Abstract:

To explore the degradation pattern of tetracycline (TC) in actual water, ZnO was used as a photocatalyst to investigate the effects of reaction time, pH, humic acid (HA) concentration and tetracycline concentration on the photocatalytic degradation process under complex natural environmental conditions (aeration, heavy metals and light). The results showed that all three environmental conditions promoted the degradation of tetracycline. The large amount of dissolved oxygen under aeration would collaboratively promote the generation of superoxide radicals and hydroxyl radicals with the catalyst, enabling TC to reach 99% photocatalytic degradation efficiency. The addition of the heavy metal Cu(Ⅱ) caused the formation of TC-Cu(Ⅱ)-ZnO composite in solution, which significantly improved the degradation efficiency of TC by ZnO, reaching 89% degradation efficiency at 30min. Natural light possessed a full spectrum and exhibited stronger TC degradation compared to visible light, with a TC degradation rate of 86%, which was 14% higher than that achieved under the visible light. The synergistic effect of the three factors could effectively reduce the degradation time of TC, reaching degradation equilibrium at 75min with 99% degradation efficiency. The photocatalytic activity in different environmental states was compared by kinetic analysis and the results were aeration>heavy metals>light.

Key words: water, tetracycline, photocatalysis, aeration, Cu(Ⅱ) coexistence, natural sunlight

摘要：

为探索实际水体中四环素（tetracycline，TC）的降解规律，以ZnO作为光催化剂研究四环素在复杂的自然环境条件（曝气、重金属、光照）下反应时间、pH、腐殖酸（humic acid，HA）浓度及四环素浓度对光催化降解过程的影响。结果表明，3种环境条件均促进了四环素的降解：曝气情况下大量的溶解氧会和催化剂协同促进超氧自由基和羟基自由基的生成，使TC达到99%的光催化降解率；重金属Cu(Ⅱ)的加入使溶液中形成TC-Cu(Ⅱ)-ZnO络合物，显著提高了ZnO对TC的降解效率，在30min时达到89%的降解率；自然光拥有全光谱，相比可见光展现出更强的TC降解作用，TC降解率达到86%，比可见光下降解率提高了14%。三因素协同作用可以有效降低TC的降解时间，在75min时达到降解平衡，降解率为99%。通过动力学分析比较了不同环境状态下的光催化活性，结果为：曝气>重金属>光照。

关键词: 水体, 四环素, 光催化, 曝气, Cu(Ⅱ)共存, 自然光