures and determined the characteristic parameters for each adsorption isotherm. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy (ΔG o ), change in enthalpy (ΔH o ) and change in entropy (ΔS o ) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. By rate expression and treatment of data it has been established that the adsorption of Tartrazine over hen feathers follows a first-order kinetics and a film diffusion mechanism operates at all the temperatures

Freundlich and Langmuir adsorption isotherms and kinetics for the removal of Tartrazine from aqueous solutions using hen feathers.

Science.gov (United States)

Mittal, Alok; Kurup, Lisha; Mittal, Jyoti

2007-07-19

Tartrazine, a yellow menace, is widely being used in cosmetics, foodstuffs, medicines and textile. It is carcinogenic and also catalyzes allergic problems. In the present work the ability to remove Tartrazine from aqueous solutions has been studied using waste material-hen feathers, as adsorbent. Effects of pH, concentration of the dye, temperature and adsorbent dosage have been studied. Equilibrium isotherms for the adsorption of the dye were measured experimentally. Results were analyzed by the Freundlich and Langmuir equation at different temperatures and determined the characteristic parameters for each adsorption isotherm. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy (DeltaG degrees), change in enthalpy (DeltaH degrees) and change in entropy (DeltaS degrees) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. By rate expression and treatment of data it has been established that the adsorption of Tartrazine over hen feathers follows a first-order kinetics and a film diffusion mechanism operates at all the temperatures.

Incorporating classic adsorption isotherms into modern surface complexation models: implications for sorption of radionuclides

International Nuclear Information System (INIS)

Kulik, D.A.

2005-01-01

Full text of publication follows: Computer-aided surface complexation models (SCM) tend to replace the classic adsorption isotherm (AI) analysis in describing mineral-water interface reactions such as radionuclide sorption onto (hydr) oxides and clays. Any site-binding SCM based on the mole balance of surface sites, in fact, reproduces the (competitive) Langmuir isotherm, optionally amended with electrostatic Coulomb's non-ideal term. In most SCM implementations, it is difficult to incorporate real-surface phenomena (site heterogeneity, lateral interactions, surface condensation) described in classic AI approaches other than Langmuir's. Thermodynamic relations between SCMs and AIs that remained obscure in the past have been recently clarified using new definitions of standard and reference states of surface species [1,2]. On this basis, a method for separating the Langmuir AI into ideal (linear) and non-ideal parts [2] was applied to multi-dentate Langmuir, Frumkin, and BET isotherms. The aim of this work was to obtain the surface activity coefficient terms that make the SCM site mole balance constraints obsolete and, in this way, extend thermodynamic SCMs to cover sorption phenomena described by the respective AIs. The multi-dentate Langmuir term accounts for the site saturation with n-dentate surface species, as illustrated on modeling bi-dentate U VI complexes on goethite or SiO 2 surfaces. The Frumkin term corrects for the lateral interactions of the mono-dentate surface species; in particular, it has the same form as the Coulombic term of the constant-capacitance EDL combined with the Langmuir term. The BET term (three parameters) accounts for more than a monolayer adsorption up to the surface condensation; it can potentially describe the surface precipitation of nickel and other cations on hydroxides and clay minerals. All three non-ideal terms (in GEM SCMs implementation [1,2]) by now are used for non-competing surface species only. Upon 'surface dilution

Adsorptive removal of malachite green from aqueous solutions by almond gum: Kinetic study and equilibrium isotherms.

Science.gov (United States)

Bouaziz, Fatma; Koubaa, Mohamed; Kallel, Fatma; Ghorbel, Rhoudha Ellouz; Chaabouni, Semia Ellouz

2017-12-01

This work aimed at investigating the potential of almond gum as low cost adsorbent for the removal of the cationic dye; malachite green from aqueous solutions. Almond gum was first analyzed by scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR), and then the adsorption behavior was studied in batch system. The effects of the adsorption parameters (adsorbent dose, pH, contact time, particle size, initial dye concentration, temperature and agitation) on the dye removal have been studied. Adsorption equilibrium and isotherms were evaluated depending on temperature using the isotherms of Freundlich, Langmuir, and Tempkin. The obtained result showed that both Langmuir and Freundlich models were adapted to study the dye sorption. The maximum adsorption capacities were equal to 172.41mg/g, 181.81mg/g, and 196.07mg/g at 303.16K, 313.16K, and 323.16K, respectively. The kinetics of sorption were following the pseudo-second order model. The thermodynamic changes in enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) indicated that the adsorption of malachite green at the surface of almond gum is endothermic and occurs spontaneously. Desorption experiments were conducted to regenerate almond gum, showing great desorption capacity when using HCl at pH 2. Copyright © 2017 Elsevier B.V. All rights reserved.

Freundlich and Langmuir adsorption isotherms and kinetics for the removal of Tartrazine from aqueous solutions using hen feathers

Energy Technology Data Exchange (ETDEWEB)

Mittal, Alok [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal, 462 007 MP (India)]. E-mail: aljymittal@yahoo.co.in; Kurup, Lisha [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal, 462 007 MP (India); Mittal, Jyoti [Department of Applied Chemistry, Maulana Azad National Institute of Technology, Bhopal, 462 007 MP (India)

2007-07-19

Tartrazine, a yellow menace, is widely being used in cosmetics, foodstuffs, medicines and textile. It is carcinogenic and also catalyzes allergic problems. In the present work the ability to remove Tartrazine from aqueous solutions has been studied using waste material-hen feathers, as adsorbent. Effects of pH, concentration of the dye, temperature and adsorbent dosage have been studied. Equilibrium isotherms for the adsorption of the dye were measured experimentally. Results were analyzed by the Freundlich and Langmuir equation at different temperatures and determined the characteristic parameters for each adsorption isotherm. The adsorption process has been found endothermic in nature and thermodynamic parameters, Gibb's free energy ({delta}G{sup o}), change in enthalpy ({delta}H{sup o}) and change in entropy ({delta}S{sup o}) have been calculated. The paper also includes results on the kinetic measurements of adsorption of the dye on hen feathers at different temperatures. By rate expression and treatment of data it has been established that the adsorption of Tartrazine over hen feathers follows a first-order kinetics and a film diffusion mechanism operates at all the temperatures.

Adsorption kinetics, isotherm, and thermodynamics studies of acetyl-11-keto-β-boswellic acids (AKBA) from Boswellia serrata extract using macroporous resin.

Science.gov (United States)

Niphadkar, Sonali S; Rathod, Virendra K

2017-09-14

An acetyl-11-keto-β-boswellic acid (AKBA) is potent anti-inflammatory agent found in Boswellia serrata oleogum resin. Adsorption characteristics of AKBA from B. serrata were studied using macroporous adsorbent resin to understand separation and adsorption mechanism of targeted molecules. Different macroporous resins were screened for adsorption and desorption of AKBA and Indion 830 was screened as it showed higher adsorption capacity. The kinetic equations were studied and results showed that the adsorption of AKBA on Indion 830 was well fitted to the pseudo first-order kinetic model. The influence of two parameters such as temperature (298, 303, and 308 K) and pH (5-8) on the adsorption process was also studied. The experimental data was further investigated using Langmuir, Freundlich, and Temkin isotherm models. It was observed that Langmuir isotherm model was found to be the best fit for AKBA adsorption by Indion 830 and highest adsorption capacity (50.34 mg/g) was obtained at temperature of 303 K. The values of thermodynamic parameters such as the change of Gibbs free energy (ΔG*), entropy (ΔS*), and enthalpy (ΔH*), indicated that the process of adsorption was spontaneous, favourable, and exothermic.

Adsorption of reactive dye from an aqueous solution by chitosan: isotherm, kinetic and thermodynamic analysis

International Nuclear Information System (INIS)

Annadurai, Gurusamy; Ling, L.Y.; Lee, J.-F.

2008-01-01

The adsorption of Remazol black 13 (Reactive) dye onto chitosan in aqueous solutions was investigated. Experiments were carried out as function of contact time, initial dye concentration (100-300 mg/L), particle size (0.177, 0.384, 1.651 mm), pH (6.7-9.0), and temperature (30-60 deg. C). The equilibrium adsorption data of reactive dye on chitosan were analyzed by Langmuir and Freundlich models. The maximum adsorption capacity (q m ) has been found to be 91.47-130.0 mg/g. The amino group nature of the chitosan provided reasonable dye removal capability. The kinetics of reactive dye adsorption nicely followed the pseudo-first and second-order rate expression which demonstrates that intraparticle diffusion plays a significant role in the adsorption mechanism. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of adsorption. The positive value of the enthalpy change (0.212 kJ/mol) indicated that the adsorption is endothermic process. The results indicate that chitosan is suitable as adsorbent material for adsorption of reactive dye form aqueous solutions

Isothermal approach to predict the removal efficiency of β-carotene adsorption from CPO using activated carbon produced from tea waste

Science.gov (United States)

Harahap, S. A. A.; Nazar, A.; Yunita, M.; Pasaribu, RA; Panjaitan, F.; Yanuar, F.; Misran, E.

2018-02-01

Adsorption of β-carotene in crude palm oil (CPO) was studied using activated carbon produced from tea waste (ACTW) an adsorbent. Isothermal studies were carried out at 60 °C with the ratio of activated carbon to CPO were 1:3, 1:4, 1:5, and 1:6, respectively. The ACTW showed excellent performance as the percentage of adsorption of β-carotene from CPO was > 99%. The best percentage removal (R) was achieved at ACTW to CPO ratio equal to 1:3, which was 99.61%. The appropriate isotherm model for this study was Freundlich isotherm model. The combination of Freundlich isotherm equation and mass balance equation showed a good agreement when validated to the experimental data. The equation subsequently executed to predict the removal efficiency under given sets of operating conditions. At a targetted R, CPO volume can be estimated for a certain initial concentration β-carotene in CPO C0 and mass of ACTW adsorbent M used.

Adsorptive Removal of Reactive Black 5 from Wastewater Using Bentonite Clay: Isotherms, Kinetics and Thermodynamics

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Muhammad Tahir Amin

2015-11-01

Full Text Available The studies of the kinetics and isotherms adsorption of the Reactive Black 5 (RB5 onto bentonite clay were explored in a batch study in a laboratory. The maximum RB5 adsorption conditions of bentonite clay were optimized such as shaking speed (100 rpm, temperature (323 K, pH (10, contact time (40 min, initial dye concentration (170 mg·L−1, and particle size (177 µm. The adsorbent surface was characterized using Fourier Transform Infrared Spectroscopy spectroscopy. The mechanisms and characteristic parameters of the adsorption process were analyzed using two parameter isotherm models which revealed the following order (based on the coefficient of determination: Harkin-Jura (0.9989 > Freundlich (0.9986 and Halsey (0.9986 > Langmuir (0.9915 > Temkin (0.9818 > Dubinin–Radushkevich (0.9678. This result suggests the heterogeneous nature of bentonite clay. Moreover, the adsorption process was chemisorption in nature because it follows the pseudo-second order reaction model with R2 value of 0.9998, 0.9933 and 0.9891 at 25, 75 and 100 mg·L−1 RB5 dye in the solution, respectively. Moreover, based on the values of standard enthalpy, Gibbs free energy change, and entropy, bentonite clay showed dual nature of exothermic and endothermic, spontaneous and non-spontaneous as well as increased and decreased randomness at solid–liquid interface at 303–313 K and 313–323 K temperature, respectively.

Moisture Adsorption Isotherm and Storability of Hazelnut Inshells and Kernels Produced in Oregon, USA.

Science.gov (United States)

Jung, Jooyeoun; Wang, Wenjie; McGorrin, Robert J; Zhao, Yanyun

2018-02-01

Moisture adsorption isotherms and storability of dried hazelnut inshells and kernels produced in Oregon were evaluated and compared among cultivars, including Barcelona, Yamhill, and Jefferson. Experimental moisture adsorption data fitted to Guggenheim-Anderson-de Boer (GAB) model, showing less hygroscopic properties in Yamhill than other cultivars of inshells and kernels due to lower content of carbohydrate and protein, but higher content of fat. The safe levels of moisture content (MC, dry basis) of dried inshells and kernels for reaching kernel water activity (a w ) ≤0.65 were estimated using the GAB model as 11.3% and 5.0% for Barcelona, 9.4% and 4.2% for Yamhill, and 10.7% and 4.9% for Jefferson, respectively. Storage conditions (2 °C at 85% to 95% relative humidity [RH], 10 °C at 65% to 75% RH, and 27 °C at 35% to 45% RH), times (0, 4, 8, or 12 mo), and packaging methods (atmosphere vs. vacuum) affected MC, a w , bioactive compounds, lipid oxidation, and enzyme activity of dried hazelnut inshells or kernels. For inshells packaged at woven polypropylene bag, MC and a w of inshells and kernels (inside shells) increased at 2 and 10 °C, but decreased at 27 °C during storage. For kernels, lipid oxidation and polyphenol oxidase activity also increased with extended storage time (P adsorption and physicochemical and enzymatic stability during storage. Moisture adsorption isotherm of hazelnut inshells and kernels is useful for predicting the storability of nuts. This study found that water adsorption and storability varied among the different cultivars of nuts, in which Yamhill was less hygroscopic than Barcelona and Jefferson, thus more stable during storage. For ensuring food safety and quality of nuts during storage, each cultivar of kernels should be dried to a certain level of MC. Lipid oxidation and enzyme activity of kernel could be increased with extended storage time. Vacuum packaging was recommended to kernels for reducing moisture adsorption

Decreasing Ni, Cu, Cd, and Zn heavy metal magnetite-bentonite nanocomposites and adsorption isotherm study

Science.gov (United States)

Eskandari, M.; Zakeri Khatir, M.; Khodadadi Darban, A.; Meshkini, M.

2018-04-01

This present study was conducted to investigate the effect of magnetite-bentonite nanocomposite on heavy metal removal from an effluent. For this purpose, magnetite-bentonite nanocomposite was prepared through the chemical method and characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, followed by studying the effect of produced nanocomposite on the removal of Ni2+, Cu2+, Cd2+, and Zn2+ heavy metal ions. The results showed that adsorption capacity of magnetite-bentonite nanocomposites for the studied ions is in the order of Zn2+ > Cd2+ > Cu2+ > Ni2+. Adsorption isotherms were drawn for Ni2+, Cu2+, Cd2+, and Zn2+ cations and found that cations adsorption on nanocomposite fit into Langmuir model.

Equilibrium isotherms, kinetics, and thermodynamics studies for congo red adsorption using calcium alginate beads impregnated with nano-goethite.

Science.gov (United States)

Munagapati, Venkata Subbaiah; Kim, Dong-Su

2017-07-01

The present study is concerned with the batch adsorption of congo red (CR) from an aqueous solution using calcium alginate beads impregnated with nano-goethite (CABI nano-goethite) as an adsorbent. The optimum conditions for CR removal were determined by studying operational variables viz. pH, adsorbent dose, contact time, initial dye ion concentration and temperature. The CABI nano-goethite was characterized by Fourier transform infrared spectroscopy (FTIR), X- ray diffraction (XRD) and Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The CR sorption data onto CABI nano-goethite were described using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherm models. The results show that the best fit was achieved with the Langmuir isotherm model. The maximum adsorption capacity (181.1mg/g) of CR was occurred at pH 3.0. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Desorption experiments were carried out to explore the feasibility of regenerating the adsorbent and the adsorbed CR from CABI nano-goethite. The best desorbing agent was 0.1M NaOH with an efficiency of 94% recovery. The thermodynamic parameters ΔG°, ΔH°, and ΔS° for the CR adsorption were determined by using adsorption capacities at five different temperatures (293, 303, 313, 323 and 303K). Results show that the adsorption process was endothermic and favoured at high temperature. Copyright © 2017 Elsevier Inc. All rights reserved.

Heavy metal ion adsorption behavior in nitrogen-doped magnetic carbon nanoparticles: Isotherms and kinetic study

International Nuclear Information System (INIS)

Shin, Keun-Young; Hong, Jin-Yong; Jang, Jyongsik

2011-01-01

Graphical abstract: Display Omitted Research highlights: → The monodisperse and multigram-scale N-MCNPs are fabricated by carbonization of polypyrrole as a carbon precursor. → The synthesized N-MCNPs provide an enhanced adsorption uptake for various heavy metal ions. → The N-MCNPs can be applied to the Langmuir model and pseudo-second-order kinetics. → The iron-impregnated N-MCNPs are reused up to 5 times with no loss of removal efficiency. - Abstract: To clarify the heavy metal adsorption mechanism of nitrogen-doped magnetic carbon nanoparticles (N-MCNPs), adsorption capacity was investigated from the adsorption isotherms, kinetics and thermodynamics points of view. The obtained results showed that the equilibrium adsorption behavior of Cr 3+ ion onto the N-MCNPs can be applied to the Langmuir model and pseudo-second-order kinetics. It indicated that the fabricated N-MCNPs had the homogenous surface for adsorption and all adsorption sites had equal adsorption energies. Furthermore, the adsorption onto N-MCNPs taken place through a chemical process involving the valence forces. According to the thermodynamics, the adsorption process is spontaneous and endothermic in nature which means that the adsorption capacity increases with increasing temperature due to the enhanced mobility of adsorbate molecules. The effects of the solution pH and the species of heavy metal ion on the adsorption uptake were also studied. The synthesized N-MCNPs exhibited an enhanced adsorption capacity for the heavy metal ions due to the high surface area and large amount of nitrogen contents.

Biosorption of the Copper and Cadmium Ions - a Study through Adsorption Isotherms Analysis

Directory of Open Access Journals (Sweden)

Marcia T. Veit

2007-10-01

Full Text Available In this work, the biosorption process of copper-cadmium ions binary mixture by using marine algae Sargassum filipendula was investigated. A set of experiments was performed to obtain equilibrium data for the given batch operational conditions - T=30°C, pH=5. The interpretation of equilibrium data was based on the binary adsorption isotherms models in the Langmuir and Freundlich forms. To evaluate the models parameters, nonlinear identification procedure was used based on the Least Square statistical method and SIMPLEX local optimizer. An analysis of the obtained results showed that the marine algae biomass has higher affinity to copper ions than to cadmium ones. The biomass maximum adsorption capacity for the binary system was about 1.16 meq/g.

Langmuir Isotherm application to the competitive adsorption of Cadmium, Nickel and Zinc on a Bentonite

International Nuclear Information System (INIS)

Silva Giraldo, German Dario; Pinzon Bello, Jorge Alejo

1999-01-01

In the present work, it was studied the simultaneous adsorption of binary and ternary mixtures of cadmium, nickel and zinc ions in aqueous solution at 25oC over a bentonite from the Cauca Valley, in its native state as well as in its sodium homo ionic form. The Langmuir isotherm, initially introduced by Murali and Aylmore for the competitive adsorption of various adsorbents, adequately describes the simultaneous adsorption of the three ions over the studied bentonite. The lineal correlation coefficient is greater than 0.900 in the major part of the systems. The competitive effect was interpreted by means of the thermodynamic distribution coefficient, Kdm. The degree of adsorption in the binary mixtures is nickel > zinc, cadmium over the natural bentonite, and nickel > cadmium > zinc over the sodium homo ionic form, whereas in the ternary mixture the order Nickel > Cadmium > Zinc is found over both adsorbents

Adsorption kinetics of surfactants on activated carbon

Science.gov (United States)

Arnelli; Aditama, WP; Fikriani, Z.; Astuti, Y.

2018-04-01

A study on the adsorption of both cationic and anionic surfactants using activated carbon as well as the investigation of the adsorption isotherms and adsorption kinetics has been conducted. The results showed that the adsorption of sodium lauryl sulfate (SLS) by activated carbon was Langmuir’s adsorption isotherm while its adsorption kinetics showed pseudo-second order with an adsorption rate constant of 2.23 x 103 g mg-1 hour-1. Meanwhile, the adsorption of HDTMA-Br by activated carbon showed that the isotherm adsorption tended to follow Freundlich’s isotherm and was pseudo-second order with an adsorption rate constant of 89.39 g mg-1 hour-1.

Freundlich adsorption isotherms of agricultural by-product-based powdered activated carbons in a geosmin-water system

Energy Technology Data Exchange (ETDEWEB)

Ng, Chilton [Food and Drug Administration, Dept. of Health and Human Services, Lenexa, KS (United States); Losso, Jack N.; Rao, Ramu M. [Louisiana State Univ. Agricultural Center, Dept. of Food Science, Baton Rouge, LA (United States); Marshall, Wayne E. [USDA-ARS, Southern Regional Research Center, New Orleans, LA (United States)

2002-11-01

The present study was designed to model the adsorption of geosmin from water under laboratory conditions using the Freundlich isotherm model. This model was used to compare the efficiency of sugarcane bagasse and pecan shell-based powdered activated carbon to the efficiency of a coal-based commercial activated carbon (Calgon Filtrasorb 400). When data were generated from Freundlich isotherms, Calgon Filtrasorb 400 had greater geosmin adsorption at all geosmin concentrations studied than the laboratory produced steam-activated pecan shell carbon, steam-activated bagasse carbon, and the CO{sub 2}-activated pecan shell carbon. At geosmin concentrations <0.07 {sup {mu}}g/l for the phosphoric acid-activated pecan shell carbon and below 0.08 {sup {mu}}g/l for a commercially produced steam-activated pecan shell carbon obtained from Scientific Carbons, these two carbons had a higher calculated geosmin adsorption than Filtrasorb 400. While the commercial carbon was more efficient than some laboratory prepared carbons at most geosmin concentrations, the results indicate that when the amount of geosmin was below the threshold level of human taste (about 0.10 {sup {mu}}g/l), the phosphoric acid-activated pecan shell carbon and the Scientific Carbons sample were more efficient than Filtrasorb 400 at geosmin removal. (Author)

Adsorption of Pb(II) from fish sauce using carboxylated cellulose nanocrystal: Isotherm, kinetics, and thermodynamic studies.

Science.gov (United States)

Wang, Nan; Jin, Ru-Na; Omer, A M; Ouyang, Xiao-Kun

2017-09-01

In the present study, a new adsorbent based on carboxylated cellulose nanocrystal (CCN) was developed for the adsorption of Pb(II) from fish sauce. The prepared adsorbent material was characterized by zeta potential, FT-IR, XRD, and XPS tools. The changes in the morphological structure of the developed CCN surface were evidenced by SEM and TEM. The favorable adsorption conditions were selected by studying the contact time, initial concentration, temperature, and concentration of the used glutamic acid and NaCl. The results indicated that the Langmuir isotherm model agrees very well with experimental adsorption data (R 2 =0.9962) with a maximum adsorption capacity 232.56mg/g of Pb(II) at 293.2K. Additionally, data of the adsorption kinetics follow the pseudo-second-order kinetics (R 2 >0.9990). On the other hand, the thermodynamics studies show that the adsorption process is spontaneous and endothermic. Furthermore, the developed CCN could be regenerated using acid treatment with a good reusability for Pb(II) adsorption. The results clearly indicated that the synthesized CCN could be effectively applied as a new material for Pb(II) adsorption from fish sauce solutions. Copyright © 2017 Elsevier B.V. All rights reserved.

Kinetic and isotherm modeling of Cd (II) adsorption by L-cysteine functionalized multi-walled carbon nanotubes as adsorbent.

Science.gov (United States)

Taghavi, Mahmoud; Zazouli, Mohammad Ali; Yousefi, Zabihollah; Akbari-adergani, Behrouz

2015-11-01

In this study, multi-walled carbon nanotubes were functionalized by L-cysteine to show the kinetic and isotherm modeling of Cd (II) ions onto L-cysteine functionalized multi-walled carbon nanotubes. The adsorption behavior of Cd (II) ion was studied by varying parameters including dose of L-MWCNTs, contact time, and cadmium concentration. Equilibrium adsorption isotherms and kinetics were also investigated based on Cd (II) adsorption tests. The results showed that an increase in contact time and adsorbent dosage resulted in increase of the adsorption rate. The optimum condition of the Cd (II) removal process was found at pH=7.0, 15 mg/L L-MWCNTs dosage, 6 mg/L cadmium concentration, and contact time of 60 min. The removal percent was equal to 89.56 at optimum condition. Langmuir and Freundlich models were employed to analyze the experimental data. The data showed well fitting with the Langmuir model (R2=0.994) with q max of 43.47 mg/g. Analyzing the kinetic data by the pseudo-first-order and pseudo-second-order equations revealed that the adsorption of cadmium using L-MWSNTs following the pseudo-second-order kinetic model with correlation coefficients (R2) equals to 0.998, 0.992, and 0.998 for 3, 6, and 9 mg/L Cd (II) concentrations, respectively. The experimental data fitted very well with the pseudo-second-order. Overall, treatment of polluted solution to Cd (II) by adsorption process using L-MWCNT can be considered as an effective technology.

Determination of Phosphorus Adsorption Using Various Forms of Isotherms in Soils of Adıyaman Çamgazi Plain

OpenAIRE

AĞCA, Necat

2014-01-01

Samples from 8 widespread soil series from Adıyaman Çamgazi Plain were equilibriated at a constant temperature with 16 different solutions containing 0 to 50 mg/ml phosphorus in batch-type experiments. The phosphorus concentrations of the equilibrium solutions and the amounts of phosphorus adsorbed by the soils at these concentrations were determined. These phosphorus-adsorption data were evaluated statistically for their suitability for adsorption isotherms in various concentration ranges.

Removal of Dye (Blue 56 From Aqueous Solution via Adsorption onto Pistachio Shell: kinetic and isotherm study of removal process

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A. Ravanpaykar

2012-03-01

Full Text Available In the present investigation, shells of pistachio are used as adsorbents and they have been successfully used for the removal of Blue 56, from water samples. The effect of various parameters such as: pH, amounts of adsorbents, size of adsorbent particles and contact time on removal processing were investigated. Inthisstudy Freundlichabsorptionisotherms and Langmuir were investigated. The experimental data were correlated reasonably well by the Freundlich adsorption isotherm and isotherm parameters were calculated. In order to investigate the efficiency of Blue 56 adsorption on the pistachio shell, pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion kinetic models were studied. Themodel that hadgoodcorrelationtoattractFreundlichwas chosenasthemodel. Its kineticsfollowsthepseudosecond order reaction.

Study on Shale Adsorption Equation Based on Monolayer Adsorption, Multilayer Adsorption, and Capillary Condensation

OpenAIRE

Chen, Qing; Tian, Yuanyuan; Li, Peng; Yan, Changhui; Pang, Yu; Zheng, Li; Deng, Hucheng; Zhou, Wen; Meng, Xianghao

2017-01-01

Shale gas is an effective gas resource all over the world. The evaluation of pore structure plays a critical role in exploring shale gas efficiently. Nitrogen adsorption experiment is one of the significant approaches to analyze pore size structure of shale. Shale is extremely heterogeneous due to component diversity and structure complexity. Therefore, adsorption isotherms for homogeneous adsorbents and empirical isotherms may not apply to shale. The shape of adsorption-desorption curve indi...

Synthesis of humidity sensitive zinc stannate nanomaterials and modelling of Freundlich adsorption isotherm model

Science.gov (United States)

Sharma, Alfa; Kumar, Yogendra; Shirage, Parasharam M.

2018-04-01

The chemi-resistive humidity sensing behaviour of as prepared and annealed ZnSnO3 nanoparticles synthesized using a wet chemical synthesis method was investigated. The effect of stirring temperature over the evolution of varied nanomorphology of zinc stannate is in accordance to Ostwald's ripening law. At room temperature, an excellent humidity sensitivity of ˜800% and response/recovery time of 70s./102s. is observed for ZnSnO3 sample within 08-97% relative humidity range. The experimental data observed over the entire range of RH values well fitted with the Freundlich adsorption isotherm model, and revealing two distinct water adsorption regimes. The excellent humidity sensitivity observed in the nanostructures is attributed to Grotthuss mechanism considering the availability and distribution of available adsorption sites. This present result proposes utilization of low cost synthesis technique of ZnSnO3 holds the promising capabilities as potential candidate for the fabrication of next generation humidity sensors.

Removal of 2,4-dichlorophenol using cyclodextrin-ionic liquid polymer as a macroporous material: Characterization, adsorption isotherm, kinetic study, thermodynamics

Energy Technology Data Exchange (ETDEWEB)

Raoov, Muggundha [University of Malaya Centre for Ionic Liquids, Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Advanced Medical and Dental Institute, University of Science Malaysia, No. 1–8 (Lot 8), Persiaran Seksyen 4/1, Bandar Putra Bertam, Kepala Batas, Pulau Pinang 13200 (Malaysia); Mohamad, Sharifah, E-mail: sharifahm@um.edu.my [University of Malaya Centre for Ionic Liquids, Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Abas, Mohd Radzi [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia)

2013-12-15

Highlights: • βCD-BIMOTs-TDI exhibits macropore size (77.66 nm) with 1.254 m{sup 2} g{sup −1} surface area. • Freundlich isotherm and pseudo-second order kinetics fit well the adsorption process. • Removal was optimum at pH 6 with 83% and reached equilibrium at 80 mg L{sup −1}. • Entropy (ΔS°) and heat of adsorption (ΔH°) estimated as −55.99 J/K mol and −18.10 J/mol. • Inclusion complex and π–π interaction were found to be dominant at pH 6. -- Abstract: Cyclodextrin-ionic liquid polymer (βCD-BIMOTs-TDI) was firstly synthesized using functionalized β-Cyclodextrin (CD) with 1-benzylimidazole (BIM) to form monofunctionalized CD (βCD-BIMOTs) and was further polymerized using toluene diisocyanate (TDI) linker to form insoluble βCD-BIMOTs-TDI. SEM characterization result shows that βCD-BIMOTs-TDI exhibits macropore size while the BET result shows low surface area (1.254 m{sup 2} g{sup −1}). The unique properties of the ILs allow us to produce materials with different morphologies. The adsorption isotherm and kinetics of 2,4-dichlorophenol (2,4-DCP) onto βCD-BIMOTs-TDI is studied. Freundlich isotherm and pseudo-second order kinetics are found to be the best to represent the data for 2,4-DCP adsorption on the βCD-BIMOTs-TDI. The presence of macropores decreases the mass transfer resistance and increases the adsorption process by reducing the diffusion distance. The change in entropy (ΔS°) and heat of adsorption (ΔH°) for 2,4-DCP on βCD-BIMOTs-TDI were estimated as −55.99 J/Kmol and −18.10 J/mol, respectively. The negative value of Gibbs free energy (ΔG°) indicates that the adsorption process is thermodynamically feasible, spontaneous and chemically controlled. Finally, the interactions between the cavity of βCD-BIMOTs and 2,4-DCP are investigated and the results shows that the inclusion of the complex formation and π–π interaction are the main processes involved in the adsorption process.

Isotherm and kinetic studies on adsorption of oil sands process-affected water organic compounds using granular activated carbon.

Science.gov (United States)

Islam, Md Shahinoor; McPhedran, Kerry N; Messele, Selamawit A; Liu, Yang; Gamal El-Din, Mohamed

2018-07-01

The production of oil from oil sands in northern Alberta has led to the generation of large volumes of oil sands process-affected water (OSPW) that was reported to be toxic to aquatic and other living organisms. The toxicity of OSPW has been attributed to the complex nature of OSPW matrix including the inorganic and organic compounds primarily naphthenic acids (NAs: C n H 2n+Z O x ). In the present study, granular activated carbon (GAC) adsorption was investigated for its potential use to treat raw and ozonated OSPW. The results indicated that NA species removal increased with carbon number (n) for a fixed Z number; however, the NA species removal decreased with Z number for a fixed carbon number. The maximum adsorption capacities obtained from Langmuir adsorption isotherm based on acid-extractable fraction (AEF) and NAs were 98.5 mg and 60.9 mg AEF/g GAC and 60 mg and 37 mg NA/g GAC for raw and ozonated OSPW, respectively. It was found that the Freundlich isotherm model best fits the AEF and NA equilibrium data (r 2  ≥ 0.88). The adsorption kinetics showed that the pseudo-second order and intraparticle diffusion models were both appropriate in modeling the adsorption kinetics of AEF and NAs to GAC (r 2  ≥ 0.97). Although pore diffusion was the rate limiting step, film diffusion was still significant for assessing the rate of diffusion of NAs. This study could be helpful to model, design and optimize the adsorption treatment technologies of OSPW and to assess the performance of other adsorbents. Copyright © 2018 Elsevier Ltd. All rights reserved.

Exploring the interaction of silver nanoparticles with pepsin and its adsorption isotherms and kinetics.

Science.gov (United States)

Li, Xiangrong; Wang, Kaiwei; Peng, Yanru

2018-04-25

The interaction of nanoparticles (NPs) with proteins is a topic of high relevance for the medical application of nanomaterials. In the study, a comprehensive investigation was performed for the binding properties of silver nanoparticles (AgNPs) to pepsin. The results indicate that the binding of AgNPs to pepsin may be a static quenching mechanism. Thermodynamic analysis reveals that AgNPs binds to pepsin is synergistically driven by enthalpy and entropy, and the major driving forces are hydrophobic and electrostatic interactions. Synchronous fluorescence spectroscopy shows that AgNPs may induce microenvironmental changes of pepsin. The hydrophobicity of Trp is increased while the hydrophility of Tyr is increased. The adsorption of pepsin on AgNPs was analyzed by Langmuir and Freundlich models, suggesting that the equilibrium adsorption data fit well with Freundlich model. The equilibrium adsorption data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations. The results indicate that pseudo-second-order kinetic equation better describes the adsorption kinetics. The study provides an accurate and full basic data for clarifying the binding mechanism, adsorption isotherms and kinetic behaviors of AgNPs with pepsin. These fundamental works will provide some new insights into the safe and effective application of AgNPs in biological and medical areas. Copyright © 2018 Elsevier B.V. All rights reserved.

Adsorption of nicotine from aqueous solution onto hydrophobic zeolite type USY

Science.gov (United States)

Lazarevic, Natasa; Adnadjevic, Borivoj; Jovanovic, Jelena

2011-07-01

The isothermal adsorption of nicotine from an aqueous solution onto zeolite type USY was investigated. The adsorption isotherms of nicotine onto the zeolite at different temperatures ranging from 298 to 322 K were determined. It was found that the adsorption isotherms can be described by the model of Freundlich adsorption isotherm. Based on the adsorption isotherms the changes of adsorption heat, free energy and entropy with adsorption degree were determined. The determined decrease of adsorption heat with adsorption degree can be explained by the presence of the adsorption centers of different energy and concentration on interface of zeolite-nicotine solution. It was found that the probability function of density distribution of the heat of adsorption (DDF) has exponential form. It was concluded that the possibility of fitting the adsorption isotherms of nicotine onto the zeolite by Freundlich adsorption isotherm was a direct consequence of that. The determined increase in entropy with the increase in adsorption degree can be explained with the change of phase state of adsorbed nicotine.

Interfacial adsorption of insulin - Conformational changes and reversibility of adsorption

NARCIS (Netherlands)

Mollmann, SH; Jorgensen, L; Bukrinsky, JT; Elofsson, U; Norde, W; Frokjaer, S

The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even

Adsorption Behaviour of La(III and Eu(III Ions from Aqueous Solutions by Hydroxyapatite: Kinetic, Isotherm, and Thermodynamic Studies

Directory of Open Access Journals (Sweden)

F. Granados-Correa

2013-01-01

Full Text Available The hydroxyapatite was successfully synthesized, characterized, and used as an alternative low-cost adsorbent material to study the adsorption behavior of La(III and Eu(III ions from nitrate aqueous solutions as a function of contact time, initial metal ion concentration, pH, and temperature by using a bath technique. The kinetic data correspond very well to the pseudo-second-order equation, and in both cases the uptake was affected by intraparticle diffusion. Isotherm adsorption data were well fitted by the Freundlich model equation with 1/n>1, indicating a multilayer and cooperative-type adsorption. Thermodynamic parameters for the adsorption systems were determinated at 293, 303, 313, and 323 K. These parameters show that adsorptions of La(III and Eu(III ions on hydroxyapatite are endothermic and spontaneous processes. The adsorption was found to follow the order Eu(III > La(III and is dependent on ion concentration, pH, and temperature.

Post synthetic modification of MIL-101(Cr) for S-shaped isotherms and fast kinetics with water adsorption

International Nuclear Information System (INIS)

Teo, How Wei Benjamin; Chakraborty, Anutosh; Kayal, Sibnath

2017-01-01

Highlights: • Modification of parent MIL-101(Cr) metal organic framework (MOF) employing alkali metal ions (Li + , Na + , K + ). • Surface characteristics of the parent and alkali doped MIL-101(Cr) adsorbents. • Water uptakes are measured for the temperatures ranging from 25 °C to 60 °C under static and dynamic conditions. • Isotherms and kinetics data are fitted with Langmuir analogy models. • The 5% Li-doped MIL-101(Cr) is suitable for adsorption cooling. - Abstract: This article presents the surface characteristics of alkali (Li + , Na + , K + ) doped MIL-101(Cr) metal organic frameworks (MOFs), and the structural properties are evaluated by scanning electron micrography (SEM), X-ray diffraction (XRD), thermo-gravimetric analyser (TGA) and N 2 adsorption analysis. The amount of water uptakes are measured by a gravimetric analyser for the temperatures ranging from 298 K to 333 K and pressures up to the saturated conditions. The experimentally measured isotherms and kinetics data are fitted with the equations developed from the concept of Langmuir analogy. The isosteric heat of adsorption is calculated employing Van’t Hoff equation in the pressure-temperature-uptake co-ordinate systems. The hydrophobic length at low pressure regions is shortened by the addition of alkali dopants. It is observed that the alkali (Na, K and Li) ions on MIL-101(Cr) MOF increase the water uptakes at lower relative pressure region with fast kinetics. We have shown here that the alkali doped MIL-101(Cr) MOFs can be used as potential adsorbents for various low temperature heat transmission applications such as adsorption assisted heat pump, cooling and desalination.

Adsorption of Cd (II) on Modified Granular Activated Carbons: Isotherm and Column Study.

Science.gov (United States)

Rodríguez-Estupiñán, Paola; Erto, Alessandro; Giraldo, Liliana; Moreno-Piraján, Juan Carlos

2017-12-20

In this work, equilibrium and dynamic adsorption tests of cadmium Cd (II) on activated carbons derived from different oxidation treatments (with either HNO₃, H₂O₂, or NaOCl, corresponding to GACoxN, GACoxP, and GACoxCl samples) are presented. The oxidation treatments determined an increase in the surface functional groups (mainly the acidic ones) and a decrease in the pH PZC (except for the GACoxCl sample). A slight alteration of the textural parameters was also observed, which was more significant for the GACoxCl sample, in terms of a decrease of both Brunauer-Emmett-Teller ( BET ) surface area and micropore volume. Adsorption isotherms were determined for all the adsorbents and a significant increase in the adsorption performances of the oxidized samples with respect to the parent material was observed. The performances ranking was GACoxCl > GACoxP > GACoxN > GAC, likely due to the chemical surface properties of the adsorbents. Dynamic tests in a fixed bed column were carried out in terms of breakthrough curves at constant Cd inlet concentration and flow rate. GACoxCl and GACoxN showed a significantly higher value of the breakpoint time, likely due to the higher adsorption capacity. Finally, the dynamic tests were analyzed in light of a kinetic model. In the adopted experimental conditions, the results showed that mass transfer is controlled by internal pore diffusion, in which surface diffusion plays a major role.

Adsorption of Cd (II on Modified Granular Activated Carbons: Isotherm and Column Study

Directory of Open Access Journals (Sweden)

Paola Rodríguez-Estupiñán

2017-12-01

Full Text Available In this work, equilibrium and dynamic adsorption tests of cadmium Cd (II on activated carbons derived from different oxidation treatments (with either HNO3, H2O2, or NaOCl, corresponding to GACoxN, GACoxP, and GACoxCl samples are presented. The oxidation treatments determined an increase in the surface functional groups (mainly the acidic ones and a decrease in the pHPZC (except for the GACoxCl sample. A slight alteration of the textural parameters was also observed, which was more significant for the GACoxCl sample, in terms of a decrease of both Brunauer-Emmett-Teller (BET surface area and micropore volume. Adsorption isotherms were determined for all the adsorbents and a significant increase in the adsorption performances of the oxidized samples with respect to the parent material was observed. The performances ranking was GACoxCl > GACoxP > GACoxN > GAC, likely due to the chemical surface properties of the adsorbents. Dynamic tests in a fixed bed column were carried out in terms of breakthrough curves at constant Cd inlet concentration and flow rate. GACoxCl and GACoxN showed a significantly higher value of the breakpoint time, likely due to the higher adsorption capacity. Finally, the dynamic tests were analyzed in light of a kinetic model. In the adopted experimental conditions, the results showed that mass transfer is controlled by internal pore diffusion, in which surface diffusion plays a major role.

Non-linear frequency response of non-isothermal adsorption controlled by micropore diffusion with variable diffusivity

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MENKA PETKOVSKA

2000-12-01

Full Text Available The concept of higher order frequency response functions (FRFs is used for the analysis of non-linear adsorption kinetics on a particle scale, for the case of non-isothermal micropore diffusion with variable diffusivity. Six series of FRFs are defined for the general non-isothermal case. A non-linerar mathematical model is postulated and the first and second order FRFs derived and simulated. A variable diffusivity influences the shapes of the second order FRFs relating the sorbate concentration in the solid phase and t he gas pressure significantly, but they still keep their characteristics which can be used for discrimination of this from other kinetic mechanisms. It is also shown that first and second order particle FRFs offter sufficient information for an easy and fast estimation of all model parameters, including those defining the system non-linearity.

Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models.

Science.gov (United States)

Rahman, Md Sayedur; Sathasivam, Kathiresan V

2015-01-01

Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb(2+), Cu(2+), Fe(2+), and Zn(2+) onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment.

Adsorption isotherms, kinetics, thermodynamics and desorption studies of 2,4,6-trichlorophenol on oil palm empty fruit bunch-based activated carbon

International Nuclear Information System (INIS)

Tan, I.A.W.; Ahmad, A.L.; Hameed, B.H.

2009-01-01

The adsorption characteristics of 2,4,6-trichlorophenol (TCP) on activated carbon prepared from oil palm empty fruit bunch (EFB) were evaluated. The effects of TCP initial concentration, agitation time, solution pH and temperature on TCP adsorption were investigated. TCP adsorption uptake was found to increase with increase in initial concentration, agitation time and solution temperature whereas adsorption of TCP was more favourable at acidic pH. The adsorption equilibrium data were best represented by the Freundlich and Redlich-Peterson isotherms. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The mechanism of the adsorption process was determined from the intraparticle diffusion model. Boyd plot revealed that the adsorption of TCP on the activated carbon was mainly governed by particle diffusion. Thermodynamic parameters such as standard enthalpy (ΔH o ), standard entropy (ΔS o ), standard free energy (ΔG o ) and activation energy were determined. The regeneration efficiency of the spent activated carbon was high, with TCP desorption of 99.6%.

Using Adsorption Isotherm Studies to Determine Crosslinked Polymeric Adsorbent Performance in Heavy Metals Removal from Water

Directory of Open Access Journals (Sweden)

Nasrin Sheikh

2015-01-01

Full Text Available Polymeric adsorbents are useful tools for removing heavy metals from aqueous solutions. Adsorption models are efficient tools for accurate prediction and evaluation of the practical adsorption process in real situation. In this study, the two isotherms of Langmuir and Dubinin-Radushkevich models were employed to investigate the absorption performance of chitosan, PVA, and chitosan/PVA blend (with a weight ratio of 1:1 in the removal of Mn (II and Ni (II from aqueous solutions. The PVA adsorbent was crosslinked by both chemical and radiation methods while the others were crosslinked only chemically due to Chitosan’s lack of resistance to radiation. The results showed that the Langmuir model fitted the experimental data better than the Dubinin-Radushkevich one for both metals. The maximum adsorption capacity (qmax of the Langmuir model showed that the PVA/Chitosan adsorbent had the best adsorption compared to other adsorbents, with 52.63 mg/g for Ni and 30.30 mg/g for Mn (evidently more Ni was absorbed than Mn. Also, maximum adsorption by the chemically crosslinked PVA was 38.46 mg/g for Ni and 19.23 mg/g for Mn, which exhibits a higher level than adsorption by the radiation crosslinked PVA The results indicate that absorption capacity depends on the type of adsorbed metal, absorbent structure, and the crosslinking method employed.

An Adsorption Equilibria Model for Steady State Analysis

KAUST Repository

Ismail, Azhar Bin

2016-02-29

The investigation of adsorption isotherms is a prime factor in the ongoing development of adsorption cycles for a spectrum of advanced, thermally-driven engineering applications, including refrigeration, natural gas storage, and desalination processes. In this work, a novel semi-empirical mathematical model has been derived that significantly enhances the prediction of the steady state uptake in adsorbent surfaces. This model, a combination of classical Langmuir and a novel modern adsorption isotherm equation, allows for a higher degree of regression of both energetically homogenous and heterogeneous adsorbent surfaces compared to several isolated classical and modern isotherm models, and has the ability to regress isotherms for all six types under the IUPAC classification. Using a unified thermodynamic framework, a single asymmetrical energy distribution function (EDF) has also been proposed that directly relates the mathematical model to the adsorption isotherm types. This fits well with the statistical rate theory approach and offers mechanistic insights into adsorption isotherms.

