Kinetics of concentration boundary layers buildup in the system consisted of microbial cellulose biomembrane and electrolyte solutions

The kinetics of concentration boundary layers (CBLs) buildup for aqueous solutions of NaCl and flat microbial cellulose biomembrane was studied. To this end time characteristics of voltage between Ag|AgCl electrodes (EMF) after turning off mechanical stirring of solutions were measured in the system with membrane in horizontal orientation and with lower density of solution over the membrane. In that case, time characteristics of EMF indicate on stable buildup of CBLs as a result of diffusion. Besides the shape of time and concentration characteristics of EMF depended on the manner of electrodes location, while EMF measured in conditions of mechanical stirring of solutions did not depend on location of electrodes in the membrane system for this same initial conditions. For greater quotient of concentrations on the membrane at the initial moment, the greater differences between time characteristics of EMF were observed for electrodes in different locations. Besides phenomenological coefficients of transport properties of that biomembrane were experimentally determined and amount: hydraulic permeability coefficient Lp = (6.5 ± 0.3) × 10−11 m3 N−1 s−1, reflection coefficient σ = (3.6 ± 0.7) × 10−3 and solute permeability coefficient of NaCl ω = (1.71 ± 0.06) × 10−9 mol N−1 s−1. These coefficients were used in the Kedem–Katchalsky model with linear profiles of concentration in CBLs in order to model concentration and voltage changes during CBLs buildup.