Experimental design and optimization of asymmetric flat-sheet membranes prepared for direct contact membrane distillation
Experimental design and optimization of asymmetric flat-sheet membranes prepared for direct contact membrane distillation
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DOI：
10.1016/j.memsci.2010.01.057
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发表时间：
2010-04
影响因子：
9.5
通讯作者：
M. Khayet;C. Cojocaru;M. García-Payo
中科院分区：
文献类型：
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作者：
M. Khayet;C. Cojocaru;M. García-Payo
采用基于分数析因设计的相转化技术制备了聚偏氟乙烯-共六氟丙烯（PVDF-HFP）薄膜。采用统计方法研究了浇注液中聚合物和添加剂（聚乙二醇，PEG）浓度、溶剂蒸发时间和凝固浴温度对所制备膜的结构特性和直接接触膜蒸馏（DCMD）性能的影响。利用扫描电子显微镜、原子力显微镜和空隙体积分数对膜的形态特性进行了研究。建立了影响dmd反应的因子线性模型，即纯水渗透通量、盐溶液渗透通量和膜的阻盐系数。方差分析表明，各因素对反应均有显著影响。混凝浴温度是影响最小的因素，而PVDF-HFP浓度对渗透通量和阻盐系数的影响最大。采用最小实验次数和拉格朗日乘子优化方法对膜的制备条件进行了优化。在获得的最优条件下，可得到19.1wt。% PVDF-HFP浓度，4.99wt。聚乙二醇浓度为%、混凝浴温度为35℃、溶剂蒸发时间为102s时，膜的阻盐系数最高，达到99.95%，渗透通量为4.41L/hm2。
Flat-sheet poly(vinylidene fluoride-co-hexafluoropropylene), PVDF-HFP, membranes have been prepared using the phase inversion technique based on fractional factorial design. Combined effects of polymer and additive (polyethylene glycol, PEG) concentrations in the casting solutions, solvent evaporation time and coagulation bath temperature on the structural characteristics of the prepared membranes as well as on their direct contact membrane distillation (DCMD) performance have been investigated using statistical approach. The morphological properties of the membranes have been studied in terms of scanning electron microscopy, atomic force microscopy and void volume fraction. The factorial linear models have been developed to describe the main effects of factors on the DCMD responses namely, pure water permeation flux, permeate flux when using salt solution and salt rejection coefficient of the prepared membranes. Analysis of variance showed that all factors have significant effects on the responses. However, the coagulation bath temperature is the least influential factor, while the PVDF-HFP concentration has the greatest effects on both the permeate flux and the salt rejection coefficient. Optimization of membrane preparation conditions has been carried out using a minimum number of experiments and applying Lagrange multipliers optimization method. Under the obtained optimum conditions, 19.1wt.% PVDF-HFP concentration, 4.99wt.% PEG concentration, 35°C coagulation bath temperature and 102s solvent evaporation time, the prepared membrane exhibits the highest salt rejection coefficient, 99.95%, with a permeate flux of 4.41L/hm2.