Effects of electrolytes on ion transport in Chitosan membranes

Recently, charged polymer membranes are widely used for water purification applications involving control of water and ion transport, such as reverse osmosis and electrodialysis. In this study, we have explored the effects of electrolyte solutions on ion transport properties of chitosan synthetic membranes via concentration gradient driven transport. Also, the water uptake of those membranes, before (control) as well used membranes have studied. The membrane used was chitosan membrane 2%. The electrolyte solutions used were HCl, KCl, CaCl2, MgCl2 and AlCl3, with various concentrations of 0.1 mM, 1 mM, 10 mM, 100 mM and 1000 mM. Ion transport experiments were carried out in a cell membrane model which composed of two compartments and the potential difference of membrane was measured using Ag/AgCl calomel electrodes. Those measurements were conducted at ambient temperature 28.8 oC. The results showed that the current density (J) increased with increased in concentration gradient of solution. The current density was higher in electrolyte solution which has higher molar conductivity than those of a solution with a small molar conductivity. Meanwhile the current density was smaller in electrolyte solution which has larger Stokes radii than those of a solution with small Stokes radii. Except membrane which has been used in HCl solution, the water uptakes of the used membranes were greater than the control membrane. These results can develop and validate a common framework to interpret data of concentration gradient driven transport in chitosan synthetic membranes and to use it to design of membranes with improved performance.