碳纳米管流动电极分散性和悬浮稳定性的优化
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摘要
流动电极作为一种由碳纳米材料、分散剂和去离子水组成的水性悬浮液体系,其良好的材料分散性和悬浮稳定性是确保流动电极电容法去离子装置(FCDI)脱盐性能的关键。本文以碳纳米管(CNT)为流动电极的活性材料,通过磺化剂实现了CNT材料表面的亲水化改性,重点研究分析了CNT改性前后流动电极的比电容、分散性和悬浮稳定性变化规律;探究了水性分散剂种类[十二烷基硫酸钠(SDS)和十六烷基三甲基溴化铵(CTAB)]和含量对流动电极性能的影响。结果表明,改性后的CNT-S流动电极的分散性和悬浮稳定性明显优于CNT流动电极,其比电容略低但比电容的稳定性较高。与CNT-S具有相同电荷特性的分散剂SDS比CTAB更有助于提高CNT-S流动电极的分散性和悬浮稳定性,当SDS比含量为0.6时,CNT-S流动电极的比电容最大,为40.04F/g。在工作电压为1.2V、SDS比含量为0.6、原料液浓度为1.0g/L (NaCl溶液)时,对FCDI装置的脱盐稳定性测试结果表明:装置的初始盐移除效率为51.9%,经20次循环脱盐后其除盐效率仍可保持在51.6%,证明所制备的流动电极具有很好的循环稳定性,为FCDI技术实用化开发提供了实验依据。
The flow-electrode is a suspension system composed of carbon nano-materials, dispersants and deionized water, and its good dispersion and suspension-stability is the key to ensure the high desalination efficiency of the flow-electrode capacitive deionization(FCDI) process. In this paper, thecarbon nanotubes(CNT) as the active materials of flow-electrode was modified by sulfonation to improvethe materials hydrophilicity, and the specific capacitance, dispersion and suspension stability of flow-electrodes of CNT and CNT-S were investigated. The sodium dodecyl sulfate(SDS) and cetyltrimethylammonium bromide(CTAB) were used to examine the effects of dispersants on the performance of flow-electrodes, and the effects of the quality-ratio of dispersants on the performance of flow-electrode were also assessed.The results showed that the CNT-S flow-electrode had a better dispersion and suspension stability than the CNT flow-electrode.In addition,compared with CTAB dispersant,the SDS with identical charge characteristics as CNT-S can enhance the specific capacitance,dispersion and suspension stability of the CNT-S flow-electrode,and the specific capacitance of the CNT-S flowelectrode was 40.04F/g at SDS quality-ratio of 0.6.For the FCDI cell assembled with the CNT-S flowelectrode at 0.6 SDS quality-ratio,the high salt removal efficiency of 51.9%was achieved in 1.0g/L NaCl solution at voltage of 1.2V and the salt removal efficiency of FCDI cell still maintained at 51.6%after 20regeneration cycles,showing that the CNT-S flow-electrode at 0.6 SDS quality-ratio had excellent recycle stability.These results provided the new evidence to the practical application of FCDI process.
The flow-electrode is a suspension system composed of carbon nano-materials, dispersants and deionized water, and its good dispersion and suspension-stability is the key to ensure the high desalination efficiency of the flow-electrode capacitive deionization(FCDI) process. In this paper, thecarbon nanotubes(CNT) as the active materials of flow-electrode was modified by sulfonation to improvethe materials hydrophilicity, and the specific capacitance, dispersion and suspension stability of flow-electrodes of CNT and CNT-S were investigated. The sodium dodecyl sulfate(SDS) and cetyltrimethylammonium bromide(CTAB) were used to examine the effects of dispersants on the performance of flow-electrodes, and the effects of the quality-ratio of dispersants on the performance of flow-electrode were also assessed.The results showed that the CNT-S flow-electrode had a better dispersion and suspension stability than the CNT flow-electrode.In addition,compared with CTAB dispersant,the SDS with identical charge characteristics as CNT-S can enhance the specific capacitance,dispersion and suspension stability of the CNT-S flow-electrode,and the specific capacitance of the CNT-S flowelectrode was 40.04F/g at SDS quality-ratio of 0.6.For the FCDI cell assembled with the CNT-S flowelectrode at 0.6 SDS quality-ratio,the high salt removal efficiency of 51.9%was achieved in 1.0g/L NaCl solution at voltage of 1.2V and the salt removal efficiency of FCDI cell still maintained at 51.6%after 20regeneration cycles,showing that the CNT-S flow-electrode at 0.6 SDS quality-ratio had excellent recycle stability.These results provided the new evidence to the practical application of FCDI process.
