Degradation of tri(2-chloroisopropyl) phosphate by the UV/H₂O₂ system: Kinetics, mechanisms and toxicity evaluation

A photodegradation technology based on the combination of ultraviolet radiation with H₂O₂ (UV/H₂O₂) for degrading tri(chloroisopropyl) phosphate (TCPP) was developed. In ultrapure water, a pseudo-first order reaction was observed, and the degradation rate constant reached 0.0035 min^-1 (R² = 0.9871) for 5 mg L^-1 TCPP using 250 W UV light irradiation with 50 mg L^-1 H₂O₂. In detail, the yield rates of Cl^- and PO₄^3- reached 0.19 mg L^-1 and 0.58 mg L^-1, respectively. The total organic carbon (TOC) removal rate was 43.02%. The pH value of the TCPP solution after the reaction was 3.46. The mass spectrometric detection data showed a partial transformation of TCPP into a series of hydroxylated and dechlorinated products. Based on the luminescent bacteria experimental data, the toxicity of TCPP products increased obviously as the reaction proceeded. In conclusion, degradation of high concentration TCPP in UV/H₂O₂ systems may result in more toxic substances, but its potential application for real wastewater is promising in the future after appropriate optimization, domestication and evaluation.