Competitive Adsorption of a Two-Component Gas on a Deformable Adsorbent

OpenAIRE

Usenko, A. S.

2013-01-01

We investigate the competitive adsorption of a two-component gas on the surface of an adsorbent whose adsorption properties vary in adsorption due to the adsorbent deformation. The essential difference of adsorption isotherms for a deformable adsorbent both from the classical Langmuir adsorption isotherms of a two-component gas and from the adsorption isotherms of a one-component gas taking into account variations in adsorption properties of the adsorbent in adsorption is obtained. We establi...

Relationship between carbon microstructure, adsorption energy and hydrogen adsorption capacity at different temperatures

International Nuclear Information System (INIS)

Jacek Jagiello; Matthias Thommes

2005-01-01

Various microporous materials such as activated carbons, nano-tubes, synthetic microporous carbons as well as metal organic framework materials are being considered for hydrogen storage applications by means of physical adsorption. To develop materials of practical significance for hydrogen storage it is important to understand the relationships between pore sizes, adsorption energies and adsorption capacities. The pore size distribution (PSD) characterization is traditionally obtained from the analysis of nitrogen adsorption isotherms measured at 77 K. However, a portion of the pores accessible to H 2 may not be accessible to N 2 at this temperature. Therefore, it was recently proposed to use the DFT analysis of H 2 adsorption isotherms to characterize pore structure of materials considered for hydrogen storage applications. In present work, adsorption isotherms of H 2 and N 2 at cryogenic temperatures are used for the characterization of carbon materials. Adsorption measurements were performed with Autosorb 1 MP (Quantachrome Instruments, Boynton Beach, Florida, USA). As an example, Fig 1 compares PSDs calculated for the activated carbon sample (F400, Calgon Carbon) using combined H 2 and N 2 data, and using N 2 isotherm only. The nitrogen derived PSD does not include certain amount of micropores which are accessible to H 2 but not to N 2 molecules. Obviously, the difference in the calculated PSDs by the two methods will depend on the actual content of small micropores in a given sample. Carbon adsorption properties can also be characterized by the isosteric heat of adsorption, Qst, related to the adsorption energy and dependent on the carbon pore/surface structure. Fig 2 shows Qst data calculated using the Clausius-Clapeyron equation from H 2 isotherms measured at 77 K and 87 K for the carbon molecular sieve CMS 5A (Takeda), oxidized single wall nano-tubes (SWNT), and graphitized carbon black (Supelco). The Qst values decrease with increasing pore sizes. The

Adsorption isotherms of some alkyl aromatic hydrocarbons and surface energies on partially dealuminated Y faujasite zeolite by inverse gas chromatography.

Science.gov (United States)

Kondor, Anett; Dallos, András

2014-10-03

Adsorption isotherm data of some alkyl aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) measured in the temperature range of 423-523K on a partially dealuminated faujasite type DAY F20 zeolite by inverse gas chromatography are presented in this work. The temperature dependent form of Tóth's equation has been fitted to the multiple temperature adsorption isotherms of benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene with standard deviations of 4.6, 5.0, 5.9, 4.3, 5.1 and 6.3mmolkg(-1) and coefficients of determinations (r(2)) of 0.977, 0.971, 0.974, 0.975, 0.991 and 0.991, respectively. The gas-solid equilibria and modeling were interpreted on the basis of the interfacial properties of the zeolite, by dispersive, specific and total surface energy heterogeneity profiles and distributions of the adsorbent measured by surface energy analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

Investigation of the effects of high-energy proton-beam irradiation on metal-oxide surfaces by using methane adsorption isotherms

International Nuclear Information System (INIS)

Kim, Euikwoun; Lee, Junggil; Kim, Jaeyong; Kim, Kyeryung

2012-01-01

The creation of possible local defects on metal-oxide surfaces due to irradiation with a high-energy proton beam was investigated by using a series of gas adsorption isotherms for methane (CH 4 ) on a MgO powder surface. After a MgO powder surface having only a (100) surface had been irradiated with a 35-MeV proton beam, the second atomic layer of methane had completely disappeared while two distinct atomic layers were found in a layer-by-layer fashion on the surfaces of unirradiated samples. This subtle modification of the surface is evidenced by a change of the contrasts in the morphologies measured a using a transmission electron microscopy. Combined results obtained from an electron microscopy and methane adsorption isotherms strongly suggest that the high-energy proton-beam irradiation induced a local surface modification by imparting kinetic energy to the sample. The calculation of the 2-dimensional compressibility values, which are responsible for the formation of the atomic layers, confirmed the surface modification after irradiating surface-clean MgO powders with a proton beam.

TWO-PARAMETER ISOTHERMS OF METHYL ORANGE SORPTION BY PINECONE DERIVED ACTIVATED CARBON

Directory of Open Access Journals (Sweden)

M. R. Samarghandi ، M. Hadi ، S. Moayedi ، F. Barjasteh Askari

2009-10-01

Full Text Available The adsorption of a mono azo dye methyl-orange (MeO onto granular pinecone derived activated carbon (GPAC, from aqueous solutions, was studied in a batch system. Seven two-parameter isotherm models Langmuir, Freundlich, Dubinin-Radushkevic, Temkin, Halsey, Jovanovic and Hurkins-Jura were used to fit the experimental data. The results revealed that the adsorption isotherm models fitted the data in the order of Jovanovic (X2=1.374 > Langmuir > Dubinin-Radushkevic > Temkin > Freundlich > Halsey > Hurkins-Jura isotherms. Adsorption isotherms modeling showed that the interaction of dye with activated carbon surface is localized monolayer adsorption. A comparison of kinetic models was evaluated for the pseudo-second order, Elovich and Lagergren kinetic models. Lagergren first order model was found to agree well with the experimental data (X2=9.231. In order to determine the best-fit isotherm and kinetic models, two error analysis methods of Residual Mean Square Error and Chi-square statistic (X2 were used to evaluate the data.

Differences in the adsorption behaviour of poly(ethylene oxide) copolymers onto model polystyrene nanoparticles assessed by isothermal titration microcalorimetry correspond to the biological differences.

Science.gov (United States)

Stolnik, S; Heald, C R; Garnett, M G; Illum, L; Davis, S S

2005-01-01

The adsorption behaviour of a tetrafunctional copolymer of poly (ethylene oxide)-poly (propylene oxide) ethylene diamine (commercially available as Poloxamine 908) and a diblock copolymer of poly (lactic acid)-poly (ethylene oxide) (PLA/PEG 2:5) onto a model colloidal drug carrier (156 nm sized polystyrene latex) is described. The adsorption isotherm, hydrodynamic thickness of the adsorbed layers and enthalpy of the adsorption were assessed. The close similarity in the conformation of the poly (ethylene oxide) (PEO) chains (molecular weight 5,000 Da) in the adsorbed layers of these two copolymers was demonstrated by combining the adsorption data with the adsorbed layer thickness data. In contrast, the results from isothermal titration microcalorimetry indicated a distinct difference in the interaction of the copolymers with the polystyrene colloid surface. Poloxamine 908 adsorption to polystyrene nanoparticles is dominated by an endothermic heat effect, whereas, PLA/PEG 2:5 adsorption is entirely an exothermic process. This difference in adsorption behaviour could provide an explanation for differences in the biodistribution of Poloxamine 908 and PLA/PEG 2:5 coated polystyrene nanoparticles observed in previous studies. A comparison with the interaction enthalpy for several other PEO-containing copolymers onto the same polystyrene colloid was made. The results demonstrate the importance of the nature of the anchoring moiety on the interaction of the adsorbing copolymer with the colloid surface. An endothermic contribution is found when an adsorbing molecule contains a poly (propylene oxide) (PPO) moiety (e.g. Poloxamine 908), whilst the adsorption is exothermic (i.e. enthalpy driven) for PEO copolymers with polylactide (PLA/PEG 2:5) or alkyl moieties.

How soil organic matter composition controls hexachlorobenzene-soil-interactions: adsorption isotherms and quantum chemical modeling.

Science.gov (United States)

Ahmed, Ashour A; Kühn, Oliver; Aziz, Saadullah G; Hilal, Rifaat H; Leinweber, Peter

2014-04-01

Hazardous persistent organic pollutants (POPs) interact in soil with the soil organic matter (SOM) but this interaction is insufficiently understood at the molecular level. We investigated the adsorption of hexachlorobenzene (HCB) on soil samples with systematically modified SOM. These samples included the original soil, the soil modified by adding a hot water extract (HWE) fraction (soil+3 HWE and soil+6 HWE), and the pyrolyzed soil. The SOM contents increased in the order pyrolyzed soilsoilsoil+3 HWEsoil+6 HWE. For the latter three samples this order was also valid for the HCB adsorption. The pyrolyzed soil adsorbed more HCB than the other samples at low initial concentrations, but at higher concentrations the HCB adsorption became weaker than in the samples with HWE addition. This adsorption combined with the differences in the chemical composition between the soil samples suggested that alkylated aromatic, phenol, and lignin monomer compounds contributed most to the HCB adsorption. To obtain a molecular level understanding, a test set has been developed on the basis of elemental analysis which comprises 32 representative soil constituents. The calculated binding energy for HCB with each representative system shows that HCB binds to SOM stronger than to soil minerals. For SOM, HCB binds to alkylated aromatic, phenols, lignin monomers, and hydrophobic aliphatic compounds stronger than to polar aliphatic compounds confirming the above adsorption isotherms. Moreover, quantitative structure-activity relationship (QSAR) of the binding energy with independent physical properties of the test set systems for the first time indicated that the polarizability, the partial charge on the carbon atoms, and the molar volume are the most important properties controlling HCB-SOM interactions. Copyright © 2013 Elsevier B.V. All rights reserved.

Removal of Pyrethrin from Aqueous Effluents by Adsorptive Micellar Flocculation

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Pardon K. Kuipa

2015-01-01

Full Text Available The equilibrium adsorption of pyrethrin onto aggregates formed by the flocculation of micelles of the surfactant sodium dodecyl sulphate (SDS with aluminium sulphate is reported. The experimental results were analysed using different adsorption isotherms (Langmuir, Freundlich, Redlich-Peterson, Sips, Radke-Prausnitz, Temkin, linear equilibrium, and the Dubin-Radushkevich isotherms. The Freundlich and linear equilibrium isotherms best describe the adsorption of pyrethrin onto SDS micellar flocs, with the Freundlich adsorption constant, KF, and the mass distribution coefficient, KD, of 64.266 ((mg/g(L/mg1/n and 119.65 L/g, respectively. Applicability of the Freundlich adsorption model suggests that heterogeneous surface adsorption affects the adsorption. The mean free energy value estimated using the Dubinin-Radushkevich isotherm was 0.136 kJ/mol indicating that physisorption may be predominant in the adsorption process.

Competitive adsorption of a two-component gas on a deformable adsorbent

International Nuclear Information System (INIS)

Usenko, A S

2014-01-01

We investigate the competitive adsorption of a two-component gas on the surface of an adsorbent whose adsorption properties vary due to the adsorbent deformation. The essential difference of adsorption isotherms for a deformable adsorbent both from the classical Langmuir adsorption isotherms of a two-component gas and from the adsorption isotherms of a one-component gas is obtained, taking into account variations in the adsorption properties of the adsorbent in adsorption. We establish bistability and tristability of the system caused by variations in adsorption properties of the adsorbent in competitive adsorption of gas particles on it. We derive conditions under which adsorption isotherms of a binary gas mixture have two stable asymptotes. It is shown that the specific features of the behavior of the system under study can be described in terms of a potential of the known explicit form. (paper)

(Amino acid + silica) adsorption thermodynamics: Effects of temperature

International Nuclear Information System (INIS)

Sebben, Damien; Pendleton, Phillip

2015-01-01

Highlights: • High resolution, low concentration Gly, Lys and Glu solution adsorption isotherms. • All isotherms fitted with Langmuir–Freundlich isotherm model. • Gly, Lys and Glu show exothermic adsorption processes. • Isosteric heat analyses reveal changes in interaction strength with surface coverage. - Abstract: A thorough understanding of amino acid adsorption by mineral and oxide surfaces has a major impact on a variety of industrial and biomedical applications. Little information currently exists regarding temperature effects on most of these adsorption processes. Deeper thermodynamic analyses of their multiple temperature adsorption isotherms would aid the interpretation of the interfacial interactions. Low solution concentration adsorption isotherms for glycine, lysine and glutamic acid on a silica adsorbent were generated for T = (291, 298 and 310) K. Data analysis via the Clausius–Clapeyron method yielded the isosteric heat of adsorption as a function of fractional monolayer coverage for each adsorptive. Each amino acid showed an exothermic adsorption response. Glycine and lysine experienced a greater negative effect of increased temperature compared with glutamic acid, indicating a greater number of adsorbed molecules than glutamic acid, with the former undergoing intermolecular clustering within the adsorbed phase. Isosteric heat analyses suggest ionic interactions for lysine and hydrogen bonding for glutamic acid, both weakening with increased coverage. In contrast, initial hydrogen bonding led to ionic bonding for glycine with increasing coverage

Sorption of Pb2+ from Aqueous Solution unto Modified Rice Husk: Isotherms Studies

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A. O. Dada

2013-01-01

Full Text Available Investigation of the sorption potential of rice husk, an agricultural waste, as an adsorbent was carried out. The rice husk was modified with orthophosphoric acid and was used for adsorption of lead (II ions (Pb2+ from aqueous solution. Physicochemical properties of the modified rice husk were determined. Equilibrium sorption data were confirmed with Langmuir, Freundlich and Temkin adsorption isotherms. On the basis of adsorption isotherm graphs, R2 values were determined to be 0.995, 0.916, and 0.797 for Langmuir, Temkin, and Freundlich isotherms, respectively, indicating that the data fitted well into the adsorption isotherms, but Langmuir isotherm is a better model. The maximum monolayer coverage from Langmuir studies, Qmax=138.89 mg/g, Langmuir isotherm constant, KL=0.699 L/mg, and the separation factor, RL=1.41×10−2 at 100 mg/L of lead(II ions indicating that the sorption process, was favourable. The suitability of modified rice husk as an adsorbent for the removal of lead ions from aqueous solution and its potential for pollution control is established.

Adsorption of Cd(II) by Mg–Al–CO{sub 3}- and magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}-layered double hydroxides: Kinetic, isothermal, thermodynamic and mechanistic studies

Energy Technology Data Exchange (ETDEWEB)

Shan, Ran-ran; Yan, Liang-guo, E-mail: yanyu-33@163.com; Yang, Kun; Hao, Yuan-feng; Du, Bin

2015-12-15

Highlights: • The Mg–Al–CO{sub 3}- and magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}–LDH can efficiently remove Cd(II) from aqueous solutions. • The adsorption mechanisms of Cd(II) were discussed in detail. • The adsorption kinetic, isothermal and thermodynamic properties of Cd(II) were studied. • Magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}–LDH can be quickly and easily separated using a magnet. - Abstract: Understanding the adsorption mechanisms of metal cations on the surfaces of solids is important for determining the fate of these metals in water and wastewater treatment. The adsorption kinetic, isothermal, thermodynamic and mechanistic properties of cadmium (Cd(II)) in an aqueous solution containing Mg–Al–CO{sub 3}- and magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}-layered double hydroxide (LDH) were studied. The results demonstrated that the adsorption kinetic and isotherm data followed the pseudo-second-order model and the Langmuir equation, respectively. The adsorption process of Cd(II) was feasible, spontaneous and endothermic in nature. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to explain the adsorption mechanisms. The characteristic XRD peaks and FTIR bands of CdCO{sub 3} emerged in the LDH spectra after Cd(II) adsorption, which indicated that the adsorption of Cd(II) by LDHs occurred mainly via CdCO{sub 3} precipitation, surface adsorption and surface complexation. Furthermore, the magnetic Fe{sub 3}O{sub 4}/Mg–Al–CO{sub 3}-LDH can be quickly and easily separated using a magnet before and after the adsorption process.

Relationship between carbon microstructure, adsorption energy and hydrogen adsorption capacity at different temperatures

International Nuclear Information System (INIS)

Jagiello, J.; Thommes, M.

2005-01-01

Various microporous materials such as activated carbons, nano-tubes, synthetic micro-porous carbons as well as metal organic framework materials are being considered for hydrogen storage applications by means of physical adsorption. To develop materials of practical significance for hydrogen storage it is important to understand the relationships between pore sizes, adsorption energies and adsorption capacities. The pore size distribution (PSD) characterization is traditionally obtained from the analysis of nitrogen adsorption isotherms measured at 77 K. However, a portion of the pores accessible to H 2 may not be accessible to N 2 at this temperature. Therefore, it was recently proposed to use the DFT analysis of H 2 adsorption isotherms to characterize pore structure of materials considered for hydrogen storage applications [1]. In present work, adsorption isotherms of H 2 and N 2 at cryogenic temperatures are used for the characterization of carbon materials. Adsorption measurements were performed with Autosorb 1 MP [Quantachrome Instruments, Boynton Beach, Florida, USA]. As an example, Fig 1 compares PSDs calculated for the activated carbon sample (F400, Calgon Carbon) using combined H 2 and N 2 data, and using N 2 isotherm only. The nitrogen derived PSD does not include certain amount of micro-pores which are accessible to H 2 but not to N 2 molecules. Obviously, the difference in the calculated PSDs by the two methods will depend on the actual content of small micro-pores in a given sample. Carbon adsorption properties can also be characterized by the isosteric heat of adsorption, Qst, related to the adsorption energy and dependent on the carbon pore/surface structure. Fig 2 shows Qst data calculated using the Clausius-Clapeyron equation from H 2 isotherms measured at 77 K and 87 K for the carbon molecular sieve CMS 5A (Takeda), oxidized single wall nano-tubes (SWNT) [2], and graphitized carbon black (Supelco). The Qst values decrease with increasing pore

Adsorption Isotherms of Cs+, Co2+, Zn2+ and Eu3+ on Zirconium Vanadate Ion-Exchanger

International Nuclear Information System (INIS)

Shady, S.A.; El-Ashery, S.M.; El-Naggar, I.M.

2009-01-01

Zirconium vanadate had been prepared by the dropwise addition of 0.1 M sodium vanadate and 0.1 M zirconyl chloride by molar ratio of zirconium/vanadium 2. Exchange isotherms for Cs + /H + , Co 2+ /H + ,Zn 2+ /H + and Eu 3+ /H + have been determined at 25, 40 and 60 degree C. Besides, it was proved that cesium, cobalt, zinc and europium are chemically adsorbed. Moreover, the heat of adsorption of these ions on zirconium vanadate had been calculated and indicated that zirconium vanadate is of endothermic behavior towards these ions

Adsorption of uranium on halloysite

International Nuclear Information System (INIS)

Kilislioglu, A.; Bilgin, B.

2002-01-01

Adsorption of uranium (U(VI)) from aqueous solutions on halloysite type clay was studied as a function of amount of adsorbent, initial concentration and pH. The values of adsorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption was calculated as 5.91 kJ/mol from D-R adsorption isotherm. Lagergren and Bangham equation has been used for dynamic modelling of process and the rate constants of adsorption of uranium on halloysite type clay were calculated at 293, 313 and 333 K. In order to explain the mechanism of adsorption reaction, the rate constants were calculated at high and low uranium concentrations. Adsorption reaction was studied at 293, 303, 313, 323 and 333 K for halloysite type clay and also thermodynamic constants have been calculated. The results show that the adsorption reaction was endothermic and more spontaneous at high temperature. (orig.)

Adsorption of uranium on halloysite

Energy Technology Data Exchange (ETDEWEB)

Kilislioglu, A.; Bilgin, B. [Istanbul Univ. (Turkey). Faculty of Engineering

2002-07-01

Adsorption of uranium (U(VI)) from aqueous solutions on halloysite type clay was studied as a function of amount of adsorbent, initial concentration and pH. The values of adsorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption was calculated as 5.91 kJ/mol from D-R adsorption isotherm. Lagergren and Bangham equation has been used for dynamic modelling of process and the rate constants of adsorption of uranium on halloysite type clay were calculated at 293, 313 and 333 K. In order to explain the mechanism of adsorption reaction, the rate constants were calculated at high and low uranium concentrations. Adsorption reaction was studied at 293, 303, 313, 323 and 333 K for halloysite type clay and also thermodynamic constants have been calculated. The results show that the adsorption reaction was endothermic and more spontaneous at high temperature. (orig.)

Adsorption of phosphate from municipal effluents using cryptocrystalline magnesite: complementing laboratory results with geochemical modelling

CSIR Research Space (South Africa)

Masindi, Vhahangwele

2015-11-01

Full Text Available chemisorption. Adsorption isotherms fitted well to Langmuir adsorption isotherm than Freundlich adsorption isotherms, demonstrating monolayer adsorption. PHREEQC geochemical model showed Mg(sub3)(PO(sub4))(sub2) and MgHPO(sub4):3H(sub2)O as the phosphatebearing...

Water adsorption on goethite: Application of multilayer adsorption models

Science.gov (United States)

Hatch, C. D.; Tumminello, R.; Meredith, R.

2016-12-01

Adsorbed water on the surface of atmospheric mineral dust has recently been shown to significantly affect the ability of mineral dust aerosol to act as cloud condensation nuclei. We have studied water adsorption as a function of relative humidity (RH) on goethite (α-FeO(OH)), a common component of atmospheric mineral dust. The goethite surface area and particle size was determined using BET analysis and with N2 as an adsorbate and scanning electron microscopy, respectively. Water adsorption on the sample was monitored using horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy equipped with a flow cell. Water content was determined using Beer's law and the optical constants for bulk water. The results were analyzed using Type II adsorption isotherms to model multilayer adsorption, including BET (Brunauer, Emmet and Teller), FHH (Frenkel, Halsey and Hill) and Freundlich. BET fits to experimental data provide parameters of monolayer coverage, while the FHH and Freundlich isotherms provide insights into multilayer adsorption mechanisms. Results indicate that goethite contains 5% H2O by mass at 50% RH, which increases to 12% by mass at 90% RH. Adsorption parameters and experimental results will be presented.

Adsorption isotherms and kinetics of activated carbons produced from coals of different ranks.

Science.gov (United States)

Purevsuren, B; Lin, Chin-Jung; Davaajav, Y; Ariunaa, A; Batbileg, S; Avid, B; Jargalmaa, S; Huang, Yu; Liou, Sofia Ya-Hsuan

2015-01-01

Activated carbons (ACs) from six coals, ranging from low-rank lignite brown coal to high-rank stone coal, were utilized as adsorbents to remove basic methylene blue (MB) from an aqueous solution. The surface properties of the obtained ACs were characterized via thermal analysis, N2 isothermal sorption, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Boehm titration. As coal rank decreased, an increase in the heterogeneity of the pore structures and abundance of oxygen-containing functional groups increased MB coverage on its surface. The equilibrium data fitted well with the Langmuir model, and adsorption capacity of MB ranged from 51.8 to 344.8 mg g⁻¹. Good correlation coefficients were obtained using the intra-particle diffusion model, indicating that the adsorption of MB onto ACs is diffusion controlled. The values of the effective diffusion coefficient ranged from 0.61 × 10⁻¹⁰ to 7.1 × 10⁻¹⁰ m² s⁻¹, indicating that ACs from lower-rank coals have higher effective diffusivities. Among all the ACs obtained from selected coals, the AC from low-rank lignite brown coal was the most effective in removing MB from an aqueous solution.

CHROMIUM (III ADSORPTION FROM AQUEOUS SOLUTION BY Rhizophora apiculata TANNINS

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C. W. Oo

2010-06-01

Full Text Available Adsorption of Cr3+ from aqueous solution by Rhizophora apiculata tannins was investigated in batch shaking experiments. Tannins extracted from R. apiculata mangrove barks was chemically modified with formaldehyde in the basic solution of sodium hydroxide. The performance of the produced adsorbent on the adsorption of Cr3+ was evaluated based on the effect of several parameters like initial pH, adsorbent dosage, initial Cr3+ concentration and contact time. Equilibrium adsorption data was analyzed by Langmuir, Freundlich, Sips and Dubinin-Raduskhevich (D-R isotherms. The fitness of the isotherms to the experimental data was determined by non-linear regression analysis. Adsorption capacity calculated from Langmuir isotherm was found to be 10.14 mg Cr3+/g of adsorbent at optimum adsorption pH of 4.5. Mean energy of adsorption with the value of 10.35 kJ/mol indicated that adsorption Cr3+ on Rhizophora apiculata tannins followed ion-exchange reaction. Kinetic study showed that the adsorption process followed the pseudo second-order kinetic model.   Keywords:  Rhizophora apiculata, tannins, isotherms, kinetic, chromium.

Thermodynamic features of dioxins’ adsorption

Energy Technology Data Exchange (ETDEWEB)

Prisciandaro, Marina [Department of Industrial and Information Engineering and of Economics, University of L’Aquila, Viale Giovanni Gronchi 18, L’Aquila 67100 (Italy); Piemonte, Vincenzo, E-mail: v.piemonte@unicampus.it [Faculty of Engineering, University Campus Biomedico of Rome, Via Alvaro del Portillo 21, Rome 00128 (Italy); Mazziotti di Celso, Giuseppe [Faculty of Bioscience, University of Teramo, Via R. Balzarini, 1, 64100 Teramo (Italy); Ronconi, Silvia [Arta Abruzzo, Department of L’Aquila, Bazzano (AQ), 67100 L’Aquila (Italy); Capocelli, Mauro [Faculty of Engineering, University Campus Biomedico of Rome, Via Alvaro del Portillo 21, Rome 00128 (Italy)

2017-02-15

Highlights: • We develop the P-T diagram for six PCDD. • We derive theoretical adsorption isotherms according to the Langmuir’s model. • We calculate K and w{sub max} values for several temperatures. • We estimate the adsorption heat with a good agreement with literature data. - Abstract: In this paper, the six more poisonous species among all congeners of dioxin group are taken into account, and the P-T diagram for each of them is developed. Starting from the knowledge of vapour tensions and thermodynamic parameters, the theoretical adsorption isotherms are calculated according to the Langmuir’s model. In particular, the Langmuir isotherm parameters (K and w{sub max}) have been validated through the estimation of the adsorption heat (ΔH{sub ads}), which varies in the range 20–24 kJ/mol, in agreement with literature values. This result will allow to put the thermodynamical basis for a rational design of different process units devoted to dioxins removal.

Adsorption Characteristics of Norfloxacin by Biochar Prepared by Cassava Dreg: Kinetics, Isotherms, and Thermodynamic Analysis

Directory of Open Access Journals (Sweden)

Dan Feng

2015-08-01

Full Text Available Biochars (BC generated from biomass residues have been recognized as effective sorbents for organic compounds. In this study, biochars as adsorbents for the removal of norfloxacin (NOR from aqueous solutions were evaluated. Biochars were prepared from cassava dregs at 350 °C, 450 °C, 550 °C, 650 °C, and 750 °C, respectively (labeled as BC350, BC450, BC550, BC650, and BC750. The results showed that the kinetic data were best fitted to the pseudo second-order model, indicating that the sorption was governed by the availability of sorption sites on the biochar surfaces rather than the NOR concentration in the solution. Sorption isotherms of NOR were well described by the Freundlich model, and the Freundlich coefficients (lgkF increased with the pyrolysis temperature of biochars. Thermodynamic analysis indicated the feasibility and spontaneity of the NOR adsorption process. The NOR adsorption on BC450, BC550, BC650, and BC750 was an endothermic process, while an exothermic process occurred for BC350. FTIR studies further suggested that the adsorption mechanism was possibly attributable to H-bond and π-π interactions between NOR and biochars. Overall, this work constitutes a basis for further research considering the bioavailability and toxicity of antibiotics in the presence of biochar.

Adsorption of the compounds encountered in monosaccharide dehydration in zeolite beta.

Science.gov (United States)

León, Marta; Swift, T Dallas; Nikolakis, Vladimiros; Vlachos, Dionisios G

2013-06-04

A comprehensive study of the adsorption of the compounds involved in the reaction of dehydration of fructose to 5-hydroxymethyl furfural (HMF) on the zeolite H-BEA with SiO2/Al2O3 = 18 has been carried out. Furthermore, a method for the estimation of the real adsorption loading from the experimentally measured excess adsorption is developed and applied to calculate the adsorption isotherms both in the case of single-solute and multisolute mixtures. It was found that zeolite H-BEA adsorbs HMF and levulinic acid from water mixtures to greater extent than sugars and formic acid, which prefer to partition in the aqueous phase. HMF and levulinic acid adsorption isotherms could be fitted in a Redlich-Peterson isotherm model, while the adsorption of formic acid is better fitted using the Freundlich model and sugars via the Henry model. Adsorption loadings decreased with increasing temperature (0, 25, and 40 °C), which is characteristic of an exothermic process. From the temperature dependence of the isotherms, the limiting heat of adsorption at zero coverage was determined using van't Hoff equation. Given the importance and the complexity of multicomponent systems, several experiments of adsorption of multisolute solutions have been carried out. In most of the cases, the ideal adsorbed solution theory (IAST) has been proven to satisfactorily predict adsorption from multisolute mixtures using as input the single-solute isotherms.

Adsorption of gas mixtures on heterogeneous solid surfaces

Energy Technology Data Exchange (ETDEWEB)

Jaroniec, M; Rudzinski, W

1977-01-01

A review of theoretical studies on the physical adsorption from gas mixtures on heterogeneous solid surfaces, mainly by Jaroniec and coworkers, covers the vector notation used in the calculations; adsorption isotherms for multicomponent gases; the generalized integral equation for adsorption of gas mixtures, its numerical and analytical solutions, applied, (e.g., to interpret the experimental adsorption isotherms of ethane/ethylene on Nuxit-AL); thermodynamic relations, applied, (e.g., to calculating isosteric adsorption heats from experimental parameters for the adsorption of propylene from propane/propylene mixtures on Nuxit-AL); and the derivation and use of a simplified integral equation for describing the adsorption from gas mixtures on heterogeneous surfaces. 75 references.

A Poromechanical Model for Coal Seams Injected with Carbon Dioxide: From an Isotherm of Adsorption to a Swelling of the Reservoir Un modéle poromécanique pour l’injection de dioxyde de carbone dans des veines de charbon : d’une isotherme d’adsorption à un gonflement du réservoir

Directory of Open Access Journals (Sweden)

Nikoosokhan S.

2012-11-01

Full Text Available Injecting carbon dioxide into deep unminable coal seams can enhance the amount of methane recovered from the seam. This process is known as CO2-Enhanced Coal Bed Methane production (CO2-ECBM. The seam is a porous medium whose porous system is made of cleats (small natural fractures and of coal pores (whose radius can be as small as a few angström. During the injection process, the molecules of CO2 get adsorbed in the coal pores. Such an adsorption makes the coal swell, which, in the confined conditions that prevail underground, induces a closure of the cleat system of the coal bed reservoir and a loss of injectivity. In this work, we develop a poromechanical model which, starting from the knowledge of an adsorption isotherm and combined with reservoir simulations, enables to estimate the variations of injectivity of the coal bed reservoir over time during the process of injection. The model for the coal bed reservoir is based on poromechanical equations that explicitly take into account the effect of adsorption on the mechanical behavior of a microporous medium. We consider the coal bed reservoir as a dual porosity (cleats and coal porosity medium, for which we derive a set of linear constitutive equations. The model requires as an input the adsorption isotherm on coal of the fluid considered. Reversely, the model provides a way to upscale an adsorption isotherm into a meaningful swelling of the coal bed reservoir at the macroscopic scale. The parameters of the model are calibrated on data on coal samples available in the literature. Reservoir simulations of an injection of carbon dioxide in a coal seam are performed with an in-house finite volume and element code. The variations of injection rate over time during the process of injection are obtained from the simulations. The effect of the compressibility of the coal matrix on those variations is discussed. L’injection de dioxyde de carbone dans des veines de charbon profondes peut augmenter

Evaluation of theoretical and empirical water vapor sorption isotherm models for soils

Science.gov (United States)

Arthur, Emmanuel; Tuller, Markus; Moldrup, Per; de Jonge, Lis W.

2016-01-01

The mathematical characterization of water vapor sorption isotherms of soils is crucial for modeling processes such as volatilization of pesticides and diffusive and convective water vapor transport. Although numerous physically based and empirical models were previously proposed to describe sorption isotherms of building materials, food, and other industrial products, knowledge about the applicability of these functions for soils is noticeably lacking. We present an evaluation of nine models for characterizing adsorption/desorption isotherms for a water activity range from 0.03 to 0.93 based on measured data of 207 soils with widely varying textures, organic carbon contents, and clay mineralogy. In addition, the potential applicability of the models for prediction of sorption isotherms from known clay content was investigated. While in general, all investigated models described measured adsorption and desorption isotherms reasonably well, distinct differences were observed between physical and empirical models and due to the different degrees of freedom of the model equations. There were also considerable differences in model performance for adsorption and desorption data. While regression analysis relating model parameters and clay content and subsequent model application for prediction of measured isotherms showed promise for the majority of investigated soils, for soils with distinct kaolinitic and smectitic clay mineralogy predicted isotherms did not closely match the measurements.

Effect of the impregnation of carbon cloth with ethylenediaminetetraacetic acid on its adsorption capacity for the adsorption of several metal ions

International Nuclear Information System (INIS)

Afkhami, Abbas; Madrakian, Tayyebeh; Amini, Azadeh; Karimi, Ziba

2008-01-01

Effect of loading of C-cloth with ethylenediaminetetraacetic acid (EDTA) on the adsorption capacity for the adsorption of several metal cations was studied. The concentration of ions in the solution was monitored using atomic absorption spectrometry. The adsorption isotherm data for the cations were derived at 25 deg. C and treated according to Langmuir and Freundlich models and was found that for most of the investigated cations Langmuir model was more successful. Adsorption capacities determined from Langmuir isotherms. Loading of the adsorbent with EDTA increased the adsorption capacity for the adsorption of all of the investigation ions

Adsorption of phenol and 1-naphthol onto XC-72 carbon

Energy Technology Data Exchange (ETDEWEB)

Zuo, Liming; Yu, Shaoming; Cheng, Leilei; Du, Erling [hefei university of technology, Hefei (China)

2013-03-15

XC-72 carbon (XC-72) was characterized by SEM, XPS, N{sub 2} adsorption-desorption, particle size distribution analysis and potentiometric acid-base titration. The adsorption of phenol and 1-naphthol on XC-72 was studied as a function of contact time, pH, adsorbent content and temperature. The kinetic adsorption data were described well by the pseudo-second-order model. The adsorption isotherms of phenol were described well by Freundlich model, while the adsorption isotherms of 1-naphthol were fitted well by Langmuir model. The results demonstrated that XC-72 had much higher adsorption capacity for 1-naphthol than for phenol. The adsorption thermodynamic data were calculated from the temperature-dependent adsorption isotherms at T=293, 313 and 333 K, and the results indicated that the adsorption of phenol was an exothermic process, whereas the adsorption of 1-naphthol was an endothermic process. XC-72 is a suitable material for the preconcentration of phenol and 1-naphthol from large volumes of aqueous solutions.

Adsorption of CO2 on KOH activated, N-enriched carbon derived from urea formaldehyde resin: kinetics, isotherm and thermodynamic studies

Science.gov (United States)

Tiwari, Deepak; Bhunia, Haripada; Bajpai, Pramod K.

2018-05-01

High surface area nitrogen enriched carbon adsorbents were prepared from a low cost and widely available urea-formaldehyde resin using a standard chemical activation with KOH and characterized using different characterization techniques for their porous structure and surface functional groups. Maximum surface area and total pore volume of 4547 m2 g-1 and 4.50 cm3 g-1 were found by controlling the activation conditions. Nitrogen content of this sample was found to be 5.62%. Adsorption of CO2 uptake for the prepared carbon adsorbents was studied using a dynamic fixed bed adsorption system at different adsorption temperatures (30-100 °C) and at different CO2 concentrations (5-12.5%), relevant from the flue gas point application. Maximum CO2 uptake of 1.40 mmol g-1 for UFA-3-700 at 30 °C under 12.5% CO2 flow was obtained. Complete regenerability of the adsorbents over multiple adsorption-desorption cycles was obtained. Fractional order kinetic model provided best description over all adsorption temperatures and CO2 concentrations. Heterogeneity of the adsorbent surface was confirmed from Temkin adsorption isotherm model fit and isosteric heat of adsorption values. Negative value of ΔG° and ΔH° confirms spontaneous, feasible nature and exothermic nature of adsorption process. Overall, very high surface area of carbon adsorbent makes this adsorbent a new promising carbon material for CO2 capture from power plant flue gas and for other relevant applications.

Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite.

Directory of Open Access Journals (Sweden)

Yajun Chen

Full Text Available Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR and ciprofloxacin (CIP, by nano-hydroxyapatite (n-HAP were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g · L(-1, in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics.

Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite

Science.gov (United States)

Chen, Yajun; Lan, Tao; Duan, Lunchao; Wang, Fenghe; Zhao, Bin; Zhang, Shengtian; Wei, Wei

2015-01-01

Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g·L-1, in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics. PMID:26698573

New apparatus for measuring radon adsorption on solid adsorbents

International Nuclear Information System (INIS)

Hassan, N.M.; Hines, A.L.; Ghosh, T.K.; Loyalka, S.K.; Ketring, A.R.

1991-01-01

A new experimental system was designed to measure radon uptake by solid adsorbents from air or other carrier gases/vapors. The total amount of radon adsorbed corresponding to a specific gas-phase concentration was determined by simultaneously measuring the solid-phase and gas-phase concentrations. The system was used to measure radon adsorption isotherms on BPL activated carbon at 288, 298, and 308 K and on silica gel and molecular sieve 13X at 298 K. The isotherms were of type III according to Brunauer's classification. The heat of adsorption data indicated that the BPL activated carbon provided a heterogeneous surface for radon adsorption. The equilibrium data were correlated by the Freundlich equation. In this paper the possible adsorption mechanism and the use of the adsorption isotherms to measure indoor radon concentrations are discussed

Statistical mechanics of binary mixture adsorption in metal-organic frameworks in the osmotic ensemble

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Dunne, Lawrence J.; Manos, George

2018-03-01

Although crucial for designing separation processes little is known experimentally about multi-component adsorption isotherms in comparison with pure single components. Very few binary mixture adsorption isotherms are to be found in the literature and information about isotherms over a wide range of gas-phase composition and mechanical pressures and temperature is lacking. Here, we present a quasi-one-dimensional statistical mechanical model of binary mixture adsorption in metal-organic frameworks (MOFs) treated exactly by a transfer matrix method in the osmotic ensemble. The experimental parameter space may be very complex and investigations into multi-component mixture adsorption may be guided by theoretical insights. The approach successfully models breathing structural transitions induced by adsorption giving a good account of the shape of adsorption isotherms of CO2 and CH4 adsorption in MIL-53(Al). Binary mixture isotherms and co-adsorption-phase diagrams are also calculated and found to give a good description of the experimental trends in these properties and because of the wide model parameter range which reproduces this behaviour suggests that this is generic to MOFs. Finally, a study is made of the influence of mechanical pressure on the shape of CO2 and CH4 adsorption isotherms in MIL-53(Al). Quite modest mechanical pressures can induce significant changes to isotherm shapes in MOFs with implications for binary mixture separation processes. This article is part of the theme issue `Modern theoretical chemistry'.

Zirconium oxide-coated sand based batch and column adsorptive removal of arsenic from water: Isotherm, kinetic and thermodynamic studies

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Saif Ali Chaudhry

2017-06-01

Full Text Available This paper reports zirconium oxide-coated sand preparation, characterization by SEM, EDX, XRD, FT-IR and thermoanalytical techniques, and use as an adsorbent for the removal of most toxic form of arsenic, As(III, from aqueous solution in both batch and column methods. Batch experimental parameters such as contact time, concentration, dose of adsorbent, pH of As(III solution and temperature were optimized. The adsorption data was fitted to Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms at 303, 308 and 313 K. The maximum Langmuir monolayer adsorption capacity was found to be 136.98 μg/g at 313 K. Values of ΔH°, ΔG° and ΔS° were found to be −12.90, −8.74 to –8.28 and 0.014 kJ/mol, suggesting exothermic and spontaneous adsorption process with slight increase in entropy. The adsorption process followed pseudo-second order kinetics and was controlled by film diffusion step. The column studies showed that when flow rate was increased from 3.0 to 5.0 mL/min, the arsenic adsorption capacity of ZrOCS increased from 33.104 to 42.231 μg/g and breakthrough, and exhaustion times got reduced reduced. The results indicated that zirconium oxide-coated sand (ZrOCS is an excellent adsorbent for the removal of As(III from water.

Selective adsorption of Pb (II) over the zinc-based MOFs in aqueous solution-kinetics, isotherms, and the ion exchange mechanism.

Science.gov (United States)

Wang, Lei; Zhao, Xinhua; Zhang, Jinmiao; Xiong, Zhenhu

2017-06-01

Two series of metal-organic frameworks (MOFs) with similar formula units but different central metal ions (M) or organic linkers (L), M-BDC (BDC = terephthalate, M = Zn, Zr, Cr, or Fe), or Zn-L (L = imidazolate-2-methyl, BDC, BDC-NH 2 ), were prepared and employed as the receptors for adsorption lead ions. It was found that the Zn-BDC exhibited a much higher adsorption capacity than the other M-BDC series with various metal ions which have very closely low capacities at same conditions. Furthermore, the Zn-L (L = imidazolate-2-methyl, BDC, BDC-NH 2 ) still have highly efficient adsorption capacity of lead ions, although the adsorption capacity varies with different ligand, as well as the adsorption rate and the equilibrium pH of the solution. This significant high adsorption over Zn-L, different from other M-BDC series with various metal ions (Zr, Cr, or Fe), can be explained by ion exchange between the central metal ions of Zn-L and lead ion in solution. Based on the analysis of FT-IR, X-ray diffraction pattern, the nitrogen adsorption isotherms, the zeta potentials, and the results, a plausible adsorption mechanism is proposed. When equivalent Zn-L were added to equal volume of aqueous solution with different concentration of lead ion, the content of zinc ion in the solution increases with the increase of the initial concentration of lead ions. The new findings could provide a potential way to fabricate new metal organic frameworks with high and selective capacities of the heavy metal ions.

Investigation of the Behavior of Ethylene Molecular Films Using High Resolution Adsorption Isotherms and Neutron Scattering

International Nuclear Information System (INIS)

Barbour, Andi M.; Telling, Mark T.; Larese, John Z.

2010-01-01

The wetting behavior of ethylene adsorbed on MgO(100) was investigated from 83-135 K using high resolution volumetric adsorption isotherms. The results are compared to ethylene adsorption on graphite, a prototype adsorption system, in an effort to gain further insight into the forces that drive the observed film growth. Layering transitions for ethylene on MgO(100) are observed below the bulk triple point of ethylene (T = 104.0 K). The formation of three discrete adlayers is observed on the MgO(100) surface; onset of the second and third layers occurs at 79.2 ± 1.3 K and 98.3 ± 0.9 K, respectively. Thermodynamic quantities such as differential enthalpy and entropy, heat of adsorption, and isosteric heat of adsorption are determined and compared to the previously published values for ethylene on graphite. The average area occupied by a ethylene molecule on MgO(100) is 22.6 ± 1.1 (angstrom) 2 molecule -1 . The locations of two phase transitions are identified (i.e., layer critical temperatures at T c2 (n=1) at 108.6 ± 1.7 K and T c2 (n=2) at 116.5 ± 1.2 K) and a phase diagram is proposed. Preliminary neutron diffraction measurements reveal evidence of a monolayer solid with a lattice constant of ∼4.2 (angstrom). High resolution INS measurements show that the onset to dynamical motion and monolayer melting take place at 35 K and 65 K, respectively. The data reported here exhibit a striking similarity to ethylene on graphite which suggests that molecule-molecule interactions play an important role in determining the physical properties and growth of molecularly thin ethylene films.

Molecular structure-adsorption study on current textile dyes.

Science.gov (United States)

Örücü, E; Tugcu, G; Saçan, M T

2014-01-01

This study was performed to investigate the adsorption of a diverse set of textile dyes onto granulated activated carbon (GAC). The adsorption experiments were carried out in a batch system. The Langmuir and Freundlich isotherm models were applied to experimental data and the isotherm constants were calculated for 33 anthraquinone and azo dyes. The adsorption equilibrium data fitted more adequately to the Langmuir isotherm model than the Freundlich isotherm model. Added to a qualitative analysis of experimental results, multiple linear regression (MLR), support vector regression (SVR) and back propagation neural network (BPNN) methods were used to develop quantitative structure-property relationship (QSPR) models with the novel adsorption data. The data were divided randomly into training and test sets. The predictive ability of all models was evaluated using the test set. Descriptors were selected with a genetic algorithm (GA) using QSARINS software. Results related to QSPR models on the adsorption capacity of GAC showed that molecular structure of dyes was represented by ionization potential based on two-dimensional topological distances, chromophoric features and a property filter index. Comparison of the performance of the models demonstrated the superiority of the BPNN over GA-MLR and SVR models.

