Low cost bio-sorbent 'wheat bran' for the removal of cadmium from wastewater: kinetic and equilibrium studies

Novel bio-sorbent wheat bran has been successfully utilized for the removal of cadmium(II) from wastewater. The maximum removal of cadmium(II) was found to be 87.15% at pH 8.6, initial Cd(II) concentration of 12.5 mg l-1 and temperature of 20 degrees C. The effect of different parameters such as contact time, adsorbate concentration, pH of the medium and temperature were investigated. Dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion and mass transfer coefficient were calculated. Different thermodynamic parameters viz., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the reaction was spontaneous and exothermic in nature. The applicability of Langmuir isotherm showed of monolayer coverage of the adsorbate on the surface of adsorbent. A generalized empirical model was proposed for the kinetics at different initial concentrations.     

Biosorption and Desorption of Lead(II) by Hydrilla verticillata

The potential of nonliving biomass of Hydrilla verticillata to adsorb Pb(II) from an aqueous solution containing very low concentrations of Pb(II) was determined in this study. Effects of shaking time, contact time, biosorbent dosage, pH of the medium, and initial Pb(II) concentration on metal-biosorbent interactions were studied through batch adsorption experiments. Maximum Pb(II) removal was obtained after 2 h of shaking. Adsorption capacity at the equilibrium increased with increasing initial Pb(II) concentration, whereas it decreased with increasing biosorbent dosage. The optimum pH of the biosorption was 4.0. Surface titrations showed that the surface of the biosorbent was positively charged at low pH and negatively charged at pH higher than 3.6. Fourier transform infrared (FT-IR) spectra of the biosorbent confirmed the involvement of hydroxyl and C?O of acylamide functional groups on the biosorbent surface in the Pb(II) binding process. Kinetic and equilibrium data showed that the adsorption process followed the pseudo-second-order kinetic model and both Langmuir and Freundlich isothermal models. The mean adsorption energy showed that the adsorption of Pb(II) was physical in nature. The monolayer adsorption capacity of Pb(II) was 125 mg g^?1. The desorption of Pb(II) from the biosorbent by selected desorbing solutions were HNO₃ > Na₂CO₃ > NaOH > NaNO₃.     

Activated carbon prepared from biomass as adsorbent: elimination of Ni(II) from aqueous solution.

Activated carbon (AC) prepared from waste Parthenium was used to eliminate Ni(lI) from aqueous solution by adsorption. Batch mode adsorption experiments are carried out, by varying contact time, metal ion concentration, carbon concentration, pH and desorption to assess kinetic and equilibrium parameters. They allowed initial adsorption coefficient, adsorption rate constant and maximum adsorption capacities to be computed. The adsorption data were modeled by using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacity (Q0) calculated from the Langmuir isotherm was 54.35 mg Ni(II)/g of AC at initial pH of 5.0 and 20 degrees C, for the particle size 250-500 microm. Increase in pH from 2 to 10 increased percent removal of metal ion. The regeneration by HCl of Ni(II)-saturated carbon by HCl, allowed suggestion of an adsorption mechanism by ion-exchange between metal ion and H+ ions on the AC surfaces. Quantitative recovery of Ni(II) was possible with HCl.     

Adsorptive removal of Pb(II) by activated carbon prepared from Spartina alterniflora: Equilibrium,kinetics and thermodynamics

Low-cost activated carbon was prepared from Spartina alterniflora by phosphoric acid activation for the removal of Pb(II) from dilute aqueous solution. The effect of experimental parameters such as pH, initial concentration, contact time and temperature on the adsorption was studied. The obtained data were fitted with the Langmuir and Freundlich equations to describe the equilibrium isotherms. The kinetic data were fitted with the Lagergren-first-order, pseudo-second-order and Elovich models. It was found that pH played a major role in the adsorption process. The maximum adsorption capacity for Pb(II) on S. alterniflora activated carbon (SAAC) calculated from Langmuir isotherm was more than 99 mg g⁻¹. The optimum pH range for the removal of Pb(II) was 4.8–5.6. The Freundlich isotherm model was found to best describe the experimental data. The kinetic rates were best fitted to the pseudo-second-order model. Thermodynamic study showed the adsorption was a spontaneous exothermic process.     

