School of Civil and Environmental Engineering, Kookmin University, Jeongneung-Dong, Seongbuk-Gu, Seoul 136-702, Republic of Korea.
Korea Institute of Construction Technology, 2311 Daehwa-Dong, Ilsan-Gu, Goyang-Si, Gyeonggi-Do 411-712, Republic of Korea.
Ultrason Sonochem. 2018 Mar;41:475-483. doi: 10.1016/j.ultsonch.2017.10.005. Epub 2017 Oct 5.
Unlike reverse osmosis (RO) that is dominated by the hydraulic pressure differential, forward osmosis (FO) uses the osmotic pressure gradient as the driving force between a dilute feed solution and a concentrated draw solution across a membrane. High pressure is not required in FO, which means that FO can be used as an alternative to RO as an energy-saving separation process in desalination technology. However, a major limiting factor of the FO process is the internal concentration polarization (ICP). Because of the stagnant environment inside the porous supporting layer of a FO membrane, it is difficult to mitigate the ICP by simply increasing the shear stress or promoting turbulence. In this study, the ICP is reduced by ultrasound. The effect of the ultrasound frequency and output power on the ICP coefficient is investigated in a flat-sheet FO membrane module with counter-current flow. The ultrasound frequency and output power are varied between 25, 45, and 72 kHz and over the range of 10-70 W, respectively. NaCl solution is used as both the feed and draw solution. The results illustrate that moderate ultrasonic irradiation is effective for reducing the ICP in a FO process. A modified solution-diffusion model based on film theory is used to assess the effect of ultrasound on the ICP in a FO process. The ICP coefficient is estimated using this model.
不同于以水力压差为主导的反渗透（RO），正向渗透（FO）利用渗透压梯度作为膜两侧稀料液和浓汲取液之间的驱动力。FO 不需要高压，这意味着 FO 可以替代 RO 成为海水淡化技术中的节能分离过程。然而，FO 过程的一个主要限制因素是内部浓差极化（ICP）。由于 FO 膜多孔支撑层内部的停滞环境，仅通过增加剪切应力或促进湍流很难减轻 ICP。在这项研究中，利用超声波来降低 ICP。在具有逆流的平板 FO 膜组件中，研究了超声波频率和输出功率对 ICP 系数的影响。超声波频率和输出功率分别在 25、45 和 72 kHz 之间变化，范围在 10-70 W 之间。NaCl 溶液同时用作料液和汲取液。结果表明，适度的超声辐照可有效降低 FO 过程中的 ICP。使用基于薄膜理论的改进溶液扩散模型来评估超声波对 FO 过程中 ICP 的影响。使用该模型估算 ICP 系数。
