Adsorption of Acid Red 57 from aqueous solutions onto surfactant-modified sepiolite

The adsorption of Acid Red 57 (AR57) onto surfactant-modified sepiolite was investigated in aqueous solution in a batch system with respect to contact time, pH and temperature. The surface modification of surfactant-modified sepiolite was controlled using the FTIR technique. The pseudo-first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted very well the pseudo-second-order kinetic model and also followed the intraparticle diffusion model up to 90 min, whereas diffusion is not only the rate controlling step. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Freundlich model agrees with experimental data well. The activation energy, change of free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of AR57 onto surfactant-modified sepiolite. The results indicate that surfactant-modified sepiolite could be employed as low-cost material for the removal of textile dyes from effluents.     

Adsorption of Acid Blue 193 from aqueous solutions onto DEDMA-sepiolite

The adsorption of Acid Blue 193 (AB193) onto dodecylethyldimethylammonium (DEDMA)-sepiolite was investigated in aqueous solution in a batch system with respect to contact time, pH and temperature. The surface modification of DEDMA-sepiolite was examined by the FT-IR technique. The pseudo-first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted very well with the pseudo-second-order kinetic model and also followed the simple external diffusion model up to initial 10 min and then by intraparticle diffusion model up to 75 min, whereas diffusion is not only the rate-controlling step. The adsorption capacities of natural sepiolite and DEDMA-sepiolite at pH 1.5 and 20 degrees C were (1.19 and 2.57) x 10(-4) mol g(-1), respectively. The above results indicate that DEDMA-sepiolite has around two times higher adsorption capacity than natural sepiolite. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Freundlich model agrees with experimental data well. The activation energy, change of Gibbs free energy, enthalpy and entropy of adsorption were also evaluated for the adsorption of AB193 onto DEDMA-sepiolite.     

Removal of disperse dye from aqueous solution by novel adsorbent prepared from biomass plant material

The adsorption of Disperse Orange 25 (3-[N-ethyl-4-(4-nitrophenylazo) phenylamino] propionitrile) onto activated carbon was investigated in a batch system with respect to contact time, carbon dosage, pH and temperature from aqueous solutions. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Langmuir isotherm model agrees with the experimental data well. Maximum adsorption capacity (q_max) of Disperse Orange 25 onto adsorbent was 118.93 mg g⁻¹ at 20 °C. The first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated as well. The experimental data fitted very well to pseudo-second-order kinetic model. The results show that activated carbon prepared from Euphorbia rigida by sulfuric acid chemical activation could be employed as low-cost material to compare with commercial activated carbon for the removal of disperse dyes from effluents.     

Equilibrium, kinetic and thermodynamic studies of adsorption of Pb(II) from aqueous solution onto Turkish kaolinite clay

The adsorption of Pb(II) onto Turkish (Bandirma region) kaolinite clay was examined in aqueous solution with respect to the pH, adsorbent dosage, contact time, and temperature. The linear Langmuir and Freundlich models were applied to describe equilibrium isotherms and both models fitted well. The monolayer adsorption capacity was found as 31.75 mg/g at pH 5 and 20 degrees C. Dubinin-Radushkevich (D-R) isotherm model was also applied to the equilibrium data. The mean free energy of adsorption (13.78 kJ/mol) indicated that the adsorption of Pb(II) onto kaolinite clay may be carried out via chemical ion-exchange mechanism. Thermodynamic parameters, free energy (deltaG degrees ), enthalpy (deltaH degrees ) and entropy (deltaS degrees ) of adsorption were also calculated. These parameters showed that the adsorption of Pb(II) onto kaolinite clay was feasible, spontaneous and exothermic process in nature. Furthermore, the Lagergren-first-order, pseudo-second-order and the intraparticle diffusion models were used to describe the kinetic data. The experimental data fitted well the pseudo-second-order kinetics.     

