Effective Removal and Resource Recovery for Heavy Metal–Organic Complex-Polluted Water via an Integrated Decomplexation–Degradation–Immobilization Pathway

Heavy metal–organic complexes widely distributed in wastewater are hazardous and urgently need to be removed and recycled. Herein, copper glycinate (CuGly) was employed as a model complex and removed with the environmentally friendly oxidant ferrate(VI) (Fe(VI)). We found that Fe(VI) can be used to effectively remove CuGly and recycle Cu via a decomplexation–degradation–immobilization coupled pathway, i.e., decomplexing CuGly, degrading organic ligands, and immobilizing the released Cu ions. Theoretical calculation results revealed that CuGly was favored to be oxidized by Fe(VI), and the CuGly decomplexation and organic ligand degradation could spontaneously thermodynamically proceed at room temperature. Although different active oxidation species, including Fe(V), Fe(IV), H2O2, and •OH, are present during the Fe(VI) decomposition process, control experiments suggested that Fe(VI), Fe(V), and Fe(IV), rather than H2O2 and •OH, played critical roles in CuGly removal. The resultant Fe and Cu precipitate could be further converted to a magnetic composite material, which could be used as a catalyst for antibiotic degradation. This study presents an effective strategy and the comprehensive underlying mechanisms of synergistic heavy metal–organic complex removal and metal resource recycling using ferrate, which could be extended to green chemical treatment of heavy metal–organic complexes in various wastewater bodies.