화학공학소재연구정보센터
Industrial & Engineering Chemistry Research, Vol.52, No.31, 10450-10459, 2013
Vapor Permeation Separation of Methanol-Water Mixtures: Effect of Experimental Conditions
Methanol water separation by membrane has always remained a big challenge for membrane researchers. In this study, sodium alginate (NaAlg)/poly(vinyl alcohol) (PVA) membranes were prepared with a blending ratio of 80/20 wt % for the separation of water methanol mixtures. The prepared membranes were then complexed with calcium ions followed by annealing at the 110 degrees C to modulate their morphology and consequently to enhance the separation performance. The change in morphology brought about by annealing was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to examine the stability of the membranes. Both nonannealed and annealed membranes were employed to investigate the vapor permeation separation characteristics of methanol water mixture. The effect of operating temperature, feed concentration, and annealing time on permeation rate and separation factor was investigated. Before annealing the permeation rate and separation factor was found to increase with a rise in operating temperature while, after annealing, the separation factor was decreased with temperature. As expected, the maximum permeation rate was observed for a feed having high water contents but interestingly a maximum in separation factor was observed for a feed with moderate water contents because of the plasticization effect of the membrane. Moreover, the annealing process was found to have an enormous effect on the membrane morphology and therefore on the separation performances. It is argued that the heat treatment is a remarkable way to tune the morphology of the NaAlg/PVA membrane and to enhance its vapor permeation separation characteristics for methanol water mixture. Eventually, a separation factor of as high as infinity can be achieved at 40 degrees C for 80 wt % methanol using a 12 h NaAlg/PVA annealed membrane.