Synthesis and modeling of composite poly (styrene-co-acrylonitrile) membrane for the separation of chromic acid

In this work, we have prepared a composite styrene acrylonitrile (SAN) membrane on a ceramic clay plate by coating a prepolymer solution prepared using a dual initiator system. This membrane is chemically modified by gas phase nitration followed by amination and quaternization to make it charged and has been characterized by FTIR, SEM, contact angle measurements, AFM, water content, water permeability measurements and molecular weight cut-off experiments. The membrane has been further characterized using chromic acid rejection (real and observed) at different pressures, feed concentrations and pH. The modified membrane is found to possess a real rejection of above 90% with high water flux at low pressure drop.The experimental data has been explained through space charge model. The solution scheme is found to be computationally intensive due to highly non-linear nature of Poisson–Boltzmann equation and to facilitate the experimental data fitting, polynomial series solution has been developed. A procedure has been evolved so as to fit the experimental results by varying the concentration at the membrane pore mouth to include concentration polarization effects. The root mean square error between the predicted and the experimental value of permeate flux has been minimized to determine the values of wall potential.