Photolysis and photocatalytic decomposition of sulfamethazine antibiotics in an aqueous solution with TiO2
Journal
RSC Advances
Journal Volume
6
Journal Volume
6
Journal Issue
73
Journal Issue
73
Start Page
69301
End Page
69310
ISSN
20462069
Date Issued
2016
Author(s)
Tzeng, Tai-Wei
Chen, Chiing-Chang
Tan, Chen-Chung
Liu, Yu-Ting
Chen, Tsan-Yao
Tzou, Yu-Min
Chen, C.C.
Hung J.T.
Abstract
Photo-decomposition of sulfamethazine (SMT) involves photolytic and photo-catalytic reactions, which occur simultaneously. The relative contributions of these two reactions to the overall SMT photo-decompositions by TiO2 and the intermediates of SMT photo-decompositions were systematically examined with the effects of TiO2 loading, and the pH and the initial SMT concentrations in the solutions. The apparent rate constants of SMT photo-decomposition reactions, which were well described by the pseudo-first-order kinetic model, ranged from 0.24 to 1.61 h-1. The overall photo-decomposition efficiencies of 0.072 mM SMT were the highest at pH 5.5 with 0.5 g L-1 TiO2 due to the adsorption-induced photocatalytic decomposition of SMT on TiO2. However, the SMT photolysis occurred more rapidly at pH 10. Two reactive species of holes and hydroxyl radicals concurrently participated in the photocatalytic decomposition of SMT, and the latter dominated the oxidative reactions of SMT on TiO2. Eight intermediates of SMT photo-decomposition were determined using LC-MS. Their time-dependent distributions indicated that the photo-decomposition of SMT was triggered by hydroxylation on aniline and dimethylpyrimidinyl moieties, followed by the cleavage of the S-N bond of SMT. Our results illustrated that the intermediates with dimethylpyrimidinyl groups possess strong resistance to photo-decomposition and played a determinant role in the photo-decomposition of SMT.
Publisher
Royal Society of Chemistry
Type
journal article