The bipolar membrane electrodialysis method was applied for the removal and recovery of boric acid from waste water stream was developed. The two-cell type electrodialysis cell, which is composed of two bipolar membrane and one anion exchange membrane, was used (Fig. 1). The volume of the feed tank fed for the recovery cell was set 1/4 of that of the feed tank for the feed cell. The boron concentration in the recovery cell decreased from 100 mg/L to 9.8 mg/L after 60 min, which is below the regulation value. On the other hand, the boron concentration increased to 400 mg/L after 60 min. In the second step, the electrodialysis was conducted for the initial boron concentration at 400 mg/L. After 60 min, the boron concentration was 50 mg/L for the feed cell, and 1500 mg/L for the recovery cell. The third step electrodialysis was conducted with the initial concentration at 1500 mg/L, and the boron concentration after 60 min was 286 mg/L for the feed cell and 4,000 mg/L for the recovery cell, respectively. The fourth step electrodialysis enabled the concentration of the boron in the recovery cell at 10,000 mg/L, which is close to the solubility of boric acid in water at room temperature condition. Based on the experimental results, the final recovery rate of boron in the initial feed was about 90%. Thus, by the four-step electrodialysis, the waste water containing boron at 100 mg/L can be concentrated to 10,000 mg/L, while the concentration of boron in the treated water flow was reduced to 9.8 mg/L.

Removal and recovery of boric acid from waste water with bipolar membrane electrodialysis

254th National Meeting (2017)

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