Oxalic acid modified copper tailings as an efficient adsorbent with super high capacities for the removal of Pb²

Comprehensive utilization of tailings is not only conducive to ensuring the sustainable use of resources but also can reduce the related environmental pollution. In the present work, a new utilization way of copper tailings was proposed and a novel composite (OMT-6) was prepared by modification of tailings with oxalic acid. The composite had super high Pb²⁺ adsorption capacity with the maximal Pb²⁺ removal capacity of 862.07 mg/g. Its Pb²⁺ removal behaviours followed pseudo-second-order kinetic equation and Langmuir model, suggesting that Pb²⁺ removal depended on monolayer adsorption. The surface of OMT-6 was rough and a lot of nanospheres were loaded on its surface. The composite had mesoporous structure and a larger specific surface area compared with tailings, the above characteristics of which facilitated Pb²⁺ removal. The major crystal structures of OMT-6 were transformed to CaC₂O₄•H₂O and FeC₂O₄•2H₂O after oxalic acid modification and Pb²⁺ could be removed by the ions exchange between Ca²⁺, Fe²⁺ and Pb²⁺. Pb²⁺ removal mechanisms of OMT-6 involved ion exchange, surface complexation and electrostatic attraction interaction, among which ion exchange played a key role. These results indicated that the prepared OMT-6 composite from copper tailings was an ideal material for Pb²⁺ removal from aqueous solution.