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抗生素被广泛的应用于医疗、畜牧业、农作物养殖等方面。抗生素的大量使用会导致其在环境中积累,并在城市污水处理厂中被检测到[1-2]。由于抗生素具有生物毒性,故其对生物降解具有很高的抗性[3]。这导致含有抗生素的医疗废水、生活废水等排放至污水处理厂却无法得到高效的去除,危害着生态以及人类健康[4-6]。
光催化技术可用于抗生素的强化去除,但也存在降解不彻底、反应不易控制、能耗较高等缺点[7]。因此,在难降解废水处理中,常将光催化作为前处理,提高废水可生化性,并与生物法耦合,提高污染物的生化降解效率。LI等[8]将TiO2负载在改进的多孔载体上,以提高三氯苯酚的降解,三氯苯酚通过吸附、光降解、光催化和生物降解4个途径得到去除。ZHOU等[9]通过将Er3+:YAlO3/TiO2负载到多孔载体上,将光催化与生物降解耦合,提高了含酚废水的降解效率。DING等[10]选择紫外光催化对含有抗生素的废水进行预处理,发现光催化有助于分解抗生素中的主要官能团以消除其抗菌活性,有利于后续生物处理。FU等[11]成功将TiO2附着在载体表面并通过光催化协同去除水体中的异味物质2-甲基异冰片和土臭素,发现该系统能保持较好的去除效率和稳定性。然而,目前该领域仍然存在一些待解决的问题。例如,光催化剂在载体表面的高效附着、光催化对生物的毒性作用、光催化与生物降解耦合后对污染物的去除途径和机理等。
好氧颗粒污泥(aerobic granular sludge, AGS)是由微生物、胞外聚合物(extracellular polymeric substances, EPS)、无机盐等聚集而成的生物聚集体。其内部环境相对稳定、菌落丰富,在处理难降解废水时具有一定的优势。HUANG等[12]利用AGS与光催化相结合处理染料废水,染料通过AGS吸附、脱附后在自净洗脱液中光解。鉴于AGS较强的吸附能力,且其紧凑的颗粒结构能为内部微生物提供很高的保护,将纳米二氧化钛(TiO2 P25)负载到AGS表面制备生物纳米材料,通过表面光催化与内部生物降解耦合,有望强化抗生素的降解。本研究综合考虑吸附动力学和负载TiO2对AGS内生物活性等方面的影响,确定了最佳TiO2负载量;考察了该生物纳米材料对磺胺类抗生素磺胺嘧啶(sulfadiazine, SDZ)的降解性能,并通过检测磺胺嘧啶及中间产物,确定了降解途径。
好氧颗粒污泥负载纳米二氧化钛强化磺胺嘧啶降解的机制及性能
Mechanisms and performance of enhanced sulfadiazine degradation by nano TiO2-loaded aerobic granular sludge
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摘要: 抗生素在传统污水处理厂的去除效果有限,基于此,制备了一种将纳米二氧化钛(TiO2)吸附在好氧颗粒污泥上的生物纳米材料,该材料可以在不影响其他污染物去除性能的情况下提高废水中磺胺嘧啶(SDZ)类抗生素的降解,并强化中间产物的进一步转化。结果表明,AGS对TiO2的吸附满足伪二级吸附动力学,得到的生物纳米材料结构稳定;在TiO2为20 mg·L−1时吸附速率最快、对污泥内细胞和胞外聚合物影响较小;用该材料降解含SDZ的模拟废水时,紫外光照会促进生物纳米材料中异养菌的活性,提高耗氧有机污染物、SDZ及其中间产物对氨基苯磺酸的去除率,10 h内SDZ平均降解速率可达0.97 mg·(L·h)−1。以上获得的新型生物纳米材料可为抗生素废水的处理提供新的技术选择。Abstract: The removal effect of antibiotics in conventional wastewater treatment plants is limited. In this study, we prepared a new biological nanomaterial by loading nano titanium dioxide (TiO2) onto aerobic granular sludge (AGS). This biological nanomaterial could improve the degradation of sulfadiazine (SDZ) and facilitate the further conversion of intermediate products without affecting the system performance. The experimental results showed that the adsorption of TiO2 on AGS was fitted with pseudo-second-order kinetics model and the structure of the prepared biological nanomaterial was stable. At TiO2 of 20 mg·L−1, the fastest adsorption rate occurred, and the TiO2 had a minor negative effect on cell viability and extracellular polymeric substances. The UV light could promote the activity of heterotrophic bacteria in biological nanomaterials, and improve the removal of COD, SDZ and SDZ intermediate products (4-ABS), and the average degradation rate could reach 0.97 mg·(L·h)−1 in 10 hours. The nanomaterial provides a new technincal choice for antibiotic wastewater treatment.
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Key words:
- aerobic granular sludge /
- nano titanium dioxide /
- sulfadiazine /
- biodegradation /
- photocatalytic
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表 1 AGS上纳米TiO2的附动力学方程拟合参数
Table 1. Adsorption kinetic fitting parameters for TiO2 on AGS
TiO2/(mg·L−1) qe,exp/(mg·g−1) 伪一级动力学 伪二级动力学 k1/(g·(mg·h)−1) qe,cal/(mg·g−1) R2 k2/(g·(mg·h)−1) qe,cal/(mg·g−1) R2 10 6.27 2.82 5.01 0.95 2.07 6.42 1.00 20 11.96 3.95 5.37 0.79 5.63 12.01 1.00 50 33.10 2.06 8.18 0.72 1.30 33.27 1.00 100 68.38 1.33 17.80 0.79 0.35 68.82 1.00 -
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