Simultaneous Copper\nand EDTA Ligands Recovery from\nElectroless Effluent with Metallic Copper and Formaldehyde

The traditional treatment of toxic and refractory copper(II)–ethylenediaminetetraacetic\nacid chelate (Cu(II)–EDTA) in electroless effluents often generates\nhazardous waste and secondary nitrogen-containing pollutants without\nmaximizing the resource recovery. This study demonstrates a facile\nstrategy to simultaneously recover Cu and EDTA ligands from Cu(II)–EDTA\nelectroless effluent with commercially available metallic Cu and formaldehyde.\nIn this strategy, metallic Cu is used to activate formaldehyde, a\nprevalent yet often overlooked cocontaminant in Cu(II)–EDTA\neffluents, to produce highly reductive hydrogen radical (<sup>•</sup>H), which in situ decomplex Cu(II)–EDTA, reduces the central\nCu(II) into metallic Cu, and release EDTA ligand. Impressively, this\nstrategy can recover 99.9% of Cu from a real Cu(II)–EDTA effluent\n(∼2000 mg/L) as a high-purity Cu powder without further treatment,\nand 99.2% of EDTA from a real Cu(II)–EDTA effluent using a\nprecipitation-acidification post-treatment procedure, earning a net\nprofit of US $72.38 per ton. The proposed approach offers a “pollution-curing-pollution”\nsolution to transform chelated metal waste into valuable resources.