引文
[1] JEON S I, PARK H R, YEO J G, et al. Desalination via a newmembrane capacitive deionization process utilizing flow-electrodes[J].Energy&Environmental Science, 2013, 6(5):1471-1475.
[2] HATZELL K B, IWAMA E, FERRIS A, et al. Capacitive deionizationconcept based on suspension electrodes without ion exchangemembranes[J]. Electrochemistry Communications, 2014, 43:18-21.
[3] ROMMERSKIRCHEN A, OHS B, HEPP K A, et al. Modelingcontinuous flow-electrode capacitive deionization processes with ion-exchange membranes[J]. Journal of Membrane Science, 2018, 546:188-196.
[4] PETEK T J, HOYT N C, SAVINELL R F, et al. Characterizing slurryelectrodes using electrochemical impedance spectroscopy[J]. Journal ofthe Electrochemical Society, 2016, 163(1):A5001-A5009.
[5] DENNISON C R, BEIDAGHI M, HATZELL K B, et al. Effects of flowcell design on charge percolation and storage in the carbon slurryelectrodes of electrochemical flow capacitors[J]. Journal of PowerSources, 2014, 247:489-496.
[6] CHOO K Y, YOO C Y, HAN M H, et al. Electrochemical analysis ofslurry electrodes for flow-electrode capacitive deionization[J]. Journalof Electroanalytical Chemistry, 2017, 806:50-60.
[7] YANG S, KIM H, JEON S I, et al. Analysis of the desaltingperformance of flow-electrode capacitive deionization under short-circuited closed cycle operation[J]. Desalination, 2017, 424:110-121.
[8] YANG S, CHOI J, YEO J G, et al. Flow-electrode capacitivedeionization using an aqueous electrolyte with a high salt concentration[J]. Environmental Science&Technology, 2016, 50(11):5892-5899.
[9] LIANG P, SUN X, BIAN Y, et al. Optimized desalination performanceof high voltage flow-electrode capacitive deionization by addingcarbon black in flow-electrode[J]. Desalination, 2017, 420:63-69.
[10] DOORNBUSCH G J, DYKSTRA J E, BIESHEUVEL P M, et al.Fluidized bed electrodes with high carbon loading for waterdesalination by capacitive deionization[J]. Journal of MaterialsChemistry A, 2016, 4(10):3642-3647.
[11] MA J, HE D, TANG W, et al. Development of redox-active flowelectrodes for high-performance capacitive deionization[J]. Environ.Sci. Technol., 2016, 50(24):13495-13501.
[12]周丽霞.非稳态碳纳米管悬浮液的聚集和沉降行为研究[D].南京:南京大学, 2014.ZHOU Lixia. The aggregation and deposition of carbon nanotubes inaqueous solution[D]. Nanjing:Nanjing University, 2014.
[13] YANG K, YI Z L, JING Q F, et al. Dispersion and aggregation ofsingle-walled carbon nanotubes in aqueous solutions of anionicsurfactants[J]. Journal of Zhejiang University SCIENCE A, 2014, 15(8):624-633.
[14]王宝民,韩瑜,宋凯,等.碳纳米管的表面修饰及分散机理研究[J].中国矿业大学学报, 2012(5):758-763.WANG Baomin, HAN Yu, SONG Kai, et al. Research on the surfacedecoration and dispersion of carbon nanotubes[J]. Journal of ChinaUniversity of Mining&Technology, 2012(5):758-763.
[15]方华,孙宇心,荆洁,等.水中多壁碳纳米管的凝聚动力学[J].环境化学, 2015(2):347-351.FANG Hua, SUN Yuxin, JING Jie, et al. Aggregation kinetics of multi-walled carbon nanotubes in aquatic systems[J]. EnvironmentalChemistry, 2015(2):347-351.
[16] AKUZUM B, AGARTAN L, LOCCO J, et al. Effects of particledispersion and slurry preparation protocol on electrochemicalperformance of capacitive flowable electrodes[J]. Journal of AppliedElectrochemistry, 2017, 47(3):369-380.
[17] ROMMERSKIRCHEN A, GENDEL Y, WESSLING M. Singlesdesalination[J]. Electrochemistry Communications, 2015, 60:34-37.
[18] JEON S I, YEO J G, YANG S, et al. Ion storage and energy recovery ofa flow-electrode capacitive deionization process[J]. Journal ofMaterials Chemistry A, 2014, 2(18):6378.
