磁性壳聚糖吸附剂的季铵盐改性及磷吸附性能

Magnetic Chitosan Modified by Quaternary Ammonium Salt and Its Phosphorus Adsorption

为提升吸附剂的固-液分离效率及磷吸附选择性,以粉煤灰磁珠(CMS)为磁核,以甲基丙烯酰丙基三甲基氯化铵(MAPTAC)改性的壳聚糖(CS)为壳层材料,制备了磁性CMS/CS/MAPTAC吸附剂。利用热重分析、X射线衍射、振动样品磁强计、扫描电镜、红外光谱仪和X射线光电子能谱对CMS/CS/MAPTAC进行了系统表征。研究表明,CMS颗粒均匀分布于CS基体中,MAPTAC以化学键形式与CS结合。所得CMS/CS/MAPTAC具有16.8 emu/g的强磁性,因而可利用磁场实现高效固-液分离。磷吸附试验表明,CMS/CS经MAPTAC修饰后,磷吸附性能大幅提升。在pH=4.0,25℃条件下,其最大磷吸附容量可达50.7 mg/g。溶液pH、时间、浓度、温度和共存阴离子等因素对磷吸附性能具有显著影响。吸附动力学和等温线模拟表明,CMS/CS/MAPTAC的磷吸附过程符合准二级动力学模型和Langmuir等温吸附模型,以单分子层化学吸附为主。经过五次循环利用后,CMS/CS/MAPTAC仍保留60%以上的磷吸附性能。

To improve the solid-liquid separation efficiency and selective adsorption of phosphorus sorbent,magnetic CMS/CS/MAPTAC composites were prepared,using coal-fly-ash magnetic spheres(CMS)and chitosan(CS)modified by methacrylamido propyl trimethyl ammonium chloride(MAPTAC)as magnetic core and shell,respectively.Thermogravimetry analysis,X-ray diffraction,vibration sample magnetometer,scanning electron microscopy,infrared spectroscopy and X-ray photoelectron spectroscopy were employed to characterize the obtained CMS/CS/MAPTAC.It is shown that CMS is uniformly distributed in the CS matrix.MAPTAC is modified onto the surface of CS by chemical bonds.The CMS/CS/MAPTAC sample has strong magnetism up to 16.8 emu/g,which enables an efficient solid-liquid separation under an applied magnetic field.Phosphorus adsorption experiments indicate that the loading of MAPTAC on the surface of CMS/CS improves the phosphorus adsorption performance.The maximum phosphorus adsorption capacity of 50.7 mg/g was obtained under the conditions of pH=4.0 and 25℃.The reaction time,pH,phosphate concentration,temperature and coexisting anions have significant effects on the phosphorus adsorption.The adsorption kinetics and adsorption thermodynamics simulation suggests that the phosphorus adsorption of CMS/CS/MAPTAC conforms to the pseudo-second-order model and Langmui-iso-absorbing model.Thus,the adsorption should mainly belong to monolayer chemisorption.The CMS/CS/MAPTAC adsorbent can be recycled and reused multiple times.After 5 recycling,the phosphorus adsorption was still more than 60%of that initial sample.