Nanofiltration Application for Concentrating Aqueous Waste Stream to Recover Sodium Sulphate

Sodium sulphate is one of most important salts of sodium which is mainly used in the manufacture of detergents, Kraft paper, glass, sodium salts, ceramic glazes, pharmaceuticals, dyeing of textile fibers etc. Part of its requirement is met from by-products of manufacturing processes like Aluminium silicate, rayon etc. Presently, evaporation followed by crystallization is the preferred technique for recovery of the salt. This technique becomes uneconomical when the waste water has low concentration of the salt. There is a need to develop new techniques for economical concentration of sodium sulphate. Keeping this in mind efforts were made to test the performance of two commercial CSM membranes Model Nos. NE-1812-70 and RE 1812-50 for concentrating the waste water stream. The results show that waste water stream could be concentrated, at pressure of 25 bar, up to 14.1% at permeate flux of 2.08L-min-1-m-2 with NE-1812-70 membrane compared to 9.29% at permeate flux of 0.62 L-min-1-m-2 with RE 1812-50 membrane