Alkaline Water Electrolysis Model to Purify GMP grade NaOH Solutions for Biopharmaceutical Manufacturing Processes

It is essential that the Cl^- ions purity contained in NaOH solutions for the use of the biopharmaceutical production processes would be below 30 ppm to meet Good Manufacturing Practice (GMP) guidelines (Gilleskie, G. et al.). The development of a commercially efficient process for purifying NaOH 50% aqueous solution of such purity is of interest in the related industry. This study describes a lab-scale electrochemical mathematical model for producing GMP grade NaOH aqueous solutions and a design of electrochemically efficient lab-scale production configuration. The model validation is carried out with experimental data for a different set of membrane configurations (Marangio, F. et al.). The model calculates the theoretical open-circuit voltage via a thermodynamic analysis of the electrochemical purifying process and then outputs the expected voltage during operation by applying the Butler-Volmer equation (Jang, D et al.). A set of physical properties of the solution are obtained from well-known theoretical equations: concentrations from Henry's law and membrane diffusivity, permeability, and ionic conductivity from the Arrhenius equation, respectively. An experimental data fitting makes it possible to obtain estimated values of critical process parameters and their data tendency at different temperatures. The proposed model shows about 90% accuracy at an electrochemical lab-scale, to produce GMP grade (Cl^- ions below 30 ppm) 50% NaOH aqueous solution, and an appropriate cation exchange membrane-based experimental configuration turns out to be of electrochemically high efficiency. Future work is to enhance the experimental scale model to scale up to a commercial scale, with an emphasis on the optimization of electrochemical reaction time, power and voltages.