Simulation study on selective recovery of Cu from Cu–Co–Ni composite system by Fe-struvite composite

The selective recycling of heavy metals is of great economic and environmental importance to human production and life. In this paper, the Fe-struvite composite (FSC) was synthesized by chemical principles and crystal growth theory, and further experimental methods such as model fitting, batch passivation experiment, mineral characterization, and chemical determination were used to explore the fixation properties and mechanisms of FSC on Cu-Co-Ni. The results demonstrate that FSC is an irregular composite of nano zero-valent iron loaded struvite. The passivation of Cu by FSC is multilayer (<i>Q</i> _max = 166.67 mg g^-1), whereas the adsorption of Co/Ni is monolayer. The passivations of Cu, Co and Ni by FSC are all physicochemical adsorption processes dominated by chemisorption. Nano-zero-valent iron undergoes the redox reaction with Cu and is accompanied by the formation of Fe²⁺. Furthermore, NO₃ ^- weakly reduces the selective immobilization of Cu by FSC through reductive competition with Cu. Studies have shown that the passivation of Cu/Co/Ni by FSC is related to phase change, chelation/complexation, redox action and ion exchange, whereas the selective immobilization of Cu is related to differences in the physical properties of Cu/Co/Ni-PO₄ and Cu concentration. This study provides theoretical basis for the selective recovery of Cu using FSC.