基于支撑层表面孔结构重构法的正渗透膜的制备与性能研究

Preparation and performance evaluation of forward osmosis membrane based on a support surface pore structure re-construction method

支撑层孔隙率是影响复合正渗透膜(TFC FO)水通量的重要因素之一.本研究采用了一种表面孔结构重构法对支撑层进行改性,以调控支撑层的孔隙率,进而提高正渗透膜的水通量.探究了重构剂中溶剂种类(N,N-二甲基甲酰胺(DMF),N,N-二甲基乙酰胺(DMAc),N-甲基吡咯烷酮(NMP))和非溶剂种类(水,乙醇,异丙醇)对FO膜水通量的影响.结果表明,当DMAc为溶剂,水为非溶剂时,制备的FO膜具有较高的水通量.在此基础上,重点研究了重构剂中溶剂与非溶剂的体积比(DMAc/水)以及重构剂与支撑层接触时间对支撑层孔隙率以及FO膜水通量的影响规律.结果表明,随着DMAc/水体积比的增大或接触时间的增加,支撑层孔隙率以及FO膜水通量均表现出先增加后减少的规律;且在DMAc/水体积比为30/70,接触时间为3 s时,支撑层孔隙率达到最大值,制备的FO膜具有最高的水通量.以1 mol/L NaCl为汲取液,去离子水为原料液,膜的活性层朝向原料液(AL-FS)模式下,改性FO膜水通量J_w可达20.06 L/(m^2·h),相比于无改性FO膜增加了50%.

The porosity of the support layer is one of the important factors affecting the separating performance of the thin film composite (TFC) forward osmosis (FO) membrane. A support surface pore structure re-construction method was developed to modify the support layer and regulate the porosity of the support layer, thereby improving the water flux of the FO membrane. The effects of solvent categories ( N,N -dimethylformamide, N,N -dimethylacetamide, and N -methyl pyrrolidone) and non-solvent categories (water, ethanol, and isopropanol) on the forward osmosis membrane water flux were researched in the re-constructing agent . The results show that, the FO membrane has higher water flux when DMAc was used as the solvent and water as non-solvent. Furthermore, when the re-constructing agent is aqueous solution of DMAc, the porosity of the support layer and the water flux of the forward osmosis membrane were mainly investigated, as the function of the volume ratio of the DMAc/water in the re-constructing agent and the contact time of the re-constructing agent. The results show that, with increasing the volume ratio and the contact time, the porosity of the support layer and the water flux of the forward osmosis membrane increase firstly and then decrease. Under the conditions that the re-constructing agent is aqueous solution of DMAc with volume ratio of 30/70, and the contacting time is 3 s, the support porosity achieves the largest value, and the water flux of the prepared forward osmosis membrane is optimal. When using 1 mol/L NaCl as draw solution and deionized water as feed solution , and the separating layer of membrane is faced to the feed solution (AL FS), the water flux of the modified forward osmosis membrane reaches up to 20.06 L/(m^ 2·h), exhibiting a 50% higher flux compared to the unmodified membrane.