Removal of phenol from aqueous solution by Mahua seed activated carbon: Kinetic, isotherm, mass transfer and isosteric heat of adsorption studies

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Singh Yadav Lallan

2016-01-01

Full Text Available Mahua (Madhuca longifolia seed activated carbon (MSAC has been developed as an effective adsorbent for the removal of phenol from contaminated wastewaters. Prepared MSAC was characterized for various physico-chemical properties, Fourier transform infra- red (FTIR and scanning electron microscopy (SEM analysis. Laboratory batch experiments were performed to investigate the effect of MSAC dosage (w, pH, contact time (t, and initial phenol concentrations (Co on sorption efficiency at optimal conditions. The maximum adsorption capacity of phenol was obtained at pH=6, t=5 h and MSAC dosage=1.2 g/l. The kinetics data of phenol adsorption was very well described by the pseudo-second-order kinetic model. The equilibrium adsorption data were best fitted to the Langmuir isotherm. The average effective diffusion coefficient 6.4×10-13 m2/s was calculated from the experimental data. Thermodynamic studies confirmed the sorption process to be spontaneous and exothermic. The isosteric heat of adsorption of phenol was found to increase with an increase in the surface loading indicating that MSAC have more homogeneous surface.

Effect of drying method on the adsorption isotherms and isosteric heat of passion fruit pulp powder

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Maria Angélica Marques Pedro

2010-12-01

Full Text Available The sorption behavior of dry products is generally affected by the drying method. The sorption isotherms are useful to determine and compare thermodynamic properties of passion fruit pulp powder processed by different drying methods. The objective of this study is to analyze the effects of different drying methods on the sorption properties of passion fruit pulp powder. Passion fruit pulp powder was dehydrated using different dryers: vacuum, spray dryer, vibro-fluidized, and freeze dryer. The moisture equilibrium data of Passion Fruit Pulp (PFP powders with 55% of maltodextrin (MD were determined at 20, 30, 40 and 50 ºC. The behavior of the curves was type III, according to Brunauer's classification, and the GAB model was fitted to the experimental equilibrium data. The equilibrium moisture contents of the samples were little affected by temperature variation. The spray dryer provides a dry product with higher adsorption capacity than that of the other methods. The vibro-fluidized bed drying showed higher adsorption capacity than that of vacuum and freeze drying. The vacuum and freeze drying presented the same adsorption capacity. The isosteric heats of sorption were found to decrease with increasing moisture content. Considering the effect of drying methods, the highest isosteric heat of sorption was observed for powders produced by spray drying, whereas powders obtained by vacuum and freeze drying showed the lowest isosteric heats of sorption.

Adsorption of methyl iodide on charcoal

International Nuclear Information System (INIS)

Hidajat, K.; Aracil, J.; Kenney, C.N.

1990-01-01

The adsorption of non-radioactive methyl iodide has been measured experimentally over a range of conditions of concentration, and temperature on an activated charcoal. This is of interest since methyl iodide is formed from iodine fission products in gas cooled nuclear reactors. A mathematical model has also been developed which describes the rate of adsorption, under isothermal and linear adsorption isotherm conditions in a recycle adsorber. This model takes into account the resistance to adsorption caused by the surface adsorption, as well as the external and internal mass transfer resistances. The solution to the model for the recycle adsorber was obtained using a semidiscretisation method to reduce the partial differential equations to a system of stiff ordinary differential equations, and the resulting differential equations solved by a standard numerical technique. (author)

Kinetic and Isotherm Modelling of the Adsorption of Phenolic Compounds from Olive Mill Wastewater onto Activated Carbon

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Alessandro A. Casazza

2015-01-01

Full Text Available The adsorption of phenolic compounds from olive oil wastewater by commercial activated carbon was studied as a function of adsorbent quantity and temperature. The sorption kinetics and the equilibrium isotherms were evaluated. Under optimum conditions (8 g of activated carbon per 100 mL, the maximum sorption capacity of activated carbon expressed as mg of caff eic acid equivalent per g of activated carbon was 35.8 at 10 °C, 35.4 at 25 °C and 36.1 at 40 °C. The pseudo-second-order model was considered as the most suitable for kinetic results, and Langmuir isotherm was chosen to bett er describe the sorption system. The results confi rmed the effi ciency of activated carbon to remove almost all phenolic compound fractions from olive mill effl uent. The preliminary results obtained will be used in future studies. The carbohydrate fraction of this upgraded residue could be employed to produce bioethanol, and adsorbed phenolic compounds can be recovered and used in different industries.

Adsorption of cellulase on cellulolytic enzyme lignin from lodgepole pine.

Science.gov (United States)

Tu, Maobing; Pan, Xuejun; Saddler, Jack N

2009-09-09

Enzymatic hydrolysis of lignocellulosic materials is significantly affected by cellulase adsorption onto the lignocellulosic substrates and lignin. The presence of lignin plays an important role in lignocellulosic hydrolysis and enzyme recycling. Three cellulase preparations (Celluclast, Spezyme CP, and MSUBC) were evaluated to determine their adsorption onto cellulolytic enzyme lignin (CEL) from steam-exploded Lodgepole pine (SELP) and ethanol (organosolv)-pretreated Lodgepole pine (EPLP). The adsorption affinity of cellulase (Celluclast) onto isolated lignin (CEL-EPLP and CEL-SELP) was slightly higher than that from corresponding EPLP and SELP substrates on the basis of the Langmuir constants. Effects of temperature, ionic strength, and surfactant on cellulase adsorption onto isolated lignin were also explored in this study. Thermodynamic analysis of enzyme adsorption onto isolated lignin (Gibbs free energy change DeltaG(0) approximately -30 kJ/mol) indicated this adsorption was a spontaneous process. The addition of surfactant (0.2% w/v) could reduce the adsorption of cellulase onto CEL-SELP by 60%. Two types of adsorption isotherm were compared for cellulase adsorption onto isolated lignin. A Langmuir adsorption isotherm showed better fit for the experimental data than a Freundlich adsorption isotherm.

Comparative evaluation of adsorption kinetics of diclofenac and isoproturon by activated carbon.

Science.gov (United States)

Torrellas, Silvia A; Rodriguez, Araceli R; Escudero, Gabriel O; Martín, José María G; Rodriguez, Juan G

2015-01-01

Adsorption mechanism of diclofenac and isoproturon onto activated carbon has been proposed using Langmuir and Freundlich isotherms. Adsorption capacity and optimum adsorption isotherms were predicted by nonlinear regression method. Different kinetic equations, pseudo-first-order, pseudo-second-order, intraparticle diffusion model and Bangham kinetic model, were applied to study the adsorption kinetics of emerging contaminants on activated carbon in two aqueous matrices.

Studies on the adsorption kinetics and isotherms for the removal and recovery of Methyl Orange from wastewaters using waste materials

International Nuclear Information System (INIS)

Mittal, Alok; Malviya, Arti; Kaur, Dipika; Mittal, Jyoti; Kurup, Lisha

2007-01-01

De-Oiled Soya a waste of Soya oil industries and Bottom Ash a waste of thermal power plants have been used as effective adsorbent for recovery and removal of hazardous dye Methyl Orange from wastewater. During the studies effects of amount of dye and adsorbents, pH, sieve sizes, column studies etc. have been carried out. Adsorption of the dye over both the adsorbents has been monitored through Langmuir and Freundlich adsorption isotherm models and feasibility of the process is predicted in both the cases. Different thermodynamic parameters like Gibb's free energy, enthalpy and entropy of the undergoing process are also evaluated through these adsorption models. The kinetic studies confirm the first order process for the adsorption reaction and also play an important role in finding out half-life of the adsorption process and rate constants for both the adsorbents. It is also found that over the entire concentration range the adsorption on Bottom Ash takes place via particle diffusion process, while that of De-Oiled Soya undergoes via film diffusion process. In order to establish the practical utility of the developed process, attempts have been made for the bulk removal of the dye through column operations. For the two columns saturation factors are found as 98.61 and 99.8%, respectively, for Bottom Ash and De-Oiled Soya with adsorption capacity of each adsorbent as 3.618 and 16.664 mg/g, respectively. The dye recovery has been achieved by eluting dil. NaOH through the exhausted columns

Adsorption of radon and water vapor on commercial activated carbons

International Nuclear Information System (INIS)

Hassan, N.M.; Ghosh, T.K.; Hines, A.L.; Loyalka, S.K.

1995-01-01

Equilibrium adsorption isotherms are reported for radon and water vapor on two commercial activated carbons: coconut shell Type PCB and hardwood Type BD. The isotherms of the water vapor were measured gravimetrically at 298 K. The isotherms of radon from dry nitrogen were obtained at 293, 298, and 308 K while the data for the mixture of radon and water vapor were measured at 298 K. The concentrations of radon in the gas and solid phases were measured simultaneously, once the adsorption equilibrium and the radioactive equilibrium between the radon and its daughter products were established. The shape of the isotherms was of Type III for the radon and Type V for the water vapor, according to Brunauer's classification. The adsorption mechanism was similar for both the radon and the water vapor, being physical adsorption on the macropore surface area in the low pressure region and micropore filling near saturation pressure. The uptake capacity of radon decreased both with increasing temperature and relative humidity. The heat of adsorption data indicated that the PCB- and the BD-activated carbons provided a heterogeneous surface for radon adsorption. The equilibrium data for radon were correlated with a modified Freundlich equation

Human hair-derived high surface area porous carbon material for the adsorption isotherm and kinetics of tetracycline antibiotics.

Science.gov (United States)

Ahmed, M J; Islam, Md Azharul; Asif, M; Hameed, B H

2017-11-01

In this work, a human hair-derived high surface area porous carbon material (HHC) was prepared using potassium hydroxide activation. The morphology and textural properties of the HHC structure, along with its adsorption performance for tetracycline (TC) antibiotics, were evaluated. HHC showed a high surface area of 1505.11m 2 /g and 68.34% microporosity. The effects of most important variables, such as initial concentration (25-355mg/L), solution pH (3-13), and temperatures (30-50°C), on the HHC adsorption performance were investigated. Isotherm data analysis revealed the favorable application of the Langmuir model, with maximum TC uptakes of 128.52, 162.62, and 210.18mg/g at 30, 40, and 50°C, respectively. The experimental data of TC uptakes versus time were analyzed efficiently using a pseudo-first order model. Porous HHC could be an efficient adsorbent for eliminating antibiotic pollutants in wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dyeing and Adsorption Studies of Madder (Rubia tinctorum on Wool Fibers

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Mahmoud FEIZ

2015-03-01

Full Text Available In this study, the dyeing behavior of wool fabrics with madder has been studied. Three well-known types of adsorption isotherms i.e. the Nernst, Freundlich and Langmuir isotherms were used to fit the data. It was found that the adsorption isotherm of madder on wool fibers follows Freundlich type of adsorption. The exponent α in Freundlich isotherm equation (Cf = k.Csα was obtained 0.61 corresponding to 0.5 for the direct dyes on cellulosic fibers. The effect of salt and pH on dyeing of wool samples was investigated by the use of color characteristics measurements. The results showed that addition of salt and acid (pH 4.5 to the dyebath resulted in an increase of adsorption. DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5150

Adsorption isotherms and kinetics for dibenzothiophene on activated ...

Indian Academy of Sciences (India)

Adsorptive desulphurization is a promising tech- nique. It is cost effective, and as ... tinct properties, is expected to improve the adsorption capa- bility for sulphur .... I.D. silica column and n-hexane as mobile phase at a flow rate 1.00 ml min. −1.

Cadmium Adsorption on HDTMA Modified Montmorillionite

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Mohd. Elmuntasir I. Ahmed

2009-06-01

Full Text Available In this paper the possibility of cadmium removal from aqueous solutions by adsorption onto modified montmorillonite clay is investigated. Batch adsorption experiments performed revealed an enhanced removal of cadmium using HDTMA modified montmorillonite to 100% of its exchange capacity. Modified montmorillonite adsorption capacity increases at higher pHs suggesting adsorption occurs as a result of surface precipitation and HDTMA complex formation due to the fact that the original negatively charged montmorillonite is now covered by a cationic layer of HDTMA. Adsorption isotherms generated followed a Langmuir isotherm equation possibly indicating a monolayer coverage. Adsorption capacities of up to 49 mg/g and removals greater than 90% were achieved. Anionic selectivity of the HDTMA modified monmorillonite is particularly advantageous in water treatment applications where high concentrations of less adsorbable species are present, and the lack of organoclay affinity for these species may allow the available capacity to be utilized selectively by the targeted species.

A Simple Adsorption Experiment

Science.gov (United States)

Guirado, Gonzalo; Ayllon, Jose A.

2011-01-01

The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

Kinetics, Thermodynamics and Isotherm studies on Adsorption of Eriochrome Black-T from aqueous solution using Rutile TiO2

Science.gov (United States)

Priyadarshini, B.; Rath, P. P.; Behera, S. S.; Panda, S. R.; Sahoo, T. R.; Parhi, P. K.

2018-02-01

In this study, rutile phase of TiO2 particles have been synthesized by co-precipitation method and is used as an adsorbent for removal of toxic azo dye Eriochrome black-T (EBT) from aqueous solution. The rutile phase of TiO2 was confirmed by the X-ray powder diffraction pattern. Effect of initial dye concentration, adsorbent dose, pH, agitation speed and temperature on the adsorption process of EBT was examined. Removal of EBT was increased by increasing in adsorbent dose and decrease in initial dye concentration and pH. The optimum conditions resulted were: 25 ppm initial dye concentration, 20 mg adsorbent dose and pH of 2. Using Langmuir, Freundlich and Temkin isotherm models, equilibrium data was determined. The Freundlich model showed the best fit for uptake of the EBT dye, which evident that the process of adsorption of EBT dye onto TiO2 particles was heterogeneous. The kinetic data were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion equation. The pseudo-second order showed the best fit for the kinetic studies (R2 = 0.999), which ascertains that the adsorption process was of chemisorptions type. The intraparticle diffusion model indicated a linear relationship (R2= 0.99) suggesting the pore diffusion to be a limiting step in the overall adsorption process.

Adsorptive property of rice husk for uranium

International Nuclear Information System (INIS)

Feng Yuan; Yi Facheng

2011-01-01

The adsorption experiments were researched by using the rice husk powder as the adsorbent to remove the U(VI) from aqueous solution. The affecting factors on the U(VI) removal rate such as rice husk particle size, pH, initial concentration, adsorption time, temperature and dosage of adsorbent were evaluated, kinetics and adsorption isotherm law were analyzed, and mechanisms for U(VI) removal were discussed by SEM, FT-IR and energy spectrum analysis. The results show that U(VI) removal rate increases with the decrease of the size of adsorbent, and with the increase of adsorbent dosage and temperature. The process of adsorption can be described by an equation of pseudo 2nd-order mode, and the relation coefficient is 1. The process of adsorption also fits to Freundlich isotherm (R 2 =0.995 4). The adsorption of uranium on rice husk changes the surface form of rice husk. Hydroxyl, carboxylic, P-O and Si-O are the main functional groups in the reaction with U(VI). The adsorption mechanism is mixture adsorption, including the physical and chemical adsorption. (authors)

Bleaching of Neutral Cotton Seed Oil Using Organic Activated Carbon in a Batch System: Kinetics and Adsorption Isotherms

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Abba Chetima

2018-03-01

Full Text Available In the processing of cotton and neem seeds to obtain oil for diverse uses, enormous quantities of seed husk are generated as waste, which when not properly disposed of, poses environmental problems. One way of reducing this waste is to use it for the production of activated carbon (AC for its multiple applications. In this work, activated carbon was produced from cotton and neem seed husks by carbonization followed by acid activation. The prepared ACs were characterized for its porosity and surface properties as well as for its ability to bleach neutral cotton seed oil. The prepared ACs are very efficient in the decoloration process, as they removed about 96–98% of the pigments compared to 98.4% removal with commercial bleaching earth. Temperature had a pronounced effect on the bleaching of neutral cotton seed oil. Maximum adsorption was observed at 60 °C for a contact time of 45 min. The adsorption kinetics were modelled by the intra-particle and the pseudo-second order equations while the adsorption isotherms followed the Langmuir and Freundlich equations. It is concluded that the organic ACs are efficient in pigment removal from neutral cotton seed oil and therefore are potential bleaching agents for the vegetable oil industry.

Malachite Green Adsorption by Spent Coffee Grounds

Science.gov (United States)

Syamimie Atirah Mat, Siti; Zati Hanani Syed Zuber, Sharifah; Rahim, Siti Kartini Enche Ab; Sohaimi, Khairunissa Syairah Ahmad; Halim, Noor Amirah Abdul; Fauziah Zainudin, Nor; Aida Yusoff, Nor; Munirah Rohaizad, Nor; Hidayah Ishak, Noor; Anuar, Adilah; Sarip, Mohd Sharizan Md

2018-03-01

In this work, the ability of spent coffee grounds (SCG) as a low-cost adsorbent to remove malachite green (MG) from aqueous solutions was studied. Batch adsorption tests were carried out to observe the effect of various experimental parameters such as contact time, initial concentration of malachite green and adsorbent dosage on the removal of dye. The results obtained show that the percentage of dye removal will decreased with the increased of initial concentration of dye in the range of 50 mg/L to 250 mg/L. Besides, percentage removal of dye was also found to be increased as the contact time increased until it reached equilibrium condition. The results also showed that the adsorbent dosage in range of 0.2 g to 1.0 g is proportional to the percentage removal of malachite green dye. Study on the kinetic adsorption and isotherm adsorption has also been investigated. The adsorption isotherm data were described by Langmuir isotherm with high-correlation coefficients while the experimental data showed the pseudo-second-order kinetics model was the best model for the adsorption of MG by SCG with the coefficients of correlation R2 > 0.9978.

Adsorption of uranyl ions in nanoparticles of magnetite

International Nuclear Information System (INIS)

Holland, Helber; Yamaura, Mitiko

2009-01-01

This work studied the uranium (VI) adsorption, in the form of UO 2 2+ ions, of the nitride solution by the syntetic magnetite. This solution was prepared by precipitation adding a solution of NaOH to the solution containing the ions Fe 2+ . The time of contact and the isothermal of equilibrium of ions UO 2 2+ adsorption was verified. The isothermal of equilibrium presented more concordance with the Freundlich model, which characterized a heterogeneous adsorption surface of the magnetite. The great advantage of this technology is the combination of two separation techniques, by adsorption and magnetic, resulting in a highly efficient and reusable system

Thermodynamic study on the adsorption of strontium on polyantimonic acid exchanger

International Nuclear Information System (INIS)

Li Mingyu; Chen Jing; Wang Jianchen; Zhao Jing

2007-01-01

The adsorption of strontium on the polyantimonic acid adsorbent was studied. The equilibrium data for the adsorption of strontium on polyantimonic acid exchanger from aqueous solutions were obtained and correlated with Langmuir-type and Freundlich-type isotherm equation within the temperature range of 293-323 K and the experimental concentration range. Freundlich adsorption isotherms and the isosteric enthalpy indicate that the adsorption of strontium on polyantimonic acid is an endothermic process from aqueous solutions. The enthalpy, free energy, and entropy of adsorption were calculated. The results indicate that the adsorption process is a complex interaction of physical and chemical processes. The adsorption behaviors were reasonably explained. (authors)

Modelling Adsorption of Foam-Forming Surfactants Modélisation de l'adsorption des produits tensio-actifs moussants

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Mannhardt K.

2006-11-01

Full Text Available There is considerable interest in the use of foam-forming surfactants for mobility control in gas flooding enhanced oil recovery processes. The success of any such process is strongly affected by the rate of propagation of the surfactant through the reservoir. A sound understanding of surfactant adsorption on rock surfaces at reservoir conditions is therefore essential. This paper describes a model for the evaluation of adsorption during flow of surfactant solutions through porous media. The adsorption term in the flow equation is expressed in terms of the surface excess which proves to be more generally applicable than, for example, the Langmuir adsorption isotherm. Adsorption isotherms of three types of commercially available foam-forming surfactants are determined from core flooding data at different temperatures and brine salinities. L'utilisation de produits tensio-actifs moussants pour le contrôle de mobilité dans les procédés de récupération assistée du pétrole par injection de gaz suscite actuellement un grand intérêt. Mais le succès d'un tel procédé dépend largement de la vitesse de propagation du tensioactif dans le réservoir. Il est donc indispensable d'avoir une bonne connaissance de l'adsorption du tensio-actif sur les surfaces de la roche, dans les conditions de réservoir. Cet article décrit un modèle qui permet d'évaluer l'adsorption pendant l'écoulement de solutions tensio-actives en milieu poreux. Le terme qui représente l'adsorption dans l'équation de l'écoulement est exprimé en fonction de l'excédent de surface, concept qui s'est révélé d'une application plus générale que, par exemple, l'isotherme d'adsorption de Langmuir. Les isothermes d'adsorption de trois types de tensio-actifs moussants disponibles sur le marché sont déterminées à partir de données obtenues lors d'essais de déplacement dans des carottes, à différentes températures et avec des saumures de différentes salinités.

Adsorption of ammonium dinitramide (ADN) from aqueous solutions. 1. Adsorption on powdered activated charcoal.

Science.gov (United States)

Santhosh, G; Venkatachalam, S; Ninan, K N; Sadhana, R; Alwan, S; Abarna, V; Joseph, M A

2003-03-17

Investigations on the adsorption of ammonium dinitramide (NH(4)N(NO(2))(2)) (ADN) from aqueous solutions on powdered activated charcoal (PAC) were carried out in order to find out an effective and easier method of separating ADN from aqueous solutions. The effectiveness of PAC in the selective adsorption of ADN from aqueous solutions of ADN (ADN-F) and ADN in presence of sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) ions (ADN-PS) was examined and compared using batch and column methods. The adsorption process follows both Langmuir and Freundlich adsorption isotherms and the isotherm parameters for the models were determined. The observed data favor the formation of monolayer adsorption. The adsorption capacities were found to be 63.3, 119, 105.3 and 82 mg of ADN per g of PAC for ADN-F (batch), ADN-PS (batch), ADN-F (column) and ADN-PS (column), respectively. Break-through curves for ADN-F and ADN-PS were obtained for the optimization of separation of ADN from aqueous solutions. Elution curves were generated for the desorption of ADN from PAC using hot water as eluent. Copyright 2003 Elsevier Science B.V.

Adsorption of dyes onto activated carbon cloth: using QSPRs as tools to approach adsorption mechanisms.

Science.gov (United States)

Metivier-Pignon, Hélène; Faur, Catherine; Le Cloirec, Pierre

2007-01-01

The present study aimed to investigate the adsorption of dyes onto activated carbon cloths. Kinetics and isotherms were studied based on results of batch reactors to constitute databases for the adsorption rates and capacities of 22 commercial dyes. Added to a qualitative analysis of experimental results, quantitative structure property relationships (QSPRs) were used to determine the structural features that influence most adsorption processes. QSPRs consisted of multiple linear regressions correlating adsorption parameters with molecular connectivity indices (MCIs) as molecular descriptors. Results related to adsorption kinetics showed that the size of molecules was the significant feature, the high order MCIs involved in QSPRs indicating the influence of a critical size on adsorption rate. Improved statistical fits were obtained when the database was divided according to the chemical classes of dyes. As regards to adsorption isotherms, their particular form led to the use of saturation capacity as the adsorption parameter. By contrast with adsorption kinetics, molecular overcrowding seemed to be of less influence on adsorption equilibrium. In this case, MCIs included in the QSPR were more related to details of the molecular structure. The robustness of the QSPR assessed for azo dyes was studied for the other dyes. Although the small size of the database limited predictive ability, features relevant to the influence of the database composition on QSPRs have been highlighted.

Highly efficient ultrasonic-assisted removal of Hg(II) ions on graphene oxide modified with 2-pyridinecarboxaldehyde thiosemicarbazone: Adsorption isotherms and kinetics studies.

Science.gov (United States)

Tadjarodi, Azadeh; Moazen Ferdowsi, Somayeh; Zare-Dorabei, Rouholah; Barzin, Ahmad

2016-11-01

A novel adsorbent, based on modifying graphene oxide (GO) chemically with 2-pyridinecarboxaldehyde thiosemicarbazone (2-PTSC) as ligand, was designed by facile process for removal of Hg(II) from aqueous solution. Characterization of the adsorbent was performed using various techniques, such as FT-IR, XRD, XPS, SEM and AFM analysis. The adsorption capacity was affected by variables such as adsorbent dosage, pH solution, Hg(2+) initial concentration and sonicating time. These variables were optimized by rotatable central composite design (CCD) under response surface methodology (RSM). The predictive model for Hg(II) adsorption was constructed and applied to find the best conditions at which the responses were maximized. In this conditions, the adsorption capacity of this adsorbent for Hg(2+) ions was calculated to be 309mgg(-1) that was higher than that of GO. Appling the ultrasound power combined with adsorption method was very efficient in shortening the removal time of Hg(2+) ions by enhancing the dispersion of adsorbent and metal ions in solution and effective interactions among them. The adsorption process was well described by second-order kinetic and Langmuir isotherm model in which the maximum adsorption capacity (Qm) was found to be 555mgg(-1) for adsorption of Hg(2+) ions over the obtained adsorbent. The performance of adsorbent was examined on the real wastewaters and confirmed the applicability of adsorbent for practical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test.

Science.gov (United States)

Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

2013-10-01

Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane. Copyright © 2013 Elsevier Ltd. All rights reserved.

Thermodynamic and topochemical aspects of the adsorption of some gaseous fluorides and solid fluorides

International Nuclear Information System (INIS)

Le Gressus, Claude

1968-01-01

This research thesis addresses the study of chemical adsorption. Such an adsorption is limited to a mono-molecular layer. As the Order Disorder Theory (ODT) allows adsorption isotherms to be calculated while taking interaction between adsorbed molecules into account, this research reports a comparison between the shape of experimental isotherms and that of theoretical isotherms. The knowledge of the involved phenomena is completed by the measurement of adsorption differential heats. After some generalities and a brief presentation of the ODT, the author presents experimental installations and techniques (micro-calorimeter, Mac-Bain balance), describes the adsorbent pre-treatment, reports the analysis performed by micro-sublimation, reports the study of the adsorption of hydrofluoric acid on CaF 2 , highlights the existence of different cases of energies increasing with the overlay rate, reports the detailed study of adsorption isotherms of ClF 3 and UF 6 on various solid fluorides. Results are finally interpreted and discussed

Limitations of sorption isotherms on modeling groundwater contaminant transport

International Nuclear Information System (INIS)

Silva, Eduardo Figueira da

2007-01-01

Design and safety assessment of radioactive waste repositories, as well as remediation of radionuclide contaminated groundwater require the development of models capable of accurately predicting trace element fate and transport. Adsorption of trace radionuclides onto soils and groundwater is an important mechanism controlling near- and far- field transport. Although surface complexation models (SCMs) can better describe the adsorption mechanisms of most radionuclides onto mineral surfaces by directly accounting for variability of system properties and mineral surface properties, isotherms are still used to model contaminant transport in groundwater, despite the much higher system dependence. The present work investigates differences between transport model results based on these two approaches for adsorption modeling. A finite element transport model is used for the isotherm model, whereas the computer program PHREEQC is used for the SCM approach. Both models are calibrated for a batch experiment, and one-dimensional transport is simulated using the calibrated parameters. At the lower injected concentrations there are large discrepancies between SCM and isotherm transport predictions, with the SCM presenting much longer tails on the breakthrough curves. Isotherms may also provide non-conservative results for time to breakthrough and for maximum concentration in a contamination plume. Isotherm models are shown not to be robust enough to predict transport behavior of some trace elements, thus discouraging their use. The results also illustrate the promise of the SCM modeling approach in safety assessment and environmental remediation applications, also suggesting that independent batch sorption measurements can be used, within the framework of the SCM, to produce a more versatile and realistic groundwater transport model for radionuclides which is capable of accounting more accurately for temporal and spatial variations in geochemical conditions. (author)

Adsorption mechanism of microcrystalline cellulose as green adsorbent for the removal of cationic methylene blue dye

International Nuclear Information System (INIS)

Tan, K.B.; Salamatinia, B.

2016-01-01

The adsorption mechanism of pure cellulose is yet to be explored. Thus, in this study, the adsorption mechanism of Microcrystalline Cellulose (MCC), a polysaccharide which is renewable, low cost and non-toxic, was studied on the adsorption of model dye Methylene blue (MB). It was found that the main adsorption mechanism of MB on MCC was due to the electrostatic attraction between the positively charged MB dye and negatively charged MCC. Thus, physical adsorption was the dominant effect, since electrostatic attraction is categorized as physical adsorption. This was verified by Dubinin-Radushkevich isotherm, whereby mean free energy adsorption value was found to be less than 8 kJ/mol. The values of Gibbs free energy for thermodynamics studies were found to be within the range of -20 kJ/mol and 0 kJ/mol, which also indicated physical adsorption. It was due to the electrostatic attraction as adsorption mechanism of this adsorption process which resulted rapid adsorption of MB dye. It was found that equilibrium dye concentration was achieved between 1-3 minutes, depending on the adsorption temperature. The rapid adsorption, as compared to a lot of materials, showed the potential of MCC as the future of green adsorbent. The adsorption of Methylene Blue on MCC fitted well in Langmuir Isotherm, with R2 values of higher than 0.99, while fitted moderately in Freundlich Isotherm, with R2 values between 0.9224 and 0.9223. Comparatively, the adsorption of MB on MCC fitted best Langmuir Isotherm as compared to Freundlich Isotherm which monolayer adsorption occurred at the homogenous surface of MCC. This also indicated adsorbed MB molecules do not interact with each other at neighboring adsorption sites. The maximum adsorption capacity calculated from Langmuir Isotherm was found to be 4.95 mg/g. Despite the potential of MCC as green adsorbent, the challenge of low adsorption capacity has to be addressed in the future. (author)

Adsorption of volatile organic compounds by polytetra-fluor ethylene; Adsorption de composes organiques volatils par le polytetrafluor ethylene

Energy Technology Data Exchange (ETDEWEB)

Martinet, J.M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The sorption of organic vapours by microporous polytetra-fluor ethylene has been studied gravimetrically using a Mc Bain-Baker type sorption balance. The amount of sorption, the peculiarities observed on the isotherm curves, the small influence of temperature, and smallness of hysteresis suggests that mainly physical adsorption occurs when the temperature is around 25 deg. C. The values of the surface areas obtained from the adsorption isotherms using organic vapours differ greatly from those derived from N{sub 2} adsorption measurements. This discrepancy cannot be completely attributed to differences in the structure and chemical function of the adsorbate molecules, or to the porous structure of the adsorbent. On the contrary, the surface area values obtained by sorbing high volatile freons conform with those measured by nitrogen adsorption, which seems to imply a connection between the area of sorbed monolayers and volatility of the adsorbate. (author) [French] La sorption de vapeurs organiques par du polytetrafluor ethylene microporeux a ete etudiee gravimetriquement a l'aide d'un appareillage du type balance de Mac Bain. La valeur de la masse adsorbee, les particularites observees dans la forme des isothermes, le peu d'influence de la temperature, la faiblesse de l'hysteresis suggerent l'intervention d'une adsorption physique, du moins au voisinage de 25 deg. C. Les isothermes relatives a l'absorption de vapeurs organiques conduisent a des valeurs de la surface specifique tres differentes de celles obtenues par adsorption d'azote. Ces divergences ne peuvent s'expliquer par la seule intervention de la structure moleculaire et de la fonction chimique de l'adsorbat, ni par la structure poreuse de l'adsorbant. Par contre, l'adsorption de freons tres volatils conduit a des valeurs de la surface specifique analogues a celles obtenues par adsorption d'azote ce qui semble etablir un lien entre la

Adsorption of volatile organic compounds by polytetra-fluor ethylene; Adsorption de composes organiques volatils par le polytetrafluor ethylene

Energy Technology Data Exchange (ETDEWEB)

Martinet, J M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The sorption of organic vapours by microporous polytetra-fluor ethylene has been studied gravimetrically using a Mc Bain-Baker type sorption balance. The amount of sorption, the peculiarities observed on the isotherm curves, the small influence of temperature, and smallness of hysteresis suggests that mainly physical adsorption occurs when the temperature is around 25 deg. C. The values of the surface areas obtained from the adsorption isotherms using organic vapours differ greatly from those derived from N{sub 2} adsorption measurements. This discrepancy cannot be completely attributed to differences in the structure and chemical function of the adsorbate molecules, or to the porous structure of the adsorbent. On the contrary, the surface area values obtained by sorbing high volatile freons conform with those measured by nitrogen adsorption, which seems to imply a connection between the area of sorbed monolayers and volatility of the adsorbate. (author) [French] La sorption de vapeurs organiques par du polytetrafluor ethylene microporeux a ete etudiee gravimetriquement a l'aide d'un appareillage du type balance de Mac Bain. La valeur de la masse adsorbee, les particularites observees dans la forme des isothermes, le peu d'influence de la temperature, la faiblesse de l'hysteresis suggerent l'intervention d'une adsorption physique, du moins au voisinage de 25 deg. C. Les isothermes relatives a l'absorption de vapeurs organiques conduisent a des valeurs de la surface specifique tres differentes de celles obtenues par adsorption d'azote. Ces divergences ne peuvent s'expliquer par la seule intervention de la structure moleculaire et de la fonction chimique de l'adsorbat, ni par la structure poreuse de l'adsorbant. Par contre, l'adsorption de freons tres volatils conduit a des valeurs de la surface specifique analogues a celles obtenues par adsorption d'azote ce qui semble etablir un lien entre la volatilite de l'adsorbat et l'etendue des couches monomoleculaires

Adsorption Characteristics of Water and Silica Gel System for Desalination Cycle

KAUST Repository

Cevallos, Oscar R.

2012-07-01

An adsorbent suitable for adsorption desalination cycles is essentially characterized by a hydrophilic and porous structure with high surface area where water molecules are adsorbed via hydrogen bonding mechanism. Silica gel type A++ possesses the highest surface area and exhibits the highest equilibrium uptake from all the silica gels available in the market, therefore being suitable for water desalination cycles; where adsorbent’s adsorption characteristics and water vapor uptake capacity are key parameters in the compactness of the system; translated as feasibility of water desalination through adsorption technologies. The adsorption characteristics of water vapor onto silica gel type A++ over a temperature range of 30 oC to 60 oC are investigated in this research. This is done using water vapor adsorption analyzer utilizing a constant volume and variable pressure method, namely the Hydrosorb-1000 instrument by Quantachrome. The experimental uptake data is studied using numerous isotherm models, i. e. the Langmuir, Tóth, generalized Dubinin-Astakhov (D-A), Dubinin-Astakhov based on pore size distribution (PSD) and Dubinin-Serpinski (D-Se) isotherm for the whole pressure range, and for a pressure range below 10 kPa, proper for desalination cycles; isotherms type V of the International Union of Pure and Applied Chemistry (IUPAC) classification were exhibited. It is observed that the D-A based on PSD and the D-Se isotherm models describe the best fitting of the experimental uptake data for desalination cycles within a regression error of 2% and 6% respectively. All isotherm models, except the D-A based on PSD, have failed to describe the obtained experimental uptake data; an empirical isotherm model is proposed by observing the behavior of Tóth and D-A isotherm models. The new empirical model describes the water adsorption onto silica gel type A++ within a regression error of 3%. This will aid to describe the advantages of silica gel type A++ for the design of

Numerical evaluation of Cs adsorption in PB column by extended Langmuir formula and one-dimensional adsorption model

International Nuclear Information System (INIS)

Hiroshi Ogawa; Akiko Kitajima; Hisashi Tanaka; Tohru Kawamoto

2015-01-01

Adsorption property of granulated Prussian blue adsorbent on radioactive cesium was evaluated for efficient decontamination in Fukushima area. The adsorbent was found to show an inflective adsorption isotherm, which was expressed by extended Langmuir formula with three adsorption sites. Adsorption speeds of each site were evaluated by time-dependent batch experiment. The simulation using derived parameters and one-dimensional adsorption model successfully reproduced the experimental data of cesium decontamination by small and large columns. (author)

Preparation and Pb(II Adsorption Properties of Crosslinked Pectin-Carboxymethyl Chitosan Film

Directory of Open Access Journals (Sweden)

Budi Hastuti

2015-11-01

Full Text Available A modified pectin has been synthesized by reacting/combining -OH group among pectin and chitosan with BADGE (Bisphenol A diglycidyl ether crosslinker agent. The structure and morphology of the new material were characterized by Fourier transform infrared (FTIR spectroscopy, scanning electron microscopy (SEM and X-ray Diffraction (XRD analysis. Thermogravimetric studies showed an improvement in thermal characteristic. Adsorption experiments were performed in batch processes; sorption isotherms and kinetics were also studied. The Langmuir and Freundlich adsorption isotherm models were applied to describe the isotherms and isotherm constants for the adsorption of Pb(II ion onto adsorbent pectin-carboxymethyl chitosan-BADGE (pec-CMC-BADGE. The dynamic study showed that the sorption process followed the second-order kinetic equation. Result indicated also that Pb(II ion uptake could be well described by the Langmuir and Freundlich adsorption model of pec-CMC-BADGE and CMC with DG° of 25.3 and 23.1 kJ mol-1,respectively, while that of pectin followed Freundlich isotherm with DG° of 16.6 kJ mol-1.

Environmentally benign working pairs for adsorption refrigeration

International Nuclear Information System (INIS)

Cui Qun; Tao Gang; Chen Haijun; Guo Xinyue; Yao Huqing

2005-01-01

This paper begins from adsorption working pairs: water and ethanol were selected as refrigerants; 13x molecular sieve, silica gel, activated carbon, adsorbent NA and NB, proposed by authors, were selected as adsorbents, and the performance of adsorption working pairs in adsorption refrigeration cycle was studied. The adsorption isotherms of adsorbents (NA and NB) were obtained by high-vacuum gravimetric method. Desorption properties of adsorbents were analyzed and compared by thermal analysis method. The performance of adsorption refrigeration was studied on simulation device of adsorption refrigeration cycle. After presentation of adsorption isotherms, the thermodynamic performance for their use in adsorption refrigeration system was calculated. The results show: (1) the maximum adsorption capacity of water on adsorbent NA reaches 0.7 kg/kg, and the maximum adsorption capacity of ethanol on adsorbent NB is 0.68 kg/kg, which is three times that of ethanol on activated carbon, (2) the refrigeration capacity of NA-water working pair is 922 kJ/kg, the refrigeration capacity of NB-ethanol is 2.4 times that of activated carbon-methanol, (3) as environmental friendly and no public hazard adsorption working pair, NA-H 2 O and NB-ethanol can substitute activated carbon-methanol in adsorption refrigeration system using low-grade heat source

Fruit waste adsorbent for ammonia nitrogen removal from synthetic solution: Isotherms and kinetics

Science.gov (United States)

Zahrim, AY; Lija, Y.; Ricky, L. N. S.; Azreen, I.

2016-06-01

In this study, four types of watermelon rind (WR) adsorbents; fresh WR, modified WR with sodium hydroxide (NaOH), potassium hydroxide (KOH) and sulphuric acid (H2SO4) were used as a potential low-cost adsorbent to remove NH3-N from solution. The adsorption data were fitted with the adsorption isotherm and kinetic models to predict the mechanisms and kinetic characteristics of the adsorption process. The equilibrium data agreed well with Langmuir isotherm model with highest correlation (R2=1.00). As for kinetic modelling, the adsorption process follows pseudo-second order for all four types of adsorbents which has R2 value of 1.0 and calculated adsorption capacity, Qe of 1.2148mg/g. The calculated Qe for pseudo-second order has the smallest difference with the experimental Qe and thus suggest that this adsorption process is mainly governed by chemical process involving cations sharing or exchange between WR adsorbent and NH3-N in the solution.

Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

International Nuclear Information System (INIS)

Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

2013-01-01

Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane

Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

Energy Technology Data Exchange (ETDEWEB)

Nam, Sangchul; Namkoong, Wan [Department of Environmental Engineering, Konkuk University, Hwayang-Dong, Gwangjin-Gu, Seoul 143-701 (Korea, Republic of); Kang, Jeong-Hee; Park, Jin-Kyu [Department of Environmental Engineering, Anyang University, Anyang 5-Dong, Manan-Gu, Anyang-Si, Gyeonggi-Do 430-714 (Korea, Republic of); Lee, Namhoon, E-mail: nhlee@anyang.ac.kr [Department of Environmental Engineering, Anyang University, Anyang 5-Dong, Manan-Gu, Anyang-Si, Gyeonggi-Do 430-714 (Korea, Republic of)

2013-10-15

Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

Optimization, isotherm, kinetic and thermodynamic studies of Pb(II) ions adsorption onto N-maleated chitosan-immobilized TiO2 nanoparticles from aqueous media

Science.gov (United States)

Shaker, Medhat A.; Yakout, Amr A.

2016-02-01

Chitosan, CS was chemically engineered by maleic anhydride via simple protocol to produce N-maleated chitosan, MCS which immobilized on anatase TiO2 to synthesize novel eco-friendly nanosorbent (51 ± 3.8 nm), MCS@TiO2 for cost-effective and efficient removal of Pb(II) ions from aqueous media. The chemical structure, surface properties and morphology of MCS@TiO2 were recognized by FTIR, 1H NMR, XRD, TEM, DLS and zeta-potential techniques. The relations between %removal of Pb(II) and different analytical parameters such as solution acidity (pH), MCS@TiO2 dosage, time of contact and initial Pb(II) concentration were optimized using response surface methodology (RSM) and Box-Behnken design (BBD) statistical procedures. The fitting of the experimental data to four different isotherm models at optimized conditions was carried out by various statistical treatments including the correlation coefficient (r), coefficient of determination (r2) and non-linear Chi-square (χ2) test analyses which all confirm the suitability of Langmuir model to explain the adsorption isotherm data. Also, statistics predicted that the pseudo-second-order model is the optimum kinetic model among four applied kinetic models to closely describe the rate equation of the adsorption process. Thermodynamics viewed the adsorption as endothermic and feasible physical process. EDTA could release the sorbed Pb(II) ions from MCS@TiO2 with a recovery above 92% after three sorption-desorption cycles. The novel synthesized nanosorbent is evidenced to be an excellent solid phase extractor for Pb(II) ions from wastewaters.

Adsorption of Water and Ethanol in MFI-Type Zeolites

KAUST Repository

Zhang, Ke

2012-06-12

Water and ethanol vapor adsorption phenomena are investigated systematically on a series of MFI-type zeolites: silicalite-1 samples synthesized via both alkaline (OH -) and fluoride (F -) routes, and ZSM-5 samples with different Si/Al ratios as well as different charge-balancing cations. Full isotherms (0.05-0.95 activity) over the range 25-55 °C are presented, and the lowest total water uptake ever reported in the literature is shown for silicalite-1 made via a fluoride-mediated route wherein internal silanol defects are significantly reduced. At a water activity level of 0.95 (35 °C), the total water uptake by silicalite-1 (F -) was found to be 0.263 mmol/g, which was only 12.6%, 9.8%, and 3.3% of the capacity for silicalite-1 (OH -), H-ZSM-5 (Si/Al:140), and H-ZSM-5 (Si/Al:15), respectively, under the same conditions. While water adsorption shows distinct isotherms for different MFI-type zeolites due to the difference in the concentration, distribution, and types of hydrophilic sites, the ethanol adsorption isotherms present relatively comparable results because of the overall organophilic nature of the zeolite framework. Due to the dramatic differences in the sorption behavior with the different sorbate-sorbent pairs, different models are applied to correlate and analyze the sorption isotherms. An adsorption potential theory was used to fit the water adsorption isotherms on all MFI-type zeolite adsorbents studied. The Langmuir model and Sircar\\'s model are applied to describe ethanol adsorption on silicalite-1 and ZSM-5 samples, respectively. An ideal ethanol/water adsorption selectivity (α) was estimated for the fluoride-mediated silicalite-1. At 35 °C, α was estimated to be 36 for a 5 mol % ethanol solution in water increasing to 53 at an ethanol concentration of 1 mol %. The adsorption data demonstrate that silicalite-1 made via the fluoride-mediated route is a promising candidate for ethanol extraction from dilute ethanol-water solutions. © 2012

Modeling and Prediction of Soil Water Vapor Sorption Isotherms

DEFF Research Database (Denmark)

Arthur, Emmanuel; Tuller, Markus; Moldrup, Per

2015-01-01

Soil water vapor sorption isotherms describe the relationship between water activity (aw) and moisture content along adsorption and desorption paths. The isotherms are important for modeling numerous soil processes and are also used to estimate several soil (specific surface area, clay content.......93) for a wide range of soils; and (ii) develop and test regression models for estimating the isotherms from clay content. Preliminary results show reasonable fits of the majority of the investigated empirical and theoretical models to the measured data although some models were not capable to fit both sorption...... directions accurately. Evaluation of the developed prediction equations showed good estimation of the sorption/desorption isotherms for tested soils....

