Effects of amorphous-zinc-silicate-catalyzed ozonation on the degradation of p-chloronitrobenzene in drinking water

This paper describes a single-step method for synthesizing amorphous zinc silicate (AZS) using Zn(NO3)2 and Na2SiO3 as precursors and the first use of AZS as an ozonation catalyst. This compound showed significant activity in the decomposition of p-chloronitrobenzene (pCNB) in aqueous solution. AZS was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transformation infrared (FTIR) analysis. The results showed that the as-synthesized sample was mainly composed of amorphous silica (AS), ZnO, and Zn–O–Si composites. The effectiveness of the removal of p-chloronitrobenzene (pCNB) by catalytic ozonation was investigated under various physicochemical conditions. The results showed that the presence of AZS in the ozonation further enhanced pCNB decomposition by 38% and TOC removal by 24%. The results of a hydroxyl radical scavenger experiment using spin-trapping/EPR technology to identify hydroxyl radicals (OH) confirmed that OH was the main active species involved in the removal of pCNB during the AZS-catalyzed ozonation process. The composition of ZnO and the Zn–O–Si composite had a positive impact on the oxidation affinity of pCNB. Our results showed that the catalytic activity of AZS decreased from 99% to 94% after six successive reuse cycles. The formation of Zn–O–Si composites inside AZS strengthened the frameworks of the AZS matrixes.

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► Amorphous zinc silicate was synthesized.
► High activity and stability for catalytic ozonation.
► The catalyst is easily recycled.