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) and Pb(II) onto expanded perlite from aqueous solution

The adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite (EP) from aqueous solution were investigated with respect to the changes in pH of solution, adsorbent dosage, contact time and temperature of solution. For the adsorption of both metal ions, the Langmuir isotherm model fitted to equilibrium data better than the Freundlich isotherm model. Using the Langmuir model equation, the monolayer adsorption capacity of EP was found to be 8.62 and 13.39 mg/g for Cu(II) and Pb(II) ions, respectively. Dubinin-Radushkevich (D-R) isotherm model was also applied to the equilibrium data and the mean free energies of adsorption were found as 10.82 kJ/mol for Cu(II) and 9.12 kJ/mol for Pb(II) indicating that the adsorption of both metal ions onto EP was taken place by chemical ion-exchange. Thermodynamic functions, the change of free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) of adsorption were also calculated for each metal ions. These parameters showed that the adsorption of Cu(II) and Pb(II) ions onto EP was feasible, spontaneous and exothermic at 20-50 degrees C. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for both metal ions followed well pseudo-second-order kinetics.     

Adsorption of chromium(III), mercury(II) and lead(II) ions onto 4-aminoantipyrine immobilized bentonite

In this work, the immobilization of 4-aminoantipyrine onto bentonite was carried out and it was then used to investigate the adsorption behavior of Cr(III), Hg(II) and Pb(II) ions from aqueous solutions. The separation and preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. Under optimum pH value (pH 4.0), the maximum static adsorption capacity of the sorbent was found to be 38.8, 52.9 and 55.5 mg g(-1) for Cr(III), Hg(II) and Pb(II), respectively. 2.0 mL of 2% thiourea in 1.0 M HCl solution effectively eluted the adsorbed metal ions. The detection limit (3σ) of this method defined by IUPAC was found to be 0.12, 0.09 and 0.23 ng mL(-1) for Cr(III), Hg(II) and Pb(II), respectively. The relative standard deviation (RSD) was lower 3.0% (n=8). The developed method has been validated by analyzing certified reference materials and successfully applied to the determination of trace Cr(III), Hg(II) and Pb(II) in water samples with satisfactory results.     

Adsorption studies on Citrus reticulata (fruit peel of orange): removal and recovery of Ni(II) from electroplating wastewater

The ability of fruit peel of orange to remove Zn, Ni, Cu, Pb and Cr from aqueous solution by adsorption was studied. The adsorption was in the order of Ni(II)>Cu(II)>Pb(II)>Zn(II)>Cr(II). The extent of removal of Ni(II) was found to be dependent on sorbent dose, initial concentration, pH and temperature. The adsorption follows first-order kinetics. The process is endothermic showing monolayer adsorption of Ni(II), with a maximum adsorption of 96% at 50 degrees C for an initial concentration of 50 mg l(-1) at pH 6. Thermodynamic parameters were also evaluated. Desorption was possible with 0.05 M HCl and was found to be 95.83% in column and 76% in batch process, respectively. The spent adsorbent was regenerated and recycled thrice. The removal and recovery was also done in wastewater and was found to be 89% and 93.33%, respectively.     

Tartrazine modified activated carbon for the removal of Pb(II), Cd(II) and Cr(III)

A two in one attempt for the removal of tartrazine and metal ions on activated carbon has been developed. The method was based on the modification of activated carbon with tartrazine then its application for the removal of Pb(II), Cd(II) and Cr(III) ions at different pH values. Tartrazine adsorption data were modelled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacities qm were 121.3, 67 and 56.7mgg(-1) at initial pH values of 1.0, 6.0 and 10, respectively. The adsorption of tartrazine onto activated carbon followed second-order kinetic model. The equilibrium time was found to be 240min at pH 1.0 and 120min at pH 10 for 500mgL(-1) tartrazine concentration. A maximum removal of 85% was obtained after 1h of contact time. The presence of tartrazine as modifier enhances attractive electrostatic interactions between metal ions and carbon surface. The adsorption capacity for Pb(II), Cd(II) and Cr(III) ions has been improved with respect to non-modified carbon reaching a maximum of 140%. The adsorption capacity was found to be a pH dependent for both modified and non-modified carbon with a greater adsorption at higher pH values except for Cr(III). The enhancement percent of Pb(II), Cd(II) and Cr(III) at different pH values was varied from 28% to 140% with respect to non-modified carbon. The amount of metal ions adsorbed using static regime was 11-40% higher than that with dynamic mode. The difference between adsorption capacities could be attributed to the applied flow rate.     

