Effect of the modification time of coal with aryldiazonium salts on the performance of cellulose–acetate coal heterogeneous reverse osmosis membranes

Spontaneous reduction of 4-nitrobenzene diazonium salt on coal in acetonitrile or HCl aqueous solution permits the strong bonding of aryl groups to its surface as shown by IR spectroscopy. Heterogeneous reverse osmosis membranes containing small particles of coal modified with aryldiazonium salts were prepared by the phase inversion process from the casting solutions of cellulose acetate and magnesium perchlorate in acetone water mixture. The weight ratio of cellulose acetate to dispersed coal particles in the casting solution was always 1:1.5. The reverse osmosis performance of the prepared heterogeneous cellulose acetate coal membranes was tested. The membranes containing coal particles modified with aryldiazonium salts for longer time showed the best performance.