Fig. 13. McCabe–Thiele diagram of boron extraction using TMPD.

3.4 Study of stripping process

Boron-loaded organics were stripped by hydrochloric acid, deionized water and different concentrations of sodium hydroxide solutions at a constant O/A of 2/1, respectively. As shown in Table 5, it is evident that the stripping efficiency of boron by NaOH is significantly higher than that of H2O and HCl, which can indicate that the complex formed by boron and 1,3-diol (TMPD) is more stable than that formed by monohydric alcohol. The stripping efficiency of H3BO3 increased with the increasing of NaOH concentration. however, emulsification occurs when the NaOH concentration is greater than 0.4 mol/L, which is not conducive to phase separation, and the stripping efficiency decreases when it continues to increase to 0.6 mol/L. Therefore, the concentration of the stripping agent is selected to be 0.4 mol/L, which can achieve a good stripping effect while avoiding the phenomenon of emulsification.
Table 5. Results of stripping H3BO3 with different stripping agents