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

摘要

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 Zn2+ with Pb2+, Cu2+ and Cd2+ 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 Pb2+, Cu2+ and Cd2+ significantly decreases the sorption of Zn2+ in either the binary system or multimetal systems. The order of adsorption preference is Pb2+ > Cu2+ > Cd2+ > Zn2+ in multimetal systems and the sequence of competitive ability to zinc is: Pb2+ > Cu2+ > Cd2+. Non-competitive Langmuir multicomponent isotherm model fits to the adsorption data of Pb2+ and Cu2+ well in aqueous solution. The co-existent Ca2+ and SO42- 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 Zn2+ and its associated metals are well below discharge limits.