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

• Published in: Environmental science & technology Vol. 57; no. 12; pp. 5034 - 5045
• Main Authors: Chen, Ying, Mu, Yi, Tian, Lei, Zheng, Ling-Ling, Mei, Yi, Xing, Qiu-Ju, Liu, Wen, Zou, Jian-Ping, Yang, Lixia, Luo, Shenglian, Wu, Daishe
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 28.03.2023
• Subjects: Amino groups; Carbonates; Contaminants; Coordination Complexes; Coordination compounds; Copper; Copper industry wastewaters; Deamination; Decarboxylation; Edetic acid; Edetic Acid - chemistry; Electroplating; Ethylenediaminetetraacetic acids; Formic acid; Hydrogen Peroxide; Industrial wastewater; Metal complexes; Metal industry wastewaters; Oxidation-Reduction; Ozone; Precipitates; Treatment and Resource Recovery; Wastewater; Water Pollutants, Chemical - chemistry; percarbonate; decomplexation; Cu recovery; carbonate radical anion; ozone
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.3c00190

Traditional methods cannot efficiently recover Cu from Cu­(II)–EDTA wastewater and encounter the formation of secondary contaminants. In this study, an ozone/percarbonate (O3/SPC) process was proposed to efficiently decomplex Cu­(II)–EDTA and simultaneously recover Cu. The results demonstrate that the O3/SPC process achieves 100% recovery of Cu with the corresponding k obs value of 0.103 min–1 compared with the typical •OH-based O3/H2O2 process (81.2%, 0.042 min–1). The carbonate radical anion (CO3 •–) is generated from the O3/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 O3/H2O2 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 (CO3 2–), accompanied by toxic-free byproducts in the O3/SPC process. More importantly, the O3/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.