Environment and Membrane Technology Laboratory, Department of Chemical Engineering, National Institute of Technology Durgapur, Durgapur, 713209, India.
Environ Sci Pollut Res Int. 2015 Aug;22(15):11401-11. doi: 10.1007/s11356-015-4333-x. Epub 2015 Mar 27.
For purifying fluoride-contaminated water, a new forward osmosis scheme in horizontal flat-sheet cross flow module was designed and investigated. Effects of pressure, cross flow rate, draw solution and alignment of membrane module on separation and flux were studied. Concentration polarization and reverse salt diffusion got significantly reduced in the new hydrodynamic regime. This resulted in less membrane fouling, better solute separation and higher pure water flux than in a conventional module. The entire scheme was completed in two stages-an upstream forward osmosis for separating pure water from contaminated water and a downstream nanofiltration operation for continuous recovery and recycle of draw solute. Synchronization of these two stages of operation resulted in a continuous, steady-state process. From a set of commercial membranes, two polyamide composite membranes were screened out for the upstream and downstream filtrations. A 0.3-M NaCl solution was found to be the best one for forward osmosis draw solution. Potable water with less than 1% residual fluoride could be produced at a high flux of 60-62 L m(-2) h(-1) whereas more than 99% draw solute could be recovered and recycled in the downstream nanofiltration stage from where flux was 62-65 L m(-2) h(-1).
为了净化含氟水，设计并研究了一种新型水平平板式错流膜组件中的正向渗透方案。考察了压力、错流速度、汲取液和膜组件排列方式对分离和通量的影响。在新的流体动力学条件下，浓差极化和反向盐扩散得到了显著抑制。这导致膜污染减轻，溶质分离更好，纯水通量更高，优于传统模块。整个方案分两个阶段完成-上游正向渗透将纯水与污染水分离，下游纳滤操作连续回收和再循环汲取液。这两个操作阶段的同步实现了连续稳定的过程。从一组商业膜中筛选出两种聚酰胺复合膜，分别用于上游和下游过滤。发现 0.3-M NaCl 溶液是正向渗透汲取液的最佳选择。在 60-62 L m(-2) h(-1)的高通量下，可以生产出残留氟化物低于 1%的饮用水，而在下游纳滤阶段，超过 99%的汲取液可以被回收和再循环，通量为 62-65 L m(-2) h(-1)。
