Abstract:Experiments of extracting boron from high concentration calcium and boron-rich old brine in Qinghai were carried out. The results show that the suitable extraction conditions including using sulfonated kerosene as diluent, volume fraction of isooctyl alcohol of 50%, extraction phase ratio O/A=1.0, and extraction time of 15 minutes, and the suitable stripping conditions including using hydrochloric acid solution with pH value of 1 as stripping agent, stripping phase ratio O/A=1.5, and stripping time of 15 minutes. Under these conditions, the continuous countercurrent extraction and stripping of boron were performed with five-stage mixer-settler. The experiment runs continuously for 45 hours. The five-stage extraction percent of boron is 95.49%, and the better separation efficacy of boron and sodium, potassium, calcium, magnesium is got. The five-stage stripping percent of boron is 99.59% and the concentration of boron in stripping solution reaches 17.17 g/L. Boron can be separated and extracted effectively by the process including solvent extraction, stripping, evaporation in high temperature and cooling crystallization in low temperature, redissolution and cooling crystallization, washing and drying. The overall recovery of boron is of 92.33%. The prepared boric acid products meet the requirements of national quality standard (GB/T 538—2018).