Biosorption of Lead from Industrial Wastewater Using Chrysophyllum albidum Seed Shell

The shell of the seed of Chrysophyllum albidum carbon was used to adsorb lead (Pb) from aqueous solution, the sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration, and particle size on adsorption were also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The first-order rate equation by Lagergren was tested on the kinetic data and the adsorption process followed first-order rate kinetics. Isotherm data were analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms; the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 72.1 mg Pb (II) g^{- 1} at initial pH of 5.0 at 30°C for the particle size of 1.00 to 1.25 mm with the use of 2.0 g/100 ml adsorbent mass. The structural features of the adsorbent were characterized by Fourier transform infrared (FTIR) spectrometry; the presence of hydroxyl, carbonyl, amide, and phosphate groups confirms the potential mechanism adsorption of the adsorbent. This readily available adsorbent is efficient in the uptake of Pb (II) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater.     

Real-time determination of kinetics of adsorption of lead(II) onto palm shell-based activated carbon using ion selective electrode

In this study, the kinetics of adsorption of Pb(II) from aqueous solution onto palm shell-based activated carbon (PSAC) were investigated by employing ion selective electrode (ISE) for real-time Pb(II) and pH monitoring. Usage of ISE was very appropriate for real-time adsorption kinetics data collection as it facilitated recording of adsorption data at very specific and short time intervals as well as provided consistent kinetics data. Parameters studied were initial Pb(II) concentration and agitation speed. It was found that increases in initial Pb(II) concentration and agitation speed resulted in higher initial rate of adsorption. Pseudo first-order, pseudo second-order, Elovich, intraparticle diffusion and liquid film diffusion models were used to fit the adsorption kinetics data. It was suggested that chemisorption was the rate-controlling step for adsorption of Pb(II) onto PSAC since the adsorption kinetics data fitted both the pseudo second-order and Elovich models well.     

Activation of pine cone using Fenton oxidation for Cd(II) and Pb(II) removal

This paper describes activation of pine cone with Fenton reagent and determines the removal of Cd(II) and Pb(II) ions from aqueous solution. Changes of the surface properties of adsorbent materials were determined by the FT-IR and SEM analysis after activation of pine cone. The effect of Fe(2+)/H(2)O(2) ratio, ORP, pH and contact time were determined. Different adsorption isotherms were also obtained using concentrations of heavy metal ions ranging from 0.1 to 150mgL(-1). The adsorption process follows pseudo-first-order reaction kinetics and follows the Langmuir adsorption isotherm. The study discusses thermodynamic parameters, including changes in Gibbs free energy, entropy, and enthalpy, for the adsorption of Cd(II) and Pb(II) on activated cone, and revealed that the adsorption process was spontaneous and exothermic under natural conditions. The maximum removal efficiencies were obtained as 91% and 89% at pH 7 with 90 and 105-min contact time for Cd(II) and Pb(II), respectively.     

Removal of Astrazon Yellow 7GL from aqueous solutions by adsorption onto wheat bran

Adsorption kinetic and equilibrium of a basic dye (Astrazon Yellow 7GL) from aqueous solutions at various initial dye concentration (50-300 mg/l), pH (4-10), adsorbent dosage (2-8 g/l), particle size (354-846 microm) and temperature (30-50 degrees C) on wheat bran were studied in a batch mode operation. The result showed that the amount adsorbed of the dye increased with increasing initial dye concentration and contact time, whereas particle size and pH had no significant affect on the amount of dye adsorbed by the adsorbent. A comparison of kinetic models on the overall adsorption rate showed that dye/adsorbent system was best described by the pseudo second-order rate model. The removal rate was also dependent on both external mass transfer and intra-particle diffusion. The low value of the intraparticle diffusivity, 10(-11) cm2/s, indicated the significant influence of intraparticle diffusion on the kinetic control. The adsorption capacity (Q0) calculated from the Langmuir isotherm was 69.06 mg/g for at pH 5.6, 303 K for the particle size of 354 microm. The experimental data yielded excellent fits with Langmuir and Tempkin isotherm equations. Different thermodynamic parameters showed that the reaction was spontaneous and endothermic in nature.     

