Concentration of potassium acetate solutions via sweeping gas pervaporation using TFC membranes comprising of a PDA sublayer and PEI/PAA bilayers

Thin film composite (TFC) membranes comprising of a self-polymerized dopamine (PDA) sublayer and self-assembled polyethyleneimine/poly(acrylic acid) (PEI/PAA) bilayers were developed to concentrate aqueous potassium acetate (KAc) solutions via sweeping gas pervaporation. To have a closer look into permeation behavior of the membrane, pervaporation with aqueous solutions containing other select salts (KCl, NaAc, NaCl and MgCl2) was also investigated. It was shown that the number of the polyelectrolyte bilayers could be reduced effectively by the use of a PDA sublayer in constructing the composite membranes. It was shown that the TFC membrane with a single PEI/PAA bilayer on top of the PDA sublayer was effective for pervaporative concentration of the salts, and a complete salt retention was achieved for essentially all feed solutions studied. The effects of operating conditions (i.e., temperature and feed concentration) and nature of the salt in the feed solution on the performance of the pervaporative separation were also studied, along with an analysis of activation energy for water permeation and mass transfer resistance of the membrane. It was shown that the membrane permeability to water was affected by the anions of the salts more significantly than the cations. The membrane was found stable in pervaporative concentration of the salt solutions at different concentrations and temperatures.