炭黑流动电极的孔径分布对流动电极电容去离子脱盐性能的影响

Effect of pore size distribution of carbon black flow electrode on the desalination of flow electrode capacitive deionization

流动电极电容去离子(flow electrode capacitive deionization,FCDI)主要依靠流动电极的电吸附来实现离子去除。而其中流动电极的孔径分布是影响FCDI的脱盐性能的重要因素。为此,选择4种具有高导电性的炭黑(carbon black,CB)作为流动电极,考察了流动电极的孔径分布对FCDI脱盐性能的影响。结果表明,在隔离闭合循环(isolated closed-cycle,ICC)模式下,脱盐性能与流动电极的比表面积呈正相关(r=0.918),并主要受介孔面积的影响。在单循环(single cycle,SC)模式下,FCDI的脱盐性能与介孔面积呈正相关(r=0.583),与微孔面积呈负相关(r=-0.725)。当使用介孔面积最大的炭黑作为流动电极时,离子在流动电极表面的解吸速率升高了53%,FCDI的脱盐率提高了702%。吸附-解吸实验结果表明,由于微孔存在尺寸小、吸附-解吸路径长等缺点,使被流动电极吸附的离子难以被快速解吸,从而抑制了在SC模式下流动电极的再生。介孔可强化FCDI在2种操作模式下的脱盐性能;而微孔却抑制了SC模式下的离子解吸,从而降低了FCDI的脱盐性能。以上研究结果可为流动电极的设计和选择提供参考。

Flow electrode capacitive deionization(FCDI)mainly relies on the electro-adsorption of the flow electrode to realize ion removal.Among them,the pore size distribution of flow electrode is an important factor affecting the desalination performance of FCDI.Therefore,four kinds of carbon black(CB)with high conductivity were selected as flow electrodes,and the influence of pore size distribution of flow electrodes on the desalination performance of FCDI was investigated.The results showed that in the isolated closed-cycle(ICC)mode,the desalination performance was positively correlated with the specific surface area of the flow electrode(r=0.918),and was mainly affected by the mesoporous area.In the single cycle(SC)mode,the desalination performance of FCDI was positively correlated with mesopore area(r=0.583)and negatively correlated with micropore area(r=-0.725).When carbon black with the largest mesoporous area was used as the flow electrode,the desorption rate of ions on the surface of the flow electrode increased by 53%,and the desalination rate of FCDI increased by 702%.The results of adsorption-desorption experiments showed that due to weakness of micropores such as small size and long path for adsorption-desorption,the rapid desorption for the ions absorbed by the flow electrode was difficult,which inhibited the regeneration of the flow electrode in SC mode.Mesopores could strengthen the desalination performance of FCDI in two operation modes,while micropore limited the desorption of ions in SC mode and the desalination performance of FCDI was weakened.The results can provide a reference for design and selection of the flow electrode.