Removal of copper(II) and lead(II) from aqueous solution by manganese oxide coated sand II. Equilibrium study and competitive adsorption

The adsorption equilibrium of MOCS and the Cu(II) and Pb(II) ions removal capacity by MOCS in single-(non-competitive) and binary-(competitive) component sorption systems from aqueous solutions were investigated. The equilibrium data were analyzed using the Langmuir, Freundlich, Temkin and Redlich-Peterson isotherms. The characteristic parameters for each isotherm were determined. The Langmuir and Redlich-Peterson isotherms provided the best correlation for both Cu(II) and Pb(II) onto MOCS. From the Langmuir isotherms, maximum adsorption capacities of MOCS towards Cu(II) and Pb(II) are determined at different temperature. The maximum adsorption capacity of Cu(II) and Pb(II) per gram MOCS in single component sorption systems were from 5.91 and 7.71 micromol to 7.56 and 9.22 micromol for the temperature range of 288-318 K, respectively. The order of affinity based on a weight uptake by MOCS was as follows: Pb(II)>Cu(II). The same behavior was observed during competitive adsorption that is in the case of adsorption from their binary solution. The thermodynamic parameters (DeltaG degrees , DeltaH degrees , and DeltaS degrees) for Cu(II) and Pb(II) sorption on MOCS were also determined from the temperature dependence. This competitive adsorption showed that the uptake of each metal was considerably reduced with an increasing concentration of the other, the adsorption of Cu(II) being more strongly influenced by Pb(II) than vice versa due to the higher affinity of MOCS for the latter.     

Grape waste as a biosorbent for removing Cr(VI) from aqueous solution

Grape waste generated in wine production is a cellulosic material rich in polyphenolic compounds which exhibits a high affinity for heavy metal ions. An adsorption gel was prepared from grape waste by cross-linking with concentrated sulfuric acid. It was characterized and utilized for the removal of Cr(VI) from synthetic aqueous solution. Adsorption tests were conducted in batch mode to study the effects of pH, contact time and adsorption isotherm of Cr(VI), which followed the Langmuir type adsorption and exhibited a maximum loading capacity of 1.91 mol/kg at pH 4. The adsorption of different metal ions like Cr(VI), Cr(III), Fe(III), Zn(II), Cd(II) and Pb(II) from aqueous solution at different pH values 1-5 has also been investigated. The cross-linked grape waste gel was found to selectively adsorb Cr(VI) over other metal ions tested. The results suggest that cross-linked grape waste gel has high possibility to be used as effective adsorbent for Cr(VI) removal.     

Celtek clay as sorbent for separation-preconcentration of metal ions from environmental samples

The sorption conditions including pH of the aqueous solution, sample volume, etc., on Celtek clay of copper(II), cadmium(II), lead(II), chromium(III), nickel(II) and cobalt(II) ions from environmental samples has been studied. The effects of electrolytes as matrix on the preconcentration were also investigated with the recoveries >95%. The 3 sigma detection limits for copper, cadmium, lead, chromium, nickel and cobalt ions were found to be 0.25, 0.32, 0.73, 0.45, 0.50 and 0.41 microg/l, respectively. The relative standard deviation was <10% for the determination of analytes. The procedure was validated by analysis of a NRCC-SLRS 4 Riverine Water, SRM 1573a Tomato leaves and IAEA 336 Lichen standard reference materials. The developed method was successively utilized for the determination of Cu(II), Cd(II), Pb(II), Cr(III), Ni(II) and Co(II) in various samples including natural waters, wheat and human hair by flame atomic absorption spectrometry (FAAS) with satisfactorily results (recoveries>95% and R.S.D.'s<10%).     