Adsorption of cadmium and copper in representative soils of Eastern Amazonia, Brazil

Directory of Open Access Journals (Sweden)

Deyvison Andrey Medrado Gonçalves

2016-10-01

Full Text Available Studies of heavy metals adsorption in soil play a key role in predicting environmental susceptibility to contamination by toxic elements. The objective of this study was to evaluate cadmium (Cd and copper (Cu adsorption in surface and subsurface soil. Samples of six soils: Xanthic Hapludox (XH1 and XH2, Typic Hapludox (TH, Typic Rhodudalf (TR, Typic Fluvaquent (TF, and Amazonian dark earths (ADE from Eastern Amazonian, Brazil. The soils were selected for chemical, physical and mineralogical characterization and to determine the adsorption by Langmuir and Freundlich isotherms. All soils characterized as kaolinitic, and among them, XH1 and XH2 showed the lowest fertility. The Langmuir and Freundlich isotherms revealed a higher Cu (H curve than Cd (L curve adsorption. Parameters of Langmuir and Freundlich isotherms indicate that soils TR, TF and ADE has the greatest capacity and affinity for metal adsorption. Correlation between the curve adsorption parameters and the soil attributes indicates that the pH, CEC, OM and MnO variables had the best influence on metal retention. The Langmuir and Freundlich isotherms satisfactorily described Cu and Cd soil adsorption, where TR, TF and ADE has a lower vulnerability to metal input to the environment. Besides the pH, CEC and OM the MnO had a significant effect on Cu and Cd adsorption in Amazon soils.

Monolayer Adsorption of Ar and Kr on Graphite: Theoretical Isotherms and Spreading Pressures

Science.gov (United States)

Mulero; Cuadros

1997-02-01

The validity of analytical equations for two-dimensional fluids in the prediction of monolayer adsorption isotherms and spreading pressures of rare gases on graphite is analyzed. The statistical mechanical theory of Steele is used to relate the properties of the adsorbed and two-dimensional fluids. In such theory the model of graphite is a perfectly flat surface, which means that only the first order contribution of the fluid-solid interactions are taken into account. Two analytical equations for two-dimensional Lennard-Jones fluids are used: one proposed by Reddy-O'Shea, based in the fit on pressure and potential energy computer simulated results, and other proposed by Cuadros-Mulero, based in the fit of the Helmholtz free energy calculated from computer simulated results of the radial distribution function. The theoretical results are compared with experimental results of Constabaris et al. (J. Chem. Phys. 37, 915 (1962)) for Ar and of Putnam and Fort (J. Phys. Chem. 79, 459 (1975)) for Kr. Good agreement is found using both equations in both cases.

Dubinin-Astakhov model for acetylene adsorption on metal-organic frameworks

International Nuclear Information System (INIS)

Cheng, Peifu; Hu, Yun Hang

2016-01-01

Graphical abstract: It was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model for C2H2 adsorption on metal-organic frameworks (MOFs), including MOF-5, ZIF-8, HKUST-1, and MIL-53. - Highlights: • Dubinin-Astakhov equation is demonstrated to be a general model for C_2H_2 adsorption on metal-organic frameworks (MOFs). • Surface areas obtained with Dubinin-Astakhov equation from C_2H_2 adsorption on MOFs are consistent with BET surface areas from N_2 adsorption. • C_2H_2 on MOF-5, ZIF-8, and MIL-53 is a physical adsorption, whereas its adsorption on HKUST-1 is due to a chemical bonding. - Abstract: Acetylene (C_2H_2) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C_2H_2 adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C_2H_2 adsorption on various MOFs has not been found. In this paper, it was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model to depict C_2H_2 adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C_2H_2 adsorption on those MOFs.

Valorization of two waste streams into activated carbon and studying its adsorption kinetics, equilibrium isotherms and thermodynamics for methylene blue removal

Directory of Open Access Journals (Sweden)

Zeid Abdullah AlOthman

2014-12-01

Full Text Available Wastes must be managed properly to avoid negative impacts that may result. Open burning of waste causes air pollution which is particularly hazardous. Flies, mosquitoes and rats are major problems in poorly managed surroundings. Uncollected wastes often cause unsanitary conditions and hinder the efforts to keep streets and open spaces in a clean and attractive condition. During final disposal methane is generated, it is much more effective than carbon dioxide as a greenhouse gas, leading to climate change. Therefore, this study describes the possible valorization of two waste streams into activated carbon (AC with added value due to copyrolysis. High efficiency activated carbon was prepared by the copyrolysis of palm stem waste and lubricating oil waste. The effects of the lubricating oil waste to palm stem ratio and the carbonization temperature on the yield and adsorption capacity of the activated carbon were investigated. The results indicated that the carbon yield depended strongly on both the carbonization temperature and the lubricating oil to palm stem ratio. The efficiency of the adsorption of methylene blue (MB onto the prepared carbons increased when the lubricating oil to palm stem ratio increased due to synergistic effect. The effects of pH, contact time, and the initial adsorbate concentration on the adsorption of methylene blue were investigated. The maximum adsorption capacity (128.89 mg/g of MB occurred at pH 8.0. The MB adsorption kinetics were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models. The results indicated that the adsorption of MB onto activated carbon is best described using a second order kinetic model. Adsorption data are well fitted with Langmuir and Freundlich isotherms. The thermodynamic parameters; ΔG°, ΔH° and ΔS° indicate that the adsorption is spontaneous and endothermic.

Kinetic and isotherm analyses for thorium (IV) adsorptive removal from aqueous solutions by modified magnetite nanoparticle using response surface methodology (RSM)

Energy Technology Data Exchange (ETDEWEB)

Karimi, Mohammad, E-mail: m.karimi407@alumni.ut.ac.ir [School of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box: 11365-4563, Tehran (Iran, Islamic Republic of); Milani, Saeid Alamdar [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 14893-836, Tehran (Iran, Islamic Republic of); Abolgashemi, Hossein [School of Chemical Engineering, College of Engineering, University of Tehran, P.O. Box: 11365-4563, Tehran (Iran, Islamic Republic of)

2016-10-15

In this study, the ability and the adsorption capacity of magnetite/aminopropyltriethoxysilane/glutaraldehyde (Fe{sub 3}O{sub 4}/APTES/GA) adsorbent were evaluated for the adsorption of thorium (IV) ions from aqueous solutions. The influence of the several variables such as pH (1–5), Th (IV) initial concentration (50–300 mg L{sup −1}) and adsorbent concentration (1–5 g L{sup −1}) on the Th (IV) adsorption were investigated by response surface methodology (RSM). The results showed that the highest absorption capacity (q) was 107.23 mg g{sup −1} with respect to pH = 4.5, initial concentration of 250 mg L{sup −1} and adsorbent concentration of 1 g L{sup −1} for 90 min. Modeling equilibrium sorption data with the Langmuir, Freundlich and Dubinin–Radushkevich models pointed out that the results were in good agreement with Langmuir model. The experimental kinetic data were well fitted to pseudo-second-order equation with R{sup 2} = 0.9739. Also thermodynamic parameters (ΔG{sup o}, ΔH{sup o}, ΔS{sup o}) declared that the Th (IV) adsorption was endothermic and spontaneous. - Highlights: • Thorium ions were removed from aqueous solutions by modified magnetite nanoparticle. • The effects of process variables on adsorption capacity were investigated by RSM. • Thermodynamic parameters showed that the adsorption was endothermic and spontaneous. • The equilibrium data for the adsorption of Thorium followed the Langmuir isotherm. • The experimental kinetic data were described by the pseudo-second-order equation.

ADSORPTION MALACHITE GREEN ON NATURAL ZEOLITE

OpenAIRE

Eko Ariyanto

2012-01-01

A natural zeolite was employed as adsorbent for reducing of malachite green from aqueous solution. A batch system was applied to study the adsorption of malachite green in single system on natural zeolite. The adsorption studies indicate that malachite green in single component system follows the second-order kinetics and the adsorption is diffusion process with two stages for malachite green. Malachite green adsorption isotherm follows the Langmuir model.

Adsorption of lysozyme unto silica and polystyrene surfaces in ...

African Journals Online (AJOL)

user

2011-04-11

Apr 11, 2011 ... surfaces were well fitted by the Langmuir adsorption isotherm model with maximum adsorption .... following reasons: (1) Lysozyme is a globular protein with ... vigorously for 1 h to attain equilibrium adsorption and allowed to.

Volatile organic compounds adsorption using different types of adsorbent

Directory of Open Access Journals (Sweden)

Pimanmes Chanayotha

2014-09-01

Full Text Available Adsorbents were synthesized from coconut shell, coal and coke by pyrolysis followed by chemical activation process. These synthesized materials were used as adsorbents in adsorption test to determine the amount of volatile organic compounds (VOCs namely, 2-Hydroxyethyl methacrylate (HEMA, Octamethylcyclotetrasiloxane and Alkanes standard solution (C8-C20. The adsorption capacities of both synthesized adsorbents and commercial grade adsorbents (Carbotrap™ B and Carbotrap™ C were also compared. It was found that adsorbent A402, which was produced from coconut shell, activated with 40% (wt. potassium hydroxide and at activating temperature of 800°C for 1 hr, could adsorb higher amount of both HEMA and Octamethylcyclotetrasiloxane than other synthesized adsorbents. The maximum adsorption capacity of adsorbent A402 in adsorbing HEMA and Octamethylcyclotetrasiloxane were 77.87% and 50.82% respectively. These adsorption capabilities were 79.73% and 70.07% of the adsorption capacity of the commercial adsorbent Carbotrap™ B respectively. All three types of the synthesized adsorbent (A402, C302, C402 showed the capability to adsorb alkanes standard solution through the range of C8-C20 . However, their adsorption capacities were high in a specific range of C10-C11. The result from the isotherm plot was indicated that surface adsorption of synthesized adsorbent was isotherm type I while the surface adsorption of commercial adsorbent was isotherm type III.

ADSORPTION OF STRONTIUM IONS FROM WATER ON MODIFIED ACTIVATED CARBONS

Directory of Open Access Journals (Sweden)

Mihai Ciobanu

2016-12-01

Full Text Available Adsorption of strontium ions from aqueous solutions on active carbons CAN-7 and oxidized CAN-8 has been studied. It has been found that allure of the adsorption isotherms for both studied active carbons are practically identical. Studies have shown that the adsorption isotherms for strontium ions from aqueous solutions are well described by the Langmuir and Dubinin-Radushkevich equations, respectively. The surface heterogeneity of activated carbons CAN-7 and oxidized CAN-8 has been assessed by using Freundlich equation.

Synthesis of hierarchical Ni(OH)(2) and NiO nanosheets and their adsorption kinetics and isotherms to Congo red in water.

Science.gov (United States)

Cheng, Bei; Le, Yao; Cai, Weiquan; Yu, Jiaguo

2011-01-30

Ni(OH)(2) and NiO nanosheets with hierarchical porous structures were synthesized by a simple chemical precipitation method using nickel chloride as precursors and urea as precipitating agent. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption isotherms. Adsorption of Congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The pore structure analyses indicate that Ni(OH)(2) and NiO nanosheets are composed of at least three levels of hierarchical porous organization: small mesopores (ca. 3-5 nm), large mesopores (ca. 10-50 nm) and macropores (100-500 nm). The equilibrium adsorption data of CR on the as-prepared samples were analyzed by Langmuir and Freundlich models, suggesting that the Langmuir model provides the better correlation of the experimental data. The adsorption capacities for removal of CR was determined using the Langmuir equation and found to be 82.9, 151.7 and 39.7 mg/g for Ni(OH)(2) nanosheets, NiO nanosheets and NiO nanoparticles, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The as-prepared Ni(OH)(2) and NiO nanosheets are found to be effective adsorbents for the removal of Congo red pollutant from wastewater as a result of their unique hierarchical porous structures and high specific surface areas. Copyright © 2010 Elsevier B.V. All rights reserved.

Synthesis of hierarchical Ni(OH)2 and NiO nanosheets and their adsorption kinetics and isotherms to Congo red in water

International Nuclear Information System (INIS)

Cheng Bei; Le Yao; Cai Weiquan; Yu Jiaguo

2011-01-01

Ni(OH) 2 and NiO nanosheets with hierarchical porous structures were synthesized by a simple chemical precipitation method using nickel chloride as precursors and urea as precipitating agent. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption isotherms. Adsorption of Congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The pore structure analyses indicate that Ni(OH) 2 and NiO nanosheets are composed of at least three levels of hierarchical porous organization: small mesopores (ca. 3-5 nm), large mesopores (ca. 10-50 nm) and macropores (100-500 nm). The equilibrium adsorption data of CR on the as-prepared samples were analyzed by Langmuir and Freundlich models, suggesting that the Langmuir model provides the better correlation of the experimental data. The adsorption capacities for removal of CR was determined using the Langmuir equation and found to be 82.9, 151.7 and 39.7 mg/g for Ni(OH) 2 nanosheets, NiO nanosheets and NiO nanoparticles, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The as-prepared Ni(OH) 2 and NiO nanosheets are found to be effective adsorbents for the removal of Congo red pollutant from wastewater as a result of their unique hierarchical porous structures and high specific surface areas.

Evaluation of theoretical and empirical water vapor sorption isotherm models for soils

DEFF Research Database (Denmark)

Arthur, Emmanuel; Tuller, Markus; Moldrup, Per

2016-01-01

sorption isotherms of building materials, food, and other industrial products, knowledge about the 24 applicability of these functions for soils is noticeably lacking. We present validation of nine models for characterizing adsorption/desorption isotherms for a water activity range from 0.03 to 0...

Thermodynamic properties and adsorption behaviour of hydrogel nanocomposites for cadmium removal from mine effluents

CSIR Research Space (South Africa)

Fosso-Kankeu, E

2017-04-01

Full Text Available followed the pseudo-second-order rate equation, whereas, the adsorption isotherm followed both the Freundlich and Langmuir isotherm models. The thermodynamics studies revealed that the adsorption processes were spontaneous and endothermic in nature...

Direct measurements of adsorption heats of hydrogen on nano-porous carbons

International Nuclear Information System (INIS)

Akihiko Matsumoto; Kazumasa Yamamoto; Tomoyuki Miyata

2005-01-01

Since a exciting report of hydrogen storage in single-walled carbon nano-tubes by Dillon and his colleagues, nano-porous carbon materials, such as carbon nano-tubes, carbon nano-horns and micro-porous activated carbon, have attracted considerable attention as hydrogen storage materials. Adsorption plays a predominating role in the hydrogen storage process on solid surfaces. The adsorption is a spontaneous process, which is caused by interaction between gas molecules and surface, hence, it is always exothermic process and observed as adsorption heats. For this reason, direct measurement of the adsorption heats by adsorption micro-calorimetry would provide quantitative information on the strength of adsorption interaction and the adsorption mechanism. However, the adsorption amounts of hydrogen on carbon materials are far less than those of condensable vapors near room temperature due to low critical temperature of hydrogen (33.2 K), therefore, the adsorption heats can not be determined accurately at conventional measurement conditions near room temperature and the atmospheric pressure. This contribution reports the calorimetric characterization of hydrogen adsorption on nano-porous carbon materials at low temperature and high-pressure conditions. The high-pressure adsorption apparatus consists of a volumetric adsorption line connected to a twin-conduction type microcalorimeter. Activated carbon fibers (ACF, Ad'all Co.) of different micro-pore sizes (Table 1) were used as model adsorbents. Each ACF has slit-shaped micropores of uniform size. The adsorption isotherms and differential heats of adsorption at high-pressure region from 0 to 10 MPa were simultaneously measured at isothermal condition from 203 to 298 K. The adsorption isotherms on ACF were of Henry type regardless of adsorption temperature and pore width; the uptakes increased linearly with equilibrium pressure. The adsorption isotherm at lower sorption temperature tended to show higher sorptivity. The

Microwave synthesis and adsorption performance of a novel crosslinked starch microsphere

Energy Technology Data Exchange (ETDEWEB)

Lin, Qintie, E-mail: qintlin@163.com [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China); National Engineering Laboratory for Rice and By-Product Deep Processing, Center South University of Forestry and Technology, Changsha 41004 (China); Pan, Jianxin [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Lin, Qinlu [National Engineering Laboratory for Rice and By-Product Deep Processing, Center South University of Forestry and Technology, Changsha 41004 (China); Liu, Qianjun [School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006 (China)

2013-12-15

Highlights: • CSM was synthesized in a microwave-assisted inversed emulsion system. • The adsorption of methyl violet on CSM was exothermic and spontaneous. • The adsorption process followed the pseudo-second-order kinetics. • The isothermal data obeyed the Langmuir model. • pH variations did not significantly affect the adsorption of methyl violet onto CSM. -- Abstract: A new crosslinked starch microsphere (CSM) was synthesized in a microwave-assisted inversed emulsion system with soluble starch (ST) as a raw material, MBAA as a crosslinker, and K{sub 2}S{sub 2}O{sub 8}–NaHSO{sub 3} as an initiator. The synthesized starch microsphere was characterized and examined by scanning electron microscope (SEM), FTIR spectroscopy and adsorption isotherms of N{sub 2} at 77 K. Adsorption performance was investigated in methyl violet solution. The results showed that the maximum adsorption capacity for MV was 99.3 mg/g at 298 K, and the adsorption fitted pseudo-second-order kinetic model well with correlation coefficients greater than 0.99. The isothermal data obeyed the Langmuir model better compared to Freundlich model and Tempkin model, and the adsorption was exothermic and spontaneous. pH variations (2.0–10.0) did not significantly affect the adsorption of MV onto CSM.

A Study on Astrazon Black AFDL Dye Adsorption onto Vietnamese Diatomite

Directory of Open Access Journals (Sweden)

Bui Hai Dang Son

2016-01-01

Full Text Available In the present paper, the adsorption of Astrazon Black AFDL dye onto Vietnamese diatomite has been demonstrated. The diatomite was characterized by XRD, SEM, TEM, EDS, and nitrogen adsorption/desorption isotherms. The results show that diatomite mainly constituted centric type frustules characterized by pores as discs or as cylindrical shapes. The adsorption kinetics and isotherms of dye onto Vietnam diatomite were investigated. The experimental data were fitted well to both Freundlich and Langmuir in the initial concentration range of 400–1400 mg L−1. The average value of maximum adsorption capacity, qm, calculated from Freundlich equation is statistically similar to the average value of maximum monolayer adsorption capacity calculated from Langmuir equation. The thermodynamic parameters evaluated from the temperature dependent on adsorption isotherms in the range of 303–343 K show that the adsorption process was spontaneous and endothermic. The Webber and pseudo-first/second-order kinetic models were used to analyze the mechanism of adsorption. The piecewise linear regression and Akaike’s Information Criterion were used to analyze experimental data. The results show that the dye adsorption onto diatomite was film diffusion controlled and the goodness of fit of experimental data for kinetics modes was dependent on the initial concentration.

Microwave Irradiation Assisted Preparation of Chitosan Composite Microsphere for Dye Adsorption

Directory of Open Access Journals (Sweden)

Xiaoyu Chen

2017-01-01

Full Text Available Chitosan-activated carbon composite microspheres were prepared by emulsion cross-linking method and its adsorption properties for methyl orange were studied. Chitosan solution was mixed with activated carbon powder and then chitosan was cross-linked by epichlorohydrin under microwave irradiation. SEM photos show that the composite microspheres have diameters of 200–400 μm and activated carbon powder dispersed on the surface of composite microsphere. FTIR spectrum indicates chitosan is successfully cross-linked. Microwave irradiation can effectively shorten the cross-linking time. Composite microspheres have enhanced dye adsorption capacity for methyl orange compared to chitosan microspheres. Kinetic studies showed that the adsorption followed a pseudo-second-order model. Isotherm studies show that the isotherm adsorption equilibrium is better described by Freundlich isotherm. Regeneration results show that adsorption capacity of composite microsphere decreased about 5.51% after being reused for three times. These results indicated that chitosan-activated carbon composite microsphere has potential application in the removal of dye from wastewaters.

Adsorption of Copper Ion using Acrylic Acid-g-Polyaniline in Aqueous Solution

Science.gov (United States)

Kamarudin, Sabariah; Mohammad, Masita

2018-04-01

A conductive polymer, polyaniline (PANI) has unique electrical behaviour, stable in the environment, easy synthesis and have wide application in various fields. Modification of PANI in order to improve its adsorption capacity has been done. In this study, the polyaniline-grafted acrylic acid has been prepared and followed by adsorption of copper ion in aqueous solution. Acrylic acid, PANI and acrylic acid-g-polyaniline (Aag-PANI) were characterized by FTIR and SEM to determine its characteristic. The adsorption capacity was investigated to study the removal capacity of Cu ion from aqueous solution. Two parameters were selected which are pH (2, 4 and 6) and initial metal ion concentration (50 mg/L, 100 mg/L and 200 mg/L). The maximum adsorption capacity for PANI and Aag-PANI are 1.7 mg/g and 64.6 mg/g, respectively, at an initial concentration of 100 mg/L. The Langmuir adsorption isotherm model and Freundlich adsorption isotherm model have been used and showed that it is heterolayer adsorption by follows the Freundlich isotherm model.

Adsorption properties of stearic acid onto untreated kaolinite | Sari ...

African Journals Online (AJOL)

The focus of the study is to investigate adsorption property and determine thermodynamic parameters for the adsorption of stearic acid onto untreated kaolinite at the temperatures of 25, 35 and 45 oC. The equilibrium adsorption isotherms were analyzed by linear Langmuir and Freundlich models. Adsorption experiments ...

ADSORPTION MALACHITE GREEN ON NATURAL ZEOLITE

Directory of Open Access Journals (Sweden)

Eko Ariyanto

2012-02-01

Full Text Available A natural zeolite was employed as adsorbent for reducing of malachite green from aqueous solution. A batch system was applied to study the adsorption of malachite green in single system on natural zeolite. The adsorption studies indicate that malachite green in single component system follows the second-order kinetics and the adsorption is diffusion process with two stages for malachite green. Malachite green adsorption isotherm follows the Langmuir model.

Fast gas adsorption measurements for complicated adsorption mechanisms

NARCIS (Netherlands)

Robens, E.; Poulis, J.A.; Massen, C.H.

2000-01-01

Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this

Single and binary adsorption of Cd (Ⅱ) and Zn (Ⅱ) ions from aqueous solutions onto bottom ash

Energy Technology Data Exchange (ETDEWEB)

Sukpreabprom, Hatairat; Arqueropanyo, Orn-anong; Naksata, Wimol; Janhom, Sorapong [Chiang Mai University, Chiang Mai (Thailand); Sooksamiti, Ponlayuth [The Office of Primary Industries and Mines Region 3, Chiang Mai (Thailand)

2015-05-15

Bottom ash, a waste obtained from coal-burning power plant, was used as a low cost adsorbent for the removal of Cd (Ⅱ) and Zn (Ⅱ) ions from single and binary systems in batch experiments. The results of adsorption capacity showed that bottom ash could be considered as a potential adsorbent. The uptake of Zn (Ⅱ) ion was greater than that of Cd (Ⅱ) ion. For single adsorption, based on the correlation coefficient (R{sup 2}) values, both Langmuir and Freundlich isotherms suitably described the adsorption equilibrium data in the initial metal ion concentration range of 10-50 mg/L. The multicomponent isotherms, including the extended Langmuir and IAST-Freundlich isotherms, were used to predict the binary adsorption of Cd (Ⅱ) and Zn (Ⅱ) ions. Furthermore, the appropriate multicomponent isotherm was investigated by minimizing the average relative error (ARE) function. It should be confirmed that the extended Langmuir isotherm fitted the binary adsorption equilibrium data satisfactorily.

Error analysis of equilibrium studies for the almond shell activated carbon adsorption of Cr(VI) from aqueous solutions

International Nuclear Information System (INIS)

Demirbas, E.; Kobya, M.; Konukman, A.E.S.

2008-01-01

In this study, the preparation of activated carbon from almond shell with H 2 SO 4 activation and its ability to remove toxic hexavalent chromium from aqueous solutions are reported. The influences of several operating parameters such as pH, particle size and temperature on the adsorption capacity were investigated. Adsorption of Cr(VI) is found to be highly pH, particle size and temperature dependent. Four adsorption isotherm models namely, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich were used to analyze the equilibrium data. The Langmuir isotherm provided the best correlation for Cr(VI) onto the almond shell activated carbon (ASC). Adsorption capacity was calculated from the Langmuir isotherm as 190.3 mg/g at 323 K. Thermodynamic parameters were evaluated and the adsorption was endothermic showing monolayer adsorption of Cr(VI). Five error functions were used to treat the equilibrium data using non-linear optimization techniques for evaluating the fit of the isotherm equations. The highest correlation for the isotherm equations in this system was obtained for the Freundlich isotherm. ASC is found to be inexpensive and effective adsorbent for removal of Cr(VI) from aqueous solutions

Modeling of boldine alkaloid adsorption onto pure and propyl-sulfonic acid-modified mesoporous silicas. A comparative study

Energy Technology Data Exchange (ETDEWEB)

Geszke-Moritz, Małgorzata, E-mail: Malgorzata.Geszke-Moritz@amu.edu.pl [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Moritz, Michał, E-mail: michal.moritz@put.poznan.pl [Poznan University of Technology, Faculty of Chemical Technology, Institute of Chemistry and Technical Electrochemistry, Berdychowo 4, 60-965 Poznań (Poland)

2016-12-01

The present study deals with the adsorption of boldine onto pure and propyl-sulfonic acid-functionalized SBA-15, SBA-16 and mesocellular foam (MCF) materials. Siliceous adsorbents were characterized by nitrogen sorption analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric analysis. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherms. Moreover, the Dubinin-Radushkevich and Dubinin-Astakhov isotherm models based on the Polanyi adsorption potential were employed. The latter was calculated using two alternative formulas including solubility-normalized (S-model) and empirical C-model. In order to find the best-fit isotherm, both linear regression and nonlinear fitting analysis were carried out. The Dubinin-Astakhov (S-model) isotherm revealed the best fit to the experimental points for adsorption of boldine onto pure mesoporous materials using both linear and nonlinear fitting analysis. Meanwhile, the process of boldine sorption onto modified silicas was described the best by the Langmuir and Temkin isotherms using linear regression and nonlinear fitting analysis, respectively. The values of adsorption energy (below 8 kJ/mol) indicate the physical nature of boldine adsorption onto unmodified silicas whereas the ionic interactions seem to be the main force of alkaloid adsorption onto functionalized sorbents (energy of adsorption above 8 kJ/mol). - Graphical abstract: Modeling of boldine adsorption onto unmodified and propyl-sulfonic acid-modified mesoporous adsorbents. - Highlights: • The process of boldine adsorption onto SBA-15, SBA-16 and MCF silicas was examined. • Siliceous adsorbents were functionalized with propyl-sulfonic acid groups. • The equilibrium adsorption data were analyzed using several isotherm models. • Both linear regression and nonlinear fitting analysis were carried out. �

Kinetic and isotherm studies of bisphenol A adsorption onto orange albedo(Citrus sinensis): Sorption mechanisms based on the main albedo components vitamin C, flavones glycosides and carotenoids.

Science.gov (United States)

Kamgaing, Theophile; Doungmo, Giscard; Melataguia Tchieno, Francis Merlin; Gouoko Kouonang, Jimmy Julio; Mbadcam, Ketcha Joseph

2017-07-03

Orange albedo and its adsorption capacity towards bisphenol A (BPA) were studied. Adsorption experiments were conducted in batch mode at 25-55°C. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared (FTIR) spectroscopy were used to characterise the biosorbent. The effects of various parameters including adsorption time, equilibrium pH, adsorbent dosage and initial adsorbate concentration were investigated. The optimum contact time and pH for the removal of BPA were 60 min and 2, respectively. It was found that the adsorption isotherms best matched the Freundlich model, the adsorption of BPA being multilayer and that of the albedo surface heterogeneous. From the kinetic studies, it was found that the removal of BPA best matched the pseudo-second order kinetic model. An adsorption mechanism based on the albedo surface molecules is proposed and gives a good account of π-π interactions and hydrogen bonding. Orange albedo, with a maximum BPA loading capacity of 82.36 mg g -1 (significantly higher than that of most agricultural residues), is a good candidate for BPA adsorption in aqueous media.

Testing isotherm models and recovering empirical relationships for adsorption in microporous carbons using virtual carbon models and grand canonical Monte Carlo simulations

International Nuclear Information System (INIS)

Terzyk, Artur P; Furmaniak, Sylwester; Gauden, Piotr A; Harris, Peter J F; Wloch, Jerzy

2008-01-01

Using the plausible model of activated carbon proposed by Harris and co-workers and grand canonical Monte Carlo simulations, we study the applicability of standard methods for describing adsorption data on microporous carbons widely used in adsorption science. Two carbon structures are studied, one with a small distribution of micropores in the range up to 1 nm, and the other with micropores covering a wide range of porosity. For both structures, adsorption isotherms of noble gases (from Ne to Xe), carbon tetrachloride and benzene are simulated. The data obtained are considered in terms of Dubinin-Radushkevich plots. Moreover, for benzene and carbon tetrachloride the temperature invariance of the characteristic curve is also studied. We show that using simulated data some empirical relationships obtained from experiment can be successfully recovered. Next we test the applicability of Dubinin's related models including the Dubinin-Izotova, Dubinin-Radushkevich-Stoeckli, and Jaroniec-Choma equations. The results obtained demonstrate the limits and applications of the models studied in the field of carbon porosity characterization

Adsorption of a textile dye from aqueous solutions by carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Machado, Fernando M.; Bergmann, Carlos P., E-mail: fernando.machado@hotmail.com.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Dept. de Materiais; Lima, Eder C.; Adebayo, Matthew A. [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Inst. de Quimica; Fagan, Solange B. [Centro Universitario Franciscano (UNIFRA), Santa Maria, RS (Brazil). Area de Ciencias Tecnologicas

2014-08-15

Multi-walled and single-walled carbon nanotubes were used as adsorbents for the removal of Reactive Blue 4 textile dye from aqueous solutions. The adsorbents were characterised using Raman spectroscopy, N{sub 2} adsorption/desorption isotherms and scanning and transmission electron microscopy. The effects of pH, agitation time and temperature on adsorption capacity were studied. In the acidic pH region, the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium isotherms at 298-323 K was fixed at 4 hours for both adsorbents. For Reactive Blue 4 dye, Liu isotherm model gave the best fit for the equilibrium data. The maximum sorption capacity for adsorption of the dye occurred at 323 K, attaining values of 502.5 and 567.7 mg g{sup -1} for MWCNT and SWCNT, respectively. (author)

Adsorption of radioactive I2 gas onto fly-ash aerosol

International Nuclear Information System (INIS)

Noguchi, Hiroshi; Murata, Mikio; Suzuki, Katsumi.

1988-01-01

The adsorption of radioactive elemental iodine (I 2 ) gas onto fly-ash aerosol has been studied to provide basic data for the realistic and precise assessment of dose to the general public from radioiodine released from nuclear facilities. A mixture of fly-ash aerosol and 131 I 2 gas was passed through a cylindrical glass vessel so that particulate iodine was formed by adsorption of I 2 onto aerosol. Then the concentrations of I 2 and particulate iodine were measured. It was found that the adsorption reached an equilibrium state between 5 and 12 min and that the proportion of iodine which was adsorbed on the aerosol decreased with increasing initial I 2 concentration ranging over 10 -13 to 10 -9 g/cm 3 . The adsorption isotherm of the aerosol for I 2 gas approximately followed Freundlich isotherm. Using the adsorption isotherm, a theoretical equation was derived to explain the adsorption on the basis of FUCHS' theory on the evaporation of droplets. A sticking probability in the equation decreased with increasing adsorbed amount. The calculated results were in good agreement with the experimental ones. (author)

Dubinin-Astakhov model for acetylene adsorption on metal-organic frameworks

Energy Technology Data Exchange (ETDEWEB)

Cheng, Peifu; Hu, Yun Hang, E-mail: yunhangh@mtu.edu

2016-07-30

Graphical abstract: It was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model for C2H2 adsorption on metal-organic frameworks (MOFs), including MOF-5, ZIF-8, HKUST-1, and MIL-53. - Highlights: • Dubinin-Astakhov equation is demonstrated to be a general model for C{sub 2}H{sub 2} adsorption on metal-organic frameworks (MOFs). • Surface areas obtained with Dubinin-Astakhov equation from C{sub 2}H{sub 2} adsorption on MOFs are consistent with BET surface areas from N{sub 2} adsorption. • C{sub 2}H{sub 2} on MOF-5, ZIF-8, and MIL-53 is a physical adsorption, whereas its adsorption on HKUST-1 is due to a chemical bonding. - Abstract: Acetylene (C{sub 2}H{sub 2}) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C{sub 2}H{sub 2} adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C{sub 2}H{sub 2} adsorption on various MOFs has not been found. In this paper, it was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model to depict C{sub 2}H{sub 2} adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C{sub 2}H{sub 2} adsorption on those MOFs.

Competitive Adsorption of Chloroform and Bromoform Using ...

African Journals Online (AJOL)

The results obtained were checked with Freundlich adsorption isotherm model. This model expresses well adsorption of one THM species in the presence of another with R2 > 0.95. Based on the model, adsorption capacity of Calgon F200 and Norit GCN1240 were found higher for bromoform than chloroform. Calgon F200 ...

Adsorption characteristics of water vapor on ferroaluminophosphate for desalination cycle

KAUST Repository

Kim, Youngdeuk

2014-07-01

The adsorption characteristics of microporous ferroaluminophosphate adsorbent (FAM-Z01, Mitsubishi Plastics) are evaluated for possible application in adsorption desalination and cooling (AD) cycles. A particular interest is its water vapor uptake behavior at assorted adsorption temperatures and pressures whilst comparing them to the commercial silica gels of AD plants. The surface characteristics are first carried out using N2 gas adsorption followed by the water vapor uptake analysis for temperature ranging from 20°C to 80°C. We propose a hybrid isotherm model, composing of the Henry and the Sips isotherms, which can be integrated to satisfactorily fit the experimental data of water adsorption on the FAM-Z01. The hybrid model is selected to fit the unusual isotherm shapes, that is, a low adsorption in the initial section and followed by a rapid vapor uptake leading to a likely micropore volume filling by hydrogen bonding and cooperative interaction in micropores. It is shown that the equilibrium adsorption capacity of FAM-Z01 can be up to 5 folds higher than that of conventional silica gels. Owing to the quantum increase in the adsorbate uptake, the FAM-Z01 has the potential to significantly reduce the footprint of an existing AD plant for the same output capacity. © 2014 Elsevier B.V.

Adsorption of dodecylamine hydrochloride on graphene oxide in water

Directory of Open Access Journals (Sweden)

Peng Chen

Full Text Available Cationic surfactants in water are difficult to be degraded, leading to serious water pollution. In this work, graphene oxide (GO was used as an adsorbent for removing Dodecylamine Hydrochloride (DACl, a representative cationic surfactant. X-ray diffraction (XRD, FT-IR spectroscopy and atomic force microscope (AFM were used to characterize the prepared GO. The adsorption of DACl on GO have been investigated through measurements of adsorption capacity, zeta potential, FTIR, and X-ray photoelectron spectroscopy (XPS. The experimental results have shown that the adsorption kinetics could be described as a rate-limiting pseudo second-order process, and the adsorption isotherm agreed well with the Freundlich model. GO was a good adsorbent for DACl removal, compared with coal fly ash and powdered activated carbon. The adsorption process was endothermic, and could be attributed to electrostatic interaction and hydrogen bonding between DACl and GO. Keywords: Graphene oxide, Dodecylamine hydrochloride, Adsorption isotherm, Adsorption mechanisms

Effect of heat treatment on CO2 adsorption of KOH-activated graphite nanofibers.

Science.gov (United States)

Meng, Long-Yue; Park, Soo-Jin

2010-12-15

In this work, graphite nanofibers (GNFs) were successfully expanded intercalating KOH followed by heat treatment in the temperature range of 700-1000 °C. The aim was to improve the CO(2) adsorption capacity of the GNFs by increasing the porosity of GNFs. The effects of heat treatment on the pore structures of GNFs were investigated by N(2) full isotherms, XRD, SEM, and TEM. The CO(2) adsorption capacity was measured by CO(2) isothermal adsorption at 25 °C and 1 atm. From the results, it was found that the activation temperature had a major influence on CO(2) adsorption capacity and textural properties of GNFs. The specific surface area, total pore volume, and mesopore volume of the GNFs increased after heat treatment. The CO(2) adsorption isotherms showed that G-900 exhibited the best CO(2) adsorption capacity with 59.2 mg/g. Copyright © 2010 Elsevier Inc. All rights reserved.

Adsorption of Organophosphate Pesticide Dimethoate on Gold Nanospheres and Nanorods

Directory of Open Access Journals (Sweden)

Tatjana Momić

2016-01-01

Full Text Available Organophosphorus pesticide dimethoate was adsorbed onto gold nanospheres and nanorods in aqueous solution using batch technique. Adsorption of dimethoate onto gold nanoparticles was confirmed by UV-Vis spectrophotometry, TEM, AFM, and FTIR analysis. The adsorption of nanospheres resulted in aggregation which was not the case with nanorods. Nanoparticles adsorption features were characterized using Langmuir and Freundlich isotherm models. The Langmuir adsorption isotherm was found to have the best fit to the experimental data for both types of nanoparticles. Adsorption capacity detected for nanospheres is 456 mg/g and for nanorods is 57.1 mg/g. Also, nanoparticles were successfully used for dimethoate removal from spiked drinking water while nanospheres were shown to be more efficient than nanorods.

Characteristics of selective fluoride adsorption by biocarbon-Mg/Al layered double hydroxides composites from protein solutions: kinetics and equilibrium isotherms study.

Science.gov (United States)

Ma, Wei; Lv, Tengfei; Song, Xiaoyan; Cheng, Zihong; Duan, Shibo; Xin, Gang; Liu, Fujun; Pan, Decong

2014-03-15

In the study, two novel applied biocarbon-Mg/Al layered double hydroxides composites (CPLDH and CPLDH-Ca) were successfully prepared and characterized by TEM, ICP-AES, XFS, EDS, FTIR, XRD, BET and pHpzc. The fluoride removal efficiency (RF) and protein recovery ratio (RP) of the adsorbents were studied in protein systems of lysozyme (LSZ) and bovine serum albumin (BSA). The results showed that the CPLDH-Ca presented remarkable performance for selective fluoride removal from protein solution. It reached the maximum RF of 92.1% and 94.8% at the CPLDH-Ca dose of 2.0g/L in LSZ and BSA system, respectively. The RP in both systems of LSZ and BSA were more than 90%. Additionally, the RP of CPLDH-Ca increased with the increase of ionic strengths, and it almost can be 100% with more than 93% RF. Fluoride adsorption by the CPLDH-Ca with different initial fluoride concentrations was found to obey the mixed surface reaction and diffusion controlled adsorption kinetic model, and the overall reaction rate is probably controlled by intra-particle diffusion, boundary layer diffusion and reaction process. The adsorption isotherms of fluoride in BSA system fit the Langmuir-Freundlich model well. The BSA has synergistic effect on fluoride adsorption and the degree increased with the increase of the initial BSA concentration. Copyright © 2014 Elsevier B.V. All rights reserved.

Batch kinetics, isotherm and thermodynamic studies of adsorption of strontium from aqueous solutions onto low cost rice-straw based carbons.

Directory of Open Access Journals (Sweden)

S. M. Yakout

2010-09-01

Full Text Available Present study explored the feasibility of using waste rice-straw based carbons as adsorbent for the removal of strontium under different experimental conditions. The batch sorption is studied with respect to solute concentration (2.8 - 110 mg/L, contact time, adsorbent dose (2.5 - 20 g/L and solution temperature (25 - 55oC. The Langmuir and Dubinin-Radushkevich adsorption models were applied to experimental equilibrium data and isotherm constants were calculated using linear regression analysis. A comparison of kinetic models applied to the adsorption of strontium on rice-straw carbon was evaluated for the pseudo-second-order, Elovich, intraparticle diffusion and Bangham’s kinetics models. The experimental data fitted very well the pseudosecond-order kinetic model and also followed by intra-particle diffusion model, whereas diffusion is not only the rate-controlling step. The results show that the sorption capacity increases with an increase in solution temperature from 25 to 55 oC. The thermodynamics parameters were evaluated. The positive value of ΔH (40.93 kJ indicated that the adsorption of strontium onto RS1 carbon was endothermic, which result was supported by the increasing adsorption of strontium with temperature. The positive value of ΔS (121.8 kJ/mol reflects good affinity of strontium ions towards the rice-straw based carbons. The results have establishedgood potentiality for the carbons particles to be used as a sorbent for the removal of strontium from wastewater.

Adsorption of homogeneous catalysts over functionalized silica adsorbents: Modelling of the competitive adsorption isotherms

NARCIS (Netherlands)

Djekic, T.; van der Ham, Aloysius G.J.; Bosch, H.; de Haan, A.B.

2007-01-01

The reverse flow adsorption (RFA) was proposed as a novel concept for the recovery of homogeneous catalysts. For the modelling of the RFA process it is important to have a good description of the adsorption of various complex species present in the solution. Therefore the goal of this paper is to

Adsorption of homogeneous catalysts over functionalized silica adsorbents : modelling of the competitive adsorption isotherms

NARCIS (Netherlands)

Djekic, T.; Ham, van der A.G.J.; Bosch, Hans; Haan, de A.B.

2007-01-01

The reverse flow adsorption (RFA) was proposed as a novel concept for the recovery of homogeneous catalysts. For the modelling of the RFA process it is important to have a good description of the adsorption of various complex species present in the solution. Therefore the goal of this paper is to

Co-adsorption of Trichloroethylene and Arsenate by Iron-Impregnated Granular Activated Carbon.

Science.gov (United States)

Deng, Baolin; Kim, Eun-Sik

2016-05-01

Co-adsorption of trichloroethylene (TCE) and arsenate [As(V)] was investigated using modified granular activated carbons (GAC): untreated, sodium hypochlorite-treated (NaClO-GAC), and NaClO with iron-treated GAC (NaClO/Fe-GAC). Batch experiments of single- [TCE or As(V)] and binary- [TCE and As(V)] components solutions are evaluated through Langmuir and Freundlich isotherm models and adsorption kinetic tests. In the single-component system, the adsorption capacity of As(V) was increased by the NaClO-GAC and the NaClO/Fe-GAC. The untreated GAC showed a low adsorption capacity for As(V). Adsorption of TCE by the NaClO/Fe-GAC was maximized, with an increased Freundlich constant. Removal of TCE in the binary-component system was decreased 15% by the untreated GAC, and NaClO- and NaClO/Fe-GAC showed similar efficiency to the single-component system because of the different chemical status of the GAC surfaces. Results of the adsorption isotherms of As(V) in the binary-component system were similar to adsorption isotherms of the single-component system. The adsorption affinities of single- and binary-component systems corresponded with electron transfer, competitive adsorption, and physicochemical properties.

Study of adsorption properties of impregnated charcoal for airborne iodine and methyl iodide

International Nuclear Information System (INIS)

Qi-dong, L.; Sui-yuang, H.

1985-01-01

The adsorption characteristics of airborne radioiodine and methyl iodide on impregnated charcoal were investigated. The activated charcoal tested was made from home-made oil-palm shells, and KI and TEDA were used as impregnants. A new technique was used to plot the dynamic partial adsorption isotherm at challenge concentrations (concentration range of iodine: 1-20 ppm v/v). Some adsorption properties of the impregnated charcoal were estimated with the dynamic partial adsorption isotherm. The dependences of the adsorption capacity and penetration behavior for airborne iodine and methyl iodide on the ambient conditions (temperature, relative humidity, and superficial velocity) were studied

Removal of metal ions from water using nanohydrogel tragacanth gum-g-polyamidoxime: isotherm and kinetic study.

