A study of temperature effect on chemical, structural and transport parameters determined for two different regenerated cellulose membranes

Chemical, structural and electrochemical characterizations of two cellophane membranes depending on both cellulose content (20 and 25 kg/m2) and thermal treatment (60 °C during 4 h), have being carried out. Different transport parameters were determined by measuring water and salt fluxes, membrane potential and impedance spectroscopy using NaCl solutions at different concentrations. Chemical degradation of the membrane surfaces due to membrane heating was obtained from XPS spectra. Electrochemical results shown that treated and untreated samples behave as weak cation-exchangers, but small differences in their electrical parameters (membrane fixed charge concentration, cation transport number and electrical resistance) due to both the thermal treatment and the amount of cellulose were obtained. Results also indicate a more open structure for the membrane with higher content of cellulose. The influence of concentration/polarization layers on salt permeation was also studied by measuring salt diffusion at different stirring rates. Moreover, variation of water permeability with temperature for untreated samples seems indicate changes in the membrane structure around 40 °C, which was confirmed by differential scanning calorimetry (DSC) thermograms.