基于静电纺丝技术的活性碳纳米纤维及其电容器脱盐研究

发布时间：2018-10-10 19:18

【摘要】：淡水是一种宝贵的资源,是人类赖以生存和发展的最基本物质之一。淡水资源紧缺将成为制约我国经济和社会可持续发展的重要因素。淡水资源的补给可通过海水、苦咸水淡化及污水的再生回用等途径,因此,开发高效脱盐技术满足缺水地区的淡水供给具有重要意义。传统的脱盐方法,如电渗析、反渗透存在能耗高、成本高、再生复杂等问题,导致其推广应用受限。电容去离子技术是近年来发展起来的新型脱盐技术,该技术以纯双电层电容原理吸附离子,脱盐过程再生可逆性好,操作压力小,能耗低,水回收率高,而且整个过程无氧化还原反应发生,无二次污染等,相比现有的反渗透(RO)和电渗析,具有良好的应用前景。本文以商业活性炭纤维毡(ACF)和基于静电纺丝技术制备的活性碳纳米纤维(A-ECNF)作为自支撑电极材料组装电容器并进行脱盐研究。分别考察了目标电压、充电电流密度及溶液流速等对电容器脱盐性能的影响,并采用循环伏安、电化学阻抗、扫描电子显微镜等多种技术表征了A-ECNF电极的特性。主要结果如下： 1、以商业ACF电极作为自支撑电极组装电容器,研究了目标电压及充电电流密度对电容器脱盐量、脱盐速率、电流效率及电极表面pH值的影响。结果表明：在一定范围内随着目标电压的升高,脱盐量逐渐增加,电流效率呈先增大后减小的趋势。目标电压过高,电极表面极化严重,导致电极表面微区pH值显著变化。研究发现,当目标电压为1.2V,充电电流为38mA/g时,该商业ACF电极的脱盐量为4.92mg/g,电流效率为32.3%。电化学表征验证,由于离子在电极表面扩散受阻,从而导致低的脱盐容量。 2、以聚丙烯腈(PAN)和N,N-二甲基甲酰胺(DMF)混合液为纺丝前驱液,采用静电纺丝技术制备碳纳米纤维(ECNF),考察了PAN浓度、纺丝电压及接收距离对ECNF形貌的影响。结果表明：PAN浓度为9%,纺丝电压为15kV,接收距离为20cm时,获得的ECNF直径在220nm左右。并采用ZnCl2试剂作为活化剂处理ECNF得到活性碳纳米纤维(A-ECNF),以改善ECNF的性能,增大其比表面积。研究发现ECNF经ZnCl2活化处理后,纤维的表面形貌无明显变化,仍保持原有良好的柔韧性,可作为自支撑电极直接用于电容器组装：接触角测试表明,与活化前相比,活化后ECNF具有更好的水润湿性。并考察了活化剂量(ZnCl2/ECNF比例)对A-ECNF的影响,BET测试表明,随着ZnCl2/ECNF比例的提高,纤维的比表面积逐渐增大,当比例为2：1时,活化得到的A-ECNF比表面积高达430m2/g,而未活化的ECNF比表面积为12.4m2/g;循环伏安及电化学阻抗测试表明,随着ZnCl2/ECNF比例的提高,获得的A-ECNF电极的电容电流逐渐增大,电阻逐渐减小,离子在电极表面的迁移速率明显提高。 3、将ZnCl2活化后的A-ECNF作为自支撑电极组装成电容器,进行恒流充放电脱盐研究,对比不同ZnCl2/ECNF比例时所得A-ECNF电极的脱盐性能,发现ZnCl2活化可以明显改善电极的脱盐性能,且脱盐速率随着其比例的提高而增大。当ZnCl2/ECNF比例为2：1时,A-ECNF的脱盐速率最快,脱盐量最高。以ZnCl2/ECNF比例为2：1时制得的A-ECNF作为电极材料,研究了电极材料的充放电稳定性及充电电流密度、溶液流速和目标电压对A-ECNF电极的脱盐速率、脱盐量和电流效率的影响。结果表明,在合适的参数下(充电电流密度为36mA/g,溶液流速为10ml/min;目标电压为1.2V), A-ECNF电极的脱盐量高达10.2mg/g,电流效率高达57.1%,明显优于ECNF电极。此外,对比现有的不同电极材料的脱盐性能,发现A-ECNF的脱盐性能和目前较好的碳材料如碳化物衍生炭材料的脱盐量相当。循环稳定性测试进一步表明该ZnCl2活化的A-ECNF有望用于电化学脱盐。
[Abstract]:Freshwater is a valuable resource, which is one of the most basic materials for human survival and development. The shortage of fresh water resources will be an important factor restricting the sustainable development of our country's economy and society. The replenishment of fresh water resources can be used in seawater, brackish water desalination and regeneration of sewage. Therefore, it is of great significance to develop efficient desalination technology to meet the freshwater supply in water shortage area. The traditional desalination method, such as electrodialysis and reverse osmosis, has the problems of high energy consumption, high cost, complex regeneration and the like, and the popularization and application of the desalination method are limited. The technology of capacitance deionization is a new kind of desalination technology developed in recent years. This technology can adsorb ions with pure double-layer capacitance principle, has good regeneration reversibility of desalting process, small operation pressure, low energy consumption, high water recovery rate, no redox reaction in the whole process, no secondary pollution and so on. Compared with the existing reverse osmosis (RO) and electrodialysis, the invention has good application prospect. Activated carbon nanofibers (A-ECF) prepared by commercial activated carbon fiber felt (ACF) and electrostatic spinning technology were used as self-supporting electrode materials to assemble capacitors and to conduct desalination. The effects of target voltage, charge current density and solution flow rate on the desalination performance of capacitor were investigated. A-ECF electrode was characterized by cyclic voltammetry, electrochemical impedance and scanning electron microscope. Properties. Main results 1. Using commercial ACF electrode as self-supporting electrode assembly capacitor, the desalting capacity, desalting rate, current efficiency and electrode surface p of capacitor were studied. The results show that, with the increase of the target voltage in a certain range, the desalting capacity increases gradually, and the current efficiency increases first. Reduced trend. The target voltage is too high, the electrode surface polarization is serious, resulting in the pH of the micro-zone on the surface of the electrode. The results show that when the target voltage is 1. 