Preparation and surface modification of PVC/SBR heterogeneous cation exchange membrane with silver nanoparticles by plasma treatment

Polyvinylchloride (PVC)/Styrene-Butadiene-Rubber (SBR) blend heterogeneous cation exchange membranes were prepared by solution casting technique using tetrahydrofuran as solvent and cation exchange resin powder as functional groups. Membrane surface modification was carried out with silver nanoparticles in a vacuum reactor by argon plasma treatment to increase the performance. The effect of deposited nano silver layer thickness on properties of prepared membranes was investigated. Scanning optical microscopy showed uniform particles distribution in the prepared membranes. The increment of plasma treatment time resulted in highly uniform distribution of silver particles. Images showed a relatively uniform surface for the membranes. The potential, surface charge density, transport number and permselectivity of membranes were initially enhanced by increasing deposited thickness up to 40 nm and then all showed decreasing trend with higher increase in layer thickness from 40 to 60 nm. However, they were increased again with more increasing of layer thickness from 60 to 120 nm. Membrane electrical conductivity, ionic permeability, flux and current efficiency were initially improved with increasing layer thickness to 40 nm with a decline for thicker thicknesses from 40 to 120 nm. Energy consumption showed an opposite trend. Membrane with 40 nm thickness exhibited appropriate performance compared to unmodified membrane. Finally the effect of salt solution concentration on the electrochemical properties of superior membrane was investigated. The results showed that the electrical resistance, membrane potential, transport number and selectivity of this membrane declined with an increase in concentration of sodium chloride solution.