Science.gov (United States)

Masoumi, Arameh; Ghaemy, Mousa

2014-08-08

A new biosorbent was prepared by grafting polyacrylonitrile onto iranian tragacanth gum (ITG), a naturally and abundantly available polysaccharide, and subsequent amidoximation in the presence of hydroxylamine hydrochloride. This nanohydrogel with amidoxime functional groups [C(NH2)NOH], named polyamidoxime-g-tragacanth (ITG-g-PAO), was characterized and used for the removal of metal ions from aqueous solution. The effect of pH, agitation time, concentration of adsorbate and amount of adsorbent on the extent of adsorption was investigated. The experimental data were analyzed by four isotherms and kinetics equations, and the results were fitted well with the Temkin isotherm and pseudo-second-order model. The maximum adsorption capacities (Qm) of ITG-g-PAO as obtained from Langmuir adsorption isotherm were found to be 100.0, 76.92, 71.42 and 66.67 (mgg(-1)) for the adsorption of metal ions in order of Co(II)>Zn(II)>Cr(III)>Cd(II). The experimental results demonstrate that the above selective order of adsorption capacity is due to formation of stable chelating ring between the bidentate amidoxime ligand and metal ion. Copyright © 2014 Elsevier Ltd. All rights reserved.

Investigation kinetics mechanisms of adsorption malachite green onto activated carbon

International Nuclear Information System (INIS)

Onal, Y.; Akmil-Basar, C.; Sarici-Ozdemir, C.

2007-01-01

Lignite was used to prepare activated carbon (T3K618) by chemical activation with KOH. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N 2 adsorption isotherm. BET surface area of activated carbon is determined as 1000 m 2 /g. Adsorption capacity of malachite green (MG) onto T3K618 activated carbon was investigated in a batch system by considering the effects of various parameters like initial concentration (100, 150 and 200 mg/L) and temperature (25, 40 and 50 deg. C). The adsorption process was relatively fast and equilibrium was reached after about 20 min for 100, 150 mg/L at all adsorption temperature. Equilibrium time for 200 mg/L was determined as 20 min and 40 min at 298, 313 and 323 K, respectively. Simple mass and kinetic models were applied to the experimental data to examine the mechanisms of adsorption and potential rate controlling steps such as external mass transfer, intraparticle diffusion. Pseudo second-order model was found to explain the kinetics of MG adsorption most effectively. It was found that both mass transfer and pore diffusion are important in determining the adsorption rates. The intraparticle diffusion rate constant, external mass transfer coefficient, film and pore diffusion coefficient at various temperatures were evaluated. The activation energy (E a ) was determined as 48.56, 63.16, 67.93 kJ/mol for 100, 150, 200 mg/L, respectively. The Langmiur and Freundlich isotherm were used to describe the adsorption equilibrium studies at different temperatures. Langmiur isotherm shows better fit than Freundlich isotherm in the temperature range studied. The thermodynamic parameters, such as ΔG o , ΔS and ΔH o were calculated. The thermodynamics of dyes-T3K618 system indicates endothermic process

Adsorption of malachite green and iodine on rice husk-based porous carbon

International Nuclear Information System (INIS)

Guo Yupeng; Zhang Hui; Tao Nannan; Liu Yanhua; Qi Juirui; Wang Zichen; Xu Hongding

2003-01-01

Adsorption isotherms of I 2 and malachite green (MG) by rice husk-based porous carbons (RHCs) from aqueous medium have been studied. Three samples of carbons prepared by NaOH-activation, three samples prepared by KOH-activation and two samples of commercial carbons have been studied. And the adsorption isotherms have been determined after modifying the carbon surfaces by oxidation with nitric acid and hydrogen peroxide and after degassing at 800 deg. C. The results have been found to follow the Freundlich adsorption isotherm. Three samples of N series have larger capacity for removing I 2 and MG from solution compared to that of the tested commercial carbons. The adsorption capacity of I 2 is similar for K series and commercial carbons. And the capacity of commercial carbons for MG is larger than K series. The adsorption capacity of I 2 on oxidation carbons has increased for hydrogen peroxide treatment and decreased for nitric acid, and that of MG is decreased. But the adsorption capacities of I 2 and MG increase on degassing. On the other hand, the adsorption of I 2 increases after modifying the carbon surfaces by HCl without oxidation. Suitable mechanisms have been proposed

Proton adsorption onto alumina: extension of multisite complexation (MUSIC) theory

Energy Technology Data Exchange (ETDEWEB)

Nagashima, K.; Blum, F.D.

1999-09-01

The adsorption isotherm of protons onto a commercial {gamma}-alumina sample was determined in aqueous nitric acid with sodium nitrate as a background electrolyte. Three discrete regions could be discerned in the log-log plots of the proton isotherm determined at the solution pH 5 to 2. The multisite complexation (MUSIC) model was modified to analyze the simultaneous adsorption of protons onto various kinds of surface species.

Dubinin-Astakhov model for acetylene adsorption on metal-organic frameworks

Science.gov (United States)

Cheng, Peifu; Hu, Yun Hang

2016-07-01

Acetylene (C2H2) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C2H2 adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C2H2 adsorption on various MOFs has not been found. In this paper, it was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model to depict C2H2 adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C2H2 adsorption on those MOFs.

On the problem of low-temperature air adsorption studies by the volume method

International Nuclear Information System (INIS)

Gur'yanov, V.V.; Gashin, V.M.; Shcherbakov, V.P.; Misin, M.S.; Sizova, G.P.

1975-01-01

The properties of a porous structure and the adsorption of a series of carbon adsorbents at 77 K were studied. It was shown that isotherms may be constructed within the framework of the theory of volume filling only for a degree of filling of theta>20.5. Deviations from theoretical curves are observed with practically no accumulation in the high-vacuum equipment of carbon-adsorbed helium, hydrogen, and neon. Therefore the initial parts of the air-adsorption isotherm at 77 K may not be used for characterizing the adsorption properties and parameters of the porous structure of a microporous adsorbent. The effect of adsorbent microporosity on the adsorption isotherm begins to appear only when the pressure of the poorly sorbed components of the air is less than the total pressure of the nitrogen and oxygen

Adsorption of gold onto γ-aminopropyltriethoxysilane grafted coconut pith

International Nuclear Information System (INIS)

Usman, M.; Akhtar, J.

2017-01-01

This study was carried out to investigate adsorption kinetic and adsorption thermodynamics of Au(III) ions onto γ-aminopropyltriethoxysilane grafted coconut pith. The results from equilibrium adsorption were fitted in various adsorption isotherm models such as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and the best fit for the experimental data was Langmuir isotherm. The maximum adsorption capacity for virgin coconut pith (VCP) and the grafted coconut pith (GCP) were 256.41 and 285.59 mg/g, respectively. The kinetic data was verified using pseudo-first-order, pseudo-second-order, elovich equation and intraparticle diffusion model. The correlation results suggested that the pseudo-second-order model fits the experimental data well. A thermodynamic study revealed the endothermic nature of reaction due to positive enthalpy (?Ho) values and negative values of Gibbs free energy (?Go) describes the spontaneity of adsorption process. The regenerability of VCP and GCP adsorbents were investigated with NaOH (1.0 M).

Adsorption of Radioactive Chromium onto Iron Oxide Coated Sand

International Nuclear Information System (INIS)

Tadros, N.

2008-01-01

Iron oxide coated sand (IOCS) has been prepared and used as granular sorbent for 51 Cr radionuclide at different and specified concentration Ievels in aqueous solutions of constant ph value. Effect of different parameters such as: ph variation, contact time, 51 Cr ion concentration and variation of temperature on the adsorption of the radionuclide onto IOCS material have been discussed. At high ph value about 9()% of 51 Cr is adsorbed onto IOCS from the aqueous solution, The sorption capability of 51 Cr and the effect of ion concentration on the adsorbitivity have been discussed. Adsorption isotherms of Langmuir and Freundlich were expressed and their adsorption isotherm parameters are tabulated

Consequence of chitosan treating on the adsorption of humic acid by granular activated carbon.

Science.gov (United States)

Maghsoodloo, Sh; Noroozi, B; Haghi, A K; Sorial, G A

2011-07-15

In this work, equilibrium and kinetic adsorption of humic acid (HA) onto chitosan treated granular activated carbon (MGAC) has been investigated and compared to the granular activated carbon (GAC). The adsorption equilibrium data showed that adsorption behaviour of HA could be described reasonably well by Langmuir adsorption isotherm for GAC and Freundlich adsorption isotherm for MGAC. It was shown that pre-adsorption of chitosan onto the surface of GAC improved the adsorption capacity of HA changing the predominant adsorption mechanism. Monolayer capacities for the adsorption of HA onto GAC and MGAC were calculated 55.8 mg/g and 71.4 mg/g, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process for MGAC. Copyright © 2011 Elsevier B.V. All rights reserved.

Mechanics of adsorption-deformation coupling in porous media

Science.gov (United States)

Zhang, Yida

2018-05-01

This work extends Coussy's macroscale theory for porous materials interacting with adsorptive fluid mixtures. The solid-fluid interface is treated as an independent phase that obeys its own mass, momentum and energy balance laws. As a result, a surface strain energy term appears in the free energy balance equation of the solid phase, which further introduces the so-called adsorption stress in the constitutive equations of the porous skeleton. This establishes a fundamental link between the adsorption characteristics of the solid-fluid interface and the mechanical response of the porous media. The thermodynamic framework is quite general in that it recovers the coupled conduction laws, Gibbs isotherm and the Shuttleworth's equation for surface stress, and imposes no constraints on the magnitude of deformation and the functional form of the adsorption isotherms. A rich variety of coupling between adsorption and deformation is recovered as a result of combining different poroelastic models (isotropic vs. anisotropic, linear vs. nonlinear) and adsorption models (unary vs. mixture adsorption, uncoupled vs. stretch-dependent adsorption). These predictions are discussed against the backdrop of recent experimental data on coal swelling subjected to CO2 and CO2sbnd CH4 injections, showing the capability and versatility of the theory in capturing adsorption-induced deformation of porous materials.

Competitive adsorption of heavy metals onto sesame straw biochar in aqueous solutions.

Science.gov (United States)

Park, Jong-Hwan; Ok, Yong Sik; Kim, Seong-Heon; Cho, Ju-Sik; Heo, Jong-Soo; Delaune, Ronald D; Seo, Dong-Cheol

2016-01-01

Objective of this research was to evaluate adsorption of heavy metals in mono and multimetal forms onto sesame straw biochar (SSB). Competitive sorption of metals by SSB has never been reported previously. The maximum adsorption capacities (mgg(-1)) of metals by SSB were in the order of Pb (102)≫Cd (86)≫Cr (65)>Cu (55)≫Zn (34) in the monometal adsorption isotherm and Pb (88)≫Cu (40)≫Cr (21)>Zn (7)⩾Cd (5) in the multimetal adsorption isotherm. Based on data obtained from the distribution coefficients, Freundlich and Langmuir adsorption models, and three-dimensional simulation, multimetal adsorption behaviors differed from monometal adsorption due to competition. Especially, during multimetal adsorption, Cd was easily exchanged and substituted by other metals. Further competitive adsorption studies are necessary in order to accurately estimate the heavy metal adsorption capacity of biochar in natural environments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Heavy metal adsorption by modified oak sawdust: Thermodynamics and kinetics

International Nuclear Information System (INIS)

Argun, Mehmet Emin; Dursun, Sukru; Ozdemir, Celalettin; Karatas, Mustafa

2007-01-01

This paper describes the adsorption of heavy metal ions from aqueous solutions by oak (Quercus coccifera) sawdust modified by means of HCl treatment. Our study tested the removal of three heavy metals: Cu, Ni, and Cr. The optimum shaking speed, adsorbent mass, contact time, and pH were determined, and adsorption isotherms were obtained using concentrations of the metal ions ranging from 0.1 to 100 mg L -1 . The adsorption process follows pseudo-second-order reaction kinetics, as well as Langmuir and D-R adsorption isotherms. The paper discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions. The maximum removal efficiencies were 93% for Cu(II) at pH 4, 82% for Ni(II) at pH 8, and 84% for Cr(VI) at pH 3

The mechanism of uranium adsorption on Resin 508 and isoelectric point of the resin

International Nuclear Information System (INIS)

Han Qingping; Lu Weichang; Su Huijuan; Hu Jinbo; Zhang Liqin; Chen Banglin

1990-01-01

The adsorption process of uranium by Resin 508 at the solid-liquid interface was investigated and the mechanism of uranium adsorption including adsorption dynamics, adsorption thermodynamics and isoelectric point of resin was studied. The results are as follows: The maximum of uranium adsorption is attained at pH5-7; Uranium adsorption isotherm by Resin 508 in experimental conditions agrees with Langmuir's adsorption isotherm, the maximum of uranium adsorbed (Vm) is 716 mg U/g-dried resin; The adsorption of uranium by Resin 508 is an endothermic reaction and ΔH = 16.87 kJ/mol; The exchange-adsorption rate is mainly controlled by liquid film diffusion; The isoelectric points of Resin 508 before and after uranium adsorption are found to be pH7.5 and pH5.7 respectively. It is a specific adsorption for uranium

Binary gas mixture adsorption-induced deformation of microporous carbons by Monte Carlo simulation.

Science.gov (United States)

Cornette, Valeria; de Oliveira, J C Alexandre; Yelpo, Víctor; Azevedo, Diana; López, Raúl H

2018-07-15

Considering the thermodynamic grand potential for more than one adsorbate in an isothermal system, we generalize the model of adsorption-induced deformation of microporous carbons developed by Kowalczyk et al. [1]. We report a comprehensive study of the effects of adsorption-induced deformation of carbonaceous amorphous porous materials due to adsorption of carbon dioxide, methane and their mixtures. The adsorption process is simulated by using the Grand Canonical Monte Carlo (GCMC) method and the calculations are then used to analyze experimental isotherms for the pure gases and mixtures with different molar fraction in the gas phase. The pore size distribution determined from an experimental isotherm is used for predicting the adsorption-induced deformation of both pure gases and their mixtures. The volumetric strain (ε) predictions from the GCMC method are compared against relevant experiments with good agreement found in the cases of pure gases. Copyright © 2018 Elsevier Inc. All rights reserved.

The adsorption of benzene from the gas phase on H-mordenite 1. A new model isotherm for adsorption on zeolites

Energy Technology Data Exchange (ETDEWEB)

Drachsel, W; Becker, K A

1977-10-01

This model was derived from considerations of the heterogeneous energy distribution of zeolite surfaces. A homogeneity parameter (m) was introduced. The isotherms approach a constant value at high pressure, and at low pressure they approach the Freundlich isotherm for m < 1 and the Henry isotherm at m > 1. Graphs and 19 references.

Direct measurements of adsorption heats of hydrogen on nano-porous carbons

International Nuclear Information System (INIS)

Akihiko, Matsumoto; Kazumasa, Yamamoto; Tomoyuki, Miyata

2005-01-01

Since a exciting report of hydrogen storage in single-walled carbon nano-tubes by Dillon and his colleagues [1], nano-porous carbon materials, such as carbon nano-tubes, carbon nano-horns and micro-porous activated carbon, have attracted considerable attention as hydrogen storage materials. Adsorption plays a predominating role in the hydrogen storage process on solid surfaces. The adsorption is a spontaneous process, which is caused by interaction between gas molecules and surface, hence, it is always exothermic process and observed as adsorption heats. For this reason, direct measurement of the adsorption heats by adsorption microcalorimetry would provide quantitative information on the strength of adsorption interaction and the adsorption mechanism. However, the adsorption amounts of hydrogen on carbon materials are far less than those of condensable vapors near room temperature due to low critical temperature of hydrogen (33.2 K), therefore, the adsorption heats can not be determined accurately at conventional measurement conditions near room temperature and the atmospheric pressure. This contribution reports the calorimetric characterization of hydrogen adsorption on nano-porous carbon materials at low temperature and high-pressure conditions. The high-pressure adsorption apparatus consists of a volumetric adsorption line connected to a twin-conduction type microcalorimeter. Activated carbon fibers (ACF, Ad'all Co.) of different micropore sizes (Table 1) were used as model adsorbents. Each ACF has slit-shaped micropores of uniform size [2]. The adsorption isotherms and differential heats of adsorption at high-pressure region from 0 to 10 MPa were simultaneously measured at isothermal condition from 203 to 298 K. The adsorption isotherms on ACF were of Henry type regardless of adsorption temperature and pore width; the uptakes increased linearly with equilibrium pressure. The adsorption isotherm at lower sorption temperature tended to show higher sorptivity

Kinetic Study of Water Contaminants Adsorption by Bamboo Granular Activated and Non-Activated Carbon

Directory of Open Access Journals (Sweden)

Opololaoluwa Oladimarun Ijaola

2013-10-01

Full Text Available The adsorptive capacity of metal ions from surface water with activated and non-activated carbon derived from bamboo was investigated. The validation of adsorption kinetics of Cl, PO4 and Pb was done by pseudo-first and second order model while adsorption isotherms was proved by Langmuir and Freundlich isotherm model for activated and non- activated bamboo granular carbon. Generally, the amount of metal ions uptake increases with time and activation levels and the pH of bamboo granular carbon increase with activation. Similarly, the pore space of the activated carbon also increases with activation levels. The correlation coefficients (R2 show that the pseudo-second order model gave a better fit to the adsorption process with 0.9918 as the least value and 1.00 as the highest value as compared with the pseudo-first order with 0.813 as the highest value and 0 as the least. The Freundlich isotherm was more favorable when compared with the Langmuir isotherm in determining the adsorptive capacity of bamboo granular activated carbon. The study has shown that chemical activation increases the pore space, surface area and the pH of bamboo granular carbon which ultimately increases the adsorption rate of metal ions in the contaminated surface water.

A comparison of basic dye adsorption onto zeolitic materials synthesized from fly ash

International Nuclear Information System (INIS)

Atun, Guelten; Hisarli, Guel; Kurtoglu, Ayse Engin; Ayar, Nihat

2011-01-01

This investigation reveals the adsorption characteristics of two basic dyes, thionine (TH) and safranine T (ST), onto fly ash (FA) and its three zeolitized products prepared at different hydrothermal conditions. Typical two-step isotherms were observed for TH adsorption onto four adsorbents, whereas the isotherms of the larger ST molecules were S-shaped. The adsorption capacities of the zeolitized fly ash (ZFA) estimated from the first plateau region of the TH isotherms was nearly twice the FA capacity. The capacities increased by up to five times in the second plateau region. The adsorption capacity of FA for ST is equivalent that of TH, whereas the capacities of ZFA are lower than those found for TH. The equilibrium results were well-described by the Freundlich isotherm model. The kinetic data obtained in the temperature range of 298-318 K was analyzed using Paterson's and Nernst Plank's approximations based on the homogeneous surface diffusion model (HSDM). The thermodynamic functions for the transition state were evaluated from the temperature-dependence of the surface diffusion coefficients by applying the Eyring model.

A comparison of basic dye adsorption onto zeolitic materials synthesized from fly ash

Energy Technology Data Exchange (ETDEWEB)

Atun, Guelten, E-mail: gultena@istanbul.edu.tr [Istanbul University, Faculty of Engineering, Department of Chemistry, 34850 Avcilar, Istanbul (Turkey); Hisarli, Guel; Kurtoglu, Ayse Engin; Ayar, Nihat [Istanbul University, Faculty of Engineering, Department of Chemistry, 34850 Avcilar, Istanbul (Turkey)

2011-03-15

This investigation reveals the adsorption characteristics of two basic dyes, thionine (TH) and safranine T (ST), onto fly ash (FA) and its three zeolitized products prepared at different hydrothermal conditions. Typical two-step isotherms were observed for TH adsorption onto four adsorbents, whereas the isotherms of the larger ST molecules were S-shaped. The adsorption capacities of the zeolitized fly ash (ZFA) estimated from the first plateau region of the TH isotherms was nearly twice the FA capacity. The capacities increased by up to five times in the second plateau region. The adsorption capacity of FA for ST is equivalent that of TH, whereas the capacities of ZFA are lower than those found for TH. The equilibrium results were well-described by the Freundlich isotherm model. The kinetic data obtained in the temperature range of 298-318 K was analyzed using Paterson's and Nernst Plank's approximations based on the homogeneous surface diffusion model (HSDM). The thermodynamic functions for the transition state were evaluated from the temperature-dependence of the surface diffusion coefficients by applying the Eyring model.

Adsorptive removal of acid blue 113 and tartrazine by fly ash from single and binary dye solutions

Energy Technology Data Exchange (ETDEWEB)

Pura, S.; Atun, G. [Istanbul University, Avcilar (Turkey). Dept. of Chemistry

2009-07-01

Adsorption of two acid dyestuffs, acid blue 113 (AB) and tartrazine (TA), has been studied from their single and binary solutions by using fly ash (FA) as an adsorbent. The S shaped isotherms observed for dye adsorption from single solutions show that both acid dyes are not preferred at a low concentration region whereas adsorption of the dyes from binary solutions is enhanced via solute-solute interactions. Although the L-shaped isotherm is observed in binary solutions adsorbability of AB decreases in concentrated solutions with respect to single one, time dependency of adsorption is well described with a pseudo-second-order kinetic model as well as the linear relation of Bt vs. t plots (not passing through origin) indicates that film diffusion is effective on dye adsorption. Modeled isotherm curves using isotherm parameters of the Freundlich and Dubinin-Radushkevich (D-R) equations adequately fit to experimental equilibrium data. Equilibrium adsorption of AB in binary solutions has been quite well predicted by the extended Freundlich and the Sheindorf-Rebuhn-Sheintuch (SRS) models. In general, the isotherm curves constructed in the temperature range of 298-328K show that the optimum temperature is 318K for AB removal from both single and binary solutions.

Influences of salt concentration, loading and pH on strontium adsorption

International Nuclear Information System (INIS)

Atun, G.; Kaplan, Z.

1996-01-01

The adsorption of Sr on clay with contains zeolites and montmorillonite mixtures was investigated in solutions of NaCl by means of a batch technique. Sr retention was reduced with increasing NaCl concentration from 5*10 -4 to 5*10 -1 M. Distribution coefficients (K d ) linearly increased with pH in the acidic region but they were almost independent of pH in neutral and alkaline solutions. By fitting the data of the Dubinin-Radushkevich (D-R) isotherm, the mean energies of adsorption and adsorption capacities of Sr at different pH values were calculated. The results showed that the mode of adsorption below pH 4.5 is ion exchange, while above that value a multilayer adsorption occurs. Adsorption data were fitted to the Freundlich isotherm and from empirical Freundlich parameters a site distribution function was calculated. (author)

Adsorption kinetics of malachite green onto activated carbon prepared from Tuncbilek lignite

International Nuclear Information System (INIS)

Onal, Y.; Akmil-Basar, C.; Eren, Didem; Sarici-Ozdemir, Cigdem; Depci, Tolga

2006-01-01

Adsorbent (T 3 K618) has been prepared from Tuncbilek lignite by chemical activation with KOH. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N 2 adsorption isotherm. The N 2 adsorption isotherm of malachite green on T 3 K618 is type I. The BET surface area of the adsorbent which was primarily contributed by micropores was determined 1000 m 2 /g. T 3 K618 was used to adsorb malachite green (MG) from an aqueous solution in a batch reactor. The effects of initial dye concentration, agitation time, initial pH and adsorption temperature have been studied. It was also found that the adsorption isotherm followed both Freundlich and Dubinin-Radushkevich models. However, the Freundlich gave a better fit to all adsorption isotherms than the Dubinin-Radushkevich. The kinetics of adsorption of MG has been tested using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Results show that the adsorption of MG from aqueous solution onto micropores T 3 K618 proceeds according to the pseudo-second-order model. The intraparticle diffusion of MG molecules within the carbon particles was identified to be the rate-limiting step. The adsorption of the MG was endothermic (ΔH o = 6.55-62.37 kJ/mol) and was accompanied by an increase in entropy (ΔS o = 74-223 J/mol K) and a decrease in mean value of Gibbs energy (ΔG o = -6.48 to -10.32 kJ/mol) in the temperature range of 20-50 deg. C

Studies on Thorium Adsorption Characteristics upon Activated Titanium Hydroxide Prepared from Rosetta Ilmenite Concentrate

International Nuclear Information System (INIS)

Gado, M; Zaki, S

2016-01-01

The titanium hydroxide prepared from Rosetta ilmenite concentrate has been applied for Th (IV) adsorption from its acid aqueous solutions. The prepared hydroxide is first characterized by both Fourier transform infrared (FT-IR) spectrum and thermogravimetric analysis. The relevant factors affecting the adsorption process have been studied. The obtained equilibrium data fits well with the Langmuir isotherm rather than Freundlich isotherm, while the adsorption kinetic data follow the pseudo-second order model. The different thermodynamic parameters have also been calculated and indicate that the adsorption process is spontaneous

Adsorption Characteristics of Water and Silica Gel System for Desalination Cycle

KAUST Repository

Cevallos, Oscar R.

2012-01-01

(D-Se) isotherm for the whole pressure range, and for a pressure range below 10 kPa, proper for desalination cycles; isotherms type V of the International Union of Pure and Applied Chemistry (IUPAC) classification were exhibited. It is observed that the D-A based on PSD and the D-Se isotherm models describe the best fitting of the experimental uptake data for desalination cycles within a regression error of 2% and 6% respectively. All isotherm models, except the D-A based on PSD, have failed to describe the obtained experimental uptake data; an empirical isotherm model is proposed by observing the behavior of Tóth and D-A isotherm models. The new empirical model describes the water adsorption onto silica gel type A++ within a regression error of 3%. This will aid to describe the advantages of silica gel type A++ for the design of adsorption desalination processes where reducing capital cost and footprint area are highly important parameters to take into account.

Thermodynamics of gas adsorption on solid adsorbents

International Nuclear Information System (INIS)

Budrugeac, P.

1979-01-01

Starting with several hypotheses about the adsorbtion system and the adsorption phenomenon, a thermodynamic treatment of gas adsorption on solid adsorbants is presented. The relationships for determination from isotherms and calorimetric data of thermodynamic functions are derived. The problem of the phase changes in adsorbed layer is discussed. (author)

Removal of nitrobenzene from aqueous solution by a novel lipoid adsorption material (LAM)

Energy Technology Data Exchange (ETDEWEB)

Wen, Qinxue [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (SKLUWRE, HIT), Harbin 150090 (China); Chen, Zhiqiang, E-mail: czq0521@tom.com [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (SKLUWRE, HIT), Harbin 150090 (China); Lian, Jiaxiang; Feng, Yujie; Ren, Nanqi [State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (SKLUWRE, HIT), Harbin 150090 (China)

2012-03-30

Highlights: Black-Right-Pointing-Pointer We synthesized a novel adsorbent-lipoid adsorption material (LAM). Black-Right-Pointing-Pointer We investigate the adsorption behavior isotherms of nitrobenzene on LAM. Black-Right-Pointing-Pointer We investigate the adsorption kinetics of nitrobenzene on LAM. Black-Right-Pointing-Pointer We proved that the reaction is spontaneous and is an exothermic reaction. Black-Right-Pointing-Pointer The removal efficiency of LAM was higher than that of GAC. - Abstract: In this study, a novel adsorbent referred to as a lipoid adsorption material (LAM) was synthesized with a hydrophobic nucleolus (triolein) and hydrophilic membrane structure (polyamide). The LAM was applied to the adsorption and removal of nitrobenzene from aqueous systems. Experiments were carried out to investigate the adsorption behavior of nitrobenzene on LAM, including the development of adsorption isotherms, the determination of adsorption kinetics, and to explore the influence of adsorbent dosage, contact time, temperature and the initial concentration of nitrobenzene on adsorption. The performance of LAM was compared with equal amounts of granular activated carbon (GAC) for adsorption. The adsorption isotherms for LAM were found to be described by the Linear equation, while the adsorption isotherms for granular activated carbon (GAC) were described by the Freundlich equation. Results indicated that the adsorption of nitrobenzene by LAM occurred mainly due to the partition function caused by the triolein nucleolus. Two kinetics models, pseudo-first-order and pseudo-second-order models were used to fit the experimental data for LAM adsorption. By comparing the correlation coefficients, it was found that the pseudo-first-order model was most suitable to describe the adsorption of nitrobenzene on LAM. The results also indicated that the factors that affect the adsorption rate would be either the nitrobenzene concentration or the character of the adsorbent

Removal of nitrobenzene from aqueous solution by a novel lipoid adsorption material (LAM)

International Nuclear Information System (INIS)

Wen, Qinxue; Chen, Zhiqiang; Lian, Jiaxiang; Feng, Yujie; Ren, Nanqi

2012-01-01

Highlights: ► We synthesized a novel adsorbent-lipoid adsorption material (LAM). ► We investigate the adsorption behavior isotherms of nitrobenzene on LAM. ► We investigate the adsorption kinetics of nitrobenzene on LAM. ► We proved that the reaction is spontaneous and is an exothermic reaction. ► The removal efficiency of LAM was higher than that of GAC. - Abstract: In this study, a novel adsorbent referred to as a lipoid adsorption material (LAM) was synthesized with a hydrophobic nucleolus (triolein) and hydrophilic membrane structure (polyamide). The LAM was applied to the adsorption and removal of nitrobenzene from aqueous systems. Experiments were carried out to investigate the adsorption behavior of nitrobenzene on LAM, including the development of adsorption isotherms, the determination of adsorption kinetics, and to explore the influence of adsorbent dosage, contact time, temperature and the initial concentration of nitrobenzene on adsorption. The performance of LAM was compared with equal amounts of granular activated carbon (GAC) for adsorption. The adsorption isotherms for LAM were found to be described by the Linear equation, while the adsorption isotherms for granular activated carbon (GAC) were described by the Freundlich equation. Results indicated that the adsorption of nitrobenzene by LAM occurred mainly due to the partition function caused by the triolein nucleolus. Two kinetics models, pseudo-first-order and pseudo-second-order models were used to fit the experimental data for LAM adsorption. By comparing the correlation coefficients, it was found that the pseudo-first-order model was most suitable to describe the adsorption of nitrobenzene on LAM. The results also indicated that the factors that affect the adsorption rate would be either the nitrobenzene concentration or the character of the adsorbent. Thermodynamic calculations indicated that the adsorption of nitrobenzene on LAM was spontaneous and was an exothermic reaction. With

The Adsorption Mechanism of Modified Activated Carbon on Phenol

Directory of Open Access Journals (Sweden)

Lin J. Q.

2016-01-01

Full Text Available Modified activated carbon was prepared by thermal treatment at high temperature under nitrogen flow. The surface properties of the activated carbon were characterized by Boehm titration, BET and point of zero charge determination. The adsorption mechanism of phenol on modified activated carbon was explained and the adsorption capacity of modified activated carbon for phenol when compared to plain activated carbon was evaluated through the analysis of adsorption isotherms, thermodynamic and kinetic properties. Results shows that after modification the surface alkaline property and pHpzc value of the activated carbon increase and the surface oxygen-containing functional groups decrease. The adsorption processes of the plain and modified carbon fit with Langmuir isotherm equation well, and the maximum adsorption capacity increase from 123.46, 111.11, 103.09mg/g to 192.31, 178.57, 163,93mg/g under 15, 25 and 35°C after modification, respectively. Thermodynamic parameters show that the adsorption of phenol on activated carbon is a spontaneously exothermic process of entropy reduction, implying that the adsorption is a physical adsorption. The adsorption of phenol on activated carbon follows the pseudo-second-order kinetics (R2>0.99. The optimum pH of adsorption is 6~8.

[Impact of regional water chemistry on the phosphorus isothermal adsorption of the sediments in three subsidence waters of the Huainan Mine areas].

Science.gov (United States)

Yi, Qi-Tao; Sun, Peng-Fei; Xie, Kai; Qu, Xi-Jie; Wang, Ting-Ting

2013-10-01

Three research sites of subsidence waters, including Panji (PJ), Guqiao (GQ) and Xieqiao (XQ) located in the Huainan "Panxie" Mine Area have been selected to address their phosphorus (P) adsorption behavior in the sediments considering the site-specific regional water chemistry. The P isothermal adsorption was measured in pure water and four different types of ion solutions, prepared through additions of sodium chloride (NaCl), calcium chloride (CaCl2), sodium bicarbonate (NaHCO3), and a mixture of sodium bicarbonate and calcium chloride (NaHCO3 + CaCI2). The first four settings were studied to analyze the individual impact of each solution on P adsorption while the last one was to study their combined effect. In general, Ca2 + could enhance P adsorption on sediment surfaces while weakly alkaline conditions caused by bicarbonates were unfavorable for its adsorption. As a comprehensive effect, the positive effect of the former was greater than the negative effect of the latter. The zero equilibrium phosphorus concentrations (EPC) in the three sites were 0. 059, 0. 032 and 0. 040 mg.L-1, respectively, showing trends of P releasing to the overlying water column. The site of PJ showed greater P releasing potential than those at the GQ and XQ sites, probably due to its higher nutrient level. Overall, P releasing risks in the researched sediments are weaker than those in eutrophic lakes, while they are very similar to lakes with lower trophic levels, because of their unique sedimentary environments from inundated agricultural soils.

Adsorption characteristics of brilliant green dye on kaolin

International Nuclear Information System (INIS)

Nandi, B.K.; Goswami, A.; Purkait, M.K.

2009-01-01

Experimental investigations were carried out to adsorb toxic brilliant green dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring: (i) particle size distribution using particle size analyzer, (ii) BET surface area using BET surface analyzer, and (iii) structural analysis using X-ray diffractometer. The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH and temperature were studied for the adsorption of brilliant green in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on pH of solution. Free energy of adsorption (ΔG 0 ), enthalpy (ΔH 0 ) and entropy (ΔS 0 ) changes are calculated to know the nature of adsorption. The calculated values of ΔG 0 at 299 K and 323 K indicate that the adsorption process is spontaneous. The estimated values of ΔH 0 and ΔS 0 both show the negative sign, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in less randomly fashion than in solution. The adsorption kinetic has been described by first-order, pseudo-second-order and intra-particle-diffusion models. It was observed that the rate of dye adsorption follows pseudo-second-order model for the dye concentration range studied in the present case. Standard adsorption isotherms were used to fit the experimental equilibrium data. It was found that the adsorption of brilliant green on kaolin follows the Langmuir adsorption isotherm

Propylene/propane mixture adsorption on faujasite sorbents

NARCIS (Netherlands)

Van Miltenburg, A.; Gascon, J.; Zhu, W.; Kapteijn, F.; Moulijn, J.A.

2008-01-01

The adsorption of propylene and propane on zeolite NaX with and without a saturated (36 wt%) amount of CuCl have been investigated. The single component adsorption isotherms could be well described with a Dual-Site Langmuir model. The dispersion of CuCl results in a decrease of the maximum

Study on the adsorption-desorption characteristics of 14C-pirimicarb in soils

International Nuclear Information System (INIS)

Guo Jiangfeng; Sun Jinhe; Li Xingming

1995-01-01

14 C-pirimicarb was used to study its adsorption-desorption behavior in 8 kinds of soils. The results indicated that there were significant differences in its adsorption with different kinds of soil. The lowest adsorption percentage was only 13.16% and the highest one was 87.75%. The amount of adsorption in the same kind of soil increased with the concentration of pesticide, but concentration had little influence on the adsorption within the certain range of concentrations. Multiple linear regression equation was developed for prediction of adsorption and determination of the relative importance of the soil parameters. It was significant that the key factors, soil pH and clay content were negatively and positively correlated with the adsorption respectively. The adsorption equilibrium of pirimicarb in soils could be well described by both the Freundlich isotherm and the Langmuir isotherm. The adsorbed 14 C-pirimicarb could disrobe from soil and its desorption was also influenced by soil properties described by multiple linear regression equation

Influence of organobentonite structure on toluene adsorption from water solution

Directory of Open Access Journals (Sweden)

Nuria Vidal

2012-12-01

Full Text Available Due to increase water pollution by organic compound derived from hydrocarbons such as toluene, several alternative technologies for remediation of polluted water have been originated. In this work natural bentonites were modified with cetyltrimethylammonium (CTMA+ for obtaining organophilic bentonites. The obtained CTMA-bentonites would be suitable for use as adsorbents of toluene present in water. The influence of structural characteristics of CTMA-bentonites on their adsorption capacity was studied. It was shown that adsorption of toluene depended on homogeneous interlayer space associated with arrangements of CTMA+ paraffin-monolayer and bilayer models, accompanied by a high degree ordering of the carbon chain of organic cation in both arrangements. However, packing density would not have an evident influence on the retention capacity of these materials. The solids obtained were characterized by chemical analysis, X-ray diffractions and infrared spectroscopy. Toluene adsorption was measured by UV-visible spectrophotometer. Adsorption capacity was studied by determining adsorption isotherms and adsorption coefficient calculation. The adsorption isotherms were straight-line indicating a partition phenomenon of toluene between the aqueous and organic phase present in organophilic bentonites.

Adsorption of Pb{sup 2+} and Cd{sup 2+} onto a novel activated carbon-chitosan complex

Energy Technology Data Exchange (ETDEWEB)

Ge, H.; Fan, X. [College of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 (China)

2011-10-15

A novel activated carbon-chitosan complex adsorbent (ACCA) was prepared via the crosslinking of glutaraldehyde and activated carbon-(NH{sub 2}-protected) chitosan complex under microwave irradiation. The surface morphology of this adsorbent was characterized. The adsorption of ACCA for Pb{sup 2+} and Cd{sup 2+} was investigated. The results demonstrate that ACCA has higher adsorption capacity than chitosan. The adsorption follows pseudo first-order kinetics. The isotherm adsorption equilibria are better described by Freundlich and Dubinin-Radushkevich isotherms than by the Langmuir isotherm. The adsorbent can be recycled. These results have important implications for the design of low-cost and effective adsorbents in the removal of heavy metal ions from wastewaters. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Improving lead adsorption through chemical modification of wheat straw by lactic acid

Science.gov (United States)

Mu, Ruimin; Wang, Minxiang; Bu, Qingwei; Liu, Dong; Zhao, Yanli

2018-01-01

This work describes the creation of a new cellulosic material derived from wheat straw modified by lactic acid for adsorption of lead in aqueous solution, called 0.3LANS (the concentration of the lactic acid were 0.3mol/L). Batch experiments were conducted to study the effects of initial pH value, contact time, adsorbent dose, initial concentration and temperature. Fourier transform infrared (FTIR), Elemental analysis, BET surface area and Scanning electron micrographs (SEM) analysis were used to investigate the chemical modification. Adsorption isotherm models namely, Langmuir, Freundlich were used to analyse the equilibrium data, and the Langmuir isotherm model provided the best correlation, means that the adsorption was chemical monolayer adsorption and the adsorption capacity qm was increased with increasing temperature, and reached 51.49mg/g for 0.3LANS at 35°C, showing adsorption was exothermic.

Nitrate Adsorption on Clay Kaolin: Batch Tests

Directory of Open Access Journals (Sweden)

Morteza Mohsenipour

2015-01-01

Full Text Available Soils possessing kaolin, gibbsite, goethite, and hematite particles have been found to have a natural capacity to attenuate pollution in aqueous phase. On the other hand, the hydroxyl group in soil increases anion exchange capacity under a low pH condition. The main objective of this paper was to evaluate effects of kaolin on nitrate reduction under acidic condition. In order to analyze the kaolin adsorption behaviour under various conditions, four different concentrations of nitrate, 45, 112.5, 225, and 450 mgNO3-/L, with a constant pH equal to 2, constant temperature equal to 25°C, and exposure period varying from 0 to 150 minutes were considered. The capacity of nitrate adsorption on kaolin has also been studied involving two well-known adsorption isotherm models, namely, Freundlich and Longmuir. The results revealed that approximately 25% of the nitrate present in the solution was adsorbed on clay kaolin. The laboratory experimental data revealed that Freundlich adsorption isotherm model was more accurate than Longmuir adsorption model in predicting of nitrate adsorption. Furthermore, the retardation factor of nitrate pollution in saturated zone has been found to be approximately 4 in presence of kaolin, which indicated that kaolin can be used for natural scavenger of pollution in the environment.

BTEX and MTBE adsorption onto raw and thermally modified diatomite.

Science.gov (United States)

Aivalioti, Maria; Vamvasakis, Ioannis; Gidarakos, Evangelos

2010-06-15

The removal of BTEX (benzene, toluene, ethyl-benzene and xylenes) and MTBE (methyl tertiary butyl ether) from aqueous solution by raw (D(R)) and thermally modified diatomite at 550, 750 and 950 degrees C (D(550), D(750) and D(950) respectively) was studied. Physical characteristics of both raw and modified diatomite such as specific surface, pore volume distribution, porosity and pH(solution) were determined, indicating important structural changes in the modified diatomite, due to exposure to high temperatures. Both adsorption kinetic and isotherm experiments were carried out. The kinetics data proved a closer fit to the pseudo-second order model. Maximum values for the rate constant, k(2), were obtained for MTBE and benzene (48.9326 and 18.0996 g mg(-1)h(-1), respectively) in sample D(550). The isotherm data proved to fit the Freundlich model more closely, which produced values of the isotherm constant 1/n higher than one, indicating unfavorable adsorption. The highest adsorption capacity, calculated through the values of the isotherm constant k(F), was obtained for MTBE (48.42 mg kg(-1) (mg/L)(n)) in sample D(950). Copyright 2010 Elsevier B.V. All rights reserved.

Effect of crosslinker on the swelling and adsorption properties of ...

Indian Academy of Sciences (India)

The SAPs were used to adsorb the dye Orange G at different initial concentrations of the dye. The equilibrium adsorption data followed the Langmuir adsorption isotherms. The SAPs were also used to adsorb three other dyes, namely, Congo red, Amido black and Alizarin cyanine green. They exhibited different adsorption ...

Fundamentals of high pressure adsorption

Energy Technology Data Exchange (ETDEWEB)

Zhou, Y.P.; Zhou, L. [Tianjin University, Tianjin (China). High Pressure Adsorption Laboratory

2009-12-15

High-pressure adsorption attracts research interests following the world's attention to alternative fuels, and it exerts essential effect on the study of hydrogen/methane storage and the development of novel materials addressing to the storage. However, theoretical puzzles in high-pressure adsorption hindered the progress of application studies. Therefore, the present paper addresses the major theoretical problems that challenged researchers: i.e., how to model the isotherms with maximum observed in high-pressure adsorption; what is the adsorption mechanism at high pressures; how do we determine the quantity of absolute adsorption based on experimental data. Ideology and methods to tackle these problems are elucidated, which lead to new insights into the nature of high-pressure adsorption and progress in application studies, for example, in modeling multicomponent adsorption, hydrogen storage, natural gas storage, and coalbed methane enrichment, was achieved.

Adsorption equilibrium studies of uranium (VI) onto cross-linked chitosan-citric acid

International Nuclear Information System (INIS)

Ho Thi Yeu Ly; Nguyen Van Suc; Vo Quang Mai; Nguyen Mong Sinh

2011-01-01

Investigation of U(VI) adsorption by the cross- linked chitosan with citric acid was conduced by bath method. Effect of parameters such as pH, contact time, adsorbent dosage and other metal cations was determined. The maximum adsorption capacity of U(VI) at pH 4 was found to be 71.43 mg U(VI) / g cross-linked chitosan - citric acid after 300 min of contact time. The Langmuir and Freundlich isotherm models were used to describe adsorption equilibrium. The correction values, R 2 of two models were found to be 0.991 and 0.997, respectively. Therefore, it could be concluded that the adsorption equilibrium for U(VI) was followed the Langmuir and the Freundlich isotherm models. (author)

Sulfur dioxide adsorption by activated carbons having different textural and chemical properties

Energy Technology Data Exchange (ETDEWEB)

Nilgun Karatepe; Ilkun Orbak; Reha Yavuz; Ayse Ozyuguran [Istanbul Technical University, Istanbul (Turkey). Institute of Energy

2008-11-15

Activated carbons from Turkish lignite were prepared with different methods to investigate the influence of physico-chemical characteristics of the carbon materials on the sulfur dioxide (SO{sub 2}) adsorption. The effects of SO{sub 2} concentration, adsorption temperature, and sample particle size on adsorption were investigated using a thermogravimetric analysis system. An intraparticle diffusion model based on Knudsen diffusion and Freundlich isotherm (or Henry isotherm) was applied for predicting the amount of SO{sub 2} adsorbed. The textural and chemical properties of the activated carbon samples, resulted from the effects of activation conditions and demineralization of the carbon precursor, on the SO{sub 2} adsorption were also analyzed. 30 refs., 7 figs., 4 tabs.

Investigation of adsorption performance deterioration in silica gel–water adsorption refrigeration

International Nuclear Information System (INIS)

Wang Dechang; Zhang Jipeng; Xia Yanzhi; Han Yanpei; Wang Shuwei

2012-01-01

Highlights: ► Adsorption deterioration of silica gel in refrigeration systems is verified. ► Possible factors to cause such deterioration are analyzed. ► Specific surface area, silanol content and adsorption capacity are tested. ► The pollution is the primary factor to decline the adsorption capacity. ► Deteriorated samples are partly restored after being processed by acid solution. - Abstract: Silica gel acts as a key role in adsorption refrigeration systems. The adsorption deterioration must greatly impact the performance of the silica gel–water adsorption refrigeration system. In order to investigate the adsorption deterioration of silica gel, many different silica gel samples were prepared according to the application surroundings of silica gel in adsorption refrigeration systems after the likely factors to cause such deterioration were analyzed. The specific surface area, silanol content, adsorption capacity and pore size distribution of those samples were tested and the corresponding adsorption isotherms were achieved. In terms of the experimental data comparisons, it could be found that there are many factors to affect the adsorption performance of silica gel, but the pollution was the primary one to decline the adsorption capacity. In addition, the adsorption performance of the deteriorated samples after being processed by acid solution was explored in order to find the possible methods to restore its adsorption performance.

