Disodium hydrogen phosphate (99.0%), phosphoric acid (85–90%), sodium dihydrogen phosphate (99.0%), metronidazole (99.0%), 4-chlorobenzoic acid (pCBA, 99.0%), t-butanol (99.7%) and fulvic acid (technical) were purchased from Sigma Aldrich. Methanol (chromatographically pure) and acetonitrile (chromatographically pure) were purchased from Merck. Hydrogen peroxide (30% by weight), concentrated sulfuric acid (superior purity), KMnO4 (analytical purity), Na2C2O4 (analytical purity), humic acid (analytical purity) was purchased from Sinopharm Chemical Reagent. Other chemical substances involved in the experiment are all superior pure. Deionized (DI) water is prepared by Molresearc 1020A ultrapure water reactor.
Stock solutions of MTZ and pCBA were prepared in DI water and stored at 4 °C in the dark. For the kinetic studies, the initial concentrations of MTZ and pCBA in the working solutions were 10 μM. Solution pH was adjusted to pH 3.0 with 10 mM phosphate buffer system. The pH value of the reaction system remained constant throughout the experiment. Experimental design and operation process had been introduced in our previous papers [36 (link),37 (link)].
Stock solutions of MTZ and pCBA were prepared in DI water and stored at 4 °C in the dark. For the kinetic studies, the initial concentrations of MTZ and pCBA in the working solutions were 10 μM. Solution pH was adjusted to pH 3.0 with 10 mM phosphate buffer system. The pH value of the reaction system remained constant throughout the experiment. Experimental design and operation process had been introduced in our previous papers [36 (link),37 (link)].
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