偕胺肟化纤维膜吸附去除溶液中的Pb^(2+)

Removal of Pb^(2+)from solution by amidoxime nanofiber membrane

以聚丙烯腈(PAN)为壳层功能材料,聚偏氟乙烯(PVDF)为核层材料,通过同轴静电纺丝和水热反应制备了柔性的偕胺肟化纤维膜(CO-AONFM),用于处理溶液中的Pb^(2+).通过等温吸附、吸附动力学模型拟合和场发射扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)等表征手段,研究了CO-AONFM对Pb^(2+)的吸附效果和吸附机理.结果表明,随溶液pH升高,纤维膜的Pb^(2+)吸附量逐渐上升,当溶液pH5.5时,CO-AONFM对Pb^(2+)的吸附量最大(140.2 mg·g^(−1)),吸附过程在12 h内基本达到平衡,5次吸附-脱附循环后,CO-AONFM的吸附量为107.19 mg·g^(−1).吸附过程符合Langmuir等温吸附模型和准二级动力学模型,SEM表征结果显示,当溶液pH5.5时,Pb^(2+)在纤维膜表面形成了均匀的六边形结晶,进一步FTIR和XRD表征结果证明该结晶为Pb_(3)(CO_(3))_(2)(OH)_(2),pH是影响Pb^(2+)在纤维膜表面结晶沉淀过程的主要因素.CO-AONFM吸附Pb^(2+)主要是化学螯合和水解沉淀.研究显示,制备的CO-AONFM吸附剂具有良好的机械性能,其回用过程便捷,可以有效去除溶液中的Pb^(2+).

A flexible amidoxime nanofiber membrane(CO-AONFM)was prepared by coaxial electrospinning and hydrothermal reaction for removing Pb^(2+) from solution.The polyacrylonitrile(PAN)and the polyvinylidene fluoride(PVDF)was used as shell functional material and inner material,respectively.The performance and mechanism of CO-AONFM for Pb^(2+) adsorption was studied by batch experiments,model fitting,and characterization analysis.The results shown that,the adsorption capacity of CO-AONFM increases with the solution pH value,and the maximum adsorption capacity for Pb^(2+) was 140.2 mg·g^(−1) at pH 5.5 within 12 h.After five adsorptions-desorption cycles,the adsorption capacity of CO-AONFM was 107.19 mg·g^(−1).The adsorption process fitted well with Langmuir model and pseudo-second-order kinetic model.The SEM pictures shown that,some hexagonal crystals formed on the surface of the fiber membrane at pH 5.5.FTIR and XRD results confirmed that the crystals were Pb_(3)(CO_(3))_(2)(OH)_(2),which determined the pH was the main factor affecting the crystallization and precipitation of Pb^(2+) on the surface of fiber membrane.The adsorption mechanism of Pb^(2+) by CO-AONFM was mainly chemical chelation and hydrolytic precipitation.Furthermore,this study demonstrated that the CO-AONFM adsorbent has good mechanical strength and better regeneration properties,which provided better application potential for this material in Pb^(2+) removing.