3. Results and Discussion

3.1 Effects of the extraction parameters on H3BO3Extraction

3.1.1 Effect of Feed pH

The pH of the aqueous solution has been considered as the crucial parameters affecting the H3BO3 extraction process[17,28]. To determine the effect of pH on H3BO3 extraction, experiments were performed at pH from 1 to 10 with a constant O/A of 1/1. As shown in Fig. 2, at a condition of initial aqueous pH value (abbreviated to pHini ) less than 7, the extraction efficiency reached a stable level of 85%, and equilibrium aqueous pH value (abbreviated to pHeq ) reduced obviously comparing to the pHini . Meanwhile, the pHeqand ΔpH (pHini -pHeq ) increased with the increasing of pHini . The extraction efficiency decreased sharply with the pHini continuously increasing, and the pHeq was slight higher than pHini . It can be concluded that the extraction efficiency and pHeq changed inversely, and a low extraction efficiency obtained when the pHeqexceeded 9.4.
Boron is mainly present in natural water in the form of boric acid, and it appears as weak Lewis acid after hydrolysis.: