Concentration of potassium cations in the permeate solution in the presence of N,N-dimethyl-N-2-propenyl-2-propen-1-aminium chloride homopolymer using dead-end nano-or ultrafiltration

Abstract

The investigation is based on the nano-or ultrafiltration of inorganic salts in the presence of a polyelectrolyte in the feed solution. Cellulose acetate membranes are selected with a pore size of 10–20 nm. The membranes are imaged using atomic force microscope. The membrane is completely impermeable to the polyelectrolyte. Polyelectrolyte concentrations are taken in the range of 0.5–1 g/l to avoid a gel layer formation over the membrane. It is discovered that, at such low polyelectrolyte concentration, inorganic salt concentration in the permeate is higher than in the feed solution. This process therefore deviates from conventional membrane separation processes, where the permeate salt concentration is lower or equal to the salt concentration in the feed solution. It is shown that during the nano-or ultrafiltration of inorganic salts in the presence of polyelectrolyte, the ratio of salt concentration in the permeate to feed increases when the initial salt concentration in the feed solution is low. Concentration polarization has a negative impact on this concentrating effect. In the case of this investigation, KCl, KNO₃, K₂SO₄ are taken as inorganic salts, N,N-dimethyl-N-2-propenyl-2-propen-1-aminium chloride homopolymer is selected as a polyelectrolyte.