Microbubble aeration enhances performance of vacuum membrane distillation desalination by alleviating membrane scaling.
Microbubble aeration enhances performance of vacuum membrane distillation desalination by alleviating membrane scaling.
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DOI：
10.1016/j.watres.2018.11.048
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发表时间：
2019-02
期刊：
影响因子：
12.8
通讯作者：
Yubing Ye;Shuili Yu;Li'an Hou;Bao-Ming Liu;Qing Xia;Guicai Liu;Pan Li
中科院分区：
文献类型：
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作者：
Yubing Ye;Shuili Yu;Li'an Hou;Bao-Ming Liu;Qing Xia;Guicai Liu;Pan Li
膜污染，特别是由于盐晶体形成和膜表面沉积而导致的无机污染，仍然是膜蒸馏（MD）应用中的主要技术问题。在这项研究中，微泡曝气 (MBA) 被纳入实验室规模的真空膜蒸馏 (VMD) 装置中，并检查了其对海水淡化过程的影响。在没有MBA的情况下，模拟高盐海水（100g.L−1盐浓度）的脱盐过程中发生了严重的膜结垢，导致120min后渗透通量急剧下降至基本为零。扫描电镜显示，膜表面均匀覆盖有一层大的长方体盐晶体。然而，MBA 的引入减轻了膜结垢，从而提高了 VMD 海水淡化性能，这与微泡 (MB) 发生器中的泵压呈正相关。结果表明，当泵压分别为0.1、0.2、0.3和0.4MPa时，VMD海水淡化处理周期的有效处理时间分别延长至150、180、300和360min以上（对比无MBA时为120 min），导致累计产水量增加。进一步的研究发现，在较高的泵压下会产生更多数量的较小尺寸的MB，这更有利于增加水蒸气的产生和减轻盐析出。蒸馏水（约-30mV）和SW100溶液（约-2mV）中MB之间的zeta电位差表明，MBA不仅通过提高膜表面的表面剪切速率有效减轻了浓差极化的负面影响，而且可能由于MB将反离子吸引到气水界面而减少了盐沉淀。最后，对改进的 VMD 海水淡化工艺的能耗分析表明，MBA 虽然在不同泵压下仅增加总能耗约 3%，但能够改善单位能耗，特别是在较高泵压下。总之，这些结果表明 MBA 是提高 VMD 海水淡化性能的有效方法。
Membrane fouling, especially inorganic fouling due to salt crystal formation and deposition on the membrane surface, is still a major technical issue in membrane distillation (MD) applications. In this study, microbubble aeration (MBA) was included in a laboratory-scale vacuum membrane distillation (VMD) rig and its effect on a desalination process was examined. Without MBA, serious membrane scaling occurred during desalination of simulated high-salinity sea water (100 g.L−1salt concentration), which resulted in a dramatic reduction of permeate flux to essentially zero after 120 min. Scanning electron microscopy showed that a layer of large cuboid salt crystals uniformly covered the membrane surface. However, membrane scaling was mitigated with the introduction of MBA, resulting in the improved VMD desalination performance, which was positively correlated with pump pressure in the microbubble (MB) generator. Results showed that the effective processing time of the VMD desalination processing cycle was respectively prolonged to 150, 180, and more than 300 and 360 min (cf. 120 min without MBA) when the pump pressure was respectively at 0.1, 0.2, 0.3 and 0.4 MPa, leading to the increase of cumulative water production. Further studies found that larger numbers of MBs of smaller size were produced at higher pump pressure, which are more beneficial for increasing water vapor production and alleviating salt precipitation. The difference in zeta potential between the MBs in distilled water (about −30 mV) and that in SW100 solution (about -2 mV) demonstrated that MBA not only effectively mitigated the negative effect of concentration polarization by enhancing the surface shear rate at the membrane surface, but also reduced salt precipitation probably due to the MBs attracting counterions to the gas-water interface. Finally, energy consumption analysis of the modified VMD desalination process revealed that MBA, while itself only adding about 3% to the total energy consumption at varied pump pressures, was able to improve the specific energy consumption, especially at higher pump pressures. Together, these results demonstrate that MBA is an effective way of improving the performance of VMD desalination of water.