Concentration of trisodium citrate by electrodialysis

•The Nernst–Planck approach was used to describe trisodium citrate concentration.•The voltage–current curves for the anionic membrane pack differed from those of univalent anions.•The limiting current for the cationic membranes was lower than that for the anionic ones.•In the ohmic region only the resistance of the latter varied linearly with ln(κ).•This experimental procedure and modelling might be used as a design short-cut method.

In this work, the experimental procedure and mathematical model formerly developed was used to describe the electrodialytic (ED) recovery of trisodium citrate. By performing several voltage–current, electro-osmosis and desalination tests, the main engineering parameters (i.e., the ion transport numbers in solution and membranes, effective solute and water transport numbers, effective surface area and resistances of membranes, and limiting electric current) of the ED process under study were assessed.As expected, the electric resistance of the cationic membranes (Rc) resulted to be about constant (0.11±0.02 Ω) and independent of solute concentration, while that of the anionic ones (Ra) was not only greater than Rc, but also dependent on both the current applied and solute concentration. Moreover, in the ohmic region of the current–voltage curves Ra appeared to be a logarithmic function of the solution electric conductivity in the dilute compartment. On condition that the current applied was less than 2/3 of the limiting current for the cationic membrane (Ilim,c) the time course of the voltage applied to the ED stack when operating at a constant current of 0.75 or 1.5 A was adequately predicted with a mean percentage error of ~20%.