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.     

Kinetics and equilibrium isotherms of adsorption of Pb(II) and Cu(II) onto raw and arginine-modified montmorillonite

Arg-Mt, was fabricated by modifying sodium montmorillonite (Na-Mt) with Arginine monohydrochloride (Arg salt), to adsorb Pb(II) and Cu(II) in aqueous solution. The X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectrum, thermal analysis (TG/DTG), Brunauer-Emmett-Teller (BET) and Scanning electron microscope (SEM) were employed to investigate the properties of Na-Mt and Arg-Mt. The effects of the amount of modifier, pH value, the initial concentration of M(II), temperature and contact time were tested in a single adsorption system. The isotherm model was well matched with the Langmuir curve and the kinetic adsorption fitted well with the pseudo-second-order rate equation. The saturated adsorption of Pb(II) and Cu(II) by Arg-Mt were 124.69 and 29.15?mg/g, respectively, which were higher than that of Na-Mt (89.08 and 23.93?mg/g). The thermodynamic equation indicated that the adsorption process was spontaneous, endothermic, and the randomness of the samples changed a little after adsorption. The adsorption capacity of heavy metal ions in the binary co-adsorption system was poor than single adsorption system. Furthermore, the adsorbed M(II) onto Arg-Mt can hardly be dissolved under weak acidic condition (pH?>?4) according to the desorption experiments. High-efficiency and low-cost make Arg-Mt to be used in the removal of heavy ions in aqueous solution.     

Efficient removal of heavy metal ions from aqueous solution using salicylic acid type chelate adsorbent

In this study, 5-aminosalicylic acid was successfully grafted onto the poly(glycidyl methacrylate) (PGMA) macromolecular chains of PGMA/SiO₂ to obtain a novel adsorbent designated as ASA-PGMA/SiO₂. The adsorption properties of ASA-PGMA/SiO₂ for heavy metal ions were studied through batch and column methods. The experimental results showed that ASA-PGMA/SiO₂ possesses strong chelating adsorption ability for heavy metal ions, and its adsorption capacity for Cu²⁺, Cd²⁺, Zn²⁺, and Pb²⁺ reaches 0.42, 0.40, 0.35, and 0.31 mmol g⁻¹, respectively. In addition, pH has a great influence on the adsorption capacity in the studied pH range. The adsorption isotherm data greatly obey the Langmuir and Freundlich model. The desorption of metal ions from ASA-PGMA/SiO₂ is effective using 0.1 mol l⁻¹ of hydrochloric acid solution as eluent. Consecutive adsorption-desorption experiments showed that ASA-PGMA/SiO₂ could be reused almost without any loss in the adsorption capacity.     

Prediction of simultaneous adsorption of Cu(II) and Pb(II) onto activated carbon by conventional Langmuir type equations

Removal of Cu(II) and Pb(II) by adsorption onto activated carbon was examined in single- and binary-component aqueous solutions representative of contaminated solutions containing heavy metals. Reversibility of adsorption of the heavy metals on the activated carbon was evaluated by desorption experiments. The number of the maximum adsorption sites and adsorption equilibrium constants of Cu(II) and Pb(II) were estimated by the results of single-component systems assuming the Langmuir adsorption model. The adsorption sites per gram of activated carbon resulted in similar values for Cu(II) and Pb(II) from the isotherms. The adsorption constant for Pb(II) was nearly 1.8 times greater than that of Cu(II). Rate constants of adsorption and desorption were also estimated from the kinetic analysis. Using the single set of common parameters obtained from the single-component systems, the experimental results for a binary-component system were quantitatively predicted. Competitive adsorption of Cu(II) and Pb(II) on the same adsorption sites was confirmed by both experimental and predicted results of adsorption in the binary mixture.     