Adsorption of copper (II), chromium (III), nickel (II) and lead (II) ions from aqueous solutions by meranti sawdust

The present study proposed the use of meranti sawdust in the removal of Cu(II), Cr(III), Ni(II) and Pb(II) ions from synthetic aqueous solutions. Batch adsorption studies showed that meranti sawdust was able to adsorb Cu(II), Cr(III), Ni(II) and Pb(II) ions from aqueous solutions in the concentration range 1–200 mg/L. The adsorption was favoured with maximum adsorption at pH 6, whereas the adsorption starts at pH 1 for all metal ions. The effects of contact time, initial concentration of metal ions, adsorbent dosage and temperature have been reported. The applicability of Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm was tried for the system to completely understand the adsorption isotherm processes. The adsorption kinetics tested with pseudo-first-order and pseudo-second-order models yielded high R² values from 0.850 to 0.932 and from 0.991 to 0.999, respectively. The meranti sawdust was found to be cost effective and has good efficiency to remove these toxic metal ions from aqueous solution.     

Adsorption of copper from aqueous solution on Brassica cumpestris (mustard oil cake)

The adsorption behavior of various heavy metals on mustard oil cake (MOC) was studied. The maximum adsorption of Cu(II) was observed followed by Zn(II), Cr(VI), Mn(II), Cd(II), Ni(II) and Pb(II). The adsorption of Cu(II) was found to be dependent on initial concentration of solution, pH, adsorbent dose, temperature and contact time. The adsorption followed pseudo-first-order and second-order kinetics but pseudo-second-order kinetic model was better obeyed since experimental data agreed well with theoretical data. Thermodynamic parameters were also evaluated. The adsorption process was found to be endothermic and spontaneous in nature. Attempts were also made to desorb Cu(II) from the adsorbent and regeneration of the spent adsorbent. The breakthrough and exhaustive capacities were found to be 5 and 10 mg g(-1), respectively.     

The sorption of lead(II) ions on rice husk ash

Present study deals with the adsorption of Pb(II) from aqueous solution on rice husk ash. Rice husk is a by-product generally obtained from rice mill. Rice husk ash is a solid obtained after burning of rice husk. Batch studies were performed to evaluate the influences of various experimental parameters like pH, initial concentration, adsorbent dosage, contact time and the effect of temperature. Optimum conditions for Pb(II) removal were found to be pH 5, adsorbent dosage 5 g/L of solution and equilibrium time 1h. Adsorption of Pb(II) followed pseudo-second-order kinetics. The effective diffusion coefficient is of the order of 10(-10)m(2)/s. The equilibrium adsorption isotherm was better described by Freuindlich adsorption isotherm model. The adsorption capacity (q(max)) of rice husk ash for Pb(II) ions in terms of monolayer adsorption was 91.74 mg/g. The change of entropy (DeltaS(0)) and enthalpy (Delta H(0)) were estimated at 0.132 kJ/(mol K) and 28.923 kJ/mol respectively. The negative value of Gibbs free energy (Delta G(0)) indicates feasible and spontaneous adsorption of Pb(II) on rice husk ash. The value of the adsorption energy (E), calculated using Dubinin-Radushkevich isotherm, was 9.901 kJ/mol and it indicated that the adsorption process was chemical in nature. Application study was also carried out to find the suitability of the process in waste water treatment operation.     

