Effect of competitive adsorption on zinc removal from aqueous solution and zinc smelting effluent by eucalyptus leaf-based magnetic biosorbent.

The objectives of this study were to investigate the competitive sorption behaviors and mechanisms of heavy metals onto ELMB, a novel eucalyptus-leaf-based magnetic biosorbent, and to study the potential application of ELMB in the treatment of actual zinc smelting effluent after a necessary pretreatment process. ELMB and ELMB-metals systems were characterized using several techniques. Competitive sorption of Zn with Pb, Cu and Cd onto ELMB was studied by batch experiments and the used sorbent was separated under a magnetic field. The results show that the ELMB can be considered as paramagnetic material with various functional groups on its surface. The presence of Pb, Cu and Cd significantly decreases the sorption of Zn in either the binary system or multimetal systems. The order of adsorption preference is Pb > Cu > Cd > Zn in multimetal systems and the sequence of competitive ability to zinc is: Pb > Cu > Cd. Non-competitive Langmuir multicomponent isotherm model fits to the adsorption data of Pb and Cu well in aqueous solution. The co-existent Ca and SO decrease the removal efficiencies of heavy metals while the presence of Na and Cl shows little effect in the multimetal solution. In the case of actual zinc smelting effluent, "pretreatment + ELMB sorption" is successfully applied to remove heavy metals and the contents of Zn and its associated metals are well below discharge limits.