Adsorption of Cu(II) and Pb(II) onto diethylenetriamine-bacterial cellulose

Diethylenetriamine-bacterial cellulose (EABC) was synthesized by amination with diethylenetriamine on bacterial cellulose (BC). Its adsorption properties for Cu(II) and Pb(II) were investigated. The parameters affecting the metal ions adsorption, such as contact time, solution pH, and initial metal ions concentration have been investigated. The adsorption kinetics and adsorption isotherms were further studied. The results show that the adsorption rate could be well fitted by pseudo-second-order rate model, and adsorption isotherm could be described by the Langmuir model. The regeneration of EABC was also studied. This study provides the relatively comprehensive data for the EABC application to the removal of metal ion in the wastewater.     

Lead removal by Spirulina platensis biomass

In this investigation, we report on the biosorption of Pb (II) from aqueous solutions by the nonliving biomass of the micro-alga (cyanobacterium) Spirulina platensis. Propagation of the micro-alga was carried out in outside oblong raceway ponds. The biomass was cleaned, dried and used for the investigation. The effects of pH, adsorbent dose, temperature, initial concentration of Pb (II), and contact time on the adsorption of lead by the dry biomass were studied. The experiments were carried out in 250 ml conical flasks containing 100 ml of test solutions using an orbital incubator at 150 rpm. Concentrations of the metal before and after the experiments were measured using Atomic Absorption Spectrophotometer. Very high levels of Pb (II) removal (>91%) were obtained. The optimum conditions for maximal adsorption by S. platensis were found to be pH 3; 2 g of adsorbent dose; incubation at 26°C; 100 mg/l of lead initial concentration and 60 minutes of contact time. The experimental data fitted well with Freundlich isotherm equation with R² values greater than 0.97. Based on our results, we recommend the utilization of S. platensis biomass for heavy metal removal from aqueous solutions.     

Equilibrium isotherm studies for the uptake of cadmium and lead ions onto sugar beet pulp

The adsorption of Cd2+ and Pb2+ on sugar beet pulp (SBP), a low-cost material, has been studied. In the present work, the abilities of native (SBP) to remove cadmium (Cd2+) and lead (Pb2+) ions from aqueous solutions were compared. The (SBP) an industrial by product and solid waste of sugar industry were used for the removal of Cd2+ and Pb2+ ions from aqueous water. Batch adsorption studies were carried out to examine the influence of various parameters such as initial pH, adsorbent dose, initial metal ion concentration, and time on uptake. The sorption process was relatively fast and equilibrium was reached after about 70 min of contact. As much as 70-75% removal of Cd2+ and Pb2+ ions for (SBP) are possible in about 70 min, respectively, under the batch test conditions. Uptake of Cd2+ and Pb2+ ions on (SBP) showed a pH-dependent profile. The overall uptake for the (SBP) is at a maximum at pH 5.3 and gives up to 46.1 mg g(-1) for Cd2+ and at pH 5.0 and gives 43.5 mg g(-1) for Pb2+ for (SBP), which seems to be removed exclusively by ion exchange, physical sorption and chelation. A dose of 8 gL(-1) was sufficient for the optimum removal of both the metal ions. The Freundlich represented the sorption data for (SBP). In the presence of 0.1M NaNO3 the level of metal ion uptake was found to reach its maximum value very rapidly with the speed increasing both with the (SPB) concentration and with increasing initial pH of the suspension. The reversibility of the process was investigated. The desorption of Cd2+ and Pb2+ ions which were previously deposited on the (SBP) back into the deionised water was observed only in acidic pH values during one day study period and was generally rather low. The extent of adsorption for both metals increased along with an increase of the (SBP) dosage. (SBP), which is cheap and highly selective, therefore seems to be a promising substrate to entrap heavy metals in aqueous solutions.     

Rapid Adsorption of Copper(II) and Lead(II) by Rice Straw/Fe3O4 Nanocomposite: Optimization,Equilibrium Isotherms,and Adsorption Kinetics Study

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.     

