Effect of modified coal through chemical activation process on performance of heterogeneous reverse osmosis membranes

Heterogeneous reverse osmosis (RO) membranes have been prepared from cellulose acetate (CA) and modified coal through chemical activation. Nitric acid of various concentrations, sulfuric and acetic acids used for various time periods have been studied with respect to modification of structure of coal and consequently structure of RO membranes. The effect of these variables on the modification of coal was examined by IR spectroscopy. All membranes prepared in such a way showed improved performance in comparison with standard CA membranes. The volume flux of the best RO membranes at 94% level of solute separation was 3.87×10–2 m3/(m2·h) at 1.76 MPa using aqueous feed solution 400 mg/dm3 of sodium chloride. The performance improvement was related to increases of charge of groups of coal particles in the membrane, affecting their rheology and morphology resulting in better membrane productivity. The SEM of some membranes have also been presented. These membranes were tested also with 1:1, 1:2, 2:2 and 1:3 inorganic salt solutions. The agreement between the calculated and experimental data of solute separation for studied solutes was reasonably good.