An electrodialysis-based coupling technique for simultaneous reclamation of waste acid and cleaner production of organic acid

Abstract

In order to promote the practical applications of the coupling technology for the simultaneous recovery of waste acid and cleaner production of organic acid, the crucial step and the relevant operating conditions of the ion substitution electrodialysis (ISED) are theoretically simulated and experimentally investigated in this work. Above all, a model is established on the basis of Nernst-Plank equation, electroneutrality theory and dissociation equilibrium of weak electrolyte to understand the competing transport phenomena between protons and dissociated metal cations. Simulation results reveal that the later stage of ISED in which energy consumption and current efficiency deteriorate significantly though the conversion rate of organic acid continues to rise requires special attention. Subsequently, a series of ISED experiments on the low concentration organic acid salt systems are carried out to investigate the corresponding later stage and the effects of the operating conditions such as current densities and organic acid products, including single and polynary organic acids. The experimental results confirm the decisive impacts of the dissociation characteristics of organic acids on the ISED process. Furthermore, similar experiments after filling resin in the weak electrolyte compartment are also performed. The results indicate that the resin-filling can significantly reduce energy consumption at the expense of sacrificing the current efficiency. At last, based on the porous plug model, the role played by the resin-filling technology is elaborated to guide our efforts going forward.