Thin film composite membrane compaction in high-pressure reverse osmosis
Thin film composite membrane compaction in high-pressure reverse osmosis
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DOI：
10.1016/j.memsci.2020.118268
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发表时间：
2020-09-01
影响因子：
9.5
通讯作者：
Elimelech, Menachem
中科院分区：
文献类型：
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作者：
Davenport, Douglas M.;Ritt, Cody L.;Elimelech, Menachem
在几乎所有压力驱动的膜过程中都观察到在施加的液压下膜变形（通常称为压实）。最值得注意的是，压实会降低传统反渗透 (RO) 中的水渗透性，并且预计会严重阻碍用于高盐水淡化的高压反渗透 (HPRO)。在这项工作中，我们证明压实会降低商用 RO 膜的水渗透率，从 70 bar 施加液压时的 2.0 L m(-2) h(-1) bar(-1) 降低到 150 bar 时的 1.3 L m(-2) h(-1) ba(r-)1。压实的形态影响主要与支撑层的变化有关，在 150 bar 液压压力下压实后，观察到横截面厚度减少了 60%。相反，正电子湮没寿命光谱表明选择性层不会不可逆地致密。研究发现，驱动压实的机制是选择性层和支撑层界面上的水压差异。我们进一步发现压实可以将支撑层表面孔隙率降低多达 95%。这种孔隙度的降低被认为是压实引起的透水率下降的原因，而选择性层的固有渗透率不受压实的影响。因此，我们得出结论，支撑层的压实对复合膜的性能有着不可避免的影响。最后，我们提出了开发抗压膜的建议，这些膜可以在高压膜应用（例如 HPRO）中保持高透水性，从而保持良好的海水淡化性能。
Membrane deformation under an applied hydraulic pressure, often termed compaction, is observed in almost all pressure-driven membrane processes. Most notably, compaction decreases water permeability in conventional reverse osmosis (RO) and is expected to critically hinder high-pressure reverse osmosis (HPRO) for hypersaline brine desalination. In this work, we demonstrated that compaction decreases the water permeability of com-mercial RO membranes from 2.0 L m(-2) h(-1) bar(-1) at 70 bar applied hydraulic pressure to 1.3 L m(-2) h(-1) ba(r-)1 at 150 bar. The morphological effects of compaction were primarily associated with changes in the support layer, where a similar to 60% decrease in cross-sectional thickness is observed following compaction at 150 bar hydraulic pressure. In contrast, positron annihilation lifetime spectroscopy demonstrates that the selective layer does not compact irreversibly. The mechanism that drives compaction was found to be the difference in hydraulic pres-sure across the interface of the selective and support layers. We further found that compaction can reduce the support layer surface porosity by up to similar to 95%. This decreased porosity is identified as the cause for compaction -induced water permeability decline, while the intrinsic permeability of the selective layer is not influenced by compaction. As such, we conclude that compaction of the support layer has an inextricable impact on composite membrane performance. Finally, we propose recommendations for developing compaction-resistant membranes that can maintain high water permeability, and thus good desalination performance, in high-pressure membrane applications, such as HPRO.