Selective oxidation of aminotrismethylene phosphonate (ATMP) by UV-Cu (II)/H2O2 system: Performance and mechanism

Abstract

Phosphonates are important water-soluble organic phosphorus compounds that are widely present in contaminated water bodies. Their oxidation and conversion to orthophosphate are often prerequisite steps for achieving deep removal of total phosphorus from water. In this study, aminotrismethylene phosphonate (ATMP) was used as a representative phosphonate, under alkaline pH conditions, we innovatively employed the UV-Cu (II)/H₂O₂ system to achieve selective oxidation of ATMP and efficient conversion to orthophosphate. Under conditions of UV irradiation, trace amount of Cu (II) (0.020 mM), and 2 mM H₂O₂, 97.43 % of ATMP (0.10 mM) was converted into orthophosphate within 30 min at pH= 8.5. Furthermore, the UV-Cu (II)/H₂O₂ system was unaffected by the presence of common cations, anions, humic acid and partial competitive ligands. The results indicated that hydroxyl radicals, singlet oxygen and trivalent copper Cu (III) were the primary active species participating in the oxidation process. The complexation of Cu (II) with ATMP, promoted the intramolecular electron transfer process, thereby improving the selectivity of the process and increasing the conversion rate to orthophosphate. Further validation involved adding H₂O₂ to concentrated reverse osmosis water with existing trace Cu (II), confirming its effectiveness in degrading ATMP and highlighting its potential for removing phosphonate scale inhibitors.