Use of chemical modification to determine the binding of Cd(II), Zn(II) and Cr(III) ions by orange waste

This study focuses on the roles played by three major functional groups (amine, carboxyl and hydroxyl) in the orange waste biomass for sorption of three heavy metals (Cd2+, Zn2+ and Cr3+). The biosorbent was chemically modified to block the mentioned functional groups in order to determine their contribution to the adsorption of metals. Fourier transform infrared (FTIR) and solid state carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy were used to investigate the chemical modification. Additionally, batch biosorption tests were carried out with the different biosorbents in order to determine the possible reduction in metal uptake with the chemically modified biosorbent. Blocking of the COOH groups by chemical esterification resulted in an important reduction in metal binding. Nevertheless, no significant modification in metal removal was observed with acetylated and methylated orange waste.