27. Using Electrodialysis to Recycle Chemical Polishing Agent from Anodizing Industry

In this study, we use the electrodialysis technique (ED) to recycle chemical polishing agents, including the removal efficiency of aluminum ions and water quality variation. Finally, the electricity consumption of the ED technique for separating aluminum ions was estimated. The ED system was composed of a cation exchange membrane, anion exchange membrane, and graphite electrode. With a current of 1.0 A and an average voltage of 70 V, the treatment time was 60 min. The results showed that variation of pH and conductivity in the wastewater has a stable status. The aluminum ion concentration was rapidly decreased from about 11,056 to 2,512 mg/L in the wastewater chamber within 30 min, and the removal efficiency reached 78%. The variation of concentration indicated that the high concentration of aluminum ion is rapidly adsorbed on the cation exchange membrane under the ion permeation in the early stage of operation, resulting in a significant decrease in the aluminum ion concentration. After the adsorption was saturated, the aluminum ion became movable from the cation exchange membrane to the cathode under electromigration. With the operating time, the concentration of aluminum ions gradually increased at the recovery chamber. The electricity consumption shows that the ED can effectively separate aluminum ions in the wastewater and recycle chemical polishing agents.