Sang Yong Nam

Pervaporation and properties of chitosan-poly(acrylic acid) complex membranes

Abstract Polyelectrolyte complex membranes between chitosan as a cationic polyelectrolyte and poly(acrylic acid) as an anionic species were prepared by blending two polymer solutions in different ratio. Characterization of chitosan-poly(acrylic acid) complex membrane was investigated by Fourier transform-infrared (FT-IR), wide angle X-ray diffractometer, dielectric analyzer. Their mechanical properties were studied by universal testing machine. The swelling of polyelectrolyte membranes was studied. Thermal properties of polyelectrolyte membranes from chitosan and poly(acrylic acid) by varying blend ratios showed a shift in transition temperatures of polyelectrolyte complexes. Polyelectrolyte complex membranes from chitosan and poly(acrylic acid) had pH sensitive characteristics as determined by FT-IR studies and swelling behaviors. Pervaporation performances were investigated with various organic mixtures; water-ethanol, water-isopropanol, methanol-methyl t -butyl ether mixtures. An increase of poly(acrylic acid) content in the polyelectrolyte complex membranes affected the swelling behavior and pervaporation performance of water-ethanol mixture. Permeation flux decreased and the water concentration in the permeate was close to 100% upon increasing the feed alcohol concentration.

Pervaporation of ionically surface crosslinked chitosan composite membranes for water-alcohol mixtures

Chitosan composite membranes were prepared by casting solution onto a porous polyethersulfone ultrafiltration membrane with various surface crosslinking densities. Pervaporation performance of water-alcohol mixtures through the surface crosslinked chitosan composite membranes exhibited a high selectivity value with a low permeation flux. By increasing feed ethanol concentration, permeate flux decreased and water concentration in the permeate decreased drastically at a feed ethanol concentration above 97 wt%. Permeation rate of chitosan composite membranes is less temperature-dependent than that of PVA. IPA-water mixture has a similar tendency as that of ethanol-water mixture in pervaporative dehydration performances.

Pervaporation separation of water-isopropanol mixture using carboxymethylated poly(vinyl alcohol) composite membranes

The pervaporation separation of water–isopropanol mixtures was carried out using carboxymethylated poly(vinyl alcohol) (CMPVA) composite membranes. Carboxymethylated PVA (CMPVA) was synthesized by reacting PVA with various concentrations of monochloroacetic acid. Substitution efficiency of the CMPVA ranged from 12–32%. The cross-sectional structure of the composite membrane for pervaporation was confirmed by scanning electron microscopy (SEM) exhibiting a 20-μm active skin layer. Glass transition temperature of the CMPVA was in the range of 74–84°C, and decreased with increasing substitution efficiency. Degree of swelling and permeation flux for water–isopropanol in pervaporation increased with the substitution degree of carboxymethylation. CMPVA composite membrane, having 16% substitution efficiency, showed the following pervaporation performance; permeation flux of 831 g/m2 h and separation factor of 362 measured at 80°C and 85 wt % feed isopropanol concentration.

Pervaporation of ethylene glycol-water mixtures I. Pervaporation performance of surface crosslinked chitosan membranes

An ionically surface crosslinked chitosan composite membrane was prepared for pervaporation of ethylene glycol‐water mixture. Chitosan membranes exhibited an optimum dehydration performance from ethylene glycol (EG)‐water mixtures at 80 min crosslinking time. At 808C and 80 wt% feed EG concentration, permeation flux of 1130 g/m 2 h and water concentration of permeate greater than 99.5 wt% were achieved. Effects of operational conditions including feed EG concentration, operating temperature, and annealing temperature of chitosan membranes on the pervaporation performances of chitosan composite membranes were investigated. At EG concentrations from 70 to 95 wt%, water concentration was higher than EG concentration in the permeate and permeation flux decreased with increasing feed EG concentrations. Annealing of chitosan composite membranes reduced the permeation flux and separation performance of chitosan composite membranes. At high EG concentration in the feed mixture, the membrane was more sensitive to operating temperatures and had higher activation energy of permeation. Water selective chitosan membranes can be applied to evaporation‐pervaporation hybrid system for dehydration in the recycle of anti-freezing agent and EG production process. # 1999 Elsevier Science B.V. All rights reserved.

Pervaporation of water-ethanol through poly(vinyl alcohol)/chitosan blend membrane

SummaryBlend membrane consisting of poly(vinyl alcohol)(PVA) and chitosan was prepared from solvent casting technique for effective separation of ethanol-water mixture by pervaporation. Selectivity toward water and the flux through the blend membrane, crosslinked with glutaraldehyde at the concention of 4×10-6 mol/g, were∼450 and 0.47 kg/m2.hr, respectively.

Pervaporation Separation of an Aqueous Organic Mixture Through a Poly(acrylonitrile-co-vinylphosphonic acid) Membrane

Polyacrylonitrile (PAN)-based copolymers containing phosphonic acid moiety were synthesized for dehydration of aqueous pyridine solution. The in situ complex, formed between the vinylphosphonic acid (VP) moiety in the membrane and the pyridine in the feed, enhanced separation capacity of poly(acrylonitrile-co-vinylphosphonic acid) (PANVP) membranes. All the PAN-based membranes containing phosphonic acid were very selective toward water. The pervaporation performances of PANVP membranes depended on the content of the phosphonic acid moiety in the membrane and operating temperature. The pervaporation separation of water/pyridine mixtures using PANVP membranes exhibited over 99.8% water concentration in permeate and flux of 4–120 g/m2/h depending on the content of vinylphosphonic acid and operating temperature.

Effect of Deacetylation Degree in Chitosan Composite Membranes on Pervaporation Performance

ABSTRACT The effect of the degree of deacetylation in chitosan composite membranes on their pervaporation performance for ethanol dehydration was investigated. The degree of deacetylation of chitosans was measured by using an infrared spectroscopic method and elemental analysis. The chitosan composite membranes were prepared by coating a chitosan solution onto a microporous polyethersulfone membrane with 3–7 nm pore sizes. Then the surface of the top layer (chitosan) of well-dried membranes was crosslinked with sulfuric acid, and pervaporation experiments for binary mixtures (water—ethanol) were carried out at various conditions. In the case of a chitosan membrane with a high degree of deacetylation, the flux increases while the separation factor decreases compared with membranes with a low degree of deacetylation.