Visible Light-Induced Catalyst-Free Activation of Peroxydisulfate: Pollutant-Dependent Production of Reactive Species

Abstract

Activation of peroxydisulfate (PDS, S2O8 2–) via various catalysts to degrade pollutants in water has been extensively investigated. However, catalyst-free activation of PDS by visible light has been largely ignored. This paper reports effective visible light activation of PDS without any additional catalyst, leading to the degradation of a wide range of organic compounds of high environmental and human health concerns. Importantly, the formation of reactive species is distinctively different in the PDS visible light system with and without pollutants [e.g., atrazine (ATZ)]. In addition to SO4 •– generated via S2O8 2– dissociation under visible light irradiation, O2 •– and 1O2 are also produced in both systems. However, in the absence of ATZ, H2O2 and O2 •– are key intermediates and precursors for 1O2, whereas in the presence of ATZ, a different pathway was followed to produce O2 •– and 1O2. Both radical and nonradical processes contribute to the degradation of ATZ in the PDS visible light system. The active role of 1O2 in the degradation of ATZ besides SO4 •– is manifested by the enhanced degradation of contaminants and electron paramagnetic resonance spectroscopy measurements in D2O.

Origin of the Excellent Activity and Selectivity of a Single-Atom Copper Catalyst with Unsaturated Cu-N2 Sites via Peroxydisulfate Activation: Cu(III) as a Dominant Oxidizing Species

“…The current work mainly focuses on the saturated configuration for PMS activation. Nevertheless, PDS ($0.74 per kg) is much cheaper than PMS (sold as Oxone (KHSO 5 ·1/2KHSO 4 ·1/2K 2 SO 4 ), $2.2 per kg), so it exhibits a better application potential. , Meanwhile, the unsaturated coordination (such as Cu-N 2 ) tends to exhibit different catalytic properties owing to distinct electronic and geometric structures . Therefore, it is highly desirable to gain insight into the generation of Cu­(III) in a single-atom Cu catalyst with unsaturated coordination for PDS activation, although PDS with a symmetrical structure is more difficult to be activated than PMS …”

Insights into singlet oxygen generation and electron-transfer process induced by a single-atom Cu catalyst with saturated Cu-N4 sites

“…High-valent metal species (e.g., Fe(IV) and Co(IV)) have been identified as active oxidants for pollutant degradation, based on the oxygen atom transfer reaction, in which methyl phenyl sulfoxide (PMSO) can be readily oxidized to the corresponding sulfone product [methyl phenyl sulfone (PMSO 2 )], which is significantly different from ⋅ OH/SO 4 ⋅− -mediated pathways ( Qian et al., 2021 ; Wen et al., 2022 ). As shown in Figure S10 , compared with PMS alone, the addition of SA-Cu-NC does not increase the generation of PMSO2, which suggests that Cu(III) may not be the active species in the SA-Cu-NC+PMS system.…”

“…In addition, the intensity of the DMPOX signal significantly decreases with the addition of BPA, indicating that the oxidizing species can effectively degrade BPA. -mediated pathways (Qian et al, 2021;Wen et al, 2022). As shown in Figure S10, compared with PMS alone, the addition of SA-Cu-NC does not increase the generation of PMSO2, which suggests that Cu(III) may not be the active species in the SA-Cu-NC+PMS system.…”

Insights into biochar supported atomically dispersed cobalt as an efficient peroxymonosulfate activator for sulfamethoxazole degradation: robust performance, ROS and surface electron-transfer pathways

“…However, the distinct DMPO–OH˙ peaks were formed by nucleophilic substitution between DMPO–SO 4 ˙ − and OH − . 51 It suggests that SO 4 ˙ − dominated in the SMX degradation, and SO 4 ˙ − was rarely converted to OH˙ (eqn (1)–(4)). 13,14…”

“…However, the distinct DMPO-OH˙peaks were formed by nucleophilic substitution between DMPO-SO 4 ˙− and OH − . 51 It suggests that SO 4 ˙− dominated in the SMX degradation, and SO 4 ˙− was rarely converted to OH˙(eqn ( 1)-( 4)). 13,14 As p-benzoquinone (p-BQ) possesses a high reaction rate with the superoxide radical (O 2 ˙−) (k = 1.0 × 10 9 M −1 s −1 ), it is frequently used as a scavenger to identify the presence of O 2 ˙−.…”