光催化降解沼液中四环素类抗生素效果及反应动力学研究

该文采用光催化降解途径探究沼液中四环素类抗生素降解的最佳光源、pH值以及光催化对不同初始质量浓度抗生素的降解效果,同时进行不同初始浓度、pH值条件下抗生素光催化降解动力学研究。结果表明:不同光源对四环素类抗生素的降解效果为:高压汞灯紫外消毒灯长弧氙灯无光。高压汞灯催化2 h后,四环素、土霉素、金霉素的降解率分别达到91.68%、85.58%、81.18%。四环素类抗生素的初始质量浓度越低,光催化效果越好。四环素、土霉素、金霉素初始质量浓度为5 mg/L时,其降解率最高可达94.80%、88.35%和95.39%,沼液初始pH值对四环素、金霉素的降解率影响存在显著性差异(P0.05)。当pH值为6时,四环素的降解率最大为96.16%,反应速率常数为1.5971h-1,半衰期为0.355 3 h;当pH值为10时,金霉素的降解率最大为90.47%,反应速率常数为1.084 4 h-1,半衰期为0.338 3 h。沼液初始pH值对土霉素的降解率影响无显著差异(P0.05)。当pH值为10时,3种抗生素的平均降解率最大为89.88%。采用高压汞灯在沼液初始pH值为10时,催化降解5 mg/L四环素类抗生素效果最佳。

Study on photocatalytic degradation and reaction kinetics of tetracycline antibiotics in biogas slurry

Abstract: As a bactericidal drug, antibiotics are widely used in animal husbandry to prevent animal diseases and treat sick animals. With the rapid development of Chinese livestock and poultry breeding industry, the use of veterinary antibiotics continues to increase. In 2013, the annual use of antibiotics in China was about 162 000 t, of which 52% was used for livestock. The production and the actual usage of tetracycline antibiotics in livestock and poultry breeding industry of the world are the largest than other antibiotics. A large number of antibiotics are difficult to be absorbed and metabolized completely in animals, then they will be excreted and stay in biogas slurry during anaerobic digestion. High concentrations of antibiotics in biogas slurry may cause some microorganisms produce resistance genes and won''t be degraded into the environment, and these resistance genes can transmit, it may make some pathogenic bacteria resist drugs, which in turn poses a great threat to ecosystems and human health. At present, the main methods of removing antibiotics include photocatalytic degradation, hydrolysis, oxidative degradation, sludge adsorption, and biodegradation. Among them, the photocatalytic degradation technology uses TiO2 as a photocatalyst, which has the advantages of high catalytic activity, high chemical stability, low cost, and low toxicity product, and has become a promising method for pollutant degradation. In this study, the photocatalytic degradation pathway was used to explore the optimal light source, pH value and the degradation effect of photocatalysis under different initial concentration of tetracyclines antibiotics in biogas slurry, and the degradation kinetics of antibiotics under different initial concentrations and pH value were studied. The results showed that the degradation effects of different light sources on tetracycline antibiotics were: High pressure mercury lamp > ultraviolet disinfection lamp > long arc xenon lamp>dark. After 2 h of high pressure mercury lamp catalysis, the degradation rates of tetracycline, oxytetracycline and chlortetracycline reached 91.68%, 85.58% and 81.18%, respectively. The lower the initial mass concentration of the tetracycline antibiotic, the better the photocatalytic effect. When the initial concentration of tetracycline, oxytetracycline and chlortetracycline is 5 mg/L, the degradation rate was up to 94.80%, 88.35% and 95.39%, the reaction rate constant was 1.505 6 h(1, and the half-life was 0.431 7 h. There was a significant difference in the degradation rate of tetracycline and chlortetracycline in the initial pH value of biogas slurry (P<0.05). When pH value was 6, the degradation rate of tetracycline was 96.16%, the reaction rate constant was 1.597 1 h(1, and the half-life was 0.355 3 h; when pH value was10, the degradation rate of chlortetracycline was 90.47%, the reaction rate constant was 1.084 4 h(1, half-life was 0.338 3 h. There was no significant difference in the degradation rate of oxytetracycline between the initial pH value of biogas slurry (P>0.05). When pH value was 10, the average degradation rate of three antibiotics was 89.88%. when the initial pH value of biogas slurry was 10, the concentration of tetracycline antibiotics was 5 mg/L, it is the best to catalytic degradation tetracycline antibiotics using the high-pressure mercury lamp.