Removal of 2,4-dimethylphenol pollutant in water by ozonation catalyzed by SOD, LTA, FAU-X zeolites particles obtained by pseudomorphic transformation (binderless)

Abstract

Advanced oxidation processes (AOP) as ozonation coupled with inorganic materials have been recently demonstrated to be highly suitable for wastewater treatment. In petrochemical wastewaters, pollutants as alkylphenols are often detected. In this paper, we highlight the efficiency to couple ozone with zeolites as SOD, LTA and FAU-X for the degradation of 2,4-dimethylphenol (2,4-DMP). For process requirement the 3 zeolites were prepared as particles of 70μm and 1mm thanks to pseudomorphic transformation without binders. The zeolites were synthesized under their sodium (Na) form and potassium (K) ion-exchange was performed to enhance their basicity. By single ozonation (without zeolite) 100% of 2,4-DMP removal occurred in 25min, but the pollutant is transformed into oxidized by-products corresponding to only 14% of the Total Organic Carbon (TOC) removal after 5h. Adding zeolites to the ozonation process increased very slightly the kinetic of disappearance of the pollutant but increased the removal of its oxidation by-products, with 34% of TOC removal after 5h. Among the zeolites, the best solid catalyst for ozonation was Na-LTA. Experiments with tert-butanol (t-BuOH) put in evidence that Na-LTA generates hydroxyl radicals from ozone, which increased the degradation of the by-products. No adsorption of 2,4-DMP and of the resulting oxidation by-products was detected by thermogravimetric analysis (TGA) on the materials after 5h of ozonation. The TOC removal is consequently equivalent to the total mineralization of the organics into CO2.