Removal of Cr(VI) from industrial wastewaters by adsorption Part I: determination of optimum conditions

Aim of this study is the determination of the Cr(VI) removal efficiency of treated pine sawdust and also to find out the thermodynamic and kinetic parameters of Cr(VI) removal process in batch systems. Sawdust has been treated with 1,5-disodium hydrogen phosphate before the adsorption experiments. The effects of initial concentration of Cr(VI) ion, temperature, amount of adsorbent and pH of the solution on adsorption have been investigated. Optimum conditions for adsorption were determined as T=40 degrees C, sawdust dose=4 g, pH 2, by using the results of these experiments and an additional set of experiments was performed under these optimum conditions in order to see the change in the adsorption efficiency. Removal of chromium ion was found as highly dependent on pH and initial Cr(VI) concentration of the solution. In order to find out thermodynamic and kinetic parameters equilibrium adsorption models were applied. Although experimental data confirm with both Langmuir and Freundlich isotherm models, they suit most on Langmuir isotherms. Adsorption rate constant was determined from Lagergren equation. Equilibrium constants, adsorption free energy, enthalpy and entropy change values were also determined. It was found that adsorption process follows first order kinetic and adsorption of Cr(VI) on sawdust has the spontaneous nature.     

Kinetic studies of adsorption of Pb(II), Cr(III) and Cu(II) from aqueous solution by sawdust and modified peanut husk

Sawdust and modified peanut husk were used as adsorbents to remove Pb(II), Cr(III) and Cu(II) from aqueous solution. Results of kinetic experiments demonstrated that the adsorption was effective and rapid. Three different kinds of kinetic models (i.e., intraparticular diffusion model, Lagergren-first-order and second-order equations) were used to investigate the adsorption mechanisms. The adsorption of heavy metals on sawdust and modified peanut husk is not an intraparticular diffusion control. The kinetic adsorption data can be described by the second-order equation and the adsorption might be a rate-limiting control. The suitability of the adsorbent was tested by fitting the adsorption data with Langmuir and Freundlich isotherms, which gave good fits with both isotherms.     

Removal of Pb(II) from aqueous solution on chitosan/TiO(2) hybrid film

This paper presents the adsorption of Pb(II) from aqueous solution using chitosan/TiO(2) hybrid film (CTF) adsorbent. Batch experiments were carried out as a function of solution pH, adsorption time, Pb(II) concentration and temperature. The equilibrium data fitted well with the linear Freundlich model. The adsorption process was proved to be the second grade reaction and the theoretically maximum adsorption amount at equilibrium was 36.8 mg-Pb/g. The influence parameters were optimized by response surface method (RSM), such as initial metal concentration, pH and temperature. The extreme points were gained by the Statistical Analysis System software: initial metal concentration is 50-55 mg/l, pH is 3-4 and temperature is 60 degrees C. Very high regression coefficient (R(2)=0.9689) indicates excellent evaluation of experimental data by second-order polynomial regression model. Under this condition the theoretical adsorption efficiency is 90.6%. It illuminates that this model is reliable to optimize the adsorption process and CTF is suitable for adsorbing Pb(II) from aqueous solution.     

Comparative study of adsorption properties of Turkish fly ashes. II. The case of chromium (VI) and cadmium (II)

