Biosorption of heavy metal

The biosorption of Cd2+ by Cocoa (Theobroma cacao) pod husk was investigated in single metal solution.
Equilibrium biosorption studies were carried out to delineate the effect of temperature variation on biosorption
capacity of cocoa pod husk. The result showed that unmodified cocoa pod husk (UCPH) and modified cocoa pod
husk (MCPH) exhibited maximum biosorption of 97.8 % and 99.5 % respectively at 303 K. Thermodynamic
parameters such as ΔG°ads, ΔH°ads, ΔS°ads, EAads and S*ads related to Gibbs free energy, enthalpy, entropy, activation
energy and sticking probability were evaluated. The result of thermodynamic investigations indicated that the
biosorption reactions were spontaneous (ΔG°<0), exothermic (ΔH°<0), irreversible (ΔS°>0), diffusion controlled (-
EA) and physisorption mechanism (S*<1).

The equilibrium and thermodynamics of the biosorption of Pb(II), Zn(II), Cu(II), and Cd(II) onto activated carbon prepared from olive branches were studied under different parameters of pH, initial concentration, and temperature. The batch biosorption procedure was used to find the optimum conditions. The biosorption of each metal ion was found to be pH-dependent. The maximum metal ion biosorption was achieved at pH value 5 for Pb, Cu, and Cd ions and at pH 3 for Zn ions. The extent of the metal ion biosorption increased with temperature (indicating the endothermic character) and initial metal ion concentration. The experimental data of metal ion biosorption were analyzed by Freundlich and Langmuir isotherm models. For all metal ions, the Freundlich isotherm model gave a better fit with higher correlation (R 2) to equilibrium data than Langmuir model. The adsorption capacity values were 41.32, 34.97, 43.10, and 38.17 (mg/g) for Pb(II), Zn(II), Cu(II) and Cd(II), respectively. Thermodynamically parameters, like Gibbs free energy (ΔG˚), enthalpy (ΔH˚), and entropy (ΔS˚) were calculated. The biosorption of each metal ion was non-spontaneous and the order of non-spontaneity of the biosorption process being Zn(II) > Cu(II) > Cd(II) > Pb(II). Likewise, change in entropy was noticed for each metal ion and the order of disorder was Pb(II) > Cd(II) > Cu(II) > Zn(II).

The present work evaluates the performance of the yeast Saccharomyces Cerevisiae to remove heavy metals from aqueous solutions. The effect of pH, temperature, initial concentration, contact time, and biosorbent dosage on biosorption capacity is studied. Experiment results show that metal uptake is a rapid process at pH values (5.0–6.0), and the order of accumulated metal ions is Pb > Zn > Cr > Co > Cd > Cu. The biosorption process obeys Freundlich and the Langmuir adsorption isotherms. The kinetics of metal ions biosorption could be described by Lagergren and Ho models. Nitric acid with low concentration of 0.05 N is effective in desorbing the biosorbed metal ions. Sodium hydroxide solution of 0.2 M is effective in regenerating the yeast; the regenerated yeast could be used for at least six cycles of biosorption, without losing its metal removal capacity. Carboxyl, amine, and phosphate groups present in the yeast were found to be the main biosorption sites for metal ions.

The chemical contamination of water with a wide range of toxic substances, in particular heavy metals, is a
serious environmental problem due to their potential toxicity to humans. Therefore, there is a need to develop
technologies that can remove toxic pollutants found in wastewaters. Adsorption is one of the more popular
methods for the removal of pollutants from the wastewater. Chitosan is a derivative from N-deacetylation
of chitin – a naturally occurring polysaccharide from crustacean and fungal biomass - and it has been found
to be capable of chemically or physically adsorbing various heavy metal ions, including lead, vanadium,
platinum, silver, cadmium, chromium and copper, from wastewaters.
In this study, a batch adsorption system was applied to study the adsorption of Cu (II) ions from aqueous
solution by chitosan. The adsorption capacities and rates of Cu (II) ions onto chitosan were evaluated.
Experiments were carried out as function of time, adsorbent mass and concentration of Cu (II) ions. Langmuir
and Freundlich adsorption models were applied to describe the isotherms. Equilibrium data agreed very
well with the Langmuir model. The kinetic experimental data correlated well with the second-order kinetic
model, indicating that the chemical sorption was the rate-limiting step.

CLAUDIA MARIA SIMONESCU1*, IRINA MARIN1, CHRISTU TARDEI2, MIOARA DRAGNE3, CAMELIA CAPATINA4 1University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, Department of Analytical Chemistry and Environmental Engineering, 1 – 7 Polizu Str., 011061, Bucharest, Romania 2National Institute for R&D in Electrical Engineering ICPE-CA, 313 Splaiul Unirii, 031066, Bucharest, Romania 3 SC KEMWATER CRISTAL SRL, 51 Muncii Str., 915200, Fundulea, Calaraoi, Romania 4University „Constantin Brâncuoi” of Târgu-Jiu, Engineering Faculty, 3 Geneva Str., 210152, Târgu-Jiu, Gorj, Romania

The equilibrium and thermodynamics of the biosorption of Pb(II), Zn(II), Cu(II), and Cd(II) onto activated carbon prepared from olive branches were studied under different parameters of pH, initial concentration, and temperature. The batch biosorption procedure was used to find the optimum conditions. The biosorption of each metal ion was found to be pH-dependent. The maximum metal ion biosorption was achieved at pH value 5 for Pb, Cu, and Cd ions and at pH 3 for Zn ions. The extent of the metal ion biosorption increased with temperature (indicating the endothermic character) and initial metal ion concentration. The experimental data of metal ion biosorption were analyzed by Freundlich and Langmuir isotherm models. For all metal ions, the Freundlich isotherm model gave a better fit with higher correlation (R&lt;sup&gt;2&lt;/sup&gt;) to equilibrium data than Langmuir model. The adsorption capacity values were 41.32, 34.97, 43.10, and 38.17 (mg/g) for Pb(II), Zn(II), Cu(II) and Cd(II)...