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Vacuum ultraviolet (VUV) based advanced oxidation processes (AOPs) recently attracted widespread interests. However, the role of UV 185 in VUV is only considered to be generating a series of active species, while the effect of photoexcitation has long been overlooked. In this work, the role of UV 185 induced high-energy excited state for the dephosphorization of organophosphorus pesticides was studied using malathion as a model. Results showed malathion degradation was highly related to radical yield, while its dephosphorization was not. It was UV 185 rather than UV 254 or radical yield that was responsible for malathion dephosphorization by VUV/persulfate. DFT calculation results demonstrated that the polarity of P-S bond was further increased during UV 185 excitation, favoring dephosphorization while UV 254 did not. The conclusion was further supported by degradation path identification. Moreover, despite the fact that anions (Cl-, SO 4 2- and NO 3 -) considerably affected radical yield, only Cl- and NO 3 - with high molar extinction coefficient at 185 nm significantly affected dephosphorization. This study shed light on the crucial role of excited states in VUV based AOPs and provided a new idea for the development of mineralization technology of organophosphorus pesticides. [Display omitted] • High-energy excited states rather than radical yield dominated OPs mineralization. • Photoexcitation altered the regioselectivity of radical attack. • UV 185 weakened P–S bond, which decided dephosphorization, while UV 254 cannot. • Anions affected mineralization via UV 185 absorption rather than radical quenching. [ABSTRACT FROM AUTHOR]

The efficiency and mechanism of heterogeneous catalytic O 3 and UV/O 3 for municipal solid waste (MSW) incineration leachate advanced treatment was systematically compared. Prior to comparison, catalyst used in heterogenous catalytic O 3 and operation parameters for each technology were optimized. The COD removal of CuO@Al 2 O 3 /O 3 under its optimal parameters was 57.2%, which failed to meet the standard (≥75%). In contrast, the COD removal by UV/O 3 could be 82.3%. The superior efficiency of UV/O 3 over CuO@Al 2 O 3 /O 3 could be summarized into three aspects: (I) Cu bounded ·OH (≡Cu–O·) preferentially attacked hydrophilic groups, while free hydroxyl radical (·OH) was non-selective, thus UV/O 3 exhibited a unique three-stage mechanism; (II) The oxidation potential of ≡Cu–O· was higher than that of ·OH, therefore was more vulnerable to the negative effect of radical self-quenching; (III) The existence of UV-induced excited states made organics in UV/O 3 more active than in CuO@Al 2 O 3 /O 3 system, thus high concentration of anions enhanced COD removal in UV/O 3 but affected that in CuO@Al 2 O 3 /O 3. The study further revealed the characteristics of heterogeneous catalytic O 3 and UV/O 3 , and UV induced excited state should be considered in UV-based advanced oxidation processes (AOPs). [Display omitted] • UV/O 3 was more efficient than CuO@Al 2 O 3 /O 3 for MSW incineration leachate treatment. • CuO@Al 2 O 3 /O 3 had stronger mineralization effect but suffered the problem of self-quenching. • UV induced excited state explained the absence of self-quenching in UV/O 3. • O 3 , ≡Cu–O·, ·OH had different selectivity, and UV/O 3 exhibited a unique three-stage mechanism. • High salinity enhanced the mineralization ability of UV/O 3 due to the presence of UV induced excited state. [ABSTRACT FROM AUTHOR]