Reductive decomplexation of Cu(II)-complexes from copper wastewater by zero-valent aluminum material

Abstract

In order to effectively remove the extremely stable Cu(II)-complexes, decomplexation is typically required, with previous efforts focusing on the destruction or substitution of organic ligands. Now, we have a new concept that if starting with Cu(II) group and reducing it directly from the complex state, the reductive decomplexation of Cu(II)-complexes may be attained along with the recovery of Cu(II) to Cu0. In this study, for the first time, we introduced a carbon-modified zero-valent aluminum material (C@mZVAl) for one-step reductive decomplexation of Cu(II)-complexes. It was found that 96.84% Cu-EDTA removal and 91.99% Cu0 recovery could be reached. Furthermore, this efficient reductive decomplexation approach was also applicable to other complexes such as copper pyrophosphate, copper tartrate and copper citrate. SEM-EDS, XPS and XRD showed that Cu0 appeared on the material's surface, providing evidences of successful reduction of complexed Cu(II). Cu-EDTA was firstly adsorbed because of the carbon’s adsorption, and then accepted the electrons released from the powerful reducer zero-valent aluminum to accomplish reductive decomplexation. Furthermore, without any pretreatment, two real industrial copper-plating wastewater containing copper pyrophosphate and Cu-EDTA were treated and the total Cu recovery rates were both achieved up to 98.00%. In conclusion, our innovative approach offers a novel method of decomplexation for the efficient recovery of reusable metal products from complexed metal wastewater through a direct reduction reaction.