Surface area and pore size characteristics of nanoporous gold subjected to thermal, mechanical, or surface modification studied using gas adsorption isotherms, cyclic voltammetry, thermogravimetric analysis, and scanning electron microscopy

Science.gov (United States)

Tan, Yih Horng; Davis, Jason A.; Fujikawa, Kohki; Ganesh, N. Vijaya; Demchenko, Alexei V.

2012-01-01

Nitrogen adsorption/desorption isotherms are used to investigate the Brunauer, Emmett, and Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size distribution of physically modified, thermally annealed, and octadecanethiol functionalized np-Au monoliths. We present the full adsorption-desorption isotherms for N2 gas on np-Au, and observe type IV isotherms and type H1 hysteresis loops. The evolution of the np-Au under various thermal annealing treatments was examined using scanning electron microscopy (SEM). The images of both the exterior and interior of the thermally annealed np-Au show that the porosity of all free standing np-Au structures decreases as the heat treatment temperature increases. The modification of the np-Au surface with a self-assembled monolayer (SAM) of C18-SH (coverage of 2.94 × 1014 molecules cm−2 based from the decomposition of the C18-SH using thermogravimetric analysis (TGA)), was found to reduce the strength of the interaction of nitrogen gas with the np-Au surface, as reflected by a decrease in the ‘C’ parameter of the BET equation. From cyclic voltammetry studies, we found that the surface area of the np-Au monoliths annealed at elevated temperatures followed the same trend with annealing temperature as found in the BET surface area study and SEM morphology characterization. The study highlights the ability to control free-standing nanoporous gold monoliths with high surface area, and well-defined, tunable pore morphology. PMID:22822294

Selective adsorption behavior of Cd(II) ion imprinted polymers synthesized by microwave-assisted inverse emulsion polymerization: Adsorption performance and mechanism

International Nuclear Information System (INIS)

Zhu, Fang; Li, Luwei; Xing, Junde

2017-01-01

Highlights: • Microwave assisted inverse emulsion polymerization was applied to prepare Cd(II) imprinted polymers. • The adsorption capacity was evaluated by static adsorption experiments. • Pseudo-second-order model and Langmuir adsorption isotherm model had the best agreement with the experimental data. • The adsorption was a spontaneous and endothermic process. • Cd(II) imprinted polymers have specific identification for Cd(II). - Abstract: Microwave-assisted inverse emulsion polymerization method was used to prepare Cd(II) imprinted polymer (IIP) by using β-cyclodextrin (β-CD) and acrylamide (AM) as functional monomer, epichlorohydrin (ECH) as crossing-linking agent, ammonium persulfate as initiator. The Cd(II) imprinted polymer was characterized by SEM, FTIR and TGA. The influences of initial concentration of Cd(II), pH values, temperature, time and competitive ions on adsorption capacity and recognition properties are investigated. Under the optimal conditions, the adsorption capacity could reach 107 mg/g. Furthermore, pseudo first order kinetic model, pseudo second order kinetic model and intra-particular diffusion model were used to describe the adsorption kinetic behavior. Results showed that the pseudo-second-order model (R"2 0.9928–0.9961) had the best agreement with the experimental data. Langmuir adsorption isotherm model described the experimental data well, which indicated that adsorption was mainly monolayer absorption. Moreover, the study of adsorption thermodynamics (ΔG"0 0, ΔS"0 > 0) suggested that the adsorption process was a spontaneous and endothermic process. Competitive selectivity experiment revealed that imprinted polymer could selectively recognize Cd(II). It provides a new idea for removing Cd(II) from aqueous solution.

Adsorption kinetics of Rhodamine-B on used black tea leaves

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Hossain Mohammad

2012-08-01

Full Text Available Abstract Rhodamine B (Rh-B is one of the most common pollutants in the effluents of textile industries effluents in developing countries. This study was carried out to evaluate the applicability of used black tea leaves (UBTL for the adsorptive removal of Rh-B from aqueous system by investigating the adsorption kinetics in batch process. The effects of concentration and temperature on adsorption kinetics were examined. First-, second- and pseudo-second order kinetic equations were used to investigate the adsorption mechanism. The adsorption of Rh-B on UBTL followed pseudo-second order kinetics. The equilibrium amount adsorbed and the equilibrium concentration were calculated from pseudo-second-order kinetic plots for different initial concentrations of Rh-B to construct the adsorption isotherm. The adsorption isotherm was well expressed by Langmuir equation. The maximum adsorption capacity of UBTL to Rh-B was found to be 53.2 mg/g at pH = 2.0. The equilibrium amount adsorbed, calculated from pseudo-second-order kinetic plots, increased with temperature increase. The positive value of enthalpy of adsorption, ΔHads = 31.22 kJ/mol, suggested that the adsorption of Rh-B on UBTL at pH = 2.0 is an endothermic process.

Adsorption induced losses in interfacial cohesion

International Nuclear Information System (INIS)

Asaro, R.J.

1977-07-01

A model for interfacial cohesion is developed which describes the loss in the strength of an interface due to the segregation and adsorption of impurities on it. Distinctions are made between interface separations that occur too rapidly for any significant redistribution of adsorbing matter to take place and separations that are slow enough to allow full adsorption equilibrium. Expressions for the total work of complete decohesion are presented for both cases. The results are applied to well-known model adsorption isotherms and some experimental data for grain boundary adsorption of phosphorus in iron is analyzed with respect to the losses in intergranular cohesion

Adsorption of copper(II) on multiwalled carbon nanotubes in the absence and presence of humic or fulvic acids

International Nuclear Information System (INIS)

Sheng Guodong; Li Jiaxing; Shao Dadong; Hu Jun; Chen Changlun; Chen Yixue; Wang Xiangke

2010-01-01

The adsorption of Cu(II) on multiwalled carbon nanotubes (MWCNTs) as a function of pH and ionic strength in the absence and presence of humic acid (HA) or fulvic acid (FA) was studied using batch technique. The results indicated that the adsorption is strongly dependent on pH but independent of ionic strength. A positive effect of HA/FA on Cu(II) adsorption was found at pH 7.5. The adsorption isotherms can be described better by the Freundlich model than by the Langmuir model in the absence and presence of HA/FA. Adsorption isotherms of Cu(II) at higher initial HA/FA concentrations are higher than those of Cu(II) at lower FA/HA concentrations. The thermodynamic data calculated from temperature-dependent adsorption isotherms suggested that the adsorption was spontaneous and enhanced at higher temperature. Results of this work suggest that MWCNTs may be a promising candidate for the removal of heavy metal ions from aqueous solutions.

Visualizing Gas Adsorption on Porous Solids: Four Simple, Effective Demonstrations

Science.gov (United States)

Cheung, Ocean

2014-01-01

Gas adsorption on porous solids is a topic that is often discussed in an undergraduate chemistry or chemical engineering course. The idea of porosity and gas adsorption on a porous solid is usually discussed with adsorption isotherms recorded using commercially available equipment. This discussion can be rather abstract and can be difficult for…

Kinetics and thermodynamics of β-carotene and chlorophyll adsorption onto acid-activated bentonite from Xinjiang in xylene solution

International Nuclear Information System (INIS)

Wu Zhansheng; Li Chun

2009-01-01

The kinetics and thermodynamics of β-carotene and chlorophyll adsorption from xylene solution onto acid-activated bentonite (AAB) within the temperature range 65-95 deg. C were investigated. Adsorption of β-carotene was described well with the Langmuir isotherm, whereas chlorophyll adsorption was determined well with the Freundlich isotherm, and the experimental data on chlorophyll adsorption were also fitted by the Langmuir isotherm to a certain extent, as reflected by correlation coefficients (R 2 ) over 0.9865. In addition, the adsorption of β-carotene and chlorophyll onto AAB are favorable. The pseudo-second-order model was found to explain the kinetics of adsorption of both pigments more effectively. Increase of temperature enhanced the adsorption rate and equilibrium adsorption capacity of β-carotene and chlorophyll on AAB. The activation energy for the sorption of β-carotene and chlorophyll on AAB was 19.808 kJ/mol and 16.475 kJ/mol, respectively. The thermodynamic parameters ΔH θ , ΔS θ and ΔG θ , computed from K F of the adsorption isotherm constant, were 21.766 kJ/mol, 92.244 J/K mol and -9.554 kJ/mol respectively for the adsorption of β-carotene on AAB at 65 deg. C, and for adsorption of chlorophyll on AAB at 65 deg. C were 31.051 kJ/mol, 93.549 J/K mol and -0.729 kJ/mol, respectively. The adsorption of β-carotene and chlorophyll in xylene solution on AAB was a spontaneous and endothermic process with increasing in the randomness at the solid-solution interface.

Adsorption of volatile organic compounds by polytetra-fluor ethylene

International Nuclear Information System (INIS)

Martinet, J.M.

1958-01-01

The sorption of organic vapours by microporous polytetra-fluor ethylene has been studied gravimetrically using a Mc Bain-Baker type sorption balance. The amount of sorption, the peculiarities observed on the isotherm curves, the small influence of temperature, and smallness of hysteresis suggests that mainly physical adsorption occurs when the temperature is around 25 deg. C. The values of the surface areas obtained from the adsorption isotherms using organic vapours differ greatly from those derived from N 2 adsorption measurements. This discrepancy cannot be completely attributed to differences in the structure and chemical function of the adsorbate molecules, or to the porous structure of the adsorbent. On the contrary, the surface area values obtained by sorbing high volatile freons conform with those measured by nitrogen adsorption, which seems to imply a connection between the area of sorbed monolayers and volatility of the adsorbate. (author) [fr

Adsorption performance of silver-loaded activated carbon fibers

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Yan Xue-Feng

2018-01-01

Full Text Available Silver-loaded activated carbon fiber is prepared, and its adsorption performance is studied experimentally using five methylene blue solutions with different concentrations under three different temperature conditions. The adsorption tests show that fibers adsorption increase as the increase of temperature, and there is an optimal value for solution concentration, beyond which its adsorption will de-crease. Fibers isothermal adsorption to methylene blue is different from those by the monolayer adsorption by Langmuir model and the multilayer adsorption by Freundlich model. Through the analysis of thermodynamic parameters, Gibbs free energy, standard entropy, and standard enthalpy, it is found that the fibers adsorption to methylene blue is an exothermic process of physical adsorption.

A pressure-amplifying framework material with negative gas adsorption transitions.

Science.gov (United States)

Krause, Simon; Bon, Volodymyr; Senkovska, Irena; Stoeck, Ulrich; Wallacher, Dirk; Többens, Daniel M; Zander, Stefan; Pillai, Renjith S; Maurin, Guillaume; Coudert, François-Xavier; Kaskel, Stefan

2016-04-21

Adsorption-based phenomena are important in gas separations, such as the treatment of greenhouse-gas and toxic-gas pollutants, and in water-adsorption-based heat pumps for solar cooling systems. The ability to tune the pore size, shape and functionality of crystalline porous coordination polymers--or metal-organic frameworks (MOFs)--has made them attractive materials for such adsorption-based applications. The flexibility and guest-molecule-dependent response of MOFs give rise to unexpected and often desirable adsorption phenomena. Common to all isothermal gas adsorption phenomena, however, is increased gas uptake with increased pressure. Here we report adsorption transitions in the isotherms of a MOF (DUT-49) that exhibits a negative gas adsorption; that is, spontaneous desorption of gas (methane and n-butane) occurs during pressure increase in a defined temperature and pressure range. A combination of in situ powder X-ray diffraction, gas adsorption experiments and simulations shows that this adsorption behaviour is controlled by a sudden hysteretic structural deformation and pore contraction of the MOF, which releases guest molecules. These findings may enable technologies using frameworks capable of negative gas adsorption for pressure amplification in micro- and macroscopic system engineering. Negative gas adsorption extends the series of counterintuitive phenomena such as negative thermal expansion and negative refractive indices and may be interpreted as an adsorptive analogue of force-amplifying negative compressibility transitions proposed for metamaterials.

Adsorption of Monobutyl Phthalate from Aqueous Phase onto Two Macroporous Anion-Exchange Resins

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Zhengwen Xu

2014-01-01

Full Text Available As new emerging pollutants, phthalic acid monoesters (PAMs pose potential ecological and human health risks. In the present study, adsorption performance of monobutyl phthalate (MBP onto two macroporous base anion-exchange resins (D-201 and D-301 was discussed. It was found that the adsorption isotherms were best fitted by the Langmuir equation while the adsorption kinetics were well described by pseudo-first-order model. Analyses of sorption isotherms and thermodynamics proved that the adsorption mechanisms for DBP onto D-201 were ion exchange. However, the obtained enthalpy values indicate that the sorption process of MBP onto D-301 is physical adsorption. The equilibrium adsorption capacities and adsorption rates of DBP on two different resins increased with the increasing temperature of the solution. D-301 exhibited a higher adsorption capacity of MBP than D-201. These results proved that D-301, as an effective sorbent, can be used to remove phthalic acid monoesters from aqueous solution.

Arsenic adsorption of lateritic soil, limestone powder, lime and fly ash on arsenic-contaminated soil

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Wuthiphun, L.

2007-05-01

Full Text Available Arsenic adsorption efficiency of soil covering materials (lateritic soil, limestone powder, lime and fly ash on arsenic-contaminated soil obtained from Ronpiboon District, Nakhon Sri Thammarat Province tosolve arsenic air pollution problem was investigated using batch experiments. The four types of the aforementioned soil covering materials were examined to determine their arsenic adsorption efficiency, equilibriumtime as well as adsorption isotherms.The results revealed that among soil covering materials mixed with arsenic-contaminated soil at 10% w/w, the efficiency of arsenic adsorption of fly ash, lateritic soil, lime and limestone powder were 84, 60,38 and 1% respectively. The equilibrium time for lateritic soil at pH 4 was achieved within 4 hrs, whereas pH 7 and 12, the equilibrium time was 6 hrs. For fly ash, 2 hrs were required to reach the equilibrium at pH 12, while the equilibrium time was attained within 6 hrs at pH 4 and 7. Furthermore, lateritic soil possessedhigh arsenic adsorption efficiency at pH 7 and 4 and best fit with the Langmuir isotherm. The fly ash showing high arsenic adsorption efficiency at pH 12 and 7 fit the Freundlich isotherm at pH 12 and Langmuirisotherm at pH 7.This indicated that lateritic soil was suitable for arsenic adsorption at low pH, whilst at high pH,arsenic was well adsorbed by fly ash. The Freundlich and Langmuir isotherm could be used to determine quantities of soil covering materials for arsenic adsorption to prevent arsenic air pollution from arseniccontaminated soils.

Hybrid empirical--theoretical approach to modeling uranium adsorption

International Nuclear Information System (INIS)

Hull, Larry C.; Grossman, Christopher; Fjeld, Robert A.; Coates, John T.; Elzerman, Alan W.

2004-01-01

An estimated 330 metric tons of U are buried in the radioactive waste Subsurface Disposal Area (SDA) at the Idaho National Engineering and Environmental Laboratory (INEEL). An assessment of U transport parameters is being performed to decrease the uncertainty in risk and dose predictions derived from computer simulations of U fate and transport to the underlying Snake River Plain Aquifer. Uranium adsorption isotherms were measured for 14 sediment samples collected from sedimentary interbeds underlying the SDA. The adsorption data were fit with a Freundlich isotherm. The Freundlich n parameter is statistically identical for all 14 sediment samples and the Freundlich K f parameter is correlated to sediment surface area (r 2 =0.80). These findings suggest an efficient approach to material characterization and implementation of a spatially variable reactive transport model that requires only the measurement of sediment surface area. To expand the potential applicability of the measured isotherms, a model is derived from the empirical observations by incorporating concepts from surface complexation theory to account for the effects of solution chemistry. The resulting model is then used to predict the range of adsorption conditions to be expected in the vadose zone at the SDA based on the range in measured pore water chemistry. Adsorption in the deep vadose zone is predicted to be stronger than in near-surface sediments because the total dissolved carbonate decreases with depth

Adsorption of gases on heterogeneous surfaces

CERN Document Server

Rudzinski, W

1991-01-01

All real solid surfaces are heterogeneous to a greater or lesser extent and this book provides a broad yet detailed survey of the present state of gas adsorption. Coverage is comprehensive and extends from basic principles to computer simulation of adsorption. Underlying concepts are clarified and the strengths and weaknesses of the various methods described are discussed.Key Features* Adsorption isotherm equations for various types of heterogeneous solid surfaces* Methods of determining the nature of surface heterogeneity and porosity from experimental data* Studies of pha

Adsorption kinetic investigations of low concentrated uranium in aqua media by polymeric adsorban

International Nuclear Information System (INIS)

Guerellier, R.

2004-02-01

In order to remove the uranium from aqueous media, the solution of polyethylene glycol in acrylonitrile was irradiated using ''6' degree Celsius Co γ-ray source and Interpenetrating Polymer Networks (IPNs) was formed. After IPNs were amidoximated at 65 0 for 3.5 hours, they were kept in 10''-''2 M of uranil nitrate solution at 17, 25, 35, 45 degree Celsius temperatures until to establish the adsorption equilibrium. Adsorption analyses were measured by gamma spectrometer, gravimetry and UV spectrofotometer. Structure analysis of IPN, before and after amidoximation and after the adsorption of uranium, was interpreted by FTIR spectrometer. It was found that as the temperature increased the amount of max adsorption also increased. The amount of max adsorption capacity at 45 degree Celsius was 602 mg U/g IPN. In addition to, it was determined that the uranium adsorption increased a little in shaking media. The reaction was determined as 'zeroth degree' until 240 minutes due to the changing of adsorption capacity by the time at different temperatures. It was observed that as the temperature increased, the adsorption rate also increased and the activation energy was calculated as 34.6 kJ/mol. By using the changing of adsorption equilibrium coefficient by the temperature, thermodynamic quantities of ΔH, ΔS and ΔG were calculated consecutively. Adsorption reaction was determined as endothermic and it was interpreted that the adsorption was controlled by particular diffusion, namely it was a physical adsorption. Adsorption isotherms were found by changing the solution concentrations from 5X10''4 to parallel x parallel O''- 2 M at 20, 25, 35, 45 degree Celsius temperatures. The obtained data from this study was applied to different adsorption isotherms. It was observed that at lower temperatures, the adsorption isotherms were fitted to Giles C type, at higher temperatures, they were fitted to Freundlich type

Adsorption of methyl orange from aqueous solution using chitosan/diatomite composite.

Science.gov (United States)

Zhao, Peng; Zhang, Runhu; Wang, Jianglin

2017-04-01

A novel chitosan/diatomite composite was prepared by a simple mixture in the mass ratio to remove methyl orange (MO) from aqueous media in this study. The composite adsorbent was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy analysis. The parameters to influence the adsorption of MO were studied under such conditions as kinetics, adsorption isotherm, pH effect, and thermodynamics. The results revealed that adsorption of MO was initially rapid and the equilibrium time was reached after 40 min. The optimal value of the pH was 5.0 for better adsorption. The equilibrium data were well fitted to the Langmuir isotherm compared to the Freundlich isotherm, and exhibited the highest capacity and a removal rate of 88.37% under an initial dye concentration of 50 mg/L. The kinetic data were well described by the pseudo-second order model. The thermodynamic calculations revealed that the sorption was viable, spontaneous, and exothermic under the conditions studied. In addition, the chitosan/diatomite composite had good adsorption and desorption performance with respect to reusability after six cycles. These results showed that the chitosan/diatomite could be considered as a potential adsorbent for the removal of MO in aqueous solution.

p-Chlorophenol adsorption on activated carbons with basic surface properties

Science.gov (United States)

Lorenc-Grabowska, Ewa; Gryglewicz, Grażyna; Machnikowski, Jacek

2010-05-01

The adsorption of p-chlorophenol (PCP) from aqueous solution on activated carbons (ACs) with basic surface properties has been studied. The ACs were prepared by two methods. The first method was based on the modification of a commercial CWZ AC by high temperature treatment in an atmosphere of ammonia, nitrogen and hydrogen. The second approach comprised the carbonization followed by activation of N-enriched polymers and coal tar pitch using CO 2 and steam as activation agent. The resultant ACs were characterized in terms of porous structure, elemental composition and surface chemistry (pH PZC, acid/base titration, XPS). The adsorption of PCP was carried out from an aqueous solution in static conditions. Equilibrium adsorption isotherm was of L2 type for polymer-based ACs, whereas L3-type isotherm was observed for CWZ ACs series. The Langmuir monolayer adsorption capacity was related to the porous structure and the amount of basic sites. A good correlation was found between the adsorption capacity and the volume of micropores with a width water molecule adsorption on the PCP uptake is discussed.

Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5.

Science.gov (United States)

Ding, Wenjin; Baracchini, Giulia; Klumpp, Michael; Schwieger, Wilhelm; Dittmeyer, Roland

2016-08-25

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 °C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 °C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 °C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 °C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example.

Adsorption of ions by colloids in electrolyte solutions

International Nuclear Information System (INIS)

Kallay, N.

1977-01-01

The adsorption isotherm for ionic adsorption by colloid particles was evaluated. The adsorption process was treated as the reaction between colloid particles and ions. The colloid particle has been here considered as a reaction entity. The possibility of the surface potential determination was presented. The analyses of the experimental data showed, that (at electrolyte concentration higher than the critical coagulation one) the surface potential reaches its zero value

Thermal activation of serpentine for adsorption of cadmium

Energy Technology Data Exchange (ETDEWEB)

Cao, Chun-Yan [College of Land and Environment, Shenyang Agricultural University, Shenyang (China); College of Chemistry, Chemical Engineering and Food Safety, Bohai University, Jinzhou (China); Liang, Cheng-Hua, E-mail: liang110161@163.com [College of Land and Environment, Shenyang Agricultural University, Shenyang (China); Yin, Yan [Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang (China); Du, Li-Yu [College of Land and Environment, Shenyang Agricultural University, Shenyang (China)

2017-05-05

Highlights: • Thermal activated serpentine was prepared by changing heated temperature. • Thermal activated serpentine exhibited excellent adsorption behavior for cadmium. • The adsorption mechanisms could be explained as formation of CdCO{sub 3} and Cd(OH){sub 2}. • The adsorption obeyed Langmuir model and pseudo second order kinetics model. - Abstract: Thermal activated serpentine with high adsorption capacity for heavy metals was prepared. The batch experiment studies were conducted to evaluate the adsorption performance of Cd{sup 2+} in aqueous solution using thermal activated serpentine as adsorbent. These samples before and after adsorption were characterized by XRD, FT-IR, SEM, XPS, and N{sub 2} adsorption-desorption at low temperature. It was found that serpentine with layered structure transformed to forsterite with amorphous structure after thermal treatment at over 700 °C, while the surface area of the samples was increased with activated temperature and the serpentine activated at 700 °C (S-700) presented the largest surface area. The pH of solution after adsorption was increased in different degrees due to hydrolysis of MgO in serpentine, resulting in enhancing adsorption of Cd{sup 2+}. The S-700 exhibited the maximum equilibrium adsorption capacity (15.21 mg/g), which was 2 times more than pristine serpentine. Langmuir isotherm was proved to describe the equilibrium adsorption data better than Freundlich isotherm and pseudo second order kinetics model could fit the adsorption kinetics processes well. Based on the results of characterization with XPS and XRD, the adsorption mechanisms could be explained as primarily formation of CdCO{sub 3} and Cd(OH){sub 2} precipitation on the surface of serpentine.

Thermal activation of serpentine for adsorption of cadmium

International Nuclear Information System (INIS)

Cao, Chun-Yan; Liang, Cheng-Hua; Yin, Yan; Du, Li-Yu

2017-01-01

Highlights: • Thermal activated serpentine was prepared by changing heated temperature. • Thermal activated serpentine exhibited excellent adsorption behavior for cadmium. • The adsorption mechanisms could be explained as formation of CdCO_3 and Cd(OH)_2. • The adsorption obeyed Langmuir model and pseudo second order kinetics model. - Abstract: Thermal activated serpentine with high adsorption capacity for heavy metals was prepared. The batch experiment studies were conducted to evaluate the adsorption performance of Cd"2"+ in aqueous solution using thermal activated serpentine as adsorbent. These samples before and after adsorption were characterized by XRD, FT-IR, SEM, XPS, and N_2 adsorption-desorption at low temperature. It was found that serpentine with layered structure transformed to forsterite with amorphous structure after thermal treatment at over 700 °C, while the surface area of the samples was increased with activated temperature and the serpentine activated at 700 °C (S-700) presented the largest surface area. The pH of solution after adsorption was increased in different degrees due to hydrolysis of MgO in serpentine, resulting in enhancing adsorption of Cd"2"+. The S-700 exhibited the maximum equilibrium adsorption capacity (15.21 mg/g), which was 2 times more than pristine serpentine. Langmuir isotherm was proved to describe the equilibrium adsorption data better than Freundlich isotherm and pseudo second order kinetics model could fit the adsorption kinetics processes well. Based on the results of characterization with XPS and XRD, the adsorption mechanisms could be explained as primarily formation of CdCO_3 and Cd(OH)_2 precipitation on the surface of serpentine.

Removal of Phenol and o-Cresol by Adsorption onto Activated Carbon

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A. Edwin Vasu

2008-01-01

Full Text Available A commercial activated carbon was utilized for the adsorptive removal of phenol and o-cresol from dilute aqueous solutions. Batch mode adsorption studies were performed by varying parameters such as concentration of phenol solution, time, pH and temperature. The well known Freundlich, Langmuir and Redlich-Peterson isotherm equations were applied for the equilibrium adsorption data and the various isotherm parameters were evaluated. The Langmuir monolayer adsorption capacities were found to be 0.7877 and 0.5936 mmole/g, respectively, for phenol and o-cresol. Kinetic studies performed indicate that the sorption processes can be better represented by the pseudo-second order kinetics. The processes were found to be endothermic and the thermodynamic parameters were evaluated. Desorption studies performed indicate that the sorbed phenol molecules can be desorbed with dil. HCl.

Adsorption of malachite green from aqueous solution onto carbon prepared from Arundo donax root

International Nuclear Information System (INIS)

Zhang Jian; Li Yan; Zhang Chenglu; Jing Yuming

2008-01-01

Arundo donax root carbon (ADRC), a new adsorbent, was prepared from Arundo donax root by carbonization. The surface area of the adsorbent was determined 158 m 2 /g by N 2 adsorption isotherm. Batch adsorption experiments were carried out for the removal of malachite green (MG) from aqueous solution using ADRC as adsorbent. The effects of various parameters such as solution pH (3-10), carbon dose (0.15-1.0 g/100 ml) and initial MG concentration (10-100 mg/l) on the adsorption system were investigated. The effective pH was 5-7 and the optimum adsorbent dose was found to be 0.6 g/100 ml. Equilibrium experimental data at 293, 303 and 313 K were better represented by Langmuir isotherm than Freundlich isotherm using linear and non-linear methods. Thermodynamic parameters such as ΔG, ΔH and ΔS were also calculated. The negative Gibbs free energy change and the positive enthalpy change indicated the spontaneous and endothermic nature of the adsorption. The adsorption equilibrium time was 180 min. Adsorption kinetics was determined using pseudo-first-order model, pseudo-second-order model and intraparticle diffusion model. The results showed that the adsorption of MG onto ADRC followed pseudo-second-order model

Adsorptive features of poli(acrylic acid-co-hydroxyapatite) composite for UO22+

International Nuclear Information System (INIS)

Liu Tonghuan; Xu Zhen; Tan Yinping; Zhong Qiangqiang; Wu Wangsuo

2016-01-01

The copolymer of poli(acrylic acid-co-hydroxyapatite) (PAA-HAP) was prepared and characterized by means of FT-IR and SEM analysis. The adsorptive features of PAA-HAP for UO 2 2+ was studied as a function of pH, adsorbent dosage, initial metal ion concentration and temperature. The adsorption isotherm data fitted well to the Langmuir isotherm model. The adsorbed UO 2 2+ can be desorbed effectively by 0.1 M HNO 3 . The maximum adsorption capacities for UO 2 2+ of the dry PAA-HAP was 1.86 x 10 -4 mol/g. The high adsorption capacity and kinetics results indicate that PAA-HAP can be used as an alternative adsorbent to remove UO 2 2+ from aqueous solution. (author)

Hydrogen Adsorption on Nanoporous Biocarbon

Science.gov (United States)

Wood, M. B.; Burress, J. W.; Lapilli, C. M.; Pfeifer, P.; Shah, P. S.; Suppes, G. J.; Dillon, A. C.; Parilla, P. A.

2007-03-01

As a part of the Alliance for Collaborative Research in Alternative Fuel Technology (http://all-craft.missouri.edu) we study activated carbons made from corncob, optimized for storing methane and hydrogen (H2) by physisorption at low pressure. We report here: (a) storage capacities of 73-91 g H2/kg carbon at 77 K and 47 bar, validated in three different laboratories (the 2010 DOE target is 60 g H2/kg system); (b) binding energies from H2 adsorption isotherms (c) temperature-programmed desorption data; (d) degree of graphitization of the carbon surface from Raman spectra; (e) pore structure of carbon from nitrogen and methane adsorption isotherms, and small-angle x-ray scattering. The structural analysis shows that the carbon is highly microporous and that the pore space is highly correlated (micropores do not scatter independently).

Adsorption of NH4+-N on Chinese loess: Non-equilibrium and equilibrium investigations.

Science.gov (United States)

Xie, Haijian; Wang, Shaoyi; Qiu, Zhanhong; Jiang, Jianqun

2017-11-01

NH 4 + -N is a crucial pollutant in landfill leachate and can be in high concentrations for a long period of time due to anaerobic condition of landfills. The adsorption properties of NH 4 + -N on the Chinese loess were investigated using Batch test. The influences of ammonium concentration, temperature, reaction time, slurry concentration, and pH on the adsorption process are evaluated. Adsorption kinetics and isotherm behaviors were studied by applying different models to the test data to determine the adsorption parameters. The equilibrating duration was shown to be less than 60 min. The data on adsorption kinetics can be well fitted by the pseudo-second-order kinetics model. According to the Langmuir isotherm model, the adsorption capacity of Chinese loess about NH 4 + -N was predicted to be 72.30 mg g -1 . The uptake of NH 4 + -N by Chinese loess was considered to be the type of physical adsorption on the basis of D-R isotherm analysis. The optimal pH and slurry concentration are 4 and 2 g/50 ml, respectively. According to the calculated values of free energy, enthalpy and entropy change, the adsorption process is determined to be exothermic. The disorder of the system appeared lowest at temperature of 308.15 K. The predicted Gibb's free energies also indicate the adsorption process is endothermic and spontaneous. The FTIR spectrum and EDX analysis showed the adsorption process of NH 4 + involves cation exchange and dissolution of calcite. Copyright © 2017 Elsevier Ltd. All rights reserved.

Extraction of Cellulose from Kepok Banana Peel (Musa parasidiaca L. for Adsorption Procion Dye

Directory of Open Access Journals (Sweden)

Poedji Loekitowati Hariani

2016-05-01

cellulose. The morphology of cellulose more homogenous than kepok banana peel powder. It was observed that the optimum adsorption of Procion dye by cellulose was on the initial concentration of 30 mg/L, pH solution of 5 and contact time within 30 minutes. The obtained result that cellulose has removal percentage to adsorp Procion dye more higher than kepok banana peel powder. The adsorption equilibrium showed the Langmuir isotherm was described well for adsorption process (R2 = 0.991 than Freundlich isotherm (R2 = 0.922.

Adsorption of precious metals in water by dendrimer modified magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Yen, Chia-Hsin [Institute of Environmental Engineering, National Chiao Tung University, 300 Hsinchu, Taiwan (China); Lien, Hsing-Lung, E-mail: lien.sam@nuk.edu.tw [Department of Civil and Environmental Engineering, National University of Kaohsiung, 811 Kaohsiung, Taiwan (China); Chung, Jung-Shing [Department of Civil and Environmental Engineering, National University of Kaohsiung, 811 Kaohsiung, Taiwan (China); Yeh, Hund-Der [Institute of Environmental Engineering, National Chiao Tung University, 300 Hsinchu, Taiwan (China)

2017-01-15

Highlights: • A reusable magnetic nano-adsorbent is prepared for precious metal adsorption. • The nano-adsorbent (MNP-G3) is synthesized by magnetic nanoparticles and dendrimer. • Higher valent ions show higher adsorption capacity by MNP-G3 suggesting complexation involved. • The pseudo second-order model best describe the adsorption kinetics. • MNP-G3 modified by EDTA significantly improve its adsorption ability for Ag(I). - Abstract: Magnetic nanoparticles modified by third-generation dendrimers (MNP-G3) and MNP-G3 further modified by ethylenediaminetetraacetic acid (EDTA) (MNP-G3-EDTA) were conducted to investigate their ability for recovery of precious metals (Pd(IV), Au(III), Pd(II) and Ag(I)) in water. Experiments were carried out using batch reactors for the studies of adsorption kinetics, adsorption isotherms, competitive adsorption and regeneration. The pseudo second-order model is the best-fit model among others suggesting that the adsorption of precious metals by MNP-G3 in water is a chemisorption process. Three adsorption isotherms namely Langmuir, Freundlich and Dubinin-Radushkevich isotherm were examined and the results showed the similarities and consistency of both linear and nonlinear analyses. Pd(IV) and Au(III) with higher valence exhibited relatively better adsorption efficiency than Pd(II) and Ag(I) with lower valence suggesting that the adsorption of precious metals by MNP-G3 is a function of valence. In the presence of the competing ion Zn(II), the adsorption efficiency of MNP-G3 for all four precious metals was declined significantly. The use of MNP-G3-EDTA revealed an increase in the adsorption efficiency for all four precious metals. However, the low selectivity of MNP-G3 towards precious metals was not enhanced by the modification of EDTA onto the MNP-G3. The regeneration of metal-laden MNP-G3 can be readily performed by using 1.0% HCl solution as a desorbent solution.

Mathematical modelling of the sorption isotherms of quince

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Mitrevski Vangelce

2017-01-01

Full Text Available The moisture adsorption isotherms of quince were determined at four temperatures 15, 30, 45, and 60°C over a range of water activity from 0.110 to 0.920 using the standard static gravimetric method. The experimental data were fitted with generated three parameter sorption isotherm models on Mitrevski et al., and the referent Anderson model known in the scientific and engineering literature as Guggenheim- Anderson-de Boer model. In order to find which models give the best results, large number of numerical experiments was performed. After that, several statistical criteria for estimation and selection of the best sorption isotherm model was used. The performed statistical analysis shows that the generated three parameter model M11 gave the best fit to the sorption data of quince than the referent three parameter Anderson model.

Thiol-functionalized polysilsesquioxane as efficient adsorbent for adsorption of Hg(II) and Mn(II) from aqueous solution

International Nuclear Information System (INIS)

Niu, Yuzhong; Qu, Rongjun; Liu, Xiguang; Mu, Lei; Bu, Baihui; Sun, Yuting; Chen, Hou; Meng, Yangfeng; Meng, Lina; Cheng, Lin

2014-01-01

Highlights: • PMPSQ was promising adsorbent for the removal of Hg(II) and Mn(II). • The adsorption kinetics followed the pseudo-second-order model. • The adsorption isotherms can be described by the monolayer Langmuir model. • The adsorption was controlled by film diffusion and chemical ion-exchange mechanism. - Abstract: Thiol-functionalized polysilsesquioxane was synthesized and used for the adsorption of Hg(II) and Mn(II) from aqueous solution. Results showed that the optimal pH was about 6 and 5 for Hg(II) and Mn(II), respectively. Adsorption kinetics showed that the adsorption equilibriums were established within 100 min and followed pseudo-second-order model. Adsorption isotherms revealed that the adsorption capacities increased with the increasing of temperature. The adsorption was found to be well described by the monolayer Langmuir isotherm model and took place by chemical ion-exchange mechanism. The thermodynamic properties indicated the adsorption processes were spontaneous and endothermic nature. Selectively adsorption showed that PMPSQ can selectively adsorb Hg(II) from binary ion systems in the presence of the coexistent ions Mn(II), Cu(II), Pb(II), Co(II), and Ni(II). Based on the results, it is concluded that PMPSQ had comparable high adsorption efficiency and could be potentially used for the removal of Hg(II) and Mn(II) from aqueous solution

Selective adsorption behavior of Cd(II) ion imprinted polymers synthesized by microwave-assisted inverse emulsion polymerization: Adsorption performance and mechanism

Energy Technology Data Exchange (ETDEWEB)

Zhu, Fang, E-mail: zhufang@tyut.edu.cn [College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, 030024 (China); Li, Luwei [College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, 030024 (China); Xing, Junde [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, 030024 (China)

2017-01-05

Highlights: • Microwave assisted inverse emulsion polymerization was applied to prepare Cd(II) imprinted polymers. • The adsorption capacity was evaluated by static adsorption experiments. • Pseudo-second-order model and Langmuir adsorption isotherm model had the best agreement with the experimental data. • The adsorption was a spontaneous and endothermic process. • Cd(II) imprinted polymers have specific identification for Cd(II). - Abstract: Microwave-assisted inverse emulsion polymerization method was used to prepare Cd(II) imprinted polymer (IIP) by using β-cyclodextrin (β-CD) and acrylamide (AM) as functional monomer, epichlorohydrin (ECH) as crossing-linking agent, ammonium persulfate as initiator. The Cd(II) imprinted polymer was characterized by SEM, FTIR and TGA. The influences of initial concentration of Cd(II), pH values, temperature, time and competitive ions on adsorption capacity and recognition properties are investigated. Under the optimal conditions, the adsorption capacity could reach 107 mg/g. Furthermore, pseudo first order kinetic model, pseudo second order kinetic model and intra-particular diffusion model were used to describe the adsorption kinetic behavior. Results showed that the pseudo-second-order model (R{sup 2} 0.9928–0.9961) had the best agreement with the experimental data. Langmuir adsorption isotherm model described the experimental data well, which indicated that adsorption was mainly monolayer absorption. Moreover, the study of adsorption thermodynamics (ΔG{sup 0} < 0, ΔH{sup 0} > 0, ΔS{sup 0} > 0) suggested that the adsorption process was a spontaneous and endothermic process. Competitive selectivity experiment revealed that imprinted polymer could selectively recognize Cd(II). It provides a new idea for removing Cd(II) from aqueous solution.

Adsorption of sugar surfactants at the air/water interface.

Science.gov (United States)

Varga, Imre; Mészáros, Róbert; Stubenrauch, Cosima; Gilányi, Tibor

2012-08-01

The adsorption isotherms of n-decyl-β-D-glucoside (β-C(10)G(1)) as well as various n-alkyl-β-D-maltosides (β-C(n)G(2)) with n=8, 10, 12 and 14 were determined from surface tension measurements. Based on the analysis of the adsorption isotherms, the total free energy change of adsorption was determined and a novel method was proposed to determine the maximum adsorbed amount of surfactant. It can be concluded that the driving force for adsorption first increases with increasing adsorbed amount of the sugar surfactants and then levels off in a plateau. This peculiar behaviour is interpreted as formation of a thin liquid-like alkane film of overlapping alkyl chains at the air/water interface once a certain adsorbed amount is exceeded. The driving force of adsorption depends on the alkyl chain length only and is not affected by the type of the head group. The hydrophobic contribution to the standard free energy change of adsorption was compared with the values of sodium alkylsulfate and alkyltrimethylammonium bromide surfactants. This comparison reveals that the hydrophobic driving force of adsorption is the largest for the sodium alkylsulfates, whereas it is the same for the sugar surfactants and the alkyltrimethylammonium bromides. Copyright © 2012 Elsevier Inc. All rights reserved.

Adsorption of rhodamine B by acid activated carbon-Kinetic, thermodynamic and equilibrium studies

Directory of Open Access Journals (Sweden)

Shanmugam Arivoli

2009-08-01

Full Text Available A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing Rhodamine B (RDB. The parameters studied include agitation time, initial dye concentration, carbon dose, pH and temperature. The adsorption followed first order kinetics and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm obtained from the Langmuir isotherm plots were 40.161, 35.700, 38.462 and 37.979 mg/g respectively at an initial pH of 7.0 at 30, 40, 50 and 60 0C. The temperature variation study showed that the RDB adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the RDB solutions. Almost 85% removal of RDB was observed at 60 0C. The Langmuir and Freundlich isotherms obtained, positive ?H0 value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of RDB by Banana bark carbon involves physisorption mechanism.

Adsorption characteristics of Pb(II) and Cu(II) ions by domestic clays

International Nuclear Information System (INIS)

Kwon, Ee Yol; Noh, Hea Ran

1990-01-01

This investigation was carried out to study the adsorption characteristics of Pb(II) and Cu(II) ions in aqueous solution by using clays of Gampo 35, Bentonite (chulwon) and Mangwoon 95 which were dug in the country. As the results, the adsorption of metal ions clays were reached equilibrium by shaking for about 40-60 minutes. In acidic solution, the adsorptivity of clays was increased as pH increased, however, Gampo 35 showed the high adsorptivity over 90% even at pH2-3. Pb(II) ion showed better removal efficiency than Cu(II) ion. The adsorptivities of adsorbents showed following order: Gampo 35>Bentonite> Mangwoon 95. The adsorption isotherms of Pb(II) ion on clays were well fitted in Freundlich's equation. Freundlich constantstion isotherms of Pb(II) ion on clays were well fitted in Freundlich's equation. Freundlich constants (1/n) of Gampo 35, Bentonite and Mangwoon 95 were 0.195, 0.271 and 0.314, respectively.(Author)

Removal of three nitrophenols from aqueous solutions by adsorption onto char ash: equilibrium and kinetic modeling

Science.gov (United States)

Magdy, Yehia M.; Altaher, Hossam; ElQada, E.

2018-03-01

In this research, the removal of 2,4 dinitrophenol, 2 nitrophenol and 4 nitrophenol from aqueous solution using char ash from animal bones was investigated using batch technique. Three 2-parameter isotherms (Freundlich, Langmuir, and Temkin) were applied to analyze the experimental data. Both linear and nonlinear regression analyses were performed for these models to estimate the isotherm parameters. Three 3-parameter isotherms (Redlich-Peterson, Sips, Toth) were also tested. Moreover, the kinetic data were tested using pseudo-first order, pseudo-second order, Elovich, Intraparticle diffusion and Boyd methods. Langmuir adsorption isotherm provided the best fit for the experimental data indicating monolayer adsorption. The maximum adsorption capacity was 8.624, 7.55, 7.384 mg/g for 2 nitrophenol, 2,4 dinitrophenol, and 4 nitrophenol, respectively. The experimental data fitted well to pseudo-second order model suggested a chemical nature of the adsorption process. The R 2 values for this model were 0.973 up to 0.999. This result with supported by the Temkin model indicating heat of adsorption to be greater than 10 kJ/mol. The rate controlling step was intraparticle diffusion for 2 nitrophenol, and a combination of intraparticle diffusion and film diffusion for the other two phenols. The pH and temperature of solution were found to have a considerable effect, and the temperature indicated the exothermic nature of the adsorption process. The highest adsorption capacity was obtained at pH 9 and 25 °C.

Adsorption Removal of Environmental Hormones of Dimethyl Phthalate Using Novel Magnetic Adsorbent

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Chia-Chi Chang

2015-01-01

Full Text Available Magnetic polyvinyl alcohol adsorbent M-PVAL was employed to remove and concentrate dimethyl phthalate DMP. The M-PVAL was prepared after sequential syntheses of magnetic Fe3O4 (M and polyvinyl acetate (M-PVAC. The saturated magnetizations of M, M-PVAC, and M-PVAL are 57.2, 26.0, and 43.2 emu g−1 with superparamagnetism, respectively. The average size of M-PVAL by number is 0.75 μm in micro size. Adsorption experiments include three cases: (1 adjustment of initial pH (pH0 of solution to 5, (2 no adjustment of pH0 with value in 6.04–6.64, and (3 adjusted pH0 = 7. The corresponding saturated amounts of adsorption of unimolecular layer of Langmuir isotherm are 4.01, 5.21, and 4.22 mg g−1, respectively. Values of heterogeneity factor of Freundlich isotherm are 2.59, 2.19, and 2.59 which are greater than 1, revealing the favorable adsorption of DMP/M-PVAL system. Values of adsorption activation energy per mole of Dubinin-Radushkevich isotherm are, respectively, of low values of 7.04, 6.48, and 7.19 kJ mol−1, indicating the natural occurring of the adsorption process studied. The tiny size of adsorbent makes the adsorption take place easily while its superparamagnetism is beneficial for the separation and recovery of micro adsorbent from liquid by applying magnetic field after completion of adsorption.

