Performance and Mechanism of UV/H2O2 Oxidation of Aminotris(Methylphosphonic Acid) Antiscalant of the Reverse Osmosis Concentrate

In wastewater treatment, reverse osmosis (RO) technology is gaining significance. However, antiscalants in RO systems harm the environment by hindering hardness removal and causing phosphorus pollution in receiving waters. This research employed the UV/H2O2 process to degrade a typical phosphoric-based antiscalant, aminotris(methylphosphonic acid) (ATMP). Compared to using UV light or H2O2 alone, the UV/ H2O2 technique significantly enhanced the degradation and conversion of ATMP. With UV irradiation and H2O2 (4 mM), at pH 8.5, 77.53% of ATMP (0.10 mM) was transformed into orthophosphate within 60 min, whereas the H2O2 and UV system showed minimal conversion. The effect of H2O2 dosage was investigated, and 4 mM was the optimal concentration. As the concentration increased, Cl-, SO42-, and NO3- exerted varying degrees of inhibitory effects on the conversion efficiency of orthophosphate. The Ca2+ and Zn2+ accelerated the process, while Mg2+ decelerated the process. Simultaneously, the impact of humic acid was examined. It was found that the final conversion to orthophosphate was reduced by about 12.37% at 5.0 mg C/L of humic acid. The effects of six organic carboxylic acids on the conversion efficiency to orthophosphate were also investigated, and the results showed that all of them had different degrees of inhibitory effects except for succinic acid. At the same time, the hydroxyl radical was identified as the primary intermediate oxidant. The efficient breakdown of ATMP was further confirmed by adding H2O2 to RO concentrates and applying ultraviolet irradiation. The research showed that UV/H2O2 is an effective technology for removing phosphonate antiscalants from RO concentrate.