Application of Electrobaromembrane Process for Separation of Aqueous Solutions of Ionic Dyes

A method for producing electrically conductive ceramic membranes based on a fly ash microsphere substrate and a selective layer of alumina nanofibers with a carbon coating is proposed. The formation of a carbon layer by chemical vapor deposition reduces the average pore size from 28 to 19 nm and decreases the water permeability of the membranes from 207 to 45 L/m2 h bar. A setup for an electro-baromembrane process was developed, based on a tangential filtration cell with radial flow and the capability of applying a potential to the membrane relative to a counter electrode. Experiments on the ultrafiltration of an aqueous solution of the ionic dye Berillon II showed that the rejection increases from 60 to 82% over time and is provided by the electrostatic interaction of negatively charged dye molecules with the pore surface. Applying a positive potential of +800 mV to the membrane increases the rejection by 20–25% at the beginning of the process and by 13% in the steady state due to enhanced sorption of dye molecules on the membrane surface. Applying a negative potential of –800 mV ensures a stable rejection of 93–96% and a flux of 160 L/m2 h at a pressure difference of 5 bar due to the enhanced Donnan exclusion of negatively charged dye molecules in the membrane pores. The obtained results can be used to improve the efficiency of separation, concentration, and purification processes of aqueous solutions of ionic dyes.