Adsorption characteristics of Cu(II) onto ion exchange resins 252H and 1500H: kinetics, isotherms and error analysis

The adsorption of Copper(II) onto Amberjet 1500H and Ambersep 252H synthetic ion exchange resins have been studied. All the studies were conducted by a batch method to determine equilibrium and kinetic studies at the solution pH of 5.8 in the concentration ranges from 10 to 20mg/L. The experimental isotherm data were analyzed using the Freundlich, Langmuir, Redlich Perterson, Temkin, Dubinin-Radushkevich equations. Correlation co-efficient was determined for each isotherm analysis. Error functions have been used to determine the alternative single component parameters by non-linear regression due to the bias in using the correlation coefficient resulting from linearisation. From the error analysis the EABS error function provides the best parameters for the isotherm equation in this system. Adsorption kinetics data were tested using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The initial sorption rate, pseudo-first-order, pseudo-second-order and intraparticle diffusion rate constants for different initial concentrations were evaluated and discussed.     

Adsorption of basic dye on high-surface-area activated carbon prepared from coconut husk: equilibrium, kinetic and thermodynamic studies

Adsorption isotherm and kinetics of methylene blue on activated carbon prepared from coconut husk were determined from batch tests. The effects of contact time (1-30 h), initial dye concentration (50-500 mg/l) and solution temperature (30-50 degrees C) were investigated. Equilibrium data were fitted to Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The equilibrium data were best represented by Langmuir isotherm model, showing maximum monolayer adsorption capacity of 434.78 mg/g. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and was found to follow closely the pseudo-second-order kinetic model. Thermodynamic parameters such as standard enthalpy (DeltaH degrees), standard entropy (DeltaS degrees) and standard free energy (DeltaG degrees) were evaluated. The adsorption interaction was found to be exothermic in nature. Coconut husk-based activated carbon was shown to be a promising adsorbent for removal of methylene blue from aqueous solutions.     

Determination of the equilibrium, kinetic and thermodynamic parameters of adsorption of copper(II) ions onto seeds of Capsicum annuum

Adsorption of copper ions onto Capsicum annuum (red pepper) seeds was investigated with the variation in the parameters of pH, contact time, adsorbent and copper(II) concentrations and temperature. The nature of the possible adsorbent and metal ion interactions was examined by the FTIR technique. The copper(II) adsorption equilibrium was attained within 60 min. Adsorption of copper(II) ions onto C. annuum seeds followed by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Maximum adsorption capacity (q(max)) of copper(II) ions onto red pepper seeds was 4.47x10(-4) molg(-1) at 50 degrees C. Three kinetic models including the pseudo-first-order, pseudo-second-order and intraparticle diffusion equations were selected to follow the adsorption process. Kinetic parameters such as rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was indicated that the adsorption of copper(II) ions onto C. annuum seeds could be described by the pseudo-second-order kinetic model and also followed the intraparticle diffusion model up to 60 min, but diffusion is not only the rate controlling step. Thermodynamics parameters such as the change of free energy, enthalpy and entropy were also evaluated for the adsorption of copper(II) ions onto C. annuum seeds.     

Characteristics of equilibrium, kinetics studies for adsorption of fluoride on magnetic-chitosan particle

The magnetic-chitosan particle was prepared and characterized by the SEM, XRD, FT-IR and employed as an adsorbent for removal fluoride from the water solution in the batch system. The Langmuir isotherms, Bradley's isotherm, Freundlich isotherm and Dubinin-Kaganer-Radushkevich (DKR) isotherm were used to describe adsorption equilibrium. The kinetic process was investigated using the pseudo-first-order model, pseudo-second-order model and intra-particle diffusion model, respectively. The results show that the magnetic-chitosan particle is amorphous of irregular clumps in the surface with groups of RNH(2), RNH(3), Fe-O, etc. Bradley's equation and two-sites Langmuir isotherms were fitted well with the adsorption equilibrium data; the maximal amount of adsorption of 20.96-23.98 mg/l and free energy of 2.48 kJ/mol were obtained from the Bradley's equation, two-sites Langmuir isotherm and DKR modeling, respectively. The pseudo-second-order with the initial adsorption rate 2.08 mg/g min was suitable to describe the kinetic process of fluoride adsorption onto the adsorbent. In overall, the major mechanism of fluoride adsorption onto the heterogeneous surface of magnetic-chitosan particle was proposed in the study.     

