Fabrication and positron annihilation spectroscopy (PAS) characterization of cellulose triacetate membranes for forward osmosis

Abstract Cellulose triacetate (CTA) membranes for forward osmosis (FO) were fabricated in this study. The fundamental engineering and science of CTA membrane formation were explored by casting the membranes from different solvent systems and characterizing the membranes’ morphology using advanced tools such as positron annihilation spectroscopy (PAS). N -Methyl-2-pyrrolidone (NMP) and dioxane were used as the solvents for CTA in the membrane fabrication process. It was found that the choice of solvents for membrane fabrication significantly affects the morphology of as-cast membranes and their FO performance. The CTA membrane cast using NMP as the main solvent has shown poor NaCl rejection but high water flux, whereas the CTA membrane cast using dioxane as the main solvent has excellent NaCl rejection but low water flux. SEM and PAS data reveal that the sublayer of CTA membranes cast from dioxane has a close-cell and much denser structure compared to that cast from NMP. As a result, the former has a significantly lower water flux than the latter in the FO process (5 vs. 27 LMH) using a 2 M NaCl draw solution. Surprisingly, with the addition of acetic acid into the dioxane/acetone solvent system, the resulting membrane has a significantly more porous and open-cell sublayer structure. In addition to the pore forming ability of acetic acid, FTIR spectra confirm the formation of acetic acid/dioxane complexes in the casting solution. Thus, as validated by PAS spectra, the free volume of the active layer of the resultant CTA membranes increases after the addition of acetic acid into the dioxane/acetone casting solution and the water flux increases to 23 LMH using a 2 M NaCl draw solution. Molecular simulations were also conducted to examine CTA polymeric chains in different solvent systems and to witness different CTA chain behaviors in these solvents that leads to significant differences in the as-cast membranes’ morphology.

[1]  C. Wilke,et al.  Correlation of diffusion coefficients in dilute solutions , 1955 .

[2]  Sherub Phuntsho,et al.  A novel low energy fertilizer driven forward osmosis desalination for direct fertigation: Evaluating , 2011 .

[3]  Tai‐Shung Chung,et al.  Formation of ultrathin high-performance polyethersulfone hollow-fiber membranes , 1997 .

[4]  Sui Zhang,et al.  Molecular design of the cellulose ester-based forward osmosis membranes for desalination , 2011 .

[5]  Ming Ming Ling,et al.  Desalination process using super hydrophilic nanoparticles via forward osmosis integrated with ultrafiltration regeneration , 2011 .

[6]  James E. Miller,et al.  Forward osmosis :a new approach to water purification and desalination. , 2006 .

[7]  Chuyang Y. Tang,et al.  Modeling double-skinned FO membranes , 2011 .

[8]  Menachem Elimelech,et al.  Energy requirements of ammonia-carbon dioxide forward osmosis desalination , 2007 .

[9]  Kai Yu Wang,et al.  Developing thin‐film‐composite forward osmosis membranes on the PES/SPSf substrate through interfacial polymerization , 2012 .

[10]  Kai Yu Wang,et al.  Double-Skinned Forward Osmosis Membranes for Reducing Internal Concentration Polarization within the Porous Sublayer , 2010 .

[11]  Menachem Elimelech,et al.  A novel ammonia-carbon dioxide forward (direct) osmosis desalination process , 2005 .

[12]  Yi-Ming Sun,et al.  Applications of positron annihilation spectroscopy to polymeric membranes , 2008 .

[13]  Robert L McGinnis,et al.  Desalination by ammonia–carbon dioxide forward osmosis: Influence of draw and feed solution concentrations on process performance , 2006 .

[14]  Chuyang Y. Tang,et al.  Coupled effects of internal concentration polarization and fouling on flux behavior of forward osmosis membranes during humic acid filtration , 2010 .

[15]  Kai Yu Wang,et al.  The characterization of flat composite nanofiltration membranes and their applications in the separation of Cephalexin , 2005 .

[16]  D. Irish,et al.  Vibrational spectral studies of ion-ion and ion-solvent interactions. III. Zinc nitrate in water/acetonitrile mixtures , 1978 .

[17]  J. W. Anthonsen.  Raman investigations of charge-transfer complexes of dioxane with iodine, bromine, chlorine, iodine bromide, iodine chloride and bromine chloride , 1976 .

[18]  Jincai Su,et al.  Sublayer structure and reflection coefficient and their effects on concentration polarization and me , 2011 .