[19] PARK H R, CHOI J, YANG S, et al. Surface-modified sphericalactivated carbon for high carbon loading and its desalting performancein flow-electrode capacitive deionization[J]. RSC Adv., 2016, 6(74):69720-69727.
[2] HATZELL K B, IWAMA E, FERRIS A, et al. Capacitive deionizationconcept based on suspension electrodes without ion exchangemembranes[J]. Electrochemistry Communications, 2014, 43:18-21.
[3] ROMMERSKIRCHEN A, OHS B, HEPP K A, et al. Modelingcontinuous flow-electrode capacitive deionization processes with ion-exchange membranes[J]. Journal of Membrane Science, 2018, 546:188-196.
[4] PETEK T J, HOYT N C, SAVINELL R F, et al. Characterizing slurryelectrodes using electrochemical impedance spectroscopy[J]. Journal ofthe Electrochemical Society, 2016, 163(1):A5001-A5009.
[5] DENNISON C R, BEIDAGHI M, HATZELL K B, et al. Effects of flowcell design on charge percolation and storage in the carbon slurryelectrodes of electrochemical flow capacitors[J]. Journal of PowerSources, 2014, 247:489-496.
[6] CHOO K Y, YOO C Y, HAN M H, et al. Electrochemical analysis ofslurry electrodes for flow-electrode capacitive deionization[J]. Journalof Electroanalytical Chemistry, 2017, 806:50-60.
[7] YANG S, KIM H, JEON S I, et al. Analysis of the desaltingperformance of flow-electrode capacitive deionization under short-circuited closed cycle operation[J]. Desalination, 2017, 424:110-121.
[8] YANG S, CHOI J, YEO J G, et al. Flow-electrode capacitivedeionization using an aqueous electrolyte with a high salt concentration[J]. Environmental Science&Technology, 2016, 50(11):5892-5899.
[9] LIANG P, SUN X, BIAN Y, et al. Optimized desalination performanceof high voltage flow-electrode capacitive deionization by addingcarbon black in flow-electrode[J]. Desalination, 2017, 420:63-69.
[10] DOORNBUSCH G J, DYKSTRA J E, BIESHEUVEL P M, et al.Fluidized bed electrodes with high carbon loading for waterdesalination by capacitive deionization[J]. Journal of MaterialsChemistry A, 2016, 4(10):3642-3647.
[11] MA J, HE D, TANG W, et al. Development of redox-active flowelectrodes for high-performance capacitive deionization[J]. Environ.Sci. Technol., 2016, 50(24):13495-13501.
[12]周丽霞.非稳态碳纳米管悬浮液的聚集和沉降行为研究[D].南京:南京大学, 2014.ZHOU Lixia. The aggregation and deposition of carbon nanotubes inaqueous solution[D]. Nanjing:Nanjing University, 2014.
[13] YANG K, YI Z L, JING Q F, et al. Dispersion and aggregation ofsingle-walled carbon nanotubes in aqueous solutions of anionicsurfactants[J]. Journal of Zhejiang University SCIENCE A, 2014, 15(8):624-633.
[14]王宝民,韩瑜,宋凯,等.碳纳米管的表面修饰及分散机理研究[J].中国矿业大学学报, 2012(5):758-763.WANG Baomin, HAN Yu, SONG Kai, et al. Research on the surfacedecoration and dispersion of carbon nanotubes[J]. Journal of ChinaUniversity of Mining&Technology, 2012(5):758-763.
[15]方华,孙宇心,荆洁,等.水中多壁碳纳米管的凝聚动力学[J].环境化学, 2015(2):347-351.FANG Hua, SUN Yuxin, JING Jie, et al. Aggregation kinetics of multi-walled carbon nanotubes in aquatic systems[J]. EnvironmentalChemistry, 2015(2):347-351.
[16] AKUZUM B, AGARTAN L, LOCCO J, et al. Effects of particledispersion and slurry preparation protocol on electrochemicalperformance of capacitive flowable electrodes[J]. Journal of AppliedElectrochemistry, 2017, 47(3):369-380.
[17] ROMMERSKIRCHEN A, GENDEL Y, WESSLING M. Singlesdesalination[J]. Electrochemistry Communications, 2015, 60:34-37.
[18] JEON S I, YEO J G, YANG S, et al. Ion storage and energy recovery ofa flow-electrode capacitive deionization process[J]. Journal ofMaterials Chemistry A, 2014, 2(18):6378.
[19] PARK H R, CHOI J, YANG S, et al. Surface-modified sphericalactivated carbon for high carbon loading and its desalting performancein flow-electrode capacitive deionization[J]. RSC Adv., 2016, 6(74):69720-69727.
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