改性磁性壳聚糖去除水中双氯芬酸

Removal of diclofenac from aqueous solution by modified magnetic chitosan

摘要:

为改善壳聚糖的吸附能力,探究壳聚糖吸附水中双氯芬酸的作用机理,采用原位共沉淀法制备磁性壳聚糖小球,并利用乙二胺对其进行改性.分别研究戊二醛、环氧氯丙烷和乙二胺等交联剂的投加量不同时,改性磁性壳聚糖对水中双氯芬酸吸附能力的差异.当戊二醛、环氧氯丙烷和乙二胺的投加量分别为4,2和6 mL时,制备的吸附剂(EMMCS-G)吸附效果最佳.通过扫描电镜(SEM)、透射电镜(TEM)、振动样品磁强计(VSM)、红外光谱(FTIR)、X射线衍射(XRD)等对EMMCS-G表征分析,讨论反应时间、温度、pH、吸附剂投加量以及再生次数等因素对EMMCS-G吸附双氯芬酸的影响.结果表明,壳聚糖已成功包覆Fe₃O₄颗粒,且改性后的磁性壳聚糖氨基数量明显增多,具有良好的磁学性能和重复利用性.反应最适pH为6.5.当双氯芬酸初始质量浓度为50 mg/L,吸附剂投加量为100 mg时,反应12 h后,去除率达到76%以上.吸附过程符合准二级动力学模型,吸附等温线符合Freundlich模型,结合热力学分析及溶液酸碱度实验表明该吸附过程是物理吸附和化学吸附共同作用的自发吸热反应.

Abstract:

In order to improve the adsorption capacity of chitosan and study the adsorption of diclofenac from aqueous solution by chitosan, magnetic chitosan beads were prepared by in-situ coprecipitation method and modified by ethylenediamine. The adsorption capacity of the modified magnetic chitosan (EMMCS-G) for removal of diclofenac in water was investigated with different dosages of cross-linking agents such as glutaraldehyde, epichlorohydrin, and ethylenediamine, and results show that the optimal adsorbent was EMMCS-G when the dosages of glutaraldehyde, epichlorohydrin, and ethylenediamine were 4,2 and 6 mL, respectively. EMMCS-G was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). Effects of time, temperature, pH, adsorbent dosage, and regeneration cycles on the adsorption of diclofenac by EMMCS-G were investigated. Results show that Fe₃O₄ particles were successfully coated by chitosan. The number of amino groups of the adsorbent increased significantly after modification, and the modified adsorbent had strong magnetic capacity and reusability. The optimum pH was 6.5. When the initial concentration of diclofenac was 50 mg/L and the dosage of the adsorbent was 100 mg, the removal rate was above 76% after 12 hours of reaction. The adsorption process accorded with the pseudo second-order kinetic model, and the adsorption data fitted well with the Freundlich model. Based on the thermodynamic analysis and pH experimental results, it demonstrates that the adsorption process was endothermic and spontaneous, which was mostly controlled by physical and chemical interactions.