Removal behaviors of sulfamonomethoxine and its degradation intermediates in fresh aquaculture wastewater using zeolite/TiO 2 composites.

Removal efficiencies of sulfamonomethoxine (SMM) and its degradation intermediates formed by treatment with zeolite/TiO ₂ composites through adsorption and photocatalysis were investigated in fresh aquaculture wastewater (FAWW). Coexistent substances in the FAWW showed no inhibitory effects against SMM adsorption. Although coexistent substances in the FAWW inhibited the photocatalytic decomposition of SMM, the composites mitigated the inhibition, possibly because of concentration of SMM on their surface by adsorption. LC/MS/MS analyses revealed that hydroxylation of amino phenyl and pyrimidinyl portions, transformation of the amino group in the amino phenyl portion into a nitroso group, and substitution of the methoxy group with a hydroxyl group occurring in the initial reaction resulted in the formation of various intermediates during the photocatalysis of SMM. All detected intermediates had a ring structure, and almost all intermediates disappeared at the same time SMM was completely decomposed. Ph-OH formed by hydroxylation of the phenyl portion was detected upon decomposition of SMM during photocatalysis. The removal of Ph-OH by the composites proceeded more rapidly than that by TiO ₂ alone under ultraviolet irradiation. The SMM and Ph-OH were completely degraded by the composites within 30min, showing that the zeolite/TiO ₂ composites were effective in removing SMM and its intermediates from FAWW.
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