Experimental design and optimization of asymmetric flat-sheet membranes prepared for direct contact membrane distillation

Abstract 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, 19.1 wt.% PVDF-HFP concentration, 4.99 wt.% PEG concentration, 35 °C coagulation bath temperature and 102 s solvent evaporation time, the prepared membrane exhibits the highest salt rejection coefficient, 99.95%, with a permeate flux of 4.41 L/h m2.

[1]  Baoli Shi,et al.  Preparation and properties of microporous membrane from poly(vinylidene fluoride-co-tetrafluoroethylene) (F2.4) for membrane distillation , 2004 .

[2]  Grazyna Zakrzewska-Trznadel,et al.  Response surface methodology for the modelling of copper removal from aqueous solutions using micellar-enhanced ultrafiltration , 2008 .

[3]  M. Qtaishat,et al.  Novel porous composite hydrophobic/hydrophilic polysulfone membranes for desalination by direct contact membrane distillation , 2009 .

[4]  Wing-Hong Chan,et al.  Fabrication of nanofiltration membranes with tunable separation characteristics using methods of uniform design and regression analysis , 2003 .

[5]  Mohd Yusof Noordin,et al.  Application of response surface methodology in describing the performance of thin film composite membrane , 2006 .

[6]  Mohamed Khayet,et al.  Porous hydrophobic/hydrophilic composite membranes: Application in desalination using direct contact membrane distillation , 2005 .

[7]  Mohamed Khayet,et al.  Response surface modelling and optimization in pervaporation , 2008 .

[8]  Cavus Falamaki,et al.  Taguchi design of experiments approach to the manufacture of one-step alumina microfilter/membrane supports by the centrifugal casting technique , 2008 .

[9]  Mohamed Khayet,et al.  Characterization of membranes for membrane distillation by atomic force microscopy and estimation of their water vapor transfer coefficients in vacuum membrane distillation process , 2004 .

[10]  Jeremiah J. Zartman,et al.  Flow-visualization during macrovoid pore formation in dry-cast cellulose acetate membranes , 2003 .

[11]  C. A. Smolders,et al.  Phase separation phenomena in solutions of polysulfone in mixtures of a solvent and a nonsolvent: relationship with membrane formation* , 1985 .

[12]  Mohamed Khayet,et al.  A framework for better understanding membrane distillation separation process , 2006 .

[13]  M. C. García-Payo,et al.  Effects of PVDF-HFP concentration on membrane distillation performance and structural morphology of hollow fiber membranes , 2010 .

[14]  T. Mohammadi,et al.  Experimental design in mullite microfilter preparation , 2005 .

[15]  José M. Gozálvez-Zafrilla,et al.  Mixture design applied to describe the influence of ionic composition on the removal of nitrate ions using nanofiltration , 2005 .

[16]  Kai Yu Wang,et al.  Hydrophobic PVDF hollow fiber membranes with narrow pore size distribution and ultra-thin skin for the fresh water production through membrane distillation , 2008 .

[17]  Juin-Yih Lai,et al.  Effect of nonsolvent additives on the porosity and morphology of asymmetric TPX membranes , 1996 .

[18]  Elisa Barbosa-Coutinho,et al.  Preparation of carbon hollow fiber membranes by pyrolysis of polyetherimide , 2003 .

[19]  Mohamed Khayet,et al.  Application of response surface methodology and experimental design in direct contact membrane distillation , 2007 .

[20]  M. Qtaishat,et al.  Design of novel direct contact membrane distillation membranes , 2006 .

[21]  Norman N. Li.  Advanced membrane technology and applications , 2008 .

[22]  Sina Bonyadi,et al.  Flux enhancement in membrane distillation by fabrication of dual layer hydrophilic–hydrophobic hollow fiber membranes , 2007 .

[23]  M. Khayet.  The effects of air gap length on the internal and external morphology of hollow fiber membranes , 2003 .

[24]  Bing Wu,et al.  Removal of 1,1,1-trichloroethane from water using a polyvinylidene fluoride hollow fiber membrane module: Vacuum membrane distillation operation , 2006 .

[25]  Jan Feijen,et al.  Phase-Separation Processes in Polymer-Solutions in Relation to Membrane Formation , 1996 .

[26]  X. Tan,et al.  Removal of Benzene/Toluene from Water by Vacuum Membrane Distillation in a PVDF Hollow Fiber Membrane Module , 2005 .

[27]  V. Musil,et al.  The wet phase separation: the effect of cast solution thickness on the appearance of macrovoids in the membrane forming ternary cellulose acetate/acetone/water system , 2002 .

[28]  Mohamed Khayet,et al.  Modelling mass transport through a porous partition: Effect of pore size distribution , 2004 .

[29]  Mohamed Khayet,et al.  Pervaporation and vacuum membrane distillation processes: Modeling and experiments , 2004 .

[30]  M. Gonçalves,et al.  Asymmetric polysulfone and polyethersulfone membranes: effects of thermodynamic conditions during formation on their performance , 2000 .

[31]  J. M. Zárate,et al.  Characterization of membrane distillation membranes prepared by phase inversion , 1995 .

[32]  Grazyna Zakrzewska-Trznadel,et al.  Response surface modeling and optimization of copper removal from aqua solutions using polymer assisted ultrafiltration , 2007 .

[33]  Wang Wei,et al.  Optimization of preparation conditions for polydimethylsiloxane (PDMS)/ceramic composite pervaporation membranes using response surface methodology , 2008 .

[34]  M. Sadrzadeh,et al.  Effect of preparation variables on morphology and pure water permeation flux through asymmetric cellulose acetate membranes , 2009 .

[35]  Ahmad Fauzi Ismail,et al.  Development of defect-free asymmetric polysulfone membranes for gas separation using response surface methodology , 2004 .

[36]  Nidal Hilal,et al.  Response surface modeling and optimization of composite nanofiltration modified membranes , 2010 .