2V and the charging current is 38mA/ g, the desalting capacity of the commercial ACF electrode is 4.92mg/ g, and the current efficiency is 3.2. 3%. Electrochemical characterization verification, resulting in low diffusion of ions on the surface of the electrode The desalting capacity of PAN and N, N-MAA (DMF) was used as spinning precursor, and carbon nanofibers (ECF) were prepared by electrostatic spinning technology. The PAN concentration, spinning voltage and receiving distance were investigated. The results show that the diameter of CNF is 9%, the spinning voltage is 15kV, and the receiving distance is 20cm. An active carbon nanofiber (A-ECNF) was obtained by using ZnCl2 reagent as an activating agent to improve the performance of ECF. It was found that after the activation treatment of ZnCl2, the surface morphology of the fiber remained unchanged, the original good flexibility was still maintained, and the self-supporting electrode could be used as the self-supporting electrode directly for capacitor assembly: the contact angle test showed that after activation, the ECF was activated. The effect of activator amount (ZnCl2/ ECF ratio) on A-ECF was investigated. BET test shows that with the increase of ZnCl2/ ECF ratio, the specific surface area of the fiber gradually increases. When the ratio is 2: 1, the surface area of A-ECF obtained by activation is higher than 0.89m2/ g, and the non-activated ECF ratio surface area is 12. 4m2/ g, cyclic voltammetry and electrochemical impedance tests show that with the increase of ZnCl2/ ECF ratio, the capacitance current of A-ECF electrode increases gradually, the resistance decreases gradually, and the ions are on the surface of the electrode. and 3, assembling the A-ECF activated by ZnCl2 as a self-supporting electrode into a capacitor, carrying out constant-current charge-discharge desalination research, comparing the desalination performance of the A-ECF electrode obtained when the ratio of different ZnCl2/ ECNF is compared, and finding that the ZnCl2 activation can obviously improve the desalination performance of the electrode, When the ratio of ZnCl2/ ECF is 2: 1, the removal of A-ECNF A A-ECF prepared by the ratio of ZnCl2/ ECF to 2: 1 is used as the electrode material, and the charge and discharge stability of the electrode material and the desalting rate of the charging current density, the solution flow rate and the target voltage on the A-ECF electrode are studied. The results show that under proper parameters (charge current density is 36mA/ g, solution flow rate is 10ml/ min; target voltage is 1. 2V), the desalting capacity of A-ECNF electrode is up to 10.2mg/ g, and the current efficiency is 57. 1%. Compared with the existing desalination performance of different electrode materials, the desalting performance of A-ECF and the better carbon material such as carbide are found. The desalination amount of the derived carbon material is comparable. The cycle stability test further indicates that the ZnCl2 activated A-EC
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TQ342.742;TU991.26

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