Targeted Decomplexation of Metal Complexes for Efficient Metal Recovery by Ozone/Percarbonate.

Traditional methods cannot efficiently recover Cu from Cu(II)-EDTA wastewater and encounter the formation of secondary contaminants. In this study, an ozone/percarbonate (O 3 /SPC) process was proposed to efficiently decomplex Cu(II)-EDTA and simultaneously recover Cu. The results demonstrate that the O 3 /SPC process achieves 100% recovery of Cu with the corresponding k obs value of 0.103 min -1 compared with the typical • OH-based O 3 /H 2 O 2 process (81.2%, 0.042 min -1 ). The carbonate radical anion (CO 3 •- ) is generated from the O 3 /SPC process and carries out the targeted attack of amino groups of Cu(II)-EDTA for decarboxylation and deamination processes, resulting in successive cleavage of Cu-O and Cu-N bonds. In comparison, the • OH-based O 3 /H 2 O 2 process is predominantly responsible for the breakage of Cu-O bonds via decarboxylation and formic acid removal. Moreover, the released Cu(II) can be transformed into stable copper precipitates by employing an endogenous precipitant (CO 3 2- ), accompanied by toxic-free byproducts in the O 3 /SPC process. More importantly, the O 3 /SPC process exhibits excellent metal recovery in the treatment of real copper electroplating wastewater and other metal-EDTA complexes. This study provides a promising technology and opens a new avenue for the efficient decomplexation of metal-organic complexes with simultaneous recovery of valuable metal resources.