The removal of antibiotic sulfamethazine (SMT) and its intermediates from water was investigated using a rotating advanced oxidation contactor (RAOC) equipped with TiO2-high-silica zeolite composite sheets. SMT was readily removed from water through adsorption onto high-silica zeolite and photocatalytic decomposition by TiO2 inside the composite sheet. Some degradation intermediates were retained and photocatalytically decomposed inside the composite sheet. Relatively hydrophobic intermediates such as hydroxylated SMT were captured inside the sheets, whereas hydrophilic intermediates were distributed in water. This was attributed to the hydrophobic interactions in the adsorption mechanism of high-silica zeolite. The time courses of the NH4+, NO3-, and SO42- ion concentration during the RAOC treatment of SMT were evaluated. After treatment by RAOC for 24 h, approximately 94% of nitrogen derived from the amino and sulfanilamide groups and 39% of sulfur from the sulfanilamide group were mineralized, which indicated that the mineralization behavior of SMT treated by RAOC was different from that treated by TiO2 powder. These results strongly suggested that the dissociation of the amino group and cleavage of the sulfonamide group and subsequent dissociation of the amino group preferentially proceeded inside the composite sheets.
Keywords: Adsorption; Intermediate products; Mineralization; Rotating advanced oxidation contactor; Sulfonamide antibiotics; TiO2-zeolite composite sheets.