Equilibrium modeling and kinetic studies on the adsorption of basic dye by a low-cost adsorbent: coconut (Cocos nucifera) bunch waste

In this paper, the ability of coconut bunch waste (CBW), an agricultural waste available in large quantity in Malaysia, to remove basic dye (methylene blue) from aqueous solution by adsorption was studied. Batch mode experiments were conducted at 30 degrees C to study the effects of pH and initial concentration of methylene blue (MB). Equilibrium adsorption isotherms and kinetics were investigated. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models of adsorption. The adsorption isotherm data were fitted well to Langmuir isotherm and the monolayer adsorption capacity was found to be 70.92 mg/g at 30 degrees C. The kinetic data obtained at different concentrations have been analyzed using a pseudo-first-order, pseudo-second-order equation and intraparticle diffusion equation. The experimental data fitted very well the pseudo-second-order kinetic model.     

Equilibrium and kinetic studies of methyl violet sorption by agricultural waste

In this work, sunflower (Helianthus annuus L.) seed hull (SSH), an agricultural waste, was evaluated for its ability to remove methyl violet (MV) from aqueous solutions. Sorption isotherm of MV onto the SSH was determined at 30 degrees C with the initial concentrations of MV in the range of 25-300 mg/L. The equilibrium data were analyzed using the Langmuir, Freundlich and Temkin isotherm models. The equilibrium process was described well by the Freundlich isotherm model. The maximum SSH sorption capacity was found to be 92.59 mg/L at 30 degrees C. The kinetic data were studied in terms of the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The pseudo-second-order model best described the sorption process. A single-stage batch-adsorber design of the adsorption of MV onto SSH was studied based on the Freundlich isotherm equation. The results indicated that sunflower seed hull was an attractive candidate for removing methyl violet from aqueous solution.     

Equilibrium and kinetic data and process design for adsorption of Congo Red onto bentonite

The adsorption of Congo Red onto bentonite in a batch adsorber has been studied. Four kinetic models, the pseudo first- and second-order equations, the Elovich equation and the intraparticle diffusion equation, were selected to follow the adsorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. It was shown that the adsorption of Congo Red onto bentonite could be described by the pseudo second-order equation. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin equations. Adsorption of Congo Red onto bentonite followed the Langmuir isotherm. A single stage batch adsorber was designed for different adsorbent mass/treated effluent volume ratios using the Langmuir isotherm.     

A novel agricultural waste adsorbent for the removal of cationic dye from aqueous solutions

In this paper, pineapple stem (PS) waste, an agricultural waste available in large quantity in Malaysia, was utilized as low-cost adsorbent to remove basic dye (methylene blue, MB) from aqueous solution by adsorption. Batch mode experiments were conducted at 30 degrees C to study the effects of initial concentration of methylene blue, contact time and pH on dye adsorption. Equilibrium adsorption isotherms and kinetic were investigated. The experimental data were analyzed by the Langmuir and Freundlich models and the isotherm data fitted well to the Langmuir isotherm with monolayer adsorption capacity of 119.05mg/g. The kinetic data obtained at different concentrations were analyzed using a pseudo-first-order and pseudo-second-order equation and intraparticle diffusion equation. The experimental data fitted very well the pseudo-second-order kinetic model. The PS was found to be very effective adsorbent for MB adsorption.     

Comparison of the efficiency of palladium and silver nanoparticles loaded on activated carbon and zinc oxide nanorods loaded on activated carbon as new adsorbents for removal of Congo red from aqueous solution: Kinetic and isotherm study

The adsorption of Congo red (CR) into three new adsorbents including Palladium and silver nanoparticles loaded on activated carbon (Pd NPs-AC, Ag NPs-AC) and zinc oxide nanorods loaded on activated carbon (ZnO-NRs-AC) in a batch method has been studied following the optimization of effective variables including pH, amount of adsorbents and time. The experimental data was fitted to conventional kinetic models including the pseudo first-order and second-order Elovich and intraparticle diffusion model and based on calculated respective parameters such as rate constants, equilibrium adsorption capacities and correlation coefficients. It was found that for all adsorbents the removal process follows the pseudo second other kinetic model with involvement of interparticle diffusion model. The experimental isotherm data were analyzed using the Langmuir, Freundlich, Tempkin and Dubinin and Radushkevich equations and it was found for all adsorbents that the removal process followed the Langmuir isotherm.     

