Efficiency of H2O2-treated eucalyptus biochar on the removal of Cu(II), Cd(II) and Ni(II) from aqueous solution

The present work had the goal to produce H2O2-treated biochar from eucalyptus wood and testing its efficiency in the removal of heavy metals from aqueous solutions. Oxidizing treatment was performed by reacting biochar with H2O2 (10% m/m) during 4 hours at pH 8.0 and 80 degrees C. Fresh and H2O2-treated biochar samples were characterized by thermogravimetry and elemental analysis. Point of zero charge and specific surface area were determined. Adsorption kinetics tests with Cu were carried out and Langmuir and Freundlich isotherms were adjusted. Adsorption tests were conducted with a mixture of Cu, Ni and Cd cations in aqueous solution. The best adsorption capacity was achieved in acid pH. H2O2-treated biochar had adsorption capacity of 170.41 mg L-1 for Cu alone and 305.35 mg L-1 for the mixture of metals. Adsorption was best predicted by the Langmuir isotherm (R-2 = 0.9976). Despite the significant decrease in the specific surface area, the H2O2-treated biochar showed better performance in the adsorption of heavy metals compared to the original biochar, especially in the presence of more than one metallic cation.