Abstract:

In order to endow magnetic bentonite (MB) with magnetic separation ability and simultaneously obtain stronger removal capacity of antibiotics, magnetic bentonite/carboxymethylcellulose-chitosan composite (MB-CC) was prepared by modifying previously fabricated MB with carboxymethylcellulose (CMC) and chitosan (CS). The characterization of both MB-CC and MB and their adsorption properties towards ciprofloxacin (CIP) and tetracycline (TC) in aqueous solution were investigated. Textural characterization results revealed that the magnetic nanoparticles (Fe₃O₄) were successfully immobilized onto bentonite and further modified with CC. The surface functionalization with CC concurrently enhanced the stability of Fe₃O₄ and removal capability of CIP and TC for the final product. Adsorption results indicated that MB-CC exhibited superior adsorption performance for CIP and TC (182mg/g and 189mg/g) to MB (147mg/g and 136mg/g) at pH 5.0 and 25℃. Adsorptive removal of CIP and TC by MB-CC was more than 90% even after 5 cycles of adsorption-desorption process. The adsorption isotherms were better described by Langmuir model than Freundlich model. The adsorption process fitted well with pseudo-second order kinetic model, indicating that the rate-determining step for MB-CC was chemical adsorption. The main steps during the successful adsorption process of MB-CC for CIP and TC included pore diffusion, ions exchange and electrostatic interaction. The current approach is credited to the simplified synthesis and high-efficiency of MB-CC which could also be deemed as a promising alternative sorbent for removal antibiotics from wastewater.

Key words: magnetic bentonite, organically modification, adsorption, ciprofloxacin, tetracyclines

摘要：

为了提高磁性膨润土（magnetic bentonite，MB）的磁分离性能，达到高效去除抗生素的目的，本文采用羧甲基纤维素（sodium carboxymethyl cellulose，CMC）和壳聚糖（chitosan，CS）相互作用所生成的有机共聚膜（chitosan/sodium carboxymethyl cellulose copolymer film，CC）对MB进行联合修饰，制得双有机修饰的有机磁性膨润土（magnetic bentonite/carboxymethyl cellulose-chitosen composite，MB-CC），同时进行了MB-CC对环丙沙星（ciprofloxacin，CIP）和四环素（tetracyclines，TC）的吸附性能研究。表征结果表明，磁性Fe₃O₄纳米粒子和有机共聚膜CC成功地固定在MB上；经过CC改性，提高了Fe₃O₄的稳定性和对CIP及TC的去除性能。吸附结果表明，在pH为5、温度为25℃的条件下，MB-CC对CIP和TC的吸附容量（182mg/g和189mg/g）高于MB对CIP和TC的吸附容量（147mg/g和136mg/g）。经过5次循环，MB-CC对CIP和TC的去除率仍然保持在90%以上。与Freundlich模型相比较而言，CIP和TC在MB和MB-CC上的吸附行为更加符合Langmuir模型；吸附过程可由准二级动力学模型描述，说明吸附速率主要由化学吸附控制。MB-CC对CIP和TC的吸附机理主要包括孔扩散、阳离子交换和静电吸引作用。综上所述，MB-CC具有合成简单、高效等优点，是一种很有前途的抗生素废水去除方法。

关键词: 磁性膨润土, 有机修饰, 吸附, 环丙沙星, 四环素