Sorption kinetics and isotherm studies of a cationic dye using agricultural waste: broad bean peels

In this paper, broad bean peels (BBP), an agricultural waste, was evaluated for its ability to remove cationic dye (methylene blue) from aqueous solutions. Batch mode experiments were conducted at 30 degrees C. Equilibrium sorption isotherms and kinetics were investigated. The kinetic data obtained at different concentrations have been analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. The experimental data fitted very well the pseudo-first-order kinetic model. Analysis of the temportal change of q indicates that at the beginning of the process the overall rate of adsorption is controlled by film-diffusion, then at later stage intraparticle-diffusion controls the rate. Diffusion coefficients and times of transition from film to pore-diffusion control were estimated by piecewise linear regression. The experimental data were analyzed by the Langmuir and Freundlich models. The sorption isotherm data fitted well to Langmuir isotherm and the monolayer adsorption capacity was found to be 192.7 mg/g and the equilibrium adsorption constant Ka is 0.07145 l/mg at 30 degrees C. The results revealed that BBP was a promising sorbent for the removal of methylene blue from aqueous solutions.     

The removal of basic dyes from aqueous solutions using agricultural by-products

The adsorption of two basic dyes, namely, Malachite Green and Methylene Blue onto both agricultural by-products (i.e. rice bran and wheat bran) has been investigated in this study. The adsorption of both basic dyes was solution pH-dependent. The kinetic experimental data were analyzed using four kinetic equations including pseudo-first-order equation, pseudo-second-order equation, external diffusion model and intraparticle diffusion model to examine the mechanism of adsorption and potential rate-controlling step. The best-fit equation was identified using normalized standard deviation. The Langmuir and Freundich isotherms were used to fit the equilibrium data and the results showed that the Langmuir isotherm exhibited a little better fit to the Methylene Blue adsorption data by both adsorbents while the Freundlich isotherm seemed to agree better with the Malachite Green adsorption. The Gibbs free energy changes at 20 degrees C were calculated and the obtained values supported the conclusion that two dyes molecules adsorbed by physical processes. The effects of particle size, adsorbent concentration and solution ionic strength on the adsorption of the two basic dyes were also studied.     

Kinetic and isotherm studies of Cu(II) biosorption onto valonia tannin resin

The biosorption of Cu(II) from aqueous solutions by valonia tannin resin was investigated as a function of particle size, initial pH, contact time and initial metal ion concentration. The aim of this study was to understand the mechanisms that govern copper removal and find a suitable equilibrium isotherm and kinetic model for the copper removal in a batch reactor. The experimental isotherm data were analysed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analysed using four sorption kinetic models - the pseudo-first- and second-order equations, the Elovich and the intraparticle diffusion model equation - to determine the best fit equation for the biosorption of copper ions onto valonia tannin resin. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process, whereas the Elovich equation also fits the experimental data well.     