Removal of Cu(II) ions by activated poplar sawdust (Samsun clone) from aqueous solutions

In this work, adsorption of Cu(II) ions on sawdust (SD) and activated sawdust (ASD) has been studied by using batch adsorption techniques. The equilibrium adsorption level was determined to be a function of the pH, initial Cu(II) concentration, and adsorbent dosage. The equilibrium nature of Cu(II) adsorption has been described by the Freundlich and Langmuir isotherms. The experimental adsorption data were fitted to the Langmuir adsorption model both sawdust and activated sawdust. The equilibrium capacity of sawdust and activated sawdust were 5.432 and 13.495 mg copper per g adsorbent, respectively at room temperature and natural pH. The maximum adsorption capacity was obtained at the maximum zeta potential value that -74.5 mV (pH 5) for activated sawdust and at -48.4 mV (pH 4) for sawdust. It was observed that activated sawdust was a suitable adsorbent than sawdust for removal of Cu(II) from aqueous solutions.     

Removal of Cu(II) from aqueous solution by adsorption onto acid-activated palygorskite

A series of activated palygorskite clay by HCl with different concentrations was prepared and applied as adsorbents for removal of Cu(II) from aqueous solutions. The effects of contact time, adsorbent dosages and pHs of suspension on the adsorption capacities for Cu(II) were investigated. The results showed that adsorption capacity of activated palygorskites increased with increasing the HCl concentration and the maximum adsorption capacity with 32.24 mg/g for Cu(II) is obtained at 12 mol/L of HCl concentration. The variations in IR spectra and pH of solution after adsorption Cu(II) confirmed that the numerous amount of silanol groups (Si-OH) originated by acid treatment were mainly responsible for Cu(II) adsorption onto acid-activated palygorskite. Kinetic studies indicated that the adsorption mechanisms in the Cu(II)/acid-activated palygorskite system followed the pseudo-second-order kinetic model with a relatively small contribution of film diffusion. Equilibrium data fitted well with Freundlich isotherm model compared to Langmuir isotherm model, indicating that adsorption takes place on heterogeneous surfaces of the acid-activated palygorskite. Adsorption-desorption studies presented that activated palygorskite has lower adsorption and desorption efficiencies using Cu(CH3COO)2 than that of other inorganic copper salts, such as CuSO4, Cu(NO3)2, and CuCl2.     

Cation exchange removal of Pb from aqueous solution by sorption onto NiO

This paper reports NiO as a novel and an efficient adsorbent for the removal of Pb from aqueous solutions. In the present investigation, Pb adsorption experiments on NiO were conducted on aqueous solution at different initial Pb concentration, pH of the solution and adsorption temperature. The mechanism of adsorption was observed to be an ion exchange between the surface proton and Pb in aqueous solution. Experimental data were best described by the Langmuir isotherms. The surface structure of the NiO before and after adsorption of Pb was analyzed by using FTIR spectroscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analyses (EDX).     

Adsorption characteristics of heavy metal ions onto a low cost biopolymeric sorbent from aqueous solutions

In this study, the adsorption conditions of Cu(II), Pb(II) and Cd(II) metal ions onto sporopollenin have been studied. The different variables effecting the sorption capacity such as pH of the solution, adsorption time, initial metal ion concentration and temperature have been investigated. Adsorption isotherms correlated well with the Freundlich type adsorption isotherm and adsorption capacities were found to be 0.0195, 0.0411 and 0.0146 mmol g(-1) for Cu(II), Pb(II) and Cd(II) metal ions, respectively. Experimental data were also evaluated to find out kinetic characteristics of the adsorption process. Adsorption processes for three target heavy metal ions were found to follow pseudo-second order type adsorption kinetics. Intraparticle diffusion was found to take part in adsorption processes but it could not be accepted as the primary rate-determining step. The mean free energies of adsorption (E) were found to be between 8 and 16 kJ mol(-1) for the metal ions studied and therefore adsorption mechanism for the adsorbent was explained as an ion-exchange process. But it was observed that chelating effect is also playing an important role in the adsorption of metal ions onto sporopollenin. Thermodynamic parameters, DeltaH degrees , DeltaS degrees and DeltaG degrees were also calculated from graphical interpretation of the experimental data. Standard heats of adsorption (DeltaH degrees ) were found to be endothermic and DeltaS degrees values were calculated to be positive for the adsorption of Cu(II), Pb(II) and Cd(II) ions onto the adsorbent. Negative DeltaG degrees values indicated that adsorption process for these three metal ions onto sporopollenin is spontaneous.     

