Key Laboratory of Integrated Regulation and Resources Development of Shallow Lakes, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China.
Key Laboratory of Integrated Regulation and Resources Development of Shallow Lakes, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China.
Chemosphere. 2018 Feb;193:989-997. doi: 10.1016/j.chemosphere.2017.11.130. Epub 2017 Nov 24.
A long-term performance of membrane capacitive deionization (MCDI) was investigated at the presence of organic matter, which has contributed to the understanding of fouling phenomena and energy efficiency. The commercial humic acid and sodium alginate were adopted as model substances representative of natural organic matter, and different ions including sodium and calcium were selected as important parameters considered in both model substances. The experimental results showed reductions in the salinity removal ability and increments of energy usage due to the organic fouling of ion-exchange membranes and carbon electrodes. Within a time interval of approximately 15 d, reductions of NaCl adsorbance with 5.3 and 3.3 mg per cycle were obtained for humics and alginate, respectively. Simultaneously, the energy consumptions increased by 56.9% for humics and 26.3% for alginate. Furthermore, the results in terms of calcium removal in organic feed and energy usage showed that it had a higher fouling potential in comparison to the ones for the sodium solution with equal conductivity and organic concentration. The morphology and composition of the fouling layer were further studied, and it was found that the organic adsorption onto the electrodes and the attachment or even penetration of organic matter on or into the ion-exchange membrane, which could not be efficiently desorbed during the regeneration cycle, were determined as a key problem of demineralized water production. Therefore, this study suggested the necessity of a pre-treatment to reduce the presence of organic matter for the sustainable operation of MCDI, hereby broaden the potential application fields.
采用商业腐殖酸和海藻酸钠作为天然有机物的模型物质，研究了有机物存在时膜电容去离子（MCDI）的长期性能，有助于理解结垢现象和能量效率。实验结果表明，由于离子交换膜和碳电极的有机物污染，脱盐能力降低，能源消耗增加。在大约 15 天的时间间隔内，腐殖酸和海藻酸钠的每周期氯化钠吸附量分别减少了 5.3 和 3.3 mg。同时，腐殖酸的能耗增加了 56.9%，海藻酸钠的能耗增加了 26.3%。此外，有机进料中钙去除率和能耗的结果表明，与具有同等电导率和有机浓度的钠溶液相比，其具有更高的结垢潜力。进一步研究了结垢层的形态和组成，发现有机物在电极上的吸附以及有机物在或进入离子交换膜上的附着甚至渗透，在再生循环中不能有效地解吸，这是导致除盐水产量下降的一个关键问题。因此，本研究建议在 MCDI 的可持续运行中需要进行预处理以减少有机物的存在，从而拓宽其潜在的应用领域。
