Removal of sulfamethoxazole and cephalexin from water by catalytic ozonation process

Abstract

This study describes the removal of sulfamethoxazole and cephalexin by catalytic ozonation process in two types of reactors i) batch stirred type and ii) water circulation type. The first step was to screen a suitable catalyst during ozonation of sulfamethoxazole in a batch type reactor. It was observed that loading of Fe2O3/CeO2 did not suppress the adsorption capacity of PAC and that adsorption process was by physisorption for Fe2O3/CeO2 loaded PAC or PAC. Moreover, the loading of Fe2O3/CeO2 synergized the effectiveness of powdered activated carbon (PAC), for removal of sulfamethoxazole during catalytic ozonation. Complete removal of sulfamethoxazole was observed using Fe2O3/CeO2 loaded PAC catalyst within 5 min of ozonation on batch reactor. Further screening of catalyst suggested granular activated carbon (GAC) was a better catalyst compared to CeO2, MnO2, and MnO2- CeO2 metal oxides. In the presence of GAC as catalyst, approximately 90 % of cephalexin was removed in 5 min during batch ozonation process. GAC assisted ozonation of two antibiotics was conducted in a newly developed circulating reactors. Circulating batch reactor removed > 98 % of sulfamethoxazole and > 80% of COD using GAC as catalyst in 15 min duration. Similarly, 80-100% of cephalexin was removed using circulation batch reactor. Biodegradability was increased to more than 90% and 98% for cephalexin and sulfamethoxazole antibiotics respectively using circulating batch ozonation. Finally, a separate study was performed for solid phase regeneration of GAC to emulate the effectiveness of in-situ regeneration during ozonation process. In situ ozonation regenerated GAC efficiently. BET analysis, TPD-N2 and TGA profiles of regenerated GAC resembled more of virgin GAC and differed from saturated GAC sample.