[19]  Yi-Ming Sun,et al.  Free-Volume Depth Profile of Polymeric Membranes Studied by Positron Annihilation Spectroscopy: Layer Structure from Interfacial Polymerization , 2007 .

[20]  Chuyang Y. Tang,et al.  Characterization of novel forward osmosis hollow fiber membranes , 2010 .

[21]  Amy E. Childress,et al.  Forward osmosis: Principles, applications, and recent developments , 2006 .

[22]  A. Lutskii,et al.  Molecular Kerr constants and structures of complexes of carboxylic acids , 1968 .

[23]  Kai Yu Wang,et al.  Study of draw solutes using 2-methylimidazole-based compounds in forward osmosis , 2010 .

[24]  D.J.H. Harmsen,et al.  Membrane fouling and process performance of forward osmosis membranes on activated sludge , 2008 .

[25]  P. Mallon,et al.  Principles and Applications of Positron & Positronium Chemistry , 2003 .

[26]  M. Guzman,et al.  Investigation on the variation in the fine structure of plasma-polymerized composite membrane by positron annihilation spectroscopy , 2009 .

[27]  Takeshi Matsuura,et al.  Synthetic Membranes and Membrane Separation Processes , 1993 .

[28]  Tai-Shung Chung,et al.  Forward osmosis processes: Yesterday, today and tomorrow , 2012 .

[29]  Menachem Elimelech,et al.  Yale constructs forward osmosis desalination pilot plant , 2007 .

[30]  Kai Yu Wang,et al.  Polybenzimidazole (PBI) nanofiltration hollow fiber membranes applied in forward osmosis process , 2007 .

[31]  Brett Digman,et al.  Functionalization of polybenzimidizole membranes to impart negative charge and hydrophilicity , 2010 .

[32]  J. Lai,et al.  Characterization of multilayer nanofiltration membranes using positron annihilation spectroscopy , 2009 .

[33]  Menachem Elimelech,et al.  High performance thin-film composite forward osmosis membrane. , 2010, Environmental science & technology.

[34]  A. K. Fritzsche,et al.  The second‐generation polysulfone gas‐separation membrane. I. The use of lewis acid: Base complexes as transient templates to increase free volume , 1990 .

[35]  Kai Yu Wang,et al.  Highly Water-Soluble Magnetic Nanoparticles as Novel Draw Solutes in Forward Osmosis for Water Reuse , 2010 .

[36]  S. J. Tao.  Positronium Annihilation in Molecular Substances , 1972 .

[37]  Qian Yang,et al.  Dual-layer hollow fibers with enhanced flux as novel forward osmosis membranes for water production. , 2009, Environmental science & technology.

[38]  Qian Yang,et al.  Enhanced forward osmosis from chemically modified polybenzimidazole (PBI) nanofiltration hollow fiber membranes with a thin wall , 2009 .

[39]  Gary L. Amy,et al.  Hydrophilic Superparamagnetic Nanoparticles: Synthesis, Characterization, and Performance in Forward Osmosis Processes , 2011 .

[40]  C. D. Moody,et al.  Drinking water from sea water by forward osmosis , 1976 .

[41]  Allan F. M. Barton,et al.  CRC Handbook of solubility parameters and other cohesion parameters , 1983 .

[42]  Y. Jean.  Positron annihilation spectroscopy for chemical analysis: A novel probe for microstructural analysis of polymers☆ , 1990 .

[43]  Menachem Elimelech,et al.  Chemical and physical aspects of organic fouling of forward osmosis membranes , 2008 .

[44]  Tai‐Shung Chung,et al.  Microscopic behavior of polyvinylpyrrolidone hydrophilizing agents on phase inversion polyethersulfone hollow fiber membranes for hemofiltration , 2009 .

[45]  Gary L. Amy,et al.  Well-constructed cellulose acetate membranes for forward osmosis: Minimized internal concentration polarization with an ultra-thin selective layer , 2010 .

[46]  Tzahi Y. Cath,et al.  Selection of inorganic-based draw solutions for forward osmosis applications , 2010 .

[47]  Sui Zhang,et al.  Effects of annealing on the microstructure and performance of cellulose acetate membranes for pressure-retarded osmosis processes , 2010 .

[48]  M. Elimelech,et al.  Organic fouling of forward osmosis membranes: Fouling reversibility and cleaning without chemical reagents , 2010 .