Effective mineralization of p-nitrophenol in water by heterogeneous catalytic ozonation using Ce-loaded sepiolite catalyst

Clay-based composite materials have been widely used for environmental remediation due to their excellent physicochemical properties , however, there are few studies on clay-based composite materials as ozone catalyst carriers. In this study, Ce-loaded sepiolite (Ce/SEP) catalyst was synthesized using an impregnation-calcination method. Ce/SEP catalysts had a higher efficiency for heterogeneous catalytic ozonation than sepiolite alone. Among different mass ratios of Ce element to sepiolite (5 % Ce/SEP, 7 % Ce/SEP, 10 % Ce/SEP, and 15 % Ce/SEP), 10 % Ce/SEP showed the best catalytic performance with the mineralization efficiency of p-nitrophenol (PNP) as 71 % that was 1.15, 1.08, and 1.18 times higher than that of 5 % Ce/SEP, 7 % Ce/SEP, and 15 % Ce/SEP, and increased by 30 % compared to that of the ozonation alone. Larger surface area and abundance of strong acid sites of Ce/SEP favored adsorption of ozone molecules on the catalyst surface. High content of oxygen vacancies in the catalyst promoted Ce 3+ /Ce 4+ cycling and subsequently a superior catalytic activity of the Ce/SEP catalyst. In addition, free radical quenching experiments as well as electron spin resonance analysis indicated that hydroxyl radical (∙OH) was the main contributor to the mineralization of PNP in this system. This study provides a novel strategy for the heterogeneous catalytic ozonation of refractory organic pollutants in water.