四氧化三铁/聚乙烯亚胺纳米颗粒的制备及除磷性能的研究

Preparation of Fe_3O_4/polyethyleneimine and its application for phosphate adsorption

采用化学共沉淀法,以聚乙烯亚胺(PEI)为改性剂,制备了聚乙烯亚胺改性的纳米四氧化三铁复合材料(Fe3O4/PEI).Zeta电位、透射电镜和FTIR表征结果显示,PEI修饰提高了纳米Fe3O4在水中的分散性和稳定性,同时也增强了其表面正电荷,从而提高了Fe3O4对水中磷酸根的去除能力.在磷酸根初始浓度为50 mg·L^(-1),Fe3O4/PEI投加量为200 mg,p H=3,温度为25℃的条件下,Fe3O4/PEI对100 m L磷酸根的吸附去除率达到91%.吸附过程在3 h内达到平衡.吸附等温数据表明,该吸附过程符合Langmuir吸附等温方程,可决系数R2达到0.99,最大吸附量为29.88 mg·L^(-1).Fe3O4/PEI复合材料重复利用性好,在第5次吸附-解析后还能保持对磷酸根75%以上的吸附去除率.磷的解析效率随着p H增加而增加,在p H=13时,解析效率达到65%.

In this study,magnetite（ Fe3 O4） modified with polyethyleneimine（ PEI） was synthesized by chemical coprecipitation method. This magnetic composite（ Fe3 O4/PEI） was characterized by X-ray diffraction（ XRD）, transmission electron microscopy（ TEM）, Fourier transform infrared spectroscopy（ FTIR） and Zeta potential. Furthermore,the adsorption-desorption process and mechanisms of Fe3 O4/PEI towards phosphate were investigated in aqueous solutions. Results indicated that adsorption efficiency of phosphate by Fe3 O4/PEI reached 91%,which was higher than that of Fe3 O4,under the condition of 50 mg·L^-1 of initial phosphate concentration,200 mg Fe3 O4/PEI,and pH 3 at room temperature,the desorption efficiency reached 65% at pH 13. Polyethyleneimine not only improved the dispersibility of Fe3 O4,but also increased the positive charge on the surface of Fe3 O4.The phosphate adsorption behavior by Fe3 O4/PEI was in good agreement with the Langmuir adsorption model. Adsorption kinetic study showed that the equilibrium was reached in 3 hours,and the adsorption process is well fit by pseudo-second-order kinetic model. Phosphate was adsorbed to the Fe3 O4/PEI surface via electrostatic attraction and ligand exchange. In conclusion,our investigation indicates that Fe3 O4/PEI is a type of stable and highly efficient material for adsorption of phosphate.