Biosorption characteristics of Aspergillus flavus biomass for removal of Pb(II) and Cu(II) ions from an aqueous solution

The Pb(II) and Cu(II) biosorption characteristics of Aspergillus flavus fungal biomass were examined as a function of initial pH, contact time and initial metal ion concentration. Heat inactivated (killed) biomass was used in the determination of optimum conditions before investigating the performance of pretreated biosorbent. The maximum biosorption values were found to be 13.46 +/- 0.99 mg/g for Pb(II) and 10.82 +/- 1.46 mg/g for Cu(II) at pH 5.0 +/- 0.1 with an equilibrium time of 2 h. Detergent, sodium hydroxide and dimethyl sulfoxide pretreatments enhanced the biosorption capacity of biomass in comparison with the heat inactivated biomass. The biosorption data obtained under the optimum conditions were well described by the Freundlich isotherm model. Competitive biosorption of Pb(II) and Cu(II) ions was also investigated to determine the selectivity of the biomass. The results indicated that A. flavus is a suitable biosorbent for the removal of Pb(II) and Cu(II) ions from aqueous solution.     

A new approach to modification of natural adsorbent for heavy metal adsorption

This paper describes modification of a natural adsorbent with Fenton reagent and determines the removal of Cd(II) ions from aqueous solution. Changes of the surface properties of adsorbent materials were determined by the FT-IR analysis after the modification of pine bark. The effect of Fe2+/H2O2 ratio, ORP, pH, and contact time were determined. Different adsorption isotherms were also obtained using concentrations of Cd(II) ions ranging from 0.1 to 100 mg L(-1). The adsorption process follows pseudo-first-order reaction kinetics and follows the Langmuir adsorption isotherm. The paper discusses thermodynamic parameters, including changes in Gibbs free energy, entropy, and enthalpy, for the adsorption of Cd(II) on modified bark, and revealed that the adsorption process was spontaneous and exothermic under natural conditions. The maximum removal efficiency obtained was 97% at pH 7 and with a 90-min contact time (for 35 mg L(-1) initial concentration and a 2.5 g L(-1) solid-to-liquid ratio).     

The adsorption of copper(II) ions on to dehydrated wheat bran (DWB): determination of the equilibrium and thermodynamic parameters

The adsorption of copper(II) ions on to dehydrated wheat bran (DWB), a by-product of the flour process, was investigated as a function of initial pH, temperature, initial metal ion concentration and adsorbent dosage. The optimum adsorption conditions were initial pH 5.0, initial copper concentration 100 mg l⁻¹, temperature 60 °C and adsorbent dosage 0.1 g. The adsorption equilibrium was described well by the Langmuir isotherm model with maximum adsorption capacity of 51.5 mg g⁻¹ of copper(II) ions on DWB. The observation of an increase in adsorption with increasing temperature leads to the result that the adsorption of copper(II) ions on DWB is endothermic in nature. The thermodynamic parameters such as enthalpy, free energy and entropy changes were calculated and these values show that the copper(II)-DWB adsorption process was favoured at high temperatures.     

Biosorption behaviors of biosorbents based on microorganisms immobilized by Ca-alginate for removing lead (II) from aqueous solution

Multiple microorganisms directly or treated with NaOH were immobilized by using Ca-alginate embedding to form biosorbents I and II, successively. The biosorption behaviors of biosorbents I and II for Pb(II) from aqueous solution were investigated in a batch system. Effects of solution pH, initial metal concentration, biosorbent dosage, contact time, temperature, and ionic strength on the adsorption process were considered to study the biosorption equilibrium, kinetics, thermodynamics, and mechanism of Pb(II) ion adsorption on the 2 types of biosorbents. The results showed that the adsorption capacity of biosorbent II for Pb(II) was higher than that of biosorbent I, and biosorbent II had a faster adsorption rate for Pb(II) ions. According to FTIR spectra, the carboxyl, amine, and hydroxyl groups on the biomass surface were involved in the biosorption of Pb(II). EDX analysis showed that ion exchange may be involved in the biosorption process, and the morphology observed by SEM micrograph of biosorbent I was completely different from that of biosorbent II. Desorption and regeneration experiments showed that the 2 types of biosorbents could be reused for 3 biosorption-desorption cycles without significant loss of their initial biosorption capacities.     