The purpose of the study described in this paper was to compare the removal of Cr(VI) and Cd(II) from an aqueous solution using two different Turkish fly ashes; Afsin-Elbistan and Seyitomer as adsorbents. The influence of four parameters (contact time, solution pH, initial metal concentration in solution and ash quality) on the removal at 20+/-2 degrees C was studied. Fly ashes were found to have a higher adsorption capacity for the adsorption of Cd(II) as compared to Cr(VI) and both Cr(VI) and Cd(II) required an equilibrium time of 2h. The adsorption of Cr(VI) was higher at pH 4.0 for Afsin-Elbistan fly ash (25.46%) and pH 3.0 for Seyitomer fly ash (30.91%) while Cd(II) was adsorbed to a greater extent (98.43% for Afsin-Elbistan fly ash and 65.24% for Seyitomer fly ash) at pH 7.0. The adsorption of Cd(II) increased with an increase in the concentrations of these metals in solution while Cr(VI) adsorption decreased by both fly ashes. The lime (crystalline CaO) content in fly ash seemed to be a significant factor in influencing Cr(VI) and Cd(II) ions removal. The linear forms of the Langmuir and Freundlich equations were utilised for experiments with metal concentrations of 55+/-2mg/l for Cr(VI) and 6+/-0.2mg/l for Cd(II) as functions of solution pH (3.0-8.0). The adsorption of Cr(VI) on both fly ashes was not described by both the Langmuir and Freundlich isotherms while Cd(II) adsorption on both fly ashes satisfied only the Langmuir isotherm model. The adsorption capacities of both fly ashes were nearly three times less than that of activated carbon for the removal of Cr(VI) while Afsin-Elbistan fly ash with high-calcium content was as effective as activated carbon for the removal of Cd(II). Therefore, there are possibilities for use the adsorption of Cd(II) ions onto fly ash with high-calcium content in practical applications in Turkey.     

Removal of Pb(II) ions from aqueous solutions by sulphuric acid-treated wheat bran

Sulphuric acid-treated wheat bran (STWB) was used as an adsorbent to remove Pb(II) ions from aqueous solution. It was observed that the adsorption yield of Pb(II) ions was found to be pH dependent. The equilibrium time for the process was determined as 2h. STWB gave the highest adsorption yield at around pH 6.0. At this pH, adsorption percentage for an initial Pb(II) ions concentration of 100mg/L was found to be 82.8 at 25 degrees C for contact time of 2h. The equilibrium data obtained at different temperatures fitted to the non-linear form of Langmuir, Freundlich and Redlich-Peterson and linear form of Langmuir and Freundlich models. Isotherm constants were calculated and compared for the models used. The maximum adsorption capacity (q(max)) which was obtained linear form of Langmuir model increased from 55.56 to 79.37mg/g with increasing temperature from 25 to 60 degrees C. Similar trend was observed for other isotherm constants related to the adsorption capacity. Linear form of Langmuir isotherm data was evaluated to determine the thermodynamic parameters for the process. Thermodynamic parameters show that adsorption process of Pb(II) ions is an endothermic and more effective process at high temperatures. The pseudo nth order kinetic model was successfully applied to the kinetic data and the order (n) of adsorption reaction was calculated at the range from 1.711 to 1.929. The values of k(ad) were found to be 5.82x10(-4) and 21.81x10(-4)(min(-1))(mg/g)(1-n) at 25 and 60 degrees C, respectively. Activation energy was determined as 29.65kJ/mol for the process. This suggest that the adsorption Pb(II) ions by STWB is chemically controlled.     

Removal of Supranol Yellow 4GL by adsorption onto Cr-intercalated montmorillonite

Cr(III)-intercalated montmorillonite was utilized as an adsorbent for the removal of the organic pollutant, Supranol Yellow 4GL, a synthetic dye used for chemical fibres. The material was prepared by the reaction of Na montmorillonite with a base-hydrolyzed solution of Cr nitrate salt (OH(-)/Cr(3+) molar ratios of 2). XRD data showed that the interlayer spacing (d(001)) of montmorillonite was increased from 12.35 to 23.06 Angstroms. The kinetics and mechanism of the adsorption of the acid dye, Supranol Yellow 4GL, on Cr(III)-intercalated montmorillonite was investigated. The equilibrium time was reached within 30 min. The process follows pseudo-second-order rate kinetics. The Langmuir isotherm described the adsorption data over the concentration range (20-160 mg/l). The separator factor R(L) revealed the favourable nature of this adsorption process. Also, the thermodynamic parameters such as DeltaS degrees, DeltaH degrees, DeltaG degrees were determined.     

