Sorption of heavy metals by canola meal

The results from this research indicate that canola meal (CM) can be used for adsorption of Zn2+, Cd2+, Cu2+, Pb2+ and Ni2+ from aqueous solutions. The order of sorption for these metals in single metal systems was as follows (molar basis): Zn2+ > Cu2+ > Cd2+ > Ni2+ > Pb2+. It was noted that a decrease in the concentration of CM caused a higher metal loading on the meal. Increases in the metal concentration, temperature or pH resulted in increased sorption of the metals by the meal. The systems with identical ratios of CM to Zn2+ concentrations, regardless of their levels, resulted in the same amount of metal adsorbed per unit weight of meal. The Freundlich isotherm type model was used in this study and was found to fit the experimental equilibrium concentration data of Zn2+ and Cd2+; however, the Langmuir isotherm model fit only the equilibrium data of Zn2+. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray (EDX) microanalyses revealed that the metal ions were sorbed mainly at the cell wall and only small amounts of ions diffused into the cytoplasm of the CM cells. The Electron Spin Resonance (ESR) tests were inconclusive regarding the direct participation of free radicals in copper sorption.