聚羟基丁酸酯/碳纳米管复合纳米纤维膜的制备及其对重金属离子吸附分离性能的研究

以聚羟基丁酸酯和碳纳米管为原料,采用三氯甲烷/二甲基甲酰胺混合溶液为溶剂,利用静电纺丝技术制备了聚羟基丁酸酯/碳纳米管复合纳米纤维膜.研究了碳纳米管的含量对纳米纤维膜形貌和力学性能的影响,探讨了复合纳米纤维膜对重金属Cu(II)、Cd(II)和Pb(II)的吸附特性.实验结果表明:加入1 wt%碳纳米管能够将纳米纤维的平均直径从(728±146)nm降低至(468±89)nm,纳米纤维膜的比表面积从27.24 m~2/g提高至43.45 m~2/g;碳纳米管的复合能够有效增强聚羟基丁酸酯纳米纤维,当碳纳米管含量1 wt%为最佳,拉伸强度可达5.85 MPa,较纯聚羟基丁酸酯纳米纤维提升了115%.复合纳米纤维膜对重金属离子具有良好的吸附特性,其对Cu(II)、Cd(II)和Pb(II)的最佳吸附pH值为5,此时最大吸附容量分别为91.04、171.05和197.03mg/g,平衡吸附时间分别约为50、60和60 min,吸附率分别为1.79、2.83和3.28 mg/g/min;热力学和动力学分析表明,复合纳米纤维膜对重金属Cu(II)、Cd(II)和Pb(II)的吸附行为更符合Freundlich模型,吸附过程更符合Pseudo-second order模型;循环使用实验表明,重复使用5次后,其吸附容量可保持在初始值的87%以上,具有较好的使用寿命.

Preparation of Polyhydroxybutyrate/Carbon Nanotubes Composite Nanofiber Membrane and Their Adsorption Performance for Heavy Metal Ions

Polyhydroxybutyrate/carbon nanotubes composite nanofiber membrane was successfully prepared via electrospinning technique using polyhydroxybutyrate and carbon nanotubes as raw materials and chloroform/dimethylformamide blend as co-solvent.The effect of carbon nanotube content on the membrane's morphology and mechanical properties was investigated,and its adsorption performance to heavy metal ions was evaluated.Increasing the content of carbon nanotubes from 0 to 1 wt％,it was found that the average diameter of composite nanofibers decreased from (728 ± 146) nm to (468 ± 89) nm while their specific surface area increased from 27.24 m2/g to 43.45 m2/g;meanwhile,the nanofiber membrane was significantly strengthened with the optimum mechanical performance obtained at the content equal to 1 wt％.A tensile stress of 5.85 MPa was achieved then,which was about 115％ improvement compared with the pure polyhydroxybutyrate nanofiber membrane.Good adsorption performance was exhibited by the composite nanofiber membrane for Cu(Ⅱ),Cd(Ⅱ) and Pb(Ⅱ) ions from aqueous solution.Under the optimum pH of 5,the maximum adsorption capacity was measured as about 91.04,171.05 and 197.03 mg/g for Cu(Ⅱ),Cd(Ⅱ) and Pb(Ⅱ) ions,respectively;the corresponding equilibrium time and adsorption rate were about 50,60 and 60 min and 1.79,2.83 and 3.28 mg/g/min,respectively.Langmuir,Freundlich and Temkin models were used to analyze the thermodynamics parameters during adsorption while Pseudo-first-order,Pseudo-second-order and Intraparticle diffusion models were applied for analysis of the kinetics parameters.It was indicated that the adsorption isotherm data fitted well with Freundlich model and the kinetic process matched Pseudo-second order model.Cycle experiments demonstrated that above 87％ of initial adsorption capacity could be maintained after 5 times of usage,which suggested the nanofiber membrane's potential of applications in wastewater treatment for the removal of heavy metal ions as a nano-adsorbent.