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

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 Pb adsorption capacity with the maximal Pb removal capacity of 862.07 mg/g. Its Pb removal behaviours followed pseudo-second-order kinetic equation and Langmuir model, suggesting that Pb 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 Pb removal. The major crystal structures of OMT-6 were transformed to CaCO•HO and FeCO•2HO after oxalic acid modification and Pb could be removed by the ions exchange between Ca, Fe and Pb. Pb 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 Pb removal from aqueous solution.