Separation of Miscible Solvent-water Solutions Using Composite Membranes Employing Hydrocolloids and Natural Rubber Latex

Anumber of composite membranes have been investigated for the separation ofwater from miscible organic-water mixtures. Organic solvents studied wereethanol, propanol-2 and acetone. Each composite membrane was formed of at least two fused layers. One layer was prepared from a mixture of natural rubber latex solution and the other layer, from a solution of hydrophilic colloid between 1.25 to 20 per-cent by weight on a dry rubber basis. Four hydrophilic colloids with not more than three different molecular masses for each type were used in the preparation of membranes. Each composite membrane was vulcanized before use in an all stainless steel membrane cell. These perm-selectivities have been compared with those obtained from the use of vulcanized natural rubber latex membranes only. The special novel design of this cell along with the entire equipment used, are described and discussed. The method of form-ing a thin film as well as the techniques for checking its soundness and finally, the pro-posed mechanism and a model that may be responsible for enhancing the permeation of water through the composite membranes are also discussed. The incorporation of a layer of alginic acid hydrocolloid in the composite membrane did increase the separation fac-tor of water from ethanol-water mixtures by a factor of 24 in comparison with that of a nat-ural rubber membrane alone. Similarly, the separation factors for water with hydrocolloid