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Photocatalysis technology exhibited promising application for advanced treatment of wastewater. Nevertheless, the design of efficient photocatalyst and the mechanism of free radicals in pollutant degradation still remained to be further investigated. Herein, BiVO 4 /CQDs/β-FeOOH photocatalyst was fabricated by electrostatic self-assembly method, which exhibited the excellent photocatalytic performance. Under visible-light irradiation, the removal rate of ofloxacin by BiVO 4 /CQDs/β-FeOOH (0.25 min -1 ) was 1.93 times than pristine BiVO 4 , and the removal efficiency in 15 min reached 99.21%. The perfect reusability of BiVO 4 /CQDs/β-FeOOH was ascribed to the persistent catalytic active centers provided by the renewable surface oxygen vacancies on the β-FeOOH. As electron transfer channels, CQDs facilitated the transfer of BiVO 4 photogeneration electrons. The matched band structure allowed the construction of S-scheme heterojunctions, and the higher conduction band position was retained while the carrier separation was promoted. More importantly, this work firstly reported the phenomenon that the main reactive groups in the photocatalysis process would be directionally transformed with the change of pH conditions. Based on the analysis of capture and electron paramagnetic resonance experiments, ·O 2 - was the main free radicals to photodegrade OFL in neutral and alkaline conditions. However, when the solution pH turned into acidic, the photodegradation of OFL was dominated by 1 O 2 . This innovative phenomenon was due to that acidic condition accelerated the reaction kinetics of spontaneous transformation of ·O 2 - to 1 O 2 and inhibited the direct oxidation of pollutants by ·O 2 - . Accordingly, this research could inspire theoretical study of free radical reaction and the design of S-scheme heterojunction photocatalysts., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Heterogeneous photocatalysis namely titanium dioxide supported on reed straw biochar (acid pre-treated) (TiO 2 /pBC) was synthesized by sol-gel method. The morphology, surface area and structure of TiO 2 /pBC were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and X-ray diffraction (XRD). Low calcination condition maintained the structure of biochar completely and prevented the agglomeration of TiO 2 particles. Due to the combination of adsorption and photocatalysis, TiO 2 /pBC performed higher removal efficiency of sulfamethoxazole (SMX) than pure TiO 2 powder under UV light irradiation. The photocatalytic degradation (PCD) of SMX was also studied with the water collected from the Yellow River. Three high concentration inorganic anions (Cl - , NO 3 - , SO 4 2- ) of the river exerted certain degree of detrimental effects on the contaminant degradation. TiO 2 /pBC showed stable photocatalytic activity after five sequential PCD cycles. The biochar was able to promote further PCD on TiO 2 by adsorbing SMX and intermediates thereby prolonging the separation lifetime of electrons (e - ) and valence band hole (h + ). The transformation intermediates of SMX were identified and three possible degradation reactions of hydroxylation, opening of isoxazole ring and cleavage of SN bond might occur during the PCD of SMX., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Hydrogen peroxide was widely selected as the chemical oxidant in chemical remediation or as the donor of oxygen in in situ aerobic bioremediation of organic pollutants. In this paper, hydrogen peroxide pretreatment and plant system was done to examine its possibility to remediate the heavy metal contaminated soil or heavy metal-organic combined contaminated soil. Heavy metal contaminated soil was collected from the heavily industrialized area, in Fuyang county, Zhejiang province, China. And heavy metal-organic combined contaminated soil was prepared from the same contaminated soil by spiking 100 microg g(-1) 2,4-dichlorophenol (2,4-DCP). Results showed that H2O2 could improve the dissipation of 2,4-DCP and enhance the availability of Cu and Zn in soil. The greatly increased DOC (dissolved organic carbon) in the oxidation process was probably the main reason for the greatly increased water soluble Cu in higher pH condition. Water soluble Zn, however, easily rebound to soil components with the time being and had no positive relation with dissolved organic carbon. Planting with ryegrass influenced the behavior of pollutants in soil. It was observed that the dissipation of 2,4-DCP could be enhanced by the presence of plant roots and the availability of Cu and Zn in the planted soil was changed due to the mobilization and rebound mechanisms in the rhizosphere. Co-contamination of 2,4-DCP caused the greater availability of Cu and Zn in H2O2 pretreatment. But with the ryegrass planting, it was easier to rebound to the less available phase in the rhizosphere. Both Cu and Zn concentration in shoots increased with the H2O2 treatment. Therefore our results suggested that H2O2 pretreatment was probably a promising way for promoting the dissipation of persistent organic pollutants and enhancing the solubility of Cu and Zn in soil. A combination of H2O2 pretreatment and suitable plant might be an efficient alternative for remedying heavy metal or heavy metal-organic contaminated soil.