Water-soluble magnetic-carbon nanotubes nanocomposites for efficient adsorption of Cu(II) from aqueous solution

In this study, the water-soluble magnetic-multi-walled carbon nanotubes nanocomposites were fabricated via a facile and efficient approach and were characterized by X-ray diffraction, energy-dispersive X-ray, and transmission electron microscopy in detail. The nanocomposites could be employed as an effective adsorbent for removal of heavy metal ions, Cu(II) ions, from aqueous solution. It is noteworthy that the novel adsorbent displayed good water-dispersibility, rapid absorption rate, high absorption capacity, and convenient magnetic separation. Furthermore, the nanocomposites could be recovered and recycled for 10 consecutive trials without significant loss of its activity.     

Kinetics and thermodynamic of adsorption of chromium(VI) from aqueous solution using puresorbe

This paper deals with an investigation on coir-based adsorbent, puresorbe, in the removal of chromium(VI) from the aqueous solutions. The adsorption of chromium(VI) was carried out by varying the parameters such as agitation time, metal concentration, adsorbent dose, temperature and pH. The experimental isotherm data were analyzed using Langmuir, Freundlich and Redlich and Peterson isotherms. Adsorption followed second order rate expression for the particle size 250–500 μm at pH 2. The monolayer adsorption capacity is 76.92 mg chromium(VI) per gram of puresorbe. Thermodynamic parameters show the endothermic nature of chromium(VI) adsorption. Desorption study carried out using distilled water adjusted to pH of 2–10, suggests that chemisorption might be the mode of adsorption.     

Cu2+, Cd2+ and Pb2+ adsorption from aqueous solutions by pyrite and synthetic iron sulphide

In this study, removal of Cu(2+), Cd(2+) and Pb(2+) from aqueous solutions by adsorption onto pyrite and synthetic iron sulphide (SIS) was investigated as a function of pH, contact time, adsorbent dosage, initial metal concentration and temperature. It has been determined that the adsorption of metal ions onto both adsorbents is pH dependent and the adsorption capacities increase with the increasing temperature. The mechanisms governing the metal removal processes were determined as chemical precipitation at low pH (<3) due to H(2)S generation and adsorption at high pH (in the range of 3-6). The metal adsorption yields also increased with the increasing adsorbent dosage and contact time and reached to equilibrium for both adsorbents. The Cu(2+), Cd(2+) and Pb(2+) adsorption capacities of both adsorbents decrease in the order of Pb(2+)>Cu(2+)>Cd(2+). Except for cadmium, little fraction of copper and lead in the solid adsorption residues was desorbed in acidic media.     

Removal of cesium ions from aqueous solution by adsorption onto local Taiwan laterite

Utilization of local Taiwan laterite (LTL) to remove aqueous cesium was investigated in this work under the conditions of various contact time, cesium (Cs) loading and temperature. Experimental results show that adsorption is instantaneous. Freundlich and Langmuir simulation results demonstrate that local Taiwan laterite has high affinity and sorption capacity for Cs at low temperatures, which may be attributed to enhanced desorption as temperature increased. Thermodynamic parameters including ΔH, ΔG and ΔS were calculated and it is indicated that Cs adsorption on LTL is an exothermic, spontaneous and physical adsorption reaction. Moreover, the adsorbed Cs is distributed evenly on the LTL surface, which is confirmed by SEM/EDS mapping images. Furthermore, the absence of apparent shifting or broadening of the kaolinite signal in XRD patterns after Cs adsorption is an indication of the non-expanding characteristic of kaolinite structure.     

Pb(II) and Cd(II) removal from aqueous solutions by olive cake

The removal of heavy metals from wastewater using olive cake as an adsorbent was investigated. The effect of the contact time, pH, temperature, and concentration of adsorbate on adsorption performance of olive cake for Pb(II) and Cd(II) ions were examined by batch method. Adsorption of Pb(II) and Cd(II) in aqueous solution onto olive cake was studied in single component. After establishing the optimum conditions, elution of these ions from the adsorbent surface was also examined. The optimum sorption conditions were determined for two elements. Maximum desorption of the Pb(II) and Cd(II) ions were found to be 95.92 and 53.97% by 0.5M HNO(3) and 0.2M HCl, respectively. The morphological analysis of the olive cake was performed by the scanning electron microscopy (SEM).     

