Abstract:

The UV/PMS, UV/PDS和UV/SPC processes were employed to degrade MeP in aqueous solution. Different free radicals during the three processes were identified by electron paramagnetic resonance. The effects of different oxidant dosages, pH, anions, $\mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}$ and HA on MeP removal were investigated. The second-order rate constants of $\mathrm{S}{\mathrm{O}}_{\mathrm{4}}^{-}$· with MeP and contributions of different free radicals on MeP removal were determined by competitive kinetics, and the economics of different oxidant dosages were evaluated. The mineralization rate, DBPs formation and the alteration of acute toxicity during the degradation of MeP were investigated. The results showed that the three oxidants had good synergistic performances with UV, the pseudo-first-order kinetic rate constants of UV/PMS, UV/PDS and UV/SPC processes under experimental conditions were 0.1615, 0.3868 ^{and 0.0798 min-1, respectively. The second-order rate constants of $\mathrm{S}{\mathrm{O}}_{\mathrm{4}}^{-}$· with MeP were determined to be 1.37×109 L·mol-1·s-1. The k_obs of MeP during the three processes increased with the increasing of oxidant dosage and the economic benefit of UV/PDS was superior to the other two processes. The k_obs of UV/PMS and UV/PDS for MeP increased slightly with the increasing of pH, while the k_obs of UV/SPC for MeP had a tendency of increasing first and then decreasing. Among the three processes, $\mathrm{N}{\mathrm{O}}_{\mathrm{3}}^{-}$ and $\mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-}$ promoted the k_obs of UV/PMS, UV/PDS and UV/SPC for MeP in varying degrees, while $\mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}$ and HA did the opposite. Cl- had an inhibiting effect on UV/PDS process, but it had a dual effect on UV/PMS and UV/SPC processes. UV/PDS manifested the highest mineralization rate of MeP among the three processes, but also generated more disinfection by-products.}

Key words: UV, advanced oxidation, free radicals, kinetics, disinfection by-products

摘要：

采用UV/过一硫酸盐(PMS)、UV/过二硫酸盐(PDS)和UV/过碳酸盐(SPC)三种工艺降解尼泊金甲酯(MeP)，通过电子顺磁共振技术鉴定了三种工艺中存在的自由基，考察了氧化剂投加量、pH、阴离子、$\mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}$和HA对MeP去除的影响，通过竞争动力学的方法测定了MeP与$\mathrm{S}{\mathrm{O}}_{\mathrm{4}}^{-}$·的二级反应速率常数及不同自由基对MeP去除的贡献，评估了不同氧化剂投加量下工艺的经济性，研究了不同工艺中有机物的矿化率和消毒副产物(DBPs)的生成。结果表明，三种氧化剂与UV联用都具有较好的协同效果，UV/PMS、UV/PDS和UV/SPC工艺降解MeP的拟一级动力学常数(k_obs)分别为0.1615、0.3868和0.0798 min^-1。$\mathrm{S}{\mathrm{O}}_{\mathrm{4}}^{-}$·与MeP的二级反应速率常数为1.37×10⁹ L·mol^-1·s^-1。三种工艺中k_obs都随氧化剂投加量的增加而增大，且UV/PDS工艺具有较好的经济效益。UV/PMS和UV/PDS工艺中k_obs值随着pH的升高略微增加，而UV/SPC工艺中k_obs则呈先上升后下降的趋势。三种工艺中$\mathrm{N}{\mathrm{O}}_{\mathrm{3}}^{-}$和$\mathrm{H}\mathrm{C}{\mathrm{O}}_{\mathrm{3}}^{-}$对MeP的去除均有不同程度的促进作用，而$\mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}$和HA则不同程度上抑制MeP的降解。Cl^-在UV/PDS工艺中对MeP的去除有抑制作用，而在UV/PMS和UV/SPC工艺中呈现双重作用。UV/PDS工艺对MeP的矿化率最高，但也生成了更多的消毒副产物。

关键词: 紫外, 高级氧化, 自由基, 动力学, 消毒副产物