Process Modeling of Boron Isotopes Separation by Cross-Current and Counter-Current Solvent Extraction

Boron has two stable isotopes, namely,10B and 11B, which play important roles in the nuclear industry due to their excellent neutron absorption (10B) and neutron transmission (11B) properties, respectively. Nevertheless, the separation of the two isotopes is extremely difficult because of their very similar chemical properties. The traditional separation method based on the chemical-exchange rectification of BF3 and ethers is highly corrosive and requires expensive equipment. The separation based on solvent extraction (SX) of boric acid is potentially a greener alternative. Here we present the process modeling of SX separation of boron isotopes. The effects of separation factor, extraction ratio, and extraction stages on the purity and yield of boron isotopes have been discussed in detail. In the cross-current SX, the enrichment of isotopes increases linearly with increasing extraction stages, while the yield decreases exponentially, consequently the separation of the isotopes is not possible. In the counter-current SX, the enrichment of the isotope increases with increasing extraction stages, and the yield is >1 - EY (EY is the extraction ratio of the less extractable isotope). Assuming the separation factor beta = 1.02, 11B and 10B can be enriched to be >95% in about 200 and 500 extraction stages, respectively. The higher the separation factor, the faster enrichment and the higher yield. Therefore, future research should focus on increasing the separation factor and on the precise