School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University, Nanjing, 210023, PR China.
School of Civil Engineering and Architecture, Anhui University of Technology, Maanshan, Anhui, 243002, China.
Water Res. 2020 Jun 15;177:115775. doi: 10.1016/j.watres.2020.115775. Epub 2020 Apr 5.
In this paper we describe the preparation and testing of a new class of chitosan-based flocculants for the treatment of surface waters containing antibiotic compounds. Three forms of moderately hydrophobic chitosan flocculants (MHCs) were prepared by chemically grafting hydrophobic branches with different lengths onto hydrophilic chitosan and these were evaluated by jar tests and a bench-scale continuous flow ultrafiltration (UF) membrane process with coagulation/sedimentation pre-treatment. Tests were conducted using both synthetic and real surface water in which norfloxacin and tylosin were added as representative antibiotics at an initial concentration of 0.1 μg/L. In jar tests, the MHCs achieved similar high removal efficiencies (REs) of turbidity and UV absorbance, but much higher REs of the two antibiotics (71.7-84.7% and 68.7-76.6% for synthetic and river waters, respectively), compared to several commercial flocculants; the superior performance was attributed to an enhanced hydrophobic interaction and H-bonding between the flocculants and antibiotics. The presence of suspended kaolin particles and humic acid enhanced the antibiotic removal, speculated to be through MHC bridging of the kaolin/humic acid and antibiotic molecules. In the continuous flow tests involving flocculation/sedimentation-UF for 40 days, an optimal MHC achieved a much greater performance than polyaluminium chloride in terms of the overall removal of antibiotics (RE (norfloxacin) of ∼90% and RE (tylosin) of ∼80%) and a greatly reduced rate of membrane fouling; the latter resulting from a more porous and looser structure of cake layer, caused by a surface-modification-like effect of residual MHC on the hydrophobic PVDF membrane. The results of this study have shown that MHCs offer a significant advance over the use of existing flocculants for the treatment of surface water.
本文描述了一类新型壳聚糖基絮凝剂的制备和测试，用于处理含有抗生素化合物的地表水。通过在亲水性壳聚糖上化学接枝不同长度的疏水性支链，制备了三种形式的中等疏水性壳聚糖絮凝剂（MHCs），并通过烧杯试验和带有混凝/沉淀预处理的台式连续流超滤（UF）膜过程进行了评估。使用添加诺氟沙星和泰乐菌素作为代表性抗生素的合成地表水和实际地表水进行了测试，初始浓度为 0.1μg/L。在烧杯试验中，MHC 实现了相似的高浊度和紫外吸光度去除效率（RE），但对两种抗生素的去除效率更高（分别为 71.7-84.7%和 68.7-76.6%，对于合成水和河水），与几种商业絮凝剂相比；优异的性能归因于絮凝剂和抗生素之间增强的疏水性相互作用和氢键。悬浮高岭土颗粒和腐殖酸的存在增强了抗生素的去除，推测是通过 MHC 桥接高岭土/腐殖酸和抗生素分子实现的。在涉及絮凝/沉淀-UF 的连续流动测试中，对于 40 天的运行，与聚合氯化铝相比，最佳 MHC 在抗生素的整体去除方面表现出更好的性能（RE（诺氟沙星）约为 90%，RE（泰乐菌素）约为 80%），并且膜污染的速率大大降低；后者是由于剩余 MHC 对疏水性 PVDF 膜的表面改性样作用导致的滤饼层具有更多孔和更疏松的结构所致。这项研究的结果表明，MHC 在处理地表水方面比使用现有絮凝剂有了显著的进步。
