Rapid acceleration of Cu(II)/peroxymonosulfate oxidation of phosphonate by hydroxylamine

Developing simple and effective activation approaches to degrade phosphonate is crucial due to its potential aquatic environmental risks. Recently, Cu(II)-mediated activation processes provide a feasible method via nonradical oxidation mechanism to remove phosphonate, but is yet challenged under neutral conditions. Herein, a strategy for enhancing the Cu(II)/peroxymonosulfate (PMS) process by adding hydroxylamine (HA) could efficiently degrade 1-hydroxyethane1,1-diphosphonic acid (HEDP) at pH = 7.0. After 15-min reaction, 85.7% of total phosphorus (TP) in HEDP transformed into PO43− in the Cu(II)/PMS/HA process is observed, which is 3.4 times than that in the Cu(II)/PMS process. The results of multiple experiments confirm that the presence of HA accelerates the reduction of Cu(II) and the generation of reactive species, SO4•− and Cu(III) induced intramolecular electron transfer as the primary reactive species play a significant role in the degradation of HEDP. Additionally, the removal of HEDP is inhibited with the addition of Cl− and HCO3− in the Cu(II)/PMS/HA process. However, the Cu(II)/PMS/HA process demonstrates a superior removal effectiveness of HEDP in different actual wastewater samples compared to the Cu(II)/PMS process under neutral conditions. This study provides an effective method for removing phosphonate from actual wastewater.