New insight to phosphonate degradation by electrochlorination: Hypochlorous acid dominated dephosphorylation through selective attacking CP bond

The dephosphorylation of N-containing phosphonates is crucial for mitigating their potential ecological risks and enabling phosphorus resource recovery. Here, we first show that the electrochlorination process outperforms other advanced oxidation methods in terms of conversion efficiency and rate constants for orthophosphate production. The high efficacy of electrochlorination process is primarily attributed to the generation of hypochlorous acid (HClO) under neutral pH conditions, as substantiated by a combination of speciation analysis, quantitative assessments, and quenching experiments. Furthermore, density functional theory (DFT) calculation and LC-MS measurements show that the degradation of nitrilotris-methylenephosphonic acid (NTMP) by HClO occurs spontaneously, with a preferential cleavage of the C P bond over the C N bond, thereby facilitating the efficiency of the dephosphorylation reaction. Altogether, our findings provide key insights into the role of reactive chlorine species in the degradation of N-containing phosphonates, offering valuable evidence for the development of next-generation, more effective phosphorus recovery strategies.