Antibiotics in environment can be of concern as they can enter the food chain posing risks to ecosystems and human health. Photodegradation has been considered as a promising way of naturally degrading antibiotics in environment. Antibiotics are usually present in mixtures in environment; however, previous studies focused on individual compounds. Therefore, this study investigated the effect of UV irradiation on the degradation of tetracycline (TC) and sulfathiazole (STH) in individual solutions and mixtures. Under dark conditions, the initial mass of TC and STH were reduced by about 35% and 26%, respectively, over 35 d-reaction period. With UV irradiation TC and STH were completely removed within 14 d and 35 d, respectively, regardless of the initial concentrations. Both the TC and STH removals were faster (i.e., 2–4 times) when they were in mixtures. This may be partly attributed to the byproducts such as sulfate that can promote indirect photolysis and partly to the enhanced hydrolysis due to changes in the solution pH. Overall, this study suggests that when photodegradation is used to remove antibiotics in water, the removal kinetics of antibiotics individually and in mixtures can be considered to develop more efficient treatment technologies.

环境中的抗生素可能会引起关注，因为它们会进入食物链，对生态系统和人类健康构成风险。光降解被认为是在环境中自然降解抗生素的一种有前途的方法。抗生素通常存在于环境中的混合物中。但是，以前的研究集中在单个化合物上。因此，本研究调查了紫外线照射对单独溶液和混合物中四环素（TC）和磺胺噻唑（STH）降解的影响。在黑暗条件下，在35 d反应期间，TC和STH的初始质量分别减少了约35％和26％。不管初始浓度如何，用紫外线照射分别在14 d和35 d内将TC和STH完全去除。TC和STH的移除速度都更快（即，混合2到4次）。这可能部分归因于副产物，例如硫酸盐，可促进间接光解，部分归因于溶液pH值的变化而增强的水解作用。总体而言，这项研究表明，当使用光降解法去除水中的抗生素时，可以考虑将抗生素单独和混合物中的去除动力学来开发更有效的处理技术。