Adsorption Isotherms from Temperature-Programmed Physiosorption - Equilibrium & Kinetics -

NARCIS (Netherlands)

Mugge, J.M.

2000-01-01

The separation of gas mixtures is a major operation in the process industry for hydrocarbon separation, removal of pollutant from effluent streams, and purification of process streams. The work in this thesis is related to gas separation by pressure swing adsorption (PSA); a well-known example is

Effects of carbon nanotubes on phosphorus adsorption behaviors on aquatic sediments.

Science.gov (United States)

Qian, Jin; Li, Kun; Wang, Peifang; Wang, Chao; Shen, Mengmeng; Liu, Jingjing; Tian, Xin; Lu, Bianhe

2017-08-01

Aquatic sediments are believed to be an important sink for carbon nanotubes (CNTs). With novel properties, CNTs can potentially disturb the fate and mobility of the co-existing contaminants in the sediments. Only toxic pollutants have been investigated previously, and to the best of our knowledge, no data has been published on how CNTs influence phosphorus (P) adsorption on aquatic sediments. In this study, multi-walled carbon nanotubes (MWCNTs) were selected as model CNTs. Experimental results indicated that compared to pseudo-first order and intraparticle diffusion models, the pseudo-second-order model is better for describing the adsorption kinetics of sediments and MWCNT-contaminated sediments. Adsorption isotherm studies suggested that the Langmuir model fits the isotherm data well. With the increase in the MWCNT-to-sediment ratio from 0.0% to 5.0%, the theoretical maximum monolayer adsorption capacity (Q max ) for P increased from 0.664 to 0.996mg/g. However, the Langmuir isotherm coefficient (K L ) significantly decreased from 4.231L/mg to 2.874L/mg, indicating the decrease in the adsorption free energy of P adsorbed on the sediments after MWCNT contamination. It was suggested that P was released more easily to the overlying water after the re-suspension of sediments. Moreover, the adsorption of sediments and sediment-MWCNT mixture was endothermic and physical in nature. Results obtained herein suggested that the change in the specific surface area and zeta potential of sediments is related to MWCNT contamination, and the large adsorption capacity of MWCNTs is probably the main factor responsible for the variation in the adsorption of P on aquatic sediments. Copyright © 2017 Elsevier Inc. All rights reserved.

Adsorption Desalination: A Novel Method

KAUST Repository

Ng, Kim Choon

2010-11-15

The search for potable water for quenching global thirst remains a pressing concern throughout many regions of the world. The demand for new and sustainable sources and the associated technologies for producing fresh water are intrinsically linked to the solving of potable water availability and hitherto, innovative and energy efficient desalination methods seems to be the practical solutions. Quenching global thirst by adsorption desalination is a practical and inexpensive method of desalinating the saline and brackish water to produce fresh water for agriculture irrigation, industrial, and building applications. This chapter provides a general overview of the adsorption fundamentals in terms of adsorption isotherms, kinetics, and heat of adsorption. It is then being more focused on the principles of thermally driven adsorption desalination methods. The recent developments of adsorption desalination plants and the effect of operating conditions on the system performance in terms of specific daily water production and performance ratio are presented. Design of a large commercial adsorption desalination plant is also discussed herein.

Off-Gas Adsorption Model Capabilities and Recommendations

Energy Technology Data Exchange (ETDEWEB)

Lyon, Kevin L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Welty, Amy K. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Law, Jack [Idaho National Lab. (INL), Idaho Falls, ID (United States); Ladshaw, Austin [Georgia Inst. of Technology, Atlanta, GA (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2016-03-01

Off-gas treatment is required to reduce emissions from aqueous fuel reprocessing. Evaluating the products of innovative gas adsorption research requires increased computational simulation capability to more effectively transition from fundamental research to operational design. Early modeling efforts produced the Off-Gas SeParation and REcoverY (OSPREY) model that, while efficient in terms of computation time, was of limited value for complex systems. However, the computational and programming lessons learned in development of the initial model were used to develop Discontinuous Galerkin OSPREY (DGOSPREY), a more effective model. Initial comparisons between OSPREY and DGOSPREY show that, while OSPREY does reasonably well to capture the initial breakthrough time, it displays far too much numerical dispersion to accurately capture the real shape of the breakthrough curves. DGOSPREY is a much better tool as it utilizes a more stable set of numerical methods. In addition, DGOSPREY has shown the capability to capture complex, multispecies adsorption behavior, while OSPREY currently only works for a single adsorbing species. This capability makes DGOSPREY ultimately a more practical tool for real world simulations involving many different gas species. While DGOSPREY has initially performed very well, there is still need for improvement. The current state of DGOSPREY does not include any micro-scale adsorption kinetics and therefore assumes instantaneous adsorption. This is a major source of error in predicting water vapor breakthrough because the kinetics of that adsorption mechanism is particularly slow. However, this deficiency can be remedied by building kinetic kernels into DGOSPREY. Another source of error in DGOSPREY stems from data gaps in single species, such as Kr and Xe, isotherms. Since isotherm data for each gas is currently available at a single temperature, the model is unable to predict adsorption at temperatures outside of the set of data currently

Dynamic modeling of fixed-bed adsorption of flue gas using a variable mass transfer model

International Nuclear Information System (INIS)

Park, Jehun; Lee, Jae W.

2016-01-01

This study introduces a dynamic mass transfer model for the fixed-bed adsorption of a flue gas. The derivation of the variable mass transfer coefficient is based on pore diffusion theory and it is a function of effective porosity, temperature, and pressure as well as the adsorbate composition. Adsorption experiments were done at four different pressures (1.8, 5, 10 and 20 bars) and three different temperatures (30, 50 and 70 .deg. C) with zeolite 13X as the adsorbent. To explain the equilibrium adsorption capacity, the Langmuir-Freundlich isotherm model was adopted, and the parameters of the isotherm equation were fitted to the experimental data for a wide range of pressures and temperatures. Then, dynamic simulations were performed using the system equations for material and energy balance with the equilibrium adsorption isotherm data. The optimal mass transfer and heat transfer coefficients were determined after iterative calculations. As a result, the dynamic variable mass transfer model can estimate the adsorption rate for a wide range of concentrations and precisely simulate the fixed-bed adsorption process of a flue gas mixture of carbon dioxide and nitrogen.

The Adsorption of Calmoduline via Nicotinamide Immobilized Poly(HEMA-GMA Cryogels

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Kadir Erol

2016-12-01

Full Text Available The separation and purification methods for the isolation of an important biomolecule calmoduline protein is extremely important. Among these methods, the adsorption technique is extremely popular, and the cryogels as adsorbents with the macro porous structure and interconnected flow channels cryogel they have are preferred in this field. In this study, the adsorption of calmoduline via Ca(II immobilized poly (2-hydroxyethyl methacrylate-glycidyl methacrylate, poly (HEMA-GMA, cryogels through changing interaction time, calmoduline initial concentration and temperature conditions. For the characterization of cryogels, the swelling test, Fourier Transform Infrared (FT-IR Spectroscopy, Scanning Electron Microscopy (SEM, surface area (BET, elemental analysis and ICP-OES methods were performed. Nicotinamide molecule was used as Ca (II chelating agent and the adsorption capacity of the cryogels was estimated as 1.812 mg calmoduline / g cryogel. The adsorption models of the adsorption reaction were examined by the Langmuir and Freundlich isotherm models and was determined to be more appropriate for Langmuir isotherm model.

Adsorptive removal of Auramine-O: Kinetic and equilibrium study

International Nuclear Information System (INIS)

Mall, Indra Deo; Srivastava, Vimal Chandra; Agarwal, Nitin Kumar

2007-01-01

Present study deals with the adsorption of Auramine-O (AO) dye by bagasse fly ash (BFA) and activated carbon-commercial grade (ACC) and laboratory grade (ACL). BFA is a solid waste obtained from the particulate collection equipment attached to the flue gas line of the bagasse fired boilers of cane sugar mills. Batch studies were performed to evaluate the influences of various experimental parameters like initial pH (pH 0 ), contact time, adsorbent dose and initial concentration (C 0 ) for the removal of AO. Optimum conditions for AO removal were found to be pH 0 ∼ 7.0 and equilibrium time ∼30 min for BFA and ∼120 min for activated carbons. Optimum BFA, ACC and ACL dosages were found to be 1, 20 and 2 g/l, respectively. Adsorption of AO followed pseudo-second order kinetics with the initial sorption rate for adsorption on BFA being the highest followed by those on ACL and ACC. The sorption process was found to be controlled by both film and pore diffusion with film diffusion at the earlier stages followed by pore diffusion at the later stages. Equilibrium isotherms for the adsorption of AO on BFA, ACC and ACL were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin isotherm equations using linear correlation coefficient. Langmuir isotherm gave the best correlation of adsorption for all the adsorbents studied. Thermodynamic study showed that adsorption of AO on ACC (with a more negative Gibbs free energy value) is more favoured. BFA which was used without any pretreatment showed high surface area, pore volume and pore size exhibiting its potential to be used as an adsorbent for the removal of AO

Modeling chromatographic columns. Non-equilibrium packed-bed adsorption with non-linear adsorption isotherms

NARCIS (Netherlands)

Özdural, A.R.; Alkan, A.; Kerkhof, P.J.A.M.

2004-01-01

In this work a new mathematical model, based on non-equilibrium conditions, describing the dynamic adsorption of proteins in columns packed with spherical adsorbent particles is used to study the performance of chromatographic systems. Simulations of frontal chromatography, including axial

Adsorption performance of titanium dioxide (TiO2) coated air filters for volatile organic compounds.

Science.gov (United States)

Zhong, Lexuan; Lee, Chang-Seo; Haghighat, Fariborz

2012-12-01

The photocatalytic oxidation (PCO) technology as an alternative method for air purification has been studied for decades and a variety of PCO models indicate that the adsorption of reactants on the catalyst surface is one of the major physical and chemical processes occurring at a heterogeneous photocatalytic reaction. However, limited study explored the adsorption effect of a photocatalyst. This study carried out a systematic evaluation of adsorption performance of titanium dioxide (TiO(2)) coated fiberglass fibers (FGFs), TiO(2) coated carbon cloth fibers (CCFs), and original CCFs air filters at various relative humidity conditions for nine volatile organic compounds. TiO(2)/FGFs, TiO(2)/CCFs, and CCFs were characterized by SEM for morphology and N(2) adsorption isotherm for BET surface area and pore structure. A bench-scale adsorption test setup was constructed and adsorption tests were performed at various relative humidity conditions and four different injected concentrations for each compound. The isothermal adsorption curves at low concentration levels were obtained and they were well described by Langmuir isotherm model. It was noticed that there were significant differences between the adsorption behaviors and photocatalytic activities of TiO(2)/FGFs and TiO(2)/CCFs. It was concluded that adsorption performance is closely related to the characteristics of substrates and therefore, the development of a substrate with high adsorption ability is a promising trend for improving the performance of the UV-PCO technology. Copyright © 2012 Elsevier B.V. All rights reserved.

Adsorption study of cadmium (II) and lead (II) on radish peels

International Nuclear Information System (INIS)

Anwar, J.; Shafique, U.; Salman, M.; Zaman, W.; Memoona, M.

2009-01-01

The removal efficiency of heavy metals like Cd(II) and Pb(II) from aqueous solutions by adsorption on Raphanus sativus (Radish peels) has been studied. The effects of time, pH, concentration of adsorbent and agitation speed on adsorption have been evaluated. It is found that radish peels powder has high removal efficiency for both the metals. Batch adsorption study has shown that Cd(II) and Pb(II) has been removed up to 88% and 86% respectively. Adsorption equilibriums for both metals have been described by the Langmuir isotherm. The maximum amount of heavy metals (Q ) adsorbed at max equilibrium were 7.5 and 1.23 mg/g for Cd(II) and Pb(II) respectively as evaluated by Langmuir isotherm. It is concluded that waste materials like radish peels can be used for removal of heavy metals from aqueous streams. (author)

Adsorptive removal of Cu(II) from aqueous solutions using collagen-tannin resin

Energy Technology Data Exchange (ETDEWEB)

Sun Xia; Huang Xin [Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China); Liao Xuepin, E-mail: xpliao@scu.edu.cn [Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China); National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China); Shi Bi, E-mail: shibi@scu.edu.cn [National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China)

2011-02-28

The collagen-tannin resin (CTR), as a novel adsorbent, was prepared via a reaction of collagen with black wattle tannin and aldehyde, and its adsorption properties to Cu(II) were systematically investigated, including pH effect, adsorption equilibrium, adsorption kinetics, and column adsorption. The adsorption capacity of Cu(II) on CTR was pH-dependent, and it increased with the increase of solution pH. The adsorption isotherms were well described by Langmuir isotherm model with correlating constant (R{sup 2}) higher than 0.99. The adsorption capacity determined at 303 K was high up to 0.26 mmol/g, which was close to the value (0.266 mmol/g) estimated from Langmuir equation. The adsorption capacity was increased with the increase of temperature, and thermodynamic calculations suggested that the adsorption of Cu(II) on CTR is an endothermic process. The adsorption kinetics were well fitted by the pseudo-second-order rate model. Further column studies suggested that CTR was effective for the removal of Cu(II) from solutions, and more than 99% of Cu(II) was desorbed from column using 0.1 mol/L HNO{sub 3} solution. The CTR column can be reused to adsorb Cu(II) without any loss of adsorption capacity.

Contribution of Ash Content Related to Methane Adsorption Behaviors of Bituminous Coals

Directory of Open Access Journals (Sweden)

Yanyan Feng

2014-01-01

Full Text Available Methane adsorption isotherms on coals with varying ash contents were investigated. The textural properties were characterized by N2 adsorption/desorption isotherm at 77 K, and methane adsorption characteristics were measured at pressures up to 4.0 MPa at 298 K, 313 K, and 328 K, respectively. The Dubinin-Astakhov model and the Polanyi potential theory were employed to fit the experimental data. As a result, ash content correlated strongly to methane adsorption capacity. Over the ash range studied, 9.35% to 21.24%, the average increase in methane adsorption capacity was 0.021 mmol/g for each 1.0% rise in ash content. With the increasing ash content range of 21.24%~43.47%, a reduction in the maximum adsorption capacities of coals was observed. In addition, there was a positive correlation between the saturated adsorption capacity and the specific surface area and micropore volume of samples. Further, this study presented the heat of adsorption, the isosteric heat of adsorption, and the adsorbed phase specific heat capacity for methane adsorption on various coals. Employing the proposed thermodynamic approaches, the thermodynamic maps of the adsorption processes of coalbed methane were conducive to the understanding of the coal and gas simultaneous extraction.

Modeling of the thermal effects of hydrogen adsorption on activated carbon

International Nuclear Information System (INIS)

Richard, M.-A.; Chahine, R.

2006-01-01

'Full text:' Heat management is one of the most critical issues for the design of efficient adsorption-based storage of hydrogen. We present simulations of mass and energy balance for hydrogen and nitrogen adsorption on activated carbon over wide temperature and pressure ranges. First, the Dubinin-Astakhov (DA) model is adapted to model excess hydrogen and nitrogen adsorption isotherms at high pressures and supercritical temperatures assuming a constant microporous adsorption volume. The five parameter modified D-A adsorption model is shown to fit the experimental data over the temperature range (35 K-293 K) for hydrogen and (93 K-298 K) for nitrogen and pressure range (0-6 MPa) within the experimental uncertainties of the measurement system. We derive the thermodynamic properties of the adsorbed phase from this analytical expression of the measured data. The mass and energy rate balance equations in a microporous adsorbent/adsorbate system are then presented and validated with nitrogen desorption experiments. Finally, simulations of adiabatic and isothermal filling of adsorption-based hydrogen storage are presented and discussed. (author)

Solution of adsorption problems involving steep moving profiles

DEFF Research Database (Denmark)

Kiil, Søren; Bhatia, Suresh K.

1998-01-01

The moving finite element collocation method proposed by Kiil et al. (1995) for solution of problems with steep gradients is further developed to solve transient problems arising in the field of adsorption. The technique is applied to a model of adsorption in solids with bidisperse pore structures....... Numerical solutions were found to match the analytical solution when it exists (i.e. when the adsorption isotherm is linear). Results of this application study show that the method is simple yet sufficiently accurate for use in adsorption problems with steep moving gradients, where global collocation...

Parameterization and evaluation of sulfate adsorption in a dynamic soil chemistry model

International Nuclear Information System (INIS)

Martinson, Liisa; Alveteg, Mattias; Warfvinge, Per

2003-01-01

Including sulfate adsorption improves the dynamic behavior of the SAFE model. - Sulfate adsorption was implemented in the dynamic, multi-layer soil chemistry model SAFE. The process is modeled by an isotherm in which sulfate adsorption is considered to be fully reversible and dependent on sulfate concentration as well as pH in soil solution. The isotherm was parameterized by a site-specific series of simple batch experiments at different pH (3.8-5.0) and sulfate concentration (10-260 μmol l -1 ) levels. Application of the model to the Lake Gaardsjoen roof covered site shows that including sulfate adsorption improves the dynamic behavior of the model and sulfate adsorption and desorption delay acidification and recovery of the soil. The modeled adsorbed pool of sulfate at the site reached a maximum level of 700 mmol/m 2 in the late 1980s, well in line with experimental data

Adsorption of amylase enzyme on ultrafiltration membranes

DEFF Research Database (Denmark)

Beier, Søren; Enevoldsen, Ann Dorrit; Kontogeorgis, Georgios

2007-01-01

A method to measure the static adsorption on membrane surfaces has been developed and described. The static adsorption of an amylase-F has been measured on two different ultrafiltration membranes, both with a cut-off value of 10 kDa (a PES membrane and the ETNA10PP membrane, which is a surface......-modified PVDF membrane). The adsorption follows the Langmuir adsorption theory. Thus, the static adsorption consists of monolayer coverage. The static adsorption is expressed both as a permeability drop and an adsorption resistance. From the adsorption isotherms the maximum static permeability drops...... and the maximum static adsorption resistances are determined. The maximum static permeability drop for the hydrophobic PES membrane is 75 % and the maximum static adsorption resistance is 0.014 m2hbar/L. The maximum static permeability drop for the hydrophilic surface-modified PVDF membrane (ETNA10PP) is 23...

Investigation of uranium (VI) adsorption by polypyrrole

Energy Technology Data Exchange (ETDEWEB)

Abdi, S. [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Nasiri, M., E-mail: mnasiri@semnan.ac.ir [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Mesbahi, A. [Faculty of Chemical, Petroleum and Gas Engineering, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Khani, M.H. [Nuclear Fuel Cycle Research School, Nuclear Science and Technology Research Institute, Tehran, 14395-836 (Iran, Islamic Republic of)

2017-06-15

Highlights: • The adsorbent (polypyrrole) was synthesized by a chemical method using PEG, DBSNa and CTAB as the surfactant. • The solution pH was one of the most important parameters affecting the adsorption of uranium. • The CTAB provided higher removal percentage compared with the other surfactants. • The maximum adsorption capacity obtained from Langmuir isotherm was 87.72 mg/g. • The pseudo second-order model fitted well with the adsorption kinetic of polypyrrole to uranium. - Abstract: The purpose of this study was to investigate the adsorption of uranium (VI) ions on the polypyrrole adsorbent. Polypyrrole was synthesized by a chemical method using polyethylene glycol, sodium dodecylbenzenesulfonate, and cetyltrimethylammonium bromide as the surfactant and iron (III) chloride as an oxidant in the aqueous solution. The effect of various surfactants on the synthesized polymers and their performance as the uranium adsorbent were investigated. Adsorbent properties were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. The effect of different parameters such as pH, contact time, initial metal ion concentrations, adsorbent dose, and the temperature was investigated in the batch system for uranium adsorption process. It has been illustrated that the adsorption equilibrium time is 7 min. The results showed that the Freundlich model had the best agreement and the maximum adsorption capacity of polypyrrole for uranium (VI) was determined 87.72 mg/g from Langmuir isotherm. In addition, the mentioned adsorption process was fast and the kinetic data were fitted to the Pseudo first and second order models. The adsorption kinetic data followed the pseudo-second-order kinetic model. Moreover, the thermodynamic parameters ΔG{sup 0}, ΔH{sup 0} and ΔS{sup 0} showed that the uranium adsorption process by polypyrrole was endothermic and spontaneous.

ADSORPTION AND RELEASING PROPERTIES OF BEAD CELLULOSE

Institute of Scientific and Technical Information of China (English)

A. Morales; E. Bordallo; V. Leon; J. Rieumont

2004-01-01

The adsorption of some dyes on samples of bead cellulose obtained in the Unit of Research-Production "Cuba 9"was studied. Methylene blue, alizarin red and congo red fitted the adsorption isotherm of Langmuir. Adsorption kinetics at pH = 6 was linear with the square root of time indicating the diffusion is the controlling step. At pH = 12 a non-Fickian trend was observed and adsorption was higher for the first two dyes. Experiments carried out to release the methylene blue occluded in the cellulose beads gave a kinetic behavior of zero order. The study of cytochrome C adsorption was included to test a proteinic material. Crosslinking of bead cellulose was performed with epichlorohydrin decreasing its adsorption capacity in acidic or alkaline solution.

Adsorption characteristics of As(III) from aqueous solution on iron oxide coated cement (IOCC)

International Nuclear Information System (INIS)

Kundu, Sanghamitra; Gupta, A.K.

2007-01-01

Contamination of potable groundwater with arsenic is a serious health hazard, which calls for proper treatment before its use as drinking water. The objective of the present study is to assess the effectiveness of iron oxide coated cement (IOCC) for As(III) adsorption from aqueous solution. Batch studies were conducted to study As(III) adsorption onto IOCC at ambient temperature as a function of adsorbent dose, pH, contact time, initial arsenic concentration and temperature. Kinetics reveal that the uptake of As(III) ion is very rapid and most of fixation occurs within the first 20 min of contact. The pseudo-second order rate equation successfully described the adsorption kinetics. Langmuir, Freundlich, Redlich-Peterson (R-P), and Dubinin-Radushkevich (D-R) models were used to describe the adsorption isotherms at different initial As(III) concentrations and at 30 g l -1 fixed adsorbent dose. The maximum adsorption capacity of IOCC for As(III) determined from the Langmuir isotherm was 0.69 mg g -1 . The mean free energy of adsorption (E) calculated from the D-R isotherm was found to be 2.86 kJ mol -1 which suggests physisorption. Thermodynamic parameters indicate an exothermic nature of adsorption and a spontaneous and favourable process. The results suggest that IOCC can be suitably used for As(III) removal from aqueous solutions

Kinetics and thermodynamics of aqueous Cu(II adsorption on heat regenerated spent bleaching earth

Directory of Open Access Journals (Sweden)

Enos W. Wambu

2011-08-01

Full Text Available This study investigated the kinetics and thermodynamics of copper(II removal from aqueous solutions using spent bleaching earth (SBE. The spent bleaching earth, a waste material from edible oil processing industries, was reactivated by heat treatment at 370 oC after residual oil extraction in excess methyl-ethyl ketone. Copper adsorption tests were carried out at room temperature (22±3 oC using 5.4 x 10-3C M metal concentrations. More than 70% metal removal was recorded in the first four hours although adsorption continued to rise to within 90% at 42 hours. The pH, adsorbent dosage and initial concentrations were master variables affecting RSBE adsorption of Cu(II ions. The adsorption equilibrium was adequately described by the Dubinin-Radushkevich (D-R and the Temkin isotherms and the maximum sorption capacity derived from the D-R isotherm was compared with those of some other low cost adsorbents. The adsorption process was found to follow Lagergren Pseudo-second order kinetics complimented by intra-particle diffusion kinetics at prolonged periods of equilibration. Based on the D-R isotherm adsorption energy and the thermodynamic adsorption free energy ∆G, it was suggested that the process is spontaneous and based on electrostatic interactions between the metal ions and exposed active sites in the adsorbent surface.

Adsorption of Cr(III) from Aqueous Solution using Borax Sludge.

Science.gov (United States)

Senberber, Fatma Tugce; Yildirim, Meral; Mermer, Nevin Karamahmut; Derun, Emek Moroydor

2017-09-01

Borax sludge is the waste produced by a trommel sieve in the borax production process and is used as an adsorbent for Cr(III) removal. The effects of various parameters, including pH, initial Cr(III) concentration and contact time were investigated for batch adsorption of Cr(III). The experimental results obtained were applied to different adsorption isotherms and kinetic models. The results indicated that the Temkin isotherm (R2 = 0.9749) was most suitable to explain the adsorption characteristics of borax sludge, and the removal of Cr(III) was achieved by a physisorption process. The overall kinetic data fitted the pseudo-second order rate model (R2 = 0.9990). According to thermodynamic studies, which were carried out at different temperatures, changes in enthalpy (ΔH) and entropy (ΔS) values for Cr(III) adsorption by borax sludge were determined to be 69.395 kJ/mol and 0.276 kJ/mol K, respectively. The study implied that borax sludge could be used as an alternative adsorbent in the adsorption of Cr(III) from aqueous solutions.

Adsorption of uranium(VI) from sulphate solutions using Amberlite IRA-402 resin: Equilibrium, kinetics and thermodynamics study

International Nuclear Information System (INIS)

Solgy, Mostafa; Taghizadeh, Majid; Ghoddocynejad, Davood

2015-01-01

Highlights: • Adsorption of uranium from sulphate solutions by an anion exchange resin. • The effects of pH, contact time and adsorbent dosage were investigated. • The adsorption equilibrium is well described by the Freundlich isotherm model. • The adsorption kinetics can be predicted by the pseudo second-order model. • The adsorption is a physical, spontaneous and endothermic process. - Abstract: In the present study, adsorption of uranium from sulphate solutions was evaluated using Amberlite IRA-402 resin. The variation of adsorption process was investigated in batch sorption mode. The parameters studied were pH, contact time and adsorbent dosage. Langmuir and Freundlich isotherm models were used in order to present a mathematical description of the equilibrium data at three different temperatures (25 °C, 35 °C and 45 °C). The final results confirmed that the equilibrium data tend to follow Freundlich isotherm model. The maximum adsorption capacity of Amberlite IRA-402 for uranium(VI) was evaluated to be 213 mg/g for the Langmuir model at 25 °C. The adsorption of uranium on the mentioned anion exchange resin was found to follow the pseudo-second order kinetic model, indicating that chemical adsorption was the rate limiting-step. The values of thermodynamic parameters proved that adsorption process of uranium onto Amberlite IRA-402 resin could be considered endothermic (ΔH > 0) and spontaneous (ΔG < 0)

Adsorption Study of Cobalt on Treated Granular Activated Carbon

OpenAIRE

Y. V. Hete; S. B. Gholase; R. U. Khope

2012-01-01

This study is carried out for the removal of cobalt from aqueous solution using granular activated carbon in combination with p-nitro benzoic acid at temperature 25±1 °C. The adsorption isotherm of cobalt on granular activated carbon has been determined and the data fitted reasonably well to the Langmuir and Freundlich isotherm for activated carbon.

Artificial neural network (ANN) approach for modeling Zn(II) adsorption in batch process

Energy Technology Data Exchange (ETDEWEB)

Yildiz, Sayiter [Engineering Faculty, Cumhuriyet University, Sivas (Turkmenistan)

2017-09-15

Artificial neural networks (ANN) were applied to predict adsorption efficiency of peanut shells for the removal of Zn(II) ions from aqueous solutions. Effects of initial pH, Zn(II) concentrations, temperature, contact duration and adsorbent dosage were determined in batch experiments. The sorption capacities of the sorbents were predicted with the aid of equilibrium and kinetic models. The Zn(II) ions adsorption onto peanut shell was better defined by the pseudo-second-order kinetic model, for both initial pH, and temperature. The highest R{sup 2} value in isotherm studies was obtained from Freundlich isotherm for the inlet concentration and from Temkin isotherm for the sorbent amount. The high R{sup 2} values prove that modeling the adsorption process with ANN is a satisfactory approach. The experimental results and the predicted results by the model with the ANN were found to be highly compatible with each other.

Artificial neural network (ANN) approach for modeling Zn(II) adsorption in batch process

International Nuclear Information System (INIS)

Yildiz, Sayiter

2017-01-01

Artificial neural networks (ANN) were applied to predict adsorption efficiency of peanut shells for the removal of Zn(II) ions from aqueous solutions. Effects of initial pH, Zn(II) concentrations, temperature, contact duration and adsorbent dosage were determined in batch experiments. The sorption capacities of the sorbents were predicted with the aid of equilibrium and kinetic models. The Zn(II) ions adsorption onto peanut shell was better defined by the pseudo-second-order kinetic model, for both initial pH, and temperature. The highest R"2 value in isotherm studies was obtained from Freundlich isotherm for the inlet concentration and from Temkin isotherm for the sorbent amount. The high R"2 values prove that modeling the adsorption process with ANN is a satisfactory approach. The experimental results and the predicted results by the model with the ANN were found to be highly compatible with each other.

Tc-99 Adsorption on Selected Activated Carbons - Batch Testing Results

Energy Technology Data Exchange (ETDEWEB)

Mattigod, Shas V.; Wellman, Dawn M.; Golovich, Elizabeth C.; Cordova, Elsa A.; Smith, Ronald M.

2010-12-01

CH2M HILL Plateau Remediation Company (CHPRC) is currently developing a 200-West Area groundwater pump-and-treat system as the remedial action selected under the Comprehensive Environmental Response, Compensation, and Liability Act Record of Decision for Operable Unit (OU) 200-ZP-1. This report documents the results of treatability tests Pacific Northwest National Laboratory researchers conducted to quantify the ability of selected activated carbon products (or carbons) to adsorb technetium-99 (Tc-99) from 200-West Area groundwater. The Tc-99 adsorption performance of seven activated carbons (J177601 Calgon Fitrasorb 400, J177606 Siemens AC1230AWC, J177609 Carbon Resources CR-1240-AW, J177611 General Carbon GC20X50, J177612 Norit GAC830, J177613 Norit GAC830, and J177617 Nucon LW1230) were evaluated using water from well 299-W19-36. Four of the best performing carbons (J177606 Siemens AC1230AWC, J177609 Carbon Resources CR-1240-AW, J177611 General Carbon GC20X50, and J177613 Norit GAC830) were selected for batch isotherm testing. The batch isotherm tests on four of the selected carbons indicated that under lower nitrate concentration conditions (382 mg/L), Kd values ranged from 6,000 to 20,000 mL/g. In comparison. Under higher nitrate (750 mg/L) conditions, there was a measureable decrease in Tc-99 adsorption with Kd values ranging from 3,000 to 7,000 mL/g. The adsorption data fit both the Langmuir and the Freundlich equations. Supplemental tests were conducted using the two carbons that demonstrated the highest adsorption capacity to resolve the issue of the best fit isotherm. These tests indicated that Langmuir isotherms provided the best fit for Tc-99 adsorption under low nitrate concentration conditions. At the design basis concentration of Tc 0.865 µg/L(14,700 pCi/L), the predicted Kd values from using Langmuir isotherm constants were 5,980 mL/g and 6,870 mL/g for for the two carbons. These Kd values did not meet the target Kd value of 9,000 mL/g. Tests

Effective adsorption of malachite green using magnetic barium phosphate composite from aqueous solution

Science.gov (United States)

Zhang, Fan; Wei, Zhong; Zhang, Wanning; Cui, Haiyan

2017-07-01

Magnetic Ba3(PO4)2/Fe3O4-nanoparticle (called BPFN) was prepared, characterized, and developed as a low-cost adsorbent for malachite green (MG) from aqueous solution. Factors such as adsorption temperature, pH of solution, dosage of adsorbent, adsorption kinetics and isotherms were investigated. The maximum adsorption capacity obtained in this work was 1639 mg g- 1 at 45 °C and pH 6. The adsorption process fitted the pseudo-first-order kinetic model and Langmuir isotherm model. Evidences from zeta potential, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) data revealed that the adsorption process was driven by electrostatic attraction, the interaction between Lewis base sbnd N(CH3)2 in MG and Lewis acid Ba sites of BPFN. In addition, the BPFN could be easily regenerated by a magnet and the adsorption capacity maintained at 70% after five cycles. The present study suggests that the BPFN had high potential of removing MG from wastewater.

Adsorption of malachite green onto carbon prepared from borassus bar

International Nuclear Information System (INIS)

Arivoli, S; Hema, M; Prasath, P Martin Deva

2009-01-01

An activated carbon prepared from Borassus bark, a low-cost source, by sulphuric acid activation, was tested for its ability to remove malachite green in aqueous solution. The parameters studied included contact time, initial dye concentration, carbon dose, pH, and temperature. The adsorption followed first order rate equation and the rate was mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacities (Qm) obtained from the Langmuir isotherm plots were 20.70, 20.25, 19.76, and 19.34 mg/g at 30, 40, 50, and 60 degree C, respectively, at an initial pH of 6.0. The temperature variation study showed that the malachite green adsorption was endothermic and spontaneous with increased randomness at the solid solution interface. (author)

Thermodynamics of hydrogen adsorption in MOF-177 at low temperatures: measurements and modelling

Energy Technology Data Exchange (ETDEWEB)

Poirier, Eric [College of Engineering, Purdue University, West Lafayette, IN 47907 (United States); Dailly, Anne [Chemical and Environmental Sciences Laboratory, General Motors Corporation, Warren, MI 48090 (United States)], E-mail: poirierem@gmail.com, E-mail: anne.dailly@gm.com

2009-05-20

Hydrogen adsorption measurements and modelling for the Zn-based microporous metal-organic framework (MOF) Zn{sub 4}O(1,3,5-benzenetribenzoate){sub 2}, MOF-177, were performed over the 50-77 K and 0-40 bar ranges. The maximum excess adsorption measured under these conditions varies over about 105-70 mg g{sup -1}. An analysis of the isotherms near saturation shows that hydrogen is ultimately adsorbed in an incompressible phase whose density is comparable to that of the bulk liquid. These liquid state properties observed under supercritical conditions reveal a remarkable effect of nanoscale confinement. The entire set of adsorption isotherms can be well described using a micropore filling model. The latter is used, in particular, to determine the absolute amounts adsorbed and the adsorption enthalpy. When expressed in terms of absolute adsorption, the isotherms show considerable hydrogen storage capacities, reaching up to 125 mg g{sup -1} at 50 K and 25 bar. The adsorption enthalpies are calculated as a function of fractional filling and range from 3 to 5 kJ mol{sup -1} in magnitude, in accordance with physisorption. These results are discussed with respect to a similar analysis performed on another Zn-based MOF, Zn{sub 4}O(1,4-benzenedicarboxylate){sub 3}, IRMOF-1, presented recently. It is found that both materials adsorb hydrogen by similar mechanisms.

Thermodynamics of hydrogen adsorption in MOF-177 at low temperatures: measurements and modelling

International Nuclear Information System (INIS)

Poirier, Eric; Dailly, Anne

2009-01-01

Hydrogen adsorption measurements and modelling for the Zn-based microporous metal-organic framework (MOF) Zn 4 O(1,3,5-benzenetribenzoate) 2 , MOF-177, were performed over the 50-77 K and 0-40 bar ranges. The maximum excess adsorption measured under these conditions varies over about 105-70 mg g -1 . An analysis of the isotherms near saturation shows that hydrogen is ultimately adsorbed in an incompressible phase whose density is comparable to that of the bulk liquid. These liquid state properties observed under supercritical conditions reveal a remarkable effect of nanoscale confinement. The entire set of adsorption isotherms can be well described using a micropore filling model. The latter is used, in particular, to determine the absolute amounts adsorbed and the adsorption enthalpy. When expressed in terms of absolute adsorption, the isotherms show considerable hydrogen storage capacities, reaching up to 125 mg g -1 at 50 K and 25 bar. The adsorption enthalpies are calculated as a function of fractional filling and range from 3 to 5 kJ mol -1 in magnitude, in accordance with physisorption. These results are discussed with respect to a similar analysis performed on another Zn-based MOF, Zn 4 O(1,4-benzenedicarboxylate) 3 , IRMOF-1, presented recently. It is found that both materials adsorb hydrogen by similar mechanisms.

Adsorption of malachite green from aqueous solution by using novel chitosan ionic liquid beads.

Science.gov (United States)

Naseeruteen, Faizah; Hamid, Nur Shahirah Abdul; Suah, Faiz Bukhari Mohd; Ngah, Wan Saime Wan; Mehamod, Faizatul Shimal

2018-02-01

Chitosan ionic liquid beads were prepared from chitosan and 1-butyl-3-methylimidazolium based ionic liquids to remove Malachite Green (MG) from aqueous solutions. Batch adsorption experiments were carried out as a function of initial pH, adsorbent dosage, agitation time and initial MG concentration. The optimum conditions were obtained at pH 4.0, 0.008g of adsorbent dosage and 20min of agitation time were utilized in the kinetic and isotherm studies. Three kinetic models were applied to analyze the kinetic data and pseudo-second order was found to be the best fitted model with R 2 >0.999. In order to determine the adsorption capacity, the sorption data were analyzed using the linear form of Langmuir, Freundlich and Temkin equations. The isotherm was best fitted by Langmuir isotherm model. The maximum adsorption capacity (q max ) obtained from Langmuir isotherm for two chitosan beads 1-butyl-3-methylimidazolium acetate A and 1-butyl-3-methylimidazolium B are 8.07mgg -1 and 0.24mgg -1 respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Adsorption of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-metylphenoxyacetic acid onto activated carbons derived from various lignocellulosic materials.

Science.gov (United States)

Doczekalska, Beata; Kuśmierek, Krzysztof; Świątkowski, Andrzej; Bartkowiak, Monika

2018-05-04

Adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-metylphenoxyacetic acid (MCPA) from aqueous solution onto activated carbons derived from various lignocellulosic materials including willow, miscanthus, flax, and hemp shives was investigated. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first order and pseudo-second order equations. The adsorption kinetics of both herbicides was better represented by the pseudo-second order model. The adsorption isotherms of 2,4-D and MCPA on the activated carbons were analyzed using the Freundlich and Langmuir isotherm models. The equilibrium data followed the Langmuir isotherm. The effect of pH on the adsorption was also studied. The results showed that the activated carbons prepared from the lignocellulosic materials are efficient adsorbents for the removal of 2,4-D and MCPA from aqueous solutions.

Adsorptive desulfurization of model oil using untreated, acid activated and magnetite nanoparticle loaded bentonite as adsorbent

Directory of Open Access Journals (Sweden)

Muhammad Ishaq

2017-02-01

Full Text Available The present research work focuses on a novel ultraclean desulfurization process of model oil by the adsorption method using untreated, acid activated and magnetite nanoparticle loaded bentonite as adsorbent. The parameters investigated are effect of contact time, adsorbent dose, initial dibenzothiophene (DBT concentration and temperature. Experimental tests were conducted in batch process. Pseudo first and second order kinetic equations were used to examine the experimental data. It was found that pseudo second order kinetic equation described the data of the DBT adsorption onto all types of adsorbents very well. The isotherm data were analyzed using Langmuir and Freundlich isotherm models. The Langmuir isotherm model fits the data very well for the adsorption of DBT onto all three forms of adsorbents. The adsorption of DBT was also investigated at different adsorbent doses and was found that the percentage adsorption of DBT was increased with increasing the adsorbent dose, while the adsorption in mg/g was decreased with increasing the adsorbent dose. The prepared adsorbents were analyzed by scanning electron microscopy (SEM, energy dispersive X-ray spectrometry (EDX and X-ray diffraction (XRD.

Equilibrium and kinetic adsorption study of Basic Yellow 28 and Basic Red 46 by a boron industry waste

International Nuclear Information System (INIS)

Olgun, Asim; Atar, Necip

2009-01-01

In this study, the adsorption characteristics of Basic Yellow 28 (BY 28) and Basic Red 46 (BR 46) onto boron waste (BW), a waste produced from boron processing plant were investigated. The equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of two dyes could be described reasonably well by a generalized isotherm. Kinetic studies indicated that the kinetics of the adsorption of BY 28 and BR 46 onto BW follows a pseudo-second-order model. The result showed that the BW exhibited high-adsorption capacity for basic dyes and the capacity slightly decreased with increasing temperature. The maximum adsorption capacities of BY 28 and BR 46 are reported at 75.00 and 74.73 mg g -1 , respectively. The dye adsorption depended on the initial pH of the solution with maximum uptake occurring at about pH 9 and electrokinetic behavior of BW. Activation energy of 15.23 kJ/mol for BY 28 and 18.15 kJ/mol for BR 46 were determined confirming the nature of the physisorption onto BW. These results indicate that BW could be employed as low-cost material for the removal of the textile dyes from effluents

Equilibrium and kinetic adsorption study of Basic Yellow 28 and Basic Red 46 by a boron industry waste

Energy Technology Data Exchange (ETDEWEB)

Olgun, Asim [Department of Chemistry, Faculty of Arts and science, University of Dumlupinar, Kuetahya (Turkey)], E-mail: aolgun@dumlupinar.edu.tr; Atar, Necip [Department of Chemistry, Faculty of Arts and science, University of Dumlupinar, Kuetahya (Turkey)

2009-01-15

In this study, the adsorption characteristics of Basic Yellow 28 (BY 28) and Basic Red 46 (BR 46) onto boron waste (BW), a waste produced from boron processing plant were investigated. The equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of two dyes could be described reasonably well by a generalized isotherm. Kinetic studies indicated that the kinetics of the adsorption of BY 28 and BR 46 onto BW follows a pseudo-second-order model. The result showed that the BW exhibited high-adsorption capacity for basic dyes and the capacity slightly decreased with increasing temperature. The maximum adsorption capacities of BY 28 and BR 46 are reported at 75.00 and 74.73 mg g{sup -1}, respectively. The dye adsorption depended on the initial pH of the solution with maximum uptake occurring at about pH 9 and electrokinetic behavior of BW. Activation energy of 15.23 kJ/mol for BY 28 and 18.15 kJ/mol for BR 46 were determined confirming the nature of the physisorption onto BW. These results indicate that BW could be employed as low-cost material for the removal of the textile dyes from effluents.

Adsorption of cadmium (II) ions from aqueous solution by a new low-cost adsorbent-Bamboo charcoal

Energy Technology Data Exchange (ETDEWEB)

Wang Fayuan [State Key Joint Laboratory of Environment Simulation and Pollution Control, Department of Environmental Science and Engineering, Tsinghua University, Qinghuayuan, Haidian District, Beijing 100084 (China); Wang Hui, E-mail: wanghui@mail.tsinghua.edu.cn [State Key Joint Laboratory of Environment Simulation and Pollution Control, Department of Environmental Science and Engineering, Tsinghua University, Qinghuayuan, Haidian District, Beijing 100084 (China); Ma Jianwei [State Key Joint Laboratory of Environment Simulation and Pollution Control, Department of Environmental Science and Engineering, Tsinghua University, Qinghuayuan, Haidian District, Beijing 100084 (China)

2010-05-15

Batch adsorption experiments were conducted for the adsorption of Cd (II) ions from aqueous solution by bamboo charcoal. The results showed that the adsorption of Cd (II) ions was very fast initially and the equilibrium time was 6 h. High pH ({>=}8.0) was favorable for the adsorption and removal of Cd (II) ions. Higher initial Cd concentrations led to lower removal percentages but higher adsorption capacity. As the adsorbent dose increased, the removal of Cd increased, while the adsorption capacity decreased. Adsorption kinetics of Cd (II) ions onto bamboo charcoal could be best described by the pseudo-second-order model. The adsorption behavior of Cd (II) ions fitted Langmuir, Temkin and Freundlich isotherms well, but followed Langmuir isotherm most precisely, with a maximum adsorption capacity of 12.08 mg/g. EDS analysis confirmed that Cd (II) was adsorbed onto bamboo charcoal. This study demonstrated that bamboo charcoal could be used for the removal of Cd (II) ions in water treatment.

Heterogeneous adsorption behavior of landfill leachate on granular activated carbon revealed by fluorescence excitation emission matrix (EEM)-parallel factor analysis (PARAFAC).

Science.gov (United States)

Lee, Sonmin; Hur, Jin

2016-04-01

Heterogeneous adsorption behavior of landfill leachate on granular activated carbon (GAC) was investigated by fluorescence excitation-emission matrix (EEM) combined with parallel factor analysis (PARAFAC). The equilibrium adsorption of two leachates on GAC was well described by simple Langmuir and Freundlich isotherm models. More nonlinear isotherm and a slower adsorption rate were found for the leachate with the higher values of specific UV absorbance and humification index, suggesting that the leachate containing more aromatic content and condensed structures might have less accessible sites of GAC surface and a lower degree of diffusive adsorption. Such differences in the adsorption behavior were found even within the bulk leachate as revealed by the dissimilarity in the isotherm and kinetic model parameters between two identified PARAFAC components. For both leachates, terrestrial humic-like fluorescence (C1) component, which is likely associated with relatively large sized and condensed aromatic structures, exhibited a higher isotherm nonlinearity and a slower kinetic rate for GAC adsorption than microbial humic-like (C2) component. Our results were consistent with size exclusion effects, a well-known GAC adsorption mechanism. This study demonstrated the promising benefit of using EEM-PARAFAC for GAC adsorption processes of landfill leachate through fast monitoring of the influent and treated leachate, which can provide valuable information on optimizing treatment processes and predicting further environmental impacts of the treated effluent. Copyright © 2016 Elsevier Ltd. All rights reserved.

