Chlorophenol Degradation in Papermaking Wastewater through a Heterogeneous Ozonation Process Catalyzed by Fe-Mn/Sepiolite

Heterogeneous Fe-Mn/sepiolite catalysts were prepared by the coprecipitation method, followed by heat treatment. The catalysts were characterized by several techniques; analysis by X-ray fluorescence (XRF) and scanning electron microscopy (SEM) confirmed the existence of fine Fe and Mn particles in the catalysts. Compared to natural sepiolite, the specific surface area of the Fe-Mn/sepiolite catalyst was increased from 125.2 to 412.7 m2/g, as measured by Brunauer-Emmett-Teller (BET) analysis. The activity of the catalysts was evaluated by the ozonation degradation of p-chlorophenol solution, and the results showed that the catalysts were highly effective, as the removal rate of p-chlorophenol was more than 98.5%, achieved in 25 min at a 20% (w/w) Mn content. The catalysts were then used for chlorophenol degradation in papermaking wastewater through a heterogeneous ozonation process. At optimal conditions, a 98% chlorophenol removal rate and a 58% COD removal efficiency were achieved in 30 min, and pollutants in the treated wastewater were more biodegradable and less toxic than in raw water. Moreover, the prepared catalysts remained stable during successive catalytic ozonation runs. The possible reaction pathway was also proposed.