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

ABSTRACT

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.

KEYWORDS:

• Competitive adsorption
• magnetic biosorbent
• smelting effluent
• zinc removal

Funding

This work was supported by the Natural Science Foundation of China (No. 51668006), the Guangxi Natural Science Foundation of China (Returned Overseas Project, No. 2015GXNSFCA139015) and the Opening Project of Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology (No. 2016K007).