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.     

Comparative study of the biosorption of Pb(II), Ni(II) and Cr(VI) ions onto S. cerevisiae: determination of biosorption heats

In this study, the biosorption of Pb(II), Ni(II) and Cr(VI) ions onto inactive Saccharomyces cerevisiae was investigated as a function of initial pH, initial metal ion concentration and temperature. The Langmuir model was applied to experimental equilibrium data of Pb(II), Ni(II) and Cr(VI) biosorption depending on temperature and the maximum metal ions uptake at optimum biosorption temperature of 25 °C, were found to be 270.3, 46.3 and 32.6 mg g⁻¹, respectively. Using the Langmuir constant, b values obtained at different temperatures, the biosorption heats of Pb(II), Ni(II) and Cr(VI) were determined as −1.125, −1.912 and −2.89 kcal mol⁻¹, respectively. The results indicated that the biosorption of Pb(II), Ni(II) and Cr(VI) ions to S. cerevisiae is by the physical adsorption and has an exothermic nature.     

Kinetic and equilibrium study for the sorption of cadmium(II) ions from aqueous phase by eucalyptus bark

The efficiency of eucalyptus bark as a low cost sorbent for removing cadmium ions from aqueous solution has been investigated in batch mode. The equilibrium data could be well described by the Langmuir isotherm but a worse fit was obtained by the Freundlich model. The five linearized forms of the Langmuir equation as well as the non-linear curve fitting analysis method were discussed. Results show that the non-linear method may be a better way to obtain the Langmuir parameters. Maximum cadmium uptake obtained at a temperature of 20 degrees C was 14.53mgg(-1). The influence of temperature on the sorption isotherms of cadmium has been also studied. The monolayer sorption capacity increased from 14.53 to 16.47 when the temperature was raised from 20 to 50 degrees C. The DeltaG degrees values were negative, which indicates that the sorption was spontaneous in nature. The effect of experimental parameters such as contact time, cadmium initial concentration, sorbent dose, temperature, solution initial pH, agitation speed, and ionic strength on the sorption kinetics of cadmium was investigated. Pseudo-second-order model was evaluated using the six linear forms as well as the non-linear curve fitting analysis method. Modeling of kinetic results shows that sorption process is best described by the pseudo-second-order model using the non-linear method. The pseudo-second-order model parameters were function of the initial concentration, the sorbent dose, the solution pH, the agitation speed, the temperature, and the ionic strength.     

Modeling the adsorption of Cr(III) from aqueous solution onto Agave lechuguilla biomass: study of the advective and dispersive transport

The biosorption of Cr(III) onto packed columns of Agave lechuguilla was analyzed using an advective-dispersive (AD) model and its analytical solution. Characteristic parameters such as axial dispersion coefficients, retardation factors, and distribution coefficients were predicted as functions of inlet ion metal concentration, time, flow rate, bed density, cross-sectional column area, and bed length. The root-mean-square-error (RMSE) values 0.122, 0.232, and 0.285 corresponding to the flow rates of 1, 2, and 3 (10(-3))dm3min(-1), respectively, indicated that the AD model provides an excellent approximation of the simulation of lumped breakthrough curves for the adsorption of Cr(III) by lechuguilla biomass. Therefore, the model can be used for design purposes to predict the effect of varying operational conditions.     

胶束强化超滤技术分离水溶液中有色金属离子的研究

胶束强化超滤是一种实现水溶液中小分子量物质分离的新技术.该技术利用表面活性剂胶束对金属离子的吸附作用,结合超滤工艺,进而达到去除Cd2 ,Cu2 ,Ni ,Pb2 ,Co2 ,Zn2 等有色金属离子的目的.介绍了胶束强化超滤技术分离水溶液中有色金属离子的研究现状,分析了该技术目前存在的问题以及今后的应用前景.