Efficient removal of EDTA-chelated Cu(II) by zero-valent iron and peroxydisulfate: Mutual activation process

Abstract

• Enhanced Cu(II)-EDTA separation by ZVI due to addition of peroxydisulfate. • Removal of 77.2% of Cu and 55.2% of TOC in Cu-EDTA solution by ZVI/PDS system. • Elucidating Cu-EDTA removal mechanism by ZVI/PDS system. • ZVI not only activates PDS to destroy organic ligands but also generate Fe(III) to displace Cu(II) from Cu(II)-EDTA. Metal complexes pose a significant challenge to remediate heavy metal-laden wastewater by classical techniques due to their stable chelating structure. The application of zero-valent iron (ZVI) to activate peroxidized sulphate (PDS) has been synergistically (ZVI/PDS) proposed for effective removal of EDTA-chelated Cu from aqueous media. In contrast to ZVI alone, ZVI/PDS process improved the EDTA-chelated Cu or total organic carbon (TOC) removal rate by 6.2 or 7.8 fold, respectively. Factors including Cu/EDTA molar ratio, initial pH, ZVI dosage, and PDS dosage affect the removal efficiency of complexed copper. The formation of Fe ions and sulfate radicals in the solution strengthens the removal effect of zero-valent iron on EDTA complexed Cu. After the reaction, ZVI EDS, XRD, and XPS analyses revealed that Cu was eventually reduced to Cu 0 and immobilized on the ZVI surface. A possible decomposition mechanism followed by a Cu reduction was also proposed. In conclusion, this study presents new perspectives for the removal of complex heavy metals from contaminated water.