Potential capacity of Beauveria bassiana and Metarhizium anisopliae in the biosorption of Cd2+ and Pb2+

In this study Beauveria bassiana and Metarhizium anisopliae were used as inexpensive and efficient biosorbents for Pb(II) and Cd(II) from aqueous metal solutions. The effects of various physicochemical factors on Pb(II) and Cd(II) biosorption by B. bassiana and M. anisopliae were studied. The optimum pH for Cd(II) and Pb(II) biosorption by two fungal species was achieved at pH 6.0 for Pb(II) and 5.0 Cd(II) at a constant time of 30 min. The nature of fungal biomass and metal ion interactions was evaluated by Fourier transform infrared. The maximum adsorption capacities (q(max)) calculated from Langmuir isotherms for Pb(II), and Cd(II) uptake by B. bassiana were 83.33±0.85, and 46.27±0.12 mg/g, respectively. However, the q(max) obtained for Pb(II) uptake by M. anisopliae was 66.66±0.28 mg/g, and 44.22±0.13 mg/g for Cd(II). B. bassiana showed higher adsorption capacity compared to M. anisopliae. The data obtained imply the potential role of B. bassiana and M. anisopliae for heavy metal removal from aqueous solutions.     

Copper removal from wastewater using spent-grain as biosorbent

The removal of Cu(II) ions from aqueous solutions using spent-grain was studied. The experimental data fitted the Langmuir isotherm and the maximum adsorption capacity of spent-grain was determined to be 10.47 mg g(-1) dry weight (pH 4.2). Kinetic studies showed the adsorption process followed pseudo second-order rate model. Column studies with synthetic Cu(II) solutions were used to investigate the effects of Cu(II) ion concentration, initial pH, flow rate and the presence of EDTA on the Cu(II) removal performance. When treating the spent-lees, the wastewater from the whisky distilling industry, the reduction of Cu(II) uptake capacity to 77.7% (solution pH adjusted to 4.5 with 1N NaOH) and 31.6% (pH 3.8 without adjustment) was observed compared to Cu(II) uptake capacity when treating synthetic Cu(II) solution. On the basis of the results and that spent-grain is an abundant and by-product from the whisky distilling industry we suggest that it can be economically and effectively applied as a biosorbent for the removal of Cu(II) ions from distilling wastewaters.     

Removal of Pb2+ from aqueous system by live Oscillatoria laete-virens (Crouan and Crouan) Gomont isolated from industrial effluents

Cyanobacteria have been found to be potential biosorbents of metal ions from waste water. The Pb(2+) removal capacity of growing cells of indigenous cyanobacterium Oscillatoria laete-virens (Crouan and Crouan) Gomont was studied under batch experiments and it was found capable of removing Pb(2+) of lower concentrations (below 100?mg L(-1)). The effects of different concentrations of Pb(2+), on the growth rate of alga were also evaluated. The research parameters include the pH of the solution, contact time, initial concentration of Pb(2+), and culture density. Of the parameters studied, the pH of the solution was found to be the most crucial. The removal of Pb(2+) peaked at an initial pH of 5. The data obtained from the equilibrium experiments were found well fitting with the Langmuir isotherm with a maximum sorptive capacity (q (max)) of 20.36?mg?g(-1), indicating a good biosorbtive potential of growing cells. This was confirmed using scanning electron microscope and energy dispersive X-ray analysis, which showed the adsorption of lead on the surface of the cell. The species could tolerate a concentration as high as 60?mg L(-1) of Pb(2+). It was observed that the removal obeyed the pseudo-second-order kinetics. The percentage removal was found to decrease with increasing metal concentration, from 10 to 100?mg L(-1). FTIR analysis indicates the involvement of amino, carboxylic and amide groups in the sorption process. Among the desorbing agents evaluated, an efficient recovery of 90.2?% was achieved by HCl, in 24?h. Thus Oscillatoria laete-virens (Crouan and Crouan) Gomont seems to be a promising metal biosorbent for the treatment of Pb(2+), in waste waters.