Tris(2-aminoethyl) amine functionalized silica gel for solid-phase extraction and preconcentration of Cr(III), Cd(II) and Pb(II) from waters

A new tris(2-aminoethyl) amine (TREN) functionalized silica gel (SG-TREN) was prepared and investigated for selective solid-phase extraction (SPE) of trace Cr(III), Cd(II) and Pb(II) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Identification of the surface modification was characterized and performed on the basis of FT-IR. The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 4, the maximum adsorption capacity of Cr(III), Cd(II) and Pb(II) onto the SG-TREN were 32.72, 36.42 and 64.61 mg g(-1), respectively. The adsorbed metal ions were quantitatively eluted by 5 mL of 0.1 mol L(-1) HCl. Common coexisting ions did not interfere with the separation. According to the definition of International Union of Pure and Applied Chemistry, the detection limits (3sigma) of this method for Cr(III), Cd(II) and Pb(II) were 0.61, 0.14 and 0.55 ng mL(-1), respectively. The relative standard deviation under optimum conditions is less than 4.0% (n=11). The application of this modified silica gel to preconcentration trace Cr(III), Cd(II) and Pb(II) of two water samples gave high accurate and precise results.     

Removal of Cr(VI) from aqueous solutions using agricultural waste 'maize bran'

Novel biosorbent 'maize bran' has been successfully utilized for the removal of Cr(VI) from aqueous solution. The effect of different parameters such as contact time, sorbate concentration, pH of the medium and temperature were investigated and maximum uptake of Cr(VI) was 312.52 (mgg(-1)) at pH 2.0, initial Cr(VI) concentration of 200mgL(-1) and temperature of 40 degrees C. Effect of pH showed that maize bran was not only removing Cr(VI) from aqueous solution but also reducing toxic Cr(VI) into less toxic Cr(III). The sorption kinetics was tested with first order reversible, pseudo-first order and pseudo-second order reaction and it was found that Cr(VI) uptake process followed the pseudo-second order rate expression. Mass transfer of Cr(VI) from bulk to the solid phase (maize bran) was studied at different temperatures. Different thermodynamic parameters, viz., DeltaG degrees , DeltaH degrees and DeltaS degrees have also been evaluated and it has been found that the sorption was feasible, spontaneous and endothermic in nature. The Langmuir and Freundlich equations for describing sorption equilibrium were applied and it was found that the process was well described by Langmuir isotherm. Desorption studies was also carried out and found that complete desorption of Cr(VI) took place at pH of 9.5.     

Adsorption of platinum (IV), palladium (II) and gold (III) from aqueous solutions onto L-lysine modified crosslinked chitosan resin

Crosslinked chitosan resin chemically modified with L-lysine has been used to investigate the adsorption of Pt(IV), Pd(II) and Au(III) from aqueous solutions. Batch adsorption studies were carried out with various parameters, such as initial metal ion concentration, contact time, pH and temperature. The maximum adsorption capacity was found at pH 1.0 for Pt(IV), at pH 2.0 for Au(III) and Pd(II). Langmuir and Freundlich isotherm models were applied to analyze the experimental data. The best interpretation for the experimental data was given by the Langmuir isotherm and the maximum adsorption capacity was found to be 129.26 mg/g for Pt(IV), 109.47 mg/g for Pd(II) and 70.34 mg/g for Au(III). The kinetic data was tested using pseudo-first-order and pseudo-second-order kinetic models. Kinetic data correlated well with the pseudo-second-order kinetic model, indicating that the chemical sorption was the rate-limiting step. Thermodynamic parameters like Gibbs free energy (DeltaG degrees), enthalpy (DeltaH degrees) and entropy (DeltaS degrees) were evaluated by applying the Van't Hoff equation. The thermodynamic study indicated that the adsorption process is spontaneous and exothermic in nature. The desorption studies were carried out using various reagents. The maximum percent desorption of precious metal ions were obtained when the reagent 0.7 M thiourea-2 M HCl was used.