Removal of basic dye by modified Unye bentonite, Turkey

The adsorption behavior of crystal violet (CV(+)) from aqueous solution onto raw (RB) and manganese oxide-modified (MMB) bentonite samples was investigated as a function of parameters such as initial CV(+) concentration, contact time and temperature. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption models were applied to describe the equilibrium isotherms. The Langmuir monolayer adsorption capacities of RB and MMB were estimated as 0.32 and 1.12 mmol/g, respectively. The mean adsorption energy derived from D-R isotherm for MMB showed that the type of adsorption of dye molecules on this material may be defined as chemical adsorption. The adsorption rate was fast and more than half of the adsorbed-CV(+) was removed in the first 55 min for RB and 5 min for MMB at the room temperature. The pseudo-first-order, pseudo-second-order kinetic and the intraparticle diffusion models were used to describe the kinetic data and rate constants were evaluated. The thermodynamic parameters such as DeltaH, DeltaS and DeltaG were found 117.41 kJ/mol, 41.50 J/(molK), -5.07 kJ/mol (RB) and 21.19 kJ/mol 98.34 J/(molK), -7.84 kJ/mol (MMB) at 295.15 K, respectively. The quite high adsorption capacity and high adsorption rate of MMB will provide an important advantage for using of this material in basic dye solution.     

Sorption of SPADNS azo dye on polystyrene anion exchangers: Equilibrium and kinetic studies

The sorption of SPANDS from aqueous solution onto the macroporous polystyrene anion exchangers of weakly basic Amberlyst A-21 and strongly basic Amberlyst A-29 in a batch method was studied. The effect of initial dye concentration and phase contact time was considered to evaluate the sorption capacity of anion exchangers. Equilibrium data were attempted by various adsorption isotherms including the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models. A comparison of kinetic models applied to the adsorption rate constants and equilibrium sorption capacities was made for the Lagergren first-order, pseudo second-order and Morris–Weber intraparticle diffusion kinetic models. The results showed that the adsorption isotherm is in the good agreement with the Langmuir equation and that the adsorption kinetics of SPADNS on both anion exchangers can be best described by the pseudo second-order model.     

Biosorption of Pb(II) ions by modified quebracho tannin resin

In this study, the effect of temperature, pH and initial metal concentration on Pb(II) biosorption on modified quebracho tannin resin (QTR) was investigated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to investigate QTR structure and morphology. Besides, the specific BET surface area and zeta-potential of the QTR were analysed. Thermodynamic functions, the change of free energy (DeltaG degrees), enthalpy (DeltaH degrees) and entropy (DeltaS degrees) of Pb adsorption on modified tannin resin were calculated as -5.43 kJ mol(-1) (at 296+/-2K), 31.84 kJ mol(-1) and 0.127 J mmol(-1) K(-1), respectively, indicating the spontaneous, endothermic and the increased randomness nature of Pb(2+) adsorption. The kinetic data was tested using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion model. The results suggested that the pseudo-second-order model (R(2)>0.999) was the best choice among all the kinetic models to describe the adsorption behavior of Pb(II) onto QTR. Langmuir, Freundlich and Tempkin adsorption models were used to represent the equilibrium data. The best interpretation for the experimental data was given by the Langmuir isotherm and the maximum adsorption capacity (86.207 mg g(-1)) of Pb(II) was obtained at pH 5 and 296 K.     

The adsorption of basic dye (Astrazon Blue FGRL) from aqueous solutions onto sepiolite, fly ash and apricot shell activated carbon: kinetic and equilibrium studies

In this study, sepiolite, fly ash and apricot stone activated carbon (ASAC) were used as adsorbents for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the basic dye (Astrazon Blue FGRL) from aqueous solutions at various concentrations (100-300 mg/L), adsorbent doses (3-12 g/L) and temperatures (303-323 K). The result showed that the adsorption capacity of the dye increased with increasing initial dye concentration, adsorbent dose and temperature. Three kinetic models, the pseudo-first-order, second-order, intraparticle diffusion, were used to predict the adsorption rate constants. The kinetics of adsorption of the basic dye followed pseudo-second-order kinetics. Equations were developed using the pseudo-second-order model which predicts the amount of the basic dye adsorbed at any contact time, initial dye concentration and adsorbent dose within the given range accurately. The adsorption equilibrium data obeyed Langmuir isotherm. The adsorption capacities (Q0) calculated from the Langmuir isotherm were 181.5 mg/g for ASAC, 155.5 mg/g for sepiolite and 128.2 mg/g for fly ash at 303 K. Thermodynamical parameters were also evaluated for the dye-adsorbent systems and revealed that the adsorption process was endothermic in nature.