Abstract:

The UV-LED/NaClO process was adopted to degrade methylparaben (MeP) in aqueous solution, the second-order rate constants of HO· and \mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-}· with MeP were determined by competitive kinetics, and the contributions of different contributions in the reaction system under different oxidant dosage, pH, HA were calculated. The mineralization rate, disinfection by-products (DBPs) formation and the alteration of acute toxicity during the degradation of MeP were investigated capered in the presence of bromine. The results showed that the synergistic effect of NaClO and UV-LED is better than other oxidants, the pseudo-first-order kinetic rate constants of UV-LED/NaClO processes under experimental conditions was 0.0854 min^-1. The second-order rate constants of HO· and \mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-}· with MeP were calculated to be 4.00×10⁹ L/(mol·s) and 5.56×10⁸ L/(mol·s), respectively. The contribution rate of each reactive species in the degradation of MeP by UV-LED/NaClO process is in order as follows: active chlorine radical (RCS)>HO·>NaClO>UV-LED. Weak acidic and neutral conditions were conducive to the degradation of MeP. HA significantly inhibited the degradation of MeP. The addition of \mathrm{N}{\mathrm{O}}_{\mathrm{3}}^{-}, \mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-}^{and Br- promoted the degradation of MEP in varying degrees. Br- can enhance the mineralization of MeP, but will lead to more DBPs generation and increase the acute toxicity of the reaction solution.}

Key words: methyparaben, UV-LED/NaClO, kinetics, radicals, disinfection by-products, acute toxicity

摘要：

采用UV-LED/NaClO工艺降解水中尼泊金甲酯(MeP)，通过竞争动力学的方法确定了MeP与HO·、\mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-}·的二级反应速率常数，考察了不同NaClO投加量、pH和腐殖酸(HA)浓度下不同活性物种对MeP去除的贡献，研究了共存Br^-对MeP矿化、消毒副产物(DBPs)生成和急性毒性变化的影响。结果表明，NaClO与UV-LED的协同效果要优于其他氧化剂，UV-LED/NaClO工艺降解MeP的拟一级动力学常数为0.0854 min^-1。MeP与HO·、\mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-}·的二级反应速率常数分别为4.00×10⁹ L/(mol·s)和5.56×10⁸ L/(mol·s)，UV-LED/NaClO工艺降解MeP时各活性物种的贡献率符合活性氯自由基(RCS)>HO·>NaClO>UV-LED的规律。弱酸性和中性条件有利于MeP降解，HA明显抑制了降解，\mathrm{N}{\mathrm{O}}_{\mathrm{3}}^{-}、\mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-}和Br^-均不同程度促进了MeP降解。Br^-可以提高MeP的矿化，但会导致更多的DBPs生成，增加反应溶液的急性毒性。

关键词: 尼泊金甲酯, UV-LED/NaClO, 动力学, 自由基, 消毒副产物, 急性毒性