Adsorption of radioactive I2 gas onto atmospheric aerosol

International Nuclear Information System (INIS)

Noguchi, Hiroshi; Murata, Mikio; Suzuki, Katsumi.

1990-01-01

Laboratory scale experiments on the adsorption of radioactive elemental iodine (I 2 ) gas onto atmospheric aerosol showed that the adsorption reached an equilibrium state in about twelve minutes at high initial I 2 concentrations. The proportion of iodine which was adsorbed on the aerosol gradually decreased with increading initial I 2 concentration ranging over 10 -13 to 10 -9 g/cm 3 at a reaction time of 31 min but was almost constant at a reaction time of 2 min. A fraction of iodine desorbed from particulate iodine as mainly I 2 gas. An adsorption isotherm of atmospheric aerosol for I 2 gas was estimated from the experimental data of long reaction time and high I 2 concentrations. Using this adsorption isotherm, a theoretical equation, which was similar to our previous equation, was derived to explain the experimental results. A geometric mean and standard deviation of sticking probability in the equation were estimated to be 1.2 x 10 -2 and 2.7, respectively. Almost all experimental data were within ranges of calculated results considering the geometric standard deviation of sticking probability. (author)

Adsorption of organic matter contained in industrial phosphoric acid onto bentonite: Batch contact time and kinetic study

International Nuclear Information System (INIS)

Mellah, Abdelhamid

1992-12-01

The soluble organic matter present in industrial phosphoric acid can strongly affect the uranium recovery during its solvent extraction by forming stable foams and emulsions. The removal of these organics is an important step both for the production of decontaminated fertilizers and the successful recovery of uranium. The equilibrium isotherms of organic matter adsorption onto bentonite show that the data correlated well with freundlich's model and that the adsorption is physical in nature. the maximum monomolecular capacity (Qo) according to the Langmuir model is 153 mg/g for an initial organic matter concentration of 251.5 mg/1, at 30 oC. The operating parameters (agitation speed, solid/liquid ratio, temperature, particle size and initial organic matter concentration) influenced the rate of adsorption. The adsorption isotherm of uranium onto bentonite exhibits and anomalous shape similar to the Z-type isotherm reported by Giles et al

Potential Theory of Multicomponent Adsorption

DEFF Research Database (Denmark)

Shapiro, Alexander; Stenby, Erling Halfdan

1998-01-01

We developed a theory of multicomponent adsorption on the basis of the potential concept originally suggested by Polanyi. The mixture is considered as a heterogeneous substance segregated in the external field emitted by the adsorbent. The same standard equation of state, with no additional fitting...... parameters, is used for the segregated and for the bulk phases. With this approach, few parameters are needed to correlate pure component adsorption isotherms. These parameters may be used to predict adsorption equilibria of multicomponent mixtures without additional adjustment. A connection between...... the potential theory and the spreading pressure concept is established, and problems of the theory consistency are studied. Numerical algorithms are suggested for evaluation of the segregated state of the mixture in the potential field of adsorption forces. Comparison with experimental data shows good agreement...

Adsorption of Cu(II) on Oxidized Multi-Walled Carbon Nanotubes in the Presence of Hydroxylated and Carboxylated Fullerenes

Science.gov (United States)

Wang, Jing; Li, Zhan; Li, Shicheng; Qi, Wei; Liu, Peng; Liu, Fuqiang; Ye, Yuanlv; Wu, Liansheng; Wang, Lei; Wu, Wangsuo

2013-01-01

The adsorption of Cu(II) on oxidized multi-walled carbon nanotubes (oMWCNTs) as a function of contact time, pH, ionic strength, temperature, and hydroxylated fullerene (C60(OH)n) and carboxylated fullerene (C60(C(COOH)2)n) were studied under ambient conditions using batch techniques. The results showed that the adsorption of Cu(II) had rapidly reached equilibrium and the kinetic process was well described by a pseudo-second-order rate model. Cu(II) adsorption on oMWCNTs was dependent on pH but independent of ionic strength. Compared with the Freundlich model, the Langmuir model was more suitable for analyzing the adsorption isotherms. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggested that Cu(II) adsorption on oMWCNTs was spontaneous and endothermic. The effect of C60(OH)n on Cu(II) adsorption of oMWCNTs was not significant at low C60(OH)n concentration, whereas a negative effect was observed at higher concentration. The adsorption of Cu(II) on oMWCNTs was enhanced with increasing pH values at pH adsorption of Cu(II) onto oMWCNTs at pH 4–6. The double sorption site model was applied to simulate the adsorption isotherms of Cu(II) in the presence of C60(OH)n and fitted the experimental data well. PMID:24009683

Adsorption Mechanisms of Dodecylbenzene Sulfonic Acid by Corn Straw and Poplar Leaf Biochars.

Science.gov (United States)

Zhao, Nan; Yang, Xixiang; Zhang, Jing; Zhu, Ling; Lv, Yizhong

2017-09-22

Biochar is an eco-friendly, renewable, and cost-effective material that can be used as an adsorbent for the remediation of contaminated environments. In this paper, two types of biochar were prepared through corn straw and poplar leaf pyrolysis at 300 °C and 700 °C (C300, C700, P300, P700). Brunaer-Emmett-Teller N₂ surface area, scanning electron microscope, elemental analysis, and infrared spectra were used to characterize their structures. These biochars were then used as adsorbents for the adsorption of dodecylbenzene sulfonic acid (DBSA). The microscopic adsorption mechanisms were studied by using infrared spectra, 13 C-nuclear magnetic resonance spectra, and electron spin resonance spectra. The surface area and pore volume of C700 (375.89 m²/g and 0.2302 cm³/g) were the highest among all samples. Elemental analysis results showed that corn straw biochars had a higher aromaticity and carbon to nitrogen (C/N) ratio than the poplar leaf biochars. High temperature caused the increase of carbon content and the decrease of oxygen content, which also gave the biochars a higher adsorption rate. Pseudo-second order kinetic provided a better fit with the experimental data. Adsorption isotherm experiments showed that the adsorption isotherm of C300 fit the linear model. For other biochars, the adsorption isotherms fitted Langmuir model. Biochars with high temperatures exhibited enhanced adsorption capacity compared with ones at low temperatures. The q max values of biochars to DBSA followed the order of P700 > C700 > P300. The adsorption mechanisms were complex, including partition, anion exchange, the formation of H bonds, covalent bonds, and charge transfer. The adsorption by covalent bonding might be the key mechanism determining the adsorption capacity of P700.

Adsorption Mechanisms of Dodecylbenzene Sulfonic Acid by Corn Straw and Poplar Leaf Biochars

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Nan Zhao

2017-09-01

Full Text Available Biochar is an eco-friendly, renewable, and cost-effective material that can be used as an adsorbent for the remediation of contaminated environments. In this paper, two types of biochar were prepared through corn straw and poplar leaf pyrolysis at 300 °C and 700 °C (C300, C700, P300, P700. Brunaer–Emmett–Teller N2 surface area, scanning electron microscope, elemental analysis, and infrared spectra were used to characterize their structures. These biochars were then used as adsorbents for the adsorption of dodecylbenzene sulfonic acid (DBSA. The microscopic adsorption mechanisms were studied by using infrared spectra, 13C-nuclear magnetic resonance spectra, and electron spin resonance spectra. The surface area and pore volume of C700 (375.89 m2/g and 0.2302 cm3/g were the highest among all samples. Elemental analysis results showed that corn straw biochars had a higher aromaticity and carbon to nitrogen (C/N ratio than the poplar leaf biochars. High temperature caused the increase of carbon content and the decrease of oxygen content, which also gave the biochars a higher adsorption rate. Pseudo-second order kinetic provided a better fit with the experimental data. Adsorption isotherm experiments showed that the adsorption isotherm of C300 fit the linear model. For other biochars, the adsorption isotherms fitted Langmuir model. Biochars with high temperatures exhibited enhanced adsorption capacity compared with ones at low temperatures. The qmax values of biochars to DBSA followed the order of P700 > C700 > P300. The adsorption mechanisms were complex, including partition, anion exchange, the formation of H bonds, covalent bonds, and charge transfer. The adsorption by covalent bonding might be the key mechanism determining the adsorption capacity of P700.

Statistical optimization of adsorption processes for removal of 2,4-dichlorophenol by activated carbon derived from oil palm empty fruit bunches

Institute of Scientific and Technical Information of China (English)

Md. Zahangir ALAM; Suleyman A. MUYIBI; Juria TORAMAE

2007-01-01

The adsorption capacity of activated carbon produced from oil palm empty fruit bunches through removal of 2,4-dichlorophenol from aqueous solution was carried out in the laboratory. The activated carbon was produced by thermal activation at 800℃ with 30 min of activation time. The adsorption process conditions were determined with the statistical optimization followed by central composite design. A developed polynomial model for operating conditions of adsorption process indicated that the optimum conditions for maximum adsorption of phenolic compound were: agitation rate of 100 r/min, contact time of 8 h, initial adsorbate concentration of 250 mg/L and pH 4. Adsorption isotherms were conducted to evaluate biosorption process. Langmuir isotherm was more favorable (R2=0.93) for removal of 2,4-dichlorophenol by the activated carbon produced rather than the Freundlich isotherm (R2=0.88).

Adsorption Study of Cobalt on Treated Granular Activated Carbon

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Y. V. Hete

2012-01-01

Full Text Available This study is carried out for the removal of cobalt from aqueous solution using granular activated carbon in combination with p-nitro benzoic acid at temperature 25±1 °C. The adsorption isotherm of cobalt on granular activated carbon has been determined and the data fitted reasonably well to the Langmuir and Freundlich isotherm for activated carbon.

Kinetic and thermodynamic studies on the adsorption of anionic surfactant on quaternary ammonium cationic cellulose.

Science.gov (United States)

Zhang, Yuanzhang; Shi, Wenjian; Zhou, Hualan; Fu, Xing; Chen, Xuan

2010-06-01

Removal of anionic surfactants from aqueous solutions by adsorption onto quaternary ammonium cationic cellulose (QACC) was investigated. The effects of solution acidity, initial concentration, adsorption time, and temperature on the adsorption of sodium dodecyl-benzene sulfonate (SDBS), sodium lauryl sulfate (SLS), and sodium dodecyl sulfonate (SDS) were studied. The kinetic experimental data fit well with the pseudo-second-order model; the rate constant of the adsorption increased with temperature. The values of apparent activation energy for the adsorption were calculated as ranging from 10.2 to 17.4 kJ/ mol. The adsorption isotherm can be described by the Langmuir isotherm. The values of thermodynamic parameters (deltaH0, deltaS0, and deltaG0) for the adsorption indicated that this process was spontaneous and endothermic. At 318 K, the saturated adsorption capacities of QACC for SDBS, SLS, and SDS were 1.75, 1.53, and 1.39 mmol/g, respectively. The adsorption process was mainly chemisorption and partially physisorption. The results show that QACC is effective for the removal of anionic surfactants.

Dynamics of CO 2 Adsorption on Amine Adsorbents. 1. Impact of Heat Effects

KAUST Repository

Bollini, Praveen

2012-11-21

The packed bed heat and mass transfer dynamics of CO2 adsorption onto a 3-aminopropylsilyl-functionalized SBA-15 silica material are reported. Concentration measurements at the outlet of the packed bed and temperature profiles inside the bed are measured simultaneously. Heat and mass transfer models in conjunction with the linear driving force rate model are used to simulate the concentration and temperature profiles in the bed. The heat and mass transfer processes in the amine adsorbent packed bed are successfully captured by the model, and comparison of isothermal and nonisothermal models reveals that isothermal models provide an accurate description of the dynamic mass transport behavior in the adsorption column under the experimental conditions used in this study. The results help establish that under certain experimental conditions, heat effects in amine adsorbent packed beds have a negligible effect on CO2 breakthrough, and simple isothermal models can be used to accurately assess adsorption kinetics. © 2012 American Chemical Society.

Adsorption of CO2 and H2O on supported amine sorbents

NARCIS (Netherlands)

Veneman, Rens; Zhao, W.; Li, Z.; Cai, N.; Brilman, Derk Willem Frederik

2014-01-01

In this work we have evaluated the H2O and CO2 adsorption characteristics of Lewatit VP OC 1065 in view of the potential application of solid sorbents in post combustion CO2 capture. Here we present single component adsorption isotherms for H2O and CO2 as well as co-adsorption experiments. It was

Adsorption of phenolic compound by aged-refuse

Energy Technology Data Exchange (ETDEWEB)

Chai Xiaoli [State Key Laboratory of Pollution Control and Resource Reuse, School of Enviromental Science and Engineering, Tongji University, Siping Road 1239, Shanghai 200092 (China)]. E-mail: xlchai@mail.tongji.edu.cn; Zhao Youcai [State Key Laboratory of Pollution Control and Resource Reuse, School of Enviromental Science and Engineering, Tongji University, Siping Road 1239, Shanghai 200092 (China)

2006-09-01

The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.

Adsorption of phenolic compound by aged-refuse

International Nuclear Information System (INIS)

Chai Xiaoli; Zhao Youcai

2006-01-01

The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic

Modification of porous starch for the adsorption of heavy metal ions from aqueous solution.

Science.gov (United States)

Ma, Xiaofei; Liu, Xueyuan; Anderson, Debbie P; Chang, Peter R

2015-08-15

Porous starch xanthate (PSX) and porous starch citrate (PSC) were prepared in anticipation of the attached xanthate and carboxylate groups respectively forming chelation and electrostatic interactions with heavy metal ions in the subsequent adsorption process. The lead(II) ion was selected as the model metal and its adsorption by PSX and PSC was characterized. The adsorption capacity was highly dependent on the carbon disulfide/starch and citric acid/starch mole ratios used during preparation. The adsorption behaviors of lead(II) ion on PSXs and PSCs fit both the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity from the Langmuir isotherm equation reached 109.1 and 57.6 mg/g for PSX and PSC when preparation conditions were optimized, and the adsorption times were just 20 and 60 min, respectively. PSX and PSC may be used as effective adsorbents for removal of heavy metals from contaminated liquid. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Adsorption Ability of Caragana Korshinskii Kom Biochar to Diuron in Soil

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XING Ze-bing

2017-10-01

Full Text Available Caragana Korshinskii Kom were charred to yield the biochar in the temperature of 200℃, 300℃, 400℃ and 600℃. The components of Caragana Korshinskii Kom biochar were analyzed, the structure was surveyed through SEM and the adsorption isotherm curve was plotted with the specific surface area analyzer. The pore volume, size, and specific surface area were calculated. Biochar were mixed into soil column to detect the adsorption ability to diuron herbicide. The results showed that the adsorption isotherm curves of Caragana Korshinskii Kom biochar were the traditional I adsorption curves, the productivity of biochar decreased with the raising of charring temperature. Biochar, charred at the temperature of 600℃, had achieved 44.71% of yield rate of carbonization, 187.56 m2·g-1 specific surface area and mean 4.83 nm pore size. The microspore volume account for 53% in total pore volume. 1% of biochar had the significant effect on adsorption of diuron in soil, 3% of biochar in soil reached an optimal application amount balancing between its properties and cost.

Isotherm, kinetic and thermodynamics study of humic acid removal process from aquatic environment by chitosan nano particle

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Maryam Ghafoori

2016-09-01

Full Text Available Background and Aim: Humic substances include natural organic polyelectrolyte materials that formed most of the dissolved organic carbon in aquatic environments. Reaction between humic substances and chlorine leading to formation of disinfection byproducts (DBPs those are toxic, carcinogenic and mutagenic. The aim of this study was investigation of isotherms, kinetics and thermodynamics of humic acid removal process by nano chitosan from aquatic environment. Materials and Methods: This practical research was an experimental study that performed in a batch system. The effect of various parameters such as pH, humic acid concentration, contact time, adsorbent dosage, isotherms, thermodynamics and Kinetics of humic acid adsorption process were investigated. Humic acid concentration measured using spectrophotometer at wave length of 254 nm. Results: The results of this research showed that maximum adsorption capacity of nanochitosan that fall out in concentration of 50 mg/l and contact time of 90 minutes was 52.34 mg/g. Also, the maximum adsorption was observed in pH = 4 and adsorbent dosage 0.02 g. Laboratory data show that adsorption of humic acid by nanochitosan follow the Langmuir isotherm model. According to result of thermodynamic study, entropy changes (ΔS was equal to 2.24 J/mol°k, enthalpy changes (ΔH was equal to 870 kJ/mol and Gibbs free energy (ΔG was negative that represent the adsorption process is spontaneous and endothermic. The kinetics of adsorption has a good compliant with pseudo second order model. Conclusion: Regarding to results of this study, nano chitosan can be suggested as a good adsorbent for the removal of humic acids from aqueous solutions.

Malachite green adsorption onto natural zeolite and reuse by microwave irradiation

International Nuclear Information System (INIS)

Han Runping; Wang Yu; Sun Qing; Wang Lulu; Song Jiyun; He Xiaotian; Dou Chanchan

2010-01-01

Natural zeolite was used for the removal of malachite green (MG) from aqueous solution in batch mode and reused by microwave irradiation. The isotherm data were analyzed by the Langmuir, Freundlich, Redlich-Peterson, and Koble-Corrigan isotherm model. The better fit for the equilibrium process was Koble-Corrigan model. The kinetic studies indicated that the adsorption followed the pseudo-second-order kinetic. Thermodynamic calculations showed that the adsorption was spontaneous and endothermic process. Spent zeolite was treated by microwave irradiation and it was found that yield of regeneration was 85.8% in the case of microwave irradiated time 10 min at 160 W.

Effect of ring rotation upon gas adsorption in SIFSIX-3-M (M = Fe, Ni) pillared square grid networks.

Science.gov (United States)

Elsaidi, Sameh K; Mohamed, Mona H; Simon, Cory M; Braun, Efrem; Pham, Tony; Forrest, Katherine A; Xu, Wenqian; Banerjee, Debasis; Space, Brian; Zaworotko, Michael J; Thallapally, Praveen K

2017-03-01

Dynamic and flexible metal-organic frameworks (MOFs) that respond to external stimuli, such as stress, light, heat, and the presence of guest molecules, hold promise for applications in chemical sensing, drug delivery, gas separations, and catalysis. A greater understanding of the relationship between flexible constituents in MOFs and gas adsorption may enable the rational design of MOFs with dynamic moieties and stimuli-responsive behavior. Here, we detail the effect of subtle structural changes upon the gas sorption behavior of two "SIFSIX" pillared square grid frameworks, namely SIFSIX-3-M (M = Ni, Fe). We observe a pronounced inflection in the Xe adsorption isotherm in the Ni variant. With evidence from X-ray diffraction studies, density functional theory, and molecular simulations, we attribute the inflection to a disordered to ordered transition of the rotational configurations of the pyrazine rings induced by sorbate-sorbent interactions. We also address the effect of cage size, temperature, and sorbate on the guest-induced ring rotation and the adsorption isotherms. The absence of an inflection in the Xe adsorption isotherm in SIFSIX-3-Fe and in the Kr, N 2 , and CO 2 adsorption isotherms in SIFSIX-3-Ni suggest that the inflection is highly sensitive to the match between the size of the cage and the guest molecule.

Ferric chloride modified zeolite in wastewater on Cr (VI) adsorption characteristics

Science.gov (United States)

Wu, Xiaoqing; Zhang, Kang; Chen, Wen; Zhang, Hua

2018-03-01

Zeolite was modified by ferric chloride(Fe-Z) removal Cr (VI) ion from wastewater. The results showed that the effect of Cr(VI) adsorption on modified zeolite depended significantly on pH. It is favorable for the adsorption of Cr(VI) in acid condition. The Langmuir isotherm model has high fitting accuracy with experimental data, demonstrated that is monolayer adsorption and chemical adsorption.The pseudo-second-order equation provided the best correlation to the data. The model can describe the adsorption reaction process well.

Removal of reactive blue 19 dyes from textile wastewater by pomegranate seed powder: Isotherm and kinetic studies

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Mahboobeh Dehvari

2016-01-01

Full Text Available Aims: The aim of this study was the evaluation of adsorption kinetics and equilibrium of reactive blue 19 dyes from textile synthetic wastewater by pomegranate seed powder. Materials and Methods: This study is an experimental research, which was performed in laboratory scale. In this study, the parameters such as adsorbent dose, pH and retention time, initial concentration of dye and agitation rate have been investigated. After washing and boiling of pomegranate seeds for 2 h, they dried, milled and finally pulverized by standard ASTM sieves (40-100 mesh. Maximum adsorption wave length (λmax by spectrophotometer ultra violet/visible (model SP-3000 Plus 592 nm was determined. The Langmuir, Freundlich and Temkin isotherm models and the pseudo-first-order and pseudo-second-order kinetic models were analyzed. Results: According to results, the removal efficiency with adsorbent dose, retention time and agitation rate has a direct relation. Maximum adsorption occurred in the first 60 min. The removal efficiency with initial concentration of dye and pH of solution has indirect relation. The Freundlich isotherm fits the experimental data better than the other isotherms. It was recognized that the adsorption followed by pseudo-second-order model (R2 > 0.99. Conclusion: Based on the results, pomegranate seeds as a new natural sorbent can be used in removal of dye and other environmental pollutants with desirable absorption capacity.

Study on adsorption refrigeration performance of MIL-101-isobutane working pair

International Nuclear Information System (INIS)

Ma, Liejun; Yang, Huan; Wu, Qi; Yin, Yu; Liu, Zongjian; Cui, Qun; Wang, Haiyan

2015-01-01

Rising concerns about pro-environment and energy conservation bring about the escalating interests in adsorption cooling systems using renewable energy. Adsorption chillers with common refrigerants (water, ethanol, methanol, etc.) face the problem that advanced technologies and intricate design considerations are required to maintain high vacuum. This paper aims at the parameters optimization of adsorption system being operated with the novel working pair, MIL-101-isobutane, under typical conditions of ice making and air-condition. Adsorption isotherms and dynamic of isobutane on MIL-101 are discussed simultaneously. When the hot water inlet temperature, cooling water temperature and desorption time are 95 °C, 30 °C and 30 min, respectively, the cooling capacity is 45.7 kJ/kg, which is 1.7 times as much as that of activated carbon–isobutane pair. Structural stability of MIL-101 subjected to 500 times adsorption/desorption cycles has been successfully verified by XRD (X-ray diffraction). - Highlights: • Adsorption isotherms and kinetic of isobutane on MIL-101 were studied. • A single bed adsorption chiller with MIL-101-isobutane pair was built. • System performed better than that using activated carbon–isobutane pair. • Stability of MIL-101 subjected to 500 ad/desorption cycles has been verified.

Resorcinol adsorption from aqueous solution over activated carbon

International Nuclear Information System (INIS)

Blanco, Diego A; Giraldo, Liliana; Moreno, Juan C

2007-01-01

In this paper, the adsorption behavior of Resorcinol a monohydroxylated phenol, poorly acid to 298 K, over activated carbon is analyzed by studying the solution's pH influence and the surface reduction in the adsorption process. To do this, an activated carbon of lignocellulose origin and a reduced activated carbon was used. The interaction solid solution is characterized by the analyses of adsorption in the isotherms to 298 K and pH values of 7. 00, 9.00 and 11.00 for a period of 48 hours. The capacity adsorption of activated carbons increases when the solution's pH decreases and the retained amount increases in the reduced coal to the pH of maximum adsorption.

Water sorption isotherms of skimmed milk powder within the temperature range of 5–20 °C

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Jitka Langová

2012-01-01

Full Text Available Moisture sorption isotherms (MSI’s of skimmed milk powder in the temperature range of 5–20 °C were determined using manometric method. MSI’s, which show the water content versus water activity (Aw at a constant temperature, are used to describe relationships between water content and equilibrium state relative vapour pressure (RVP. The equilibrium moisture content (EMC of skimmed milk powder samples is growing with an increase of Aw at a constant temperature both for water adsorption and desorption. Isotherms were found to be type II of Brunauer-Emmett-Teller classification. It is the type most common for foods. The shape of created isotherms was sigmoid. Structural modifications of crystals were observed during adsorption in the microscope, too. Critical value of EMC of tested samples corresponding to the Aw equal to 0.6 for adsorption was 6.50% MC (w.b. at temperature 5 °C, 9.15% MC (w.b. at temperature 10 °C, and 7.71% MC (w.b. at temperature 20 °C. These values determine optimal conditions for storage from the point of view microorganisms grow, Aw<0.6.

Isotermas de adsorção do pedúnculo seco do caju Adsorption isotherms of the dry cashew apple

Directory of Open Access Journals (Sweden)

Siumara R. Alcântara

2009-02-01

Full Text Available A atividade de água constitui um fator importante no processo de fermentação semi-sólida, haja vista sua relação com a quantidade de água disponível ao microrganismo responsável pelo metabolismo do produto, sendo necessário à obtenção de isotermas de sorção para caracterização do substrato. Ante o exposto, objetivou-se a construção das isotermas de adsorção do pedúnculo seco do caju (Anacardium occidentale L. nas temperaturas usuais de fermentação (25, 30, 35 e 40 ºC. Ajustaram-se as isotermas com os modelos de BET, GAB, Oswin, Henderson e Smith. Observou-se que o modelo de GAB apresentou melhor ajuste, de vez que, na faixa de atividade de água que maximiza a biossíntese do microrganismo, para produção de pectinases por Aspergillus niger, a umidade do substrato deve estar acima de 35% b.s.Water activity is a very important factor in a solid state fermentation process due to its relation with the water quantity available to the microorganism that will synthesize the product. Therefore, it is necessary to obtain the sorption isotherms for the characterization of the substrate. The objective of this study is to obtain adsorption isotherms of the dry cashew apple (Anacardium occidentale L. at normal temperatures of fermentation process (25, 30, 35 e 40 ºC. Five mathematical models were fitted to the experimental data: BET, GAB, Oswin, Henderson e Smith. The GAB model was better fitted to the product. The isotherms allowed the determination of the appropriate moisture content to obtain the water activities that maximize the biosynthesis of the microorganism for the pectin production by solid state fermentation process. The moisture content of the substrate should be above 35% d.b.

Activated carbon oxygen content influence on water and surfactant adsorption.

Science.gov (United States)

Pendleton, Phillip; Wu, Sophie Hua; Badalyan, Alexander

2002-02-15

This research investigates the adsorption properties of three activated carbons (AC) derived from coconut, coal, and wood origin. Each carbon demonstrates different levels of resistance to 2 M NaOH treatment. The coconut AC offers the greatest and wood AC the least resistance. The influence of base treatment is mapped in terms of its effects on specific surface area, micropore volume, water adsorption, and dodecanoic acid adsorption from both water and 2 M NaOH solution. A linear relationship exists between the number of water molecules adsorbed at the B-point of the water adsorption isotherm and the oxygen content determined from elemental analysis. Surfactant adsorption isotherms from water and 2 M NaOH indicate that the AC oxygen content effects a greater dependence on affinity for surfactant than specific surface area and micropore volume. We show a linear relationship between the plateau amount of surfactant adsorbed and the AC oxygen content in both water and NaOH phases. The higher the AC oxygen content, the lower the amount of surfactant adsorbed. In contrast, no obvious relationship could be drawn between the surfactant amount adsorbed and the surface area.

Adsorption of Cu, As, Pb and Zn by Banana Trunk

International Nuclear Information System (INIS)

Nurzulaifa Shaheera Erne Mohd Yasim; Zitty Sarah Ismail; Suhanom Mohd Zaki; Mohd Fahmi Abd Azis

2016-01-01

The purpose of this study is to investigate the effectiveness of banana trunk as an adsorbent in removal of heavy metals in aqueous solution. Functional groups of adsorbent were determined using Fourier Transform Infrared spectroscopy (FTIR). Batch experiments were conducted to determine the adsorption percentage of heavy metals (Cu, As, Pb and Zn). The optimum adsorption using banana trunk was based on pH difference, contact time and dosage. Adsorption percentage was found to be proportional to pH, contact time and dosage. Maximum adsorption percentage of Cu, As, Pb and Zn at pH 6, 100 minutes and 8 gram of dosage are 95.80 %, 75.40 %, 99.36 % and 97.24 %, respectively. Langmuir and Freundlich isotherms were used to determine the equilibrium state for heavy metals ion adsorption experiments. All equilibrium heavy metals were well explained by the Freundlich isotherm model with R"2= 0.9441, R"2= 0.8671, R"2= 0.9489 and R"2= 0.9375 for Cu, As, Pb and Zn respectively. It is concluded that banana trunk has considerable potential for the removal of heavy metals from aqueous solution. (author)

Removal of Basic Red 46 dye from aqueous solution by adsorption onto Moroccan clay

International Nuclear Information System (INIS)

Karim, A. Bennani; Mounir, B.; Hachkar, M.; Bakasse, M.; Yaacoubi, A.

2009-01-01

In this study, Moroccan crude clay of Safi, which was characterized by X-ray diffraction, is used as adsorbent for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the Basic Red 46 (BR46) in aqueous solutions at various dye concentrations, adsorbent masses and pH values. The results showed that the adsorption capacity of the dye increased by initial dye concentration and pH values. Two kinetic models (the pseudo-first-order and the pseudo-second-order) were used to calculate the adsorption rate constants. The adsorption kinetics of the basic dye followed pseudo-second-order model. The experimental data isotherms were analyzed using the Langmuir, Freundlich and Dubinin-Radushkevish equations. The monolayer adsorption capacity for BR46 dye is 54 mg/g of crude clay. Nearly 20 min of contact time was found to be sufficient for the dye adsorption to reach equilibrium. Thermodynamical parameters were also evaluated for the dye-adsorbent system and revealed that the adsorption process is exothermic in nature.

Batch study, equilibrium and kinetics of adsorption of naphthalene using waste tyre rubber granules

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Felix A. Aisien

2014-04-01

Full Text Available The potential use of waste tyre rubber granules (WTRG for the batch adsorption of naphthalene from aqueous solutions was investigated. The effect of various operational variables such as contact time, initial naphthalene concentration, adsorbent dose, size of adsorbent particles, and temperature of solution on the adsorption capacity of WTRG was evaluated. The adsorption of naphthalene by WTRG was a fast kinetic process with an equilibrium contact time of 60 min. A low temperature (5°C, small adsorbent particle size (0.212 mm and higher adsorbent dosage favored the adsorption process. Results of isotherm studies revealed that adsorption of naphthalene was best described by the Langmuir isotherm equation (R2=0.997 while the kinetics of the process was best described by the Lagergren pseudofirst order kinetic equation (R2=0.998. This study has demonstrated the suitability of WTRG for the removal of naphthalene from aqueous solution.

Comparison of adsorption of Remazol Black B and Acidol Red on microporous activated carbon felt.

Science.gov (United States)

Donnaperna, L; Duclaux, L; Gadiou, R; Hirn, M-P; Merli, C; Pietrelli, L

2009-11-15

The adsorption of two anionic dyes, Remazol Black B (RB5) and Acidol Red 2BE-NW (AR42), onto a microporous activated carbon felt was investigated. The characterization of carbon surface chemistry by X-ray microanalysis, Boehm titrations, and pH-PZC measurements indicates that the surface oxygenated groups are mainly acidic. The rate of adsorption depends on the pH and the experimental data fit the intraparticle diffusion model. The pore size distribution obtained by DFT analysis shows that the mean pore size is close to 1nm, which indicates that a slow intraparticle diffusion process control the adsorption. The adsorption isotherms were measured for different pH values. The Khan and the Langmuir-Freundlich models lead to the best agreement with experimental data for RB5 and AR42, respectively. These isotherm simulations and the pH dependence of adsorption show that the adsorption capacity is mainly controlled by nondispersive electrostatic interactions for pH values below 4. The adsorption kinetics, the irreversibility of the process, and the influence of the pH indicate that the rate of adsorption in this microporous felt proceeds through two steps. The first one is fast and results from direct interaction of dye molecules with the external surface of the carbon material (which account for 10% of the whole surface area); in the second, slow step, the adsorption rate is controlled by the slow diffusion of dye molecules into the narrow micropores. The influence of temperature on the adsorption isotherms was studied and the thermodynamic parameters were obtained. They show that the process is spontaneous and exothermic.

Predicting mixed-gas adsorption equilibria on activated carbon for precombustion CO2 capture.

Science.gov (United States)

García, S; Pis, J J; Rubiera, F; Pevida, C

2013-05-21

We present experimentally measured adsorption isotherms of CO2, H2, and N2 on a phenol-formaldehyde resin-based activated carbon, which had been previously synthesized for the separation of CO2 in a precombustion capture process. The single component adsorption isotherms were measured in a magnetic suspension balance at three different temperatures (298, 318, and 338 K) and over a large range of pressures (from 0 to 3000-4000 kPa). These values cover the temperature and pressure conditions likely to be found in a precombustion capture scenario, where CO2 needs to be separated from a CO2/H2/N2 gas stream at high pressure (~1000-1500 kPa) and with a high CO2 concentration (~20-40 vol %). Data on the pure component isotherms were correlated using the Langmuir, Sips, and dual-site Langmuir (DSL) models, i.e., a two-, three-, and four-parameter model, respectively. By using the pure component isotherm fitting parameters, adsorption equilibrium was then predicted for multicomponent gas mixtures by the extended models. The DSL model was formulated considering the energetic site-matching concept, recently addressed in the literature. Experimental gas-mixture adsorption equilibrium data were calculated from breakthrough experiments conducted in a lab-scale fixed-bed reactor and compared with the predictions from the models. Breakthrough experiments were carried out at a temperature of 318 K and five different pressures (300, 500, 1000, 1500, and 2000 kPa) where two different CO2/H2/N2 gas mixtures were used as the feed gas in the adsorption step. The DSL model was found to be the one that most accurately predicted the CO2 adsorption equilibrium in the multicomponent mixture. The results presented in this work highlight the importance of performing experimental measurements of mixture adsorption equilibria, as they are of utmost importance to discriminate between models and to correctly select the one that most closely reflects the actual process.

Adsorption of strontium on different sodium-enriched bentonites

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Marinović Sanja R.

2017-01-01

Full Text Available Bentonites from three different deposits (Wyoming, TX, USA and Bogovina, Serbia with similar cation exchange capacities were sodium enriched and tested as adsorbents for Sr2+ in aqueous solutions. X-Ray diffraction analysis confirmed successful Na-exchange. The textural properties of the bentonite samples were determined using low-temperature the nitrogen physisorption method. Significant differences in the textural properties between the different sodium enriched bentonites were found. Adsorption was investigated with respect to adsorbent dosage, pH, contact time and the initial concentration of Sr2+. The adsorption capacity increased with pH. In the pH range from 4.0–8.5, the amount of adsorbed Sr2+ was almost constant but 2–3 times smaller than at pH ≈11. Further experiments were performed at the unadjusted pH since extreme alkaline conditions are environmentally hostile and inapplicable in real systems. The adsorption capacity of all the investigated adsorbents toward Sr2+ was similar under the investigated conditions, regardless of significant differences in the specific surface areas. It was shown and confirmed by the Dubinin–Radushkevich model that the cation exchange mechanism was the dominant mechanism of Sr2+ adsorption. Their developed microporous structures contributed to the Sr2+ adsorption process. The adsorption kinetics obeyed the pseudo-second-order model. The isotherm data were best fitted with the Langmuir isotherm model. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45001

Trichloroethylene (TCE) adsorption using sustainable organic mulch

Energy Technology Data Exchange (ETDEWEB)

Wei Zongsu [Department of Civil Engineering, University of Toledo, Mail Stop 307, 3031 Nitschke Hall, 2801 W. Bancroft St., Toledo, OH, 43606-3390 (United States); Seo, Youngwoo, E-mail: youngwoo.seo@utoledo.edu [Department of Civil Engineering, University of Toledo, Mail Stop 307, 3031 Nitschke Hall, 2801 W. Bancroft St., Toledo, OH, 43606-3390 (United States)

2010-09-15

Soluble substrates (electron donors) have been commonly injected into chlorinated solvent contaminated plume to stimulate reductive dechlorination. Recently, different types of organic mulches with economic advantages and sustainable benefits have received much attention as new supporting materials that can provide long term sources of electron donors for chlorinated solvent bioremediation in engineered biowall systems. However, sorption capacities of organic mulches for chlorinated solvents have not been studied yet. In this study, the physiochemical properties of organic mulches (pine, hardwood and cypress mulches) were measured and their adsorption capacity as a potential media was elucidated. Single, binary and quaternary isotherm tests were conducted with trichloroethylene (TCE), tetrachloroethylene (PCE), trans-dichloroethylene (trans-DCE) and cis-dichloroethylene (cis-DCE). Among the three tested mulches, pine mulch showed the highest sorption capacity for the majority of the tested chemicals in single isotherm test. In binary or quaternary isotherm tests, competition among chemicals appears to diminish the differences in Q{sub e} for tested mulches. However, pine mulch also showed higher adsorption capacity for most chemicals when compared to hardwood and cypress mulches in the two isotherm tests. Based upon physicochemical properties of the three mulches, higher sorption capacity of pine mulch over hardwood and cypress mulches appears to be attributed to a higher organic carbon content and the lower polarity.

Study of Cadmium adsorption of Nickel and Zinc on a natural bentonite and homo ionic of sodium

International Nuclear Information System (INIS)

Silva Giraldo, German Dario; Pinzon Bello, Jorge Alejo

1999-01-01

It was studied the adsorption of cadmium, nickel and zinc in aqueous solution at 25oC over a bentonite from the Cauca Valley, in its native state as well as in its sodium homo ionic form. The Langmuir isotherm adequately describes the adsorption of these metal ions over both bentonites, and the thermodynamic distribution coefficient, Kdm, which allow quantifying the degree of adsorption, can be calculated. Baeyens-bradbury model correlates well the adsorption of the metal ions over both bentonites but Kdm cannot be calculated from it. The adsorption data do not adjust to freundlich isotherm or B.E.T. As well as they do to the previously mentioned models. The sodium homo ionic bentonite adsorbs nickel and zinc better than the native bentonite, whereas there are not significant differences in cadmium adsorption. The order of adsorption over both bentonites, Cadmium > Zinc > Nickel, follow the HSAB principle

Adsorption of U(VI) onto kaolin studied by batch method

International Nuclear Information System (INIS)

Hongxia Zhang; Zhi Liu; Peizhuo Hu; Tonghuan Liu; Wangsuo Wu

2013-01-01

Adsorption of U(VI) on purified kaolin was studied by batch methods under ambient conditions, including contact time, pH, fulvic acid, etc. Three kinetic models were used to model the kinetic adsorption which was very well described by the pseudo-second-order rate equation, and the activation energy of adsorption was 52.20 kJ/mol. The Freundlich and Dubinin-Radushkevich models fitted the experimental data better than the Langmuir model for the adsorption and desorption isotherms. The thermodynamic parameters indicated that the adsorption of U(VI) on kaolin was an endothermic and spontaneous process. (author)

Co adsorption in kaolinite

International Nuclear Information System (INIS)

Souza, Eliel S.; Silva, Paulo S.C.

2017-01-01

Adsorption of metal ions in clay minerals has been used as an alternative to water and effluents treatment. Kaolinite is a clay mineral that presents low specific surface area and exchange ion capacity. Nevertheless, structural modifications can be achieved by means of acid or thermal activation. In this paper, it was studied the surface area of kaolinite/bentonite, kaolinite/activated carbon mixtures, thermal activated kaolinite and thermal activated kaolinite/activated carbon mixture. The mixture of kaolinite/activated carbon was tested for pH, contact time, interfering ions and initial concentration effects in the cobalt adsorption. Results showed that the optimized parameters are pH 6 and contact time of 30 min. Chromium acted as a competitive ion, zinc does not appear to have affected adsorption while iron seems to have favored it. Langmuir and Freundlich isotherms indicated that the adsorption of Co in the mixture of kaolinite/activated carbon is a spontaneous process. (author)

Co adsorption in kaolinite

Energy Technology Data Exchange (ETDEWEB)

Souza, Eliel S.; Silva, Paulo S.C., E-mail: eliel201019@hotmail.com, E-mail: pscsilva@ipen.br [Instituto de Pesquisas Energética s e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

2017-07-01

Adsorption of metal ions in clay minerals has been used as an alternative to water and effluents treatment. Kaolinite is a clay mineral that presents low specific surface area and exchange ion capacity. Nevertheless, structural modifications can be achieved by means of acid or thermal activation. In this paper, it was studied the surface area of kaolinite/bentonite, kaolinite/activated carbon mixtures, thermal activated kaolinite and thermal activated kaolinite/activated carbon mixture. The mixture of kaolinite/activated carbon was tested for pH, contact time, interfering ions and initial concentration effects in the cobalt adsorption. Results showed that the optimized parameters are pH 6 and contact time of 30 min. Chromium acted as a competitive ion, zinc does not appear to have affected adsorption while iron seems to have favored it. Langmuir and Freundlich isotherms indicated that the adsorption of Co in the mixture of kaolinite/activated carbon is a spontaneous process. (author)

Characterization of DOM adsorption of CNTs by using excitation-emission matrix fluorescence spectroscopy and multiway analysis.

Science.gov (United States)

Peng, Mingguo; Li, Huajie; Li, Dongdong; Du, Erdeng; Li, Zhihong

2017-06-01

Carbon nanotubes (CNTs) were utilized to adsorb DOM in micro-polluted water. The characteristics of DOM adsorption on CNTs were investigated based on UV 254 , TOC, and fluorescence spectrum measurements. Based on PARAFAC (parallel factor) analysis, four fluorescent components were extracted, including one protein-like component (C4) and three humic acid-like components (C1, C2, and C3). The adsorption isotherms, kinetics, and thermodynamics of DOM adsorption on CNTs were further investigated. A Freundlich isotherm model fit the adsorption data well with high values of correlation. As a type of macro-porous and meso-porous adsorbent, CNTs preferably adsorb humic acid-like substances rather than protein-like substances. The increasing temperature will speed up the adsorption process. The self-organizing map (SOM) analysis further explains the fluorescent properties of water samples. The results provide a new insight into the adsorption behaviour of DOM fluorescent components on CNTs.

The surface characteristics of hyperbranched polyamide modified corncob and its adsorption property for Cr(VI)

Energy Technology Data Exchange (ETDEWEB)

Lin, Hai, E-mail: linhai@ces.ustb.edu.cn [School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory on Resource-oriented Treatment of Industrial Pollutants, Beijing 100083 (China); Han, Shaoke; Dong, Yingbo; He, Yinhai [School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory on Resource-oriented Treatment of Industrial Pollutants, Beijing 100083 (China)

2017-08-01

Highlights: • An anion adsorbent was synthesized by hyperbranched polyamide modified corncob (HPMC). • The surface characteristics of samples (RCC, HPMC, HPMC-Cr) were studied. • Langmuir isotherm provided more fit and maximum adsorption capacity was 131.6 mg/g. • The adsorption process was chemisorption, controlled by intra-particle diffusion and film diffusion. • Adsorption is fast, stable, spontaneous and endothermic. - Abstract: A low-cost anion adsorbent for Cr(VI) effectively removing was synthesized by hyperbranched polyamide modified corncob (HPMC). Samples were characterized by Brunauer–Emmett–Teller (BET) surface area analysis, field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy, Fourier transform infrared (FTIR) and zeta potential analysis. Kinetics, isotherms and thermodynamics studies of HPMC for Cr(VI) adsorption were investigated in batch static experiments, in the temperature range of 25–45 °C, pH = 2.0. Results showed that the adsorption was rapid and stable, with the uptake capacity higher than 80% after 30 min. Adsorption behavior and rate-controlling mechanisms were analyzed using three kinetic models (pseudo-first order, pseudo-second order, intra-particle kinetic model). Kinetic studies showed that the adsorption of HPMC to Cr(VI) relied the pseudo-second-order model, and controlled both by the intra-particle diffusion and film diffusion. Equilibrium data was tested by Langmuir and Freundlich adsorption isotherm models. Langmuir model was more suitable to indicate a homogeneous distribution of active sites on HPMC and monolayer adsorption. The maximum adsorption capacity from the Langmuir model, q{sub max}, was 131.6 mg/g at pH 2.0 and 45 °C for HPMC. Thermodynamic parameters revealed spontaneous and endothermic nature of the Cr(VI) adsorption onto HPMC.

Comparison of cadmium adsorption onto chitosan and epichlorohydrin crosslinked chitosan/eggshell composite