Selective removal of chloride from the adipate formation bath in foil industry by diffusion dialysis

Abstract Aluminum electrode foils are the most essential components inside electrolytic capacitors, which are widely used in diverse electronic systems. The production involves the usage of various chemicals, and it generates a huge amount of exhausted bath solution consisting of highly-concentrated ammonium adipate and trace Cl- impurity. The loss of these expensive chemicals is a heavy burden for the foil manufacturers. The current work innovatively applies diffusion dialysis (DD) to selectively remove the chloride from this abandoned solution, which makes the reuse of these chemicals possible. In the process, Cl- ion presents a superior permeability compared with adipate2- ion, and a high permselectivity of 6 is obtained by using conventional anion exchange membranes. The effects of flow intensity and chloride concentration on the selective dechlorination performance have been thoroughly studied, respectively. Furthermore, the long-term stability of the membranes has been carefully investigated, and their performance is unchanged during a six-month period. The overall economics of this new process is very encouraging, and a stunningly short pay-off period (43 days) is achieved. This work not only solves the problem of reusing the exhausted adipate bath solution, but also further demonstrates the great potential of the DD process in selective ion separation applications.