Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520-8286, USA.
Environ Sci Technol. 2011 May 15;45(10):4360-9. doi: 10.1021/es104325z. Epub 2011 Apr 14.
Pressure retarded osmosis has the potential to produce renewable energy from natural salinity gradients. This work presents the fabrication of thin-film composite membranes customized for high performance in pressure retarded osmosis. We also present the development of a theoretical model to predict the water flux in pressure retarded osmosis, from which we can predict the power density that can be achieved by a membrane. The model is the first to incorporate external concentration polarization, a performance limiting phenomenon that becomes significant for high-performance membranes. The fabricated membranes consist of a selective polyamide layer formed by interfacial polymerization on top of a polysulfone support layer made by phase separation. The highly porous support layer (structural parameter S = 349 μm), which minimizes internal concentration polarization, allows the transport properties of the active layer to be customized to enhance PRO performance. It is shown that a hand-cast membrane that balances permeability and selectivity (A = 5.81 L m(-2) h(-1) bar(-1), B = 0.88 L m(-2) h(-1)) is projected to achieve the highest potential peak power density of 10.0 W/m(2) for a river water feed solution and seawater draw solution. The outstanding performance of this membrane is attributed to the high water permeability of the active layer, coupled with a moderate salt permeability and the ability of the support layer to suppress the undesirable accumulation of leaked salt in the porous support. Membranes with greater selectivity (i.e., lower salt permeability, B = 0.16 L m(-2) h(-1)) suffered from a lower water permeability (A = 1.74 L m(-2) h(-1) bar(-1)) and would yield a lower peak power density of 6.1 W/m(2), while membranes with a higher permeability and lower selectivity (A = 7.55 L m(-2) h(-1) bar(-1), B = 5.45 L m(-2) h(-1)) performed poorly due to severe reverse salt permeation, resulting in a similar projected peak power density of 6.1 W/m(2).
压力延迟渗透有可能从自然盐度梯度中产生可再生能源。本工作介绍了定制高性能压力延迟渗透用薄膜复合膜的制备。我们还提出了一种预测压力延迟渗透中水通量的理论模型，从中可以预测膜可以实现的功率密度。该模型首次将外部浓差极化纳入其中，这是一种对于高性能膜而言具有重要意义的性能限制现象。所制备的膜由界面聚合在相分离得到的聚砜支撑层上形成的选择性聚酰胺层组成。高度多孔的支撑层（结构参数 S = 349 μm）最大限度地减少了内部浓差极化，使活性层的传输特性能够定制，以增强 PRO 性能。结果表明，平衡渗透性和选择性的手铸膜（A = 5.81 L m(-2) h(-1) bar(-1)，B = 0.88 L m(-2) h(-1)）预计将为河水进料溶液和海水汲取溶液实现最高的潜在峰值功率密度 10.0 W/m(2)。该膜的出色性能归因于活性层的高水渗透性，与适中的盐渗透性以及支撑层抑制多孔支撑中泄漏盐的不良积累的能力相结合。选择性更高的膜（即盐渗透性更低，B = 0.16 L m(-2) h(-1)）的水渗透性更低（A = 1.74 L m(-2) h(-1) bar(-1)），峰值功率密度为 6.1 W/m(2)，而渗透性更高、选择性更低的膜（A = 7.55 L m(-2) h(-1) bar(-1)，B = 5.45 L m(-2) h(-1)）由于严重的反向盐渗透而性能不佳，导致相似的预测峰值功率密度为 6.1 W/m(2)。
