Removal of metalloids and heavy metals from acid mine drainage using biosynthesized Fe/Cu NPs

Abstract

Acid mine drainage (AMD) has long been an environmental problem due to its acidic solution containing toxic metal ions. Despite the fact that a variety of nanomaterials have been devised to remove metallic contaminants from aqueous solutions, there are large differences between real AMD and aqueous solutions. Here, biosynthesized Fe/Cu nanoparticles (Fe/Cu NPs) functioned to remove metalloids and heavy metals from real AMD. The removal capacities of As, Mn, Ni, Cr and Cd were severally 1.305, 0.095, 0.027, 0.082 and 0.028 mg/g, which were consistent with the pseudo-first order kinetic model but not with the intraparticle diffusion model. After removal in AMD, the particle size and pore diameter of Fe/Cu NPs rose from 86.63 ± 0.88 nm and 56.36 nm to 110.53 ± 1.40 nm and 71.51 nm, respectively. Furthermore, organic substances on Fe/Cu NPs were able to adsorb heavy metals, namely Ni, Mn, and Cd from the AMD because they acted as an encapsulant able to maintain the stability of Fe/Cu NPs. Consequently, a mechanism for the removal of As and other heavy metal ions from AMD was proposed, one which was based on the rapid adsorption of multiple heavy metals through electrostatic interaction and ion exchange. This study provides a new and important insight into removing metalloids and heavy metals from AMD using green nanomaterials.