Department of Chemical and Environmental Engineering, University of California, Riverside , Riverside, California 92521, United States.
Department of Energy, National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
ACS Appl Mater Interfaces. 2017 Nov 8;9(44):38594-38605. doi: 10.1021/acsami.7b12615. Epub 2017 Oct 30.
The desalination of inland brackish groundwater offers the opportunity to provide potable drinking water to residents and industrial cooling water to industries located in arid regions. Geothermal brines are used to generate electricity, but often contain high concentrations of dissolved salt. Here, we demonstrate how the residual heat left in spent geothermal brines can be used to drive a membrane distillation (MD) process and recover desalinated water. Porous polypropylene membranes were coated with a carbon nanotube (CNT)/poly(vinyl alcohol) layer, resulting in composite membranes having a binary structure that combines the hydrophobic properties critical for MD with the hydrophilic and conductive properties of the CNTs. We demonstrate that the addition of the CNT layer increases membrane flux due to enhanced heat transport from the bulk feed to the membrane surface, a result of CNT's high thermal transport properties. Furthermore, we show how hydroxide ion generation, driven by water electrolysis on the electrically conducting membrane surface, can be used to efficiently dissolve silicate scaling that developed during the process of desalinating the geothermal brine, negating the need for chemical cleaning.
内陆咸水的脱盐为干旱地区的居民提供了可饮用的饮用水，并为工业提供了工业冷却用水。地热水被用来发电，但通常含有高浓度的溶解盐。在这里，我们展示了如何利用废地热水中残留的余热来驱动膜蒸馏（MD）过程并回收脱盐水。多孔聚丙烯膜涂覆有碳纳米管（CNT）/聚乙烯醇（PVA）层，从而形成具有二元结构的复合膜，该二元结构将 MD 所需的疏水性与 CNT 的亲水性和导电性结合在一起。我们证明，由于 CNT 的高导热性能，从主体进料到膜表面的热传递增强，添加 CNT 层会增加膜通量。此外，我们展示了如何通过在导电膜表面上进行水电解来生成氢氧根离子，从而有效地溶解在脱盐地热水过程中形成的硅酸盐结垢，从而无需进行化学清洗。
