An in situ coupling separation process of electro-electrodialysis with back-extraction

To intensify mass transfer and simplify the separation processes in recovering and concentrating organic acids from their fermentation broths, an in situ coupling separation process of electro-electrodialysis with back-extraction has been developed. In this new process an oil-in-water disperse system comprised by extractant phase and stripping phase flew in the cathode chamber concurrently. The two steps, including back-extraction and concentration, happen at the same time in one module. The experimental studies on the process were carried out, with a mixed solvent of a kind of tertiary amine with long aliphatic chains and n-octanol as the extractant, and citric acid as the solute. The salt aqueous solution of mono-sodium citrate was used as the stripping phase. The influence of the current density, phase ratio of the extractant phase to the stripping phase, salt concentration of the stripping phase and initial concentration of receptor was investigated. The experimental results showed that the new process integrated the EED process with the back-extraction process in one module successfully, which made the separation process simple and the equipment cost less. The current efficiency of 103.5% and the specific energy consumption of 2.48 kW h/kg were reached. Meanwhile the voltage was not higher than 24 V. Compared with a normal EED process, it is a process with the advantages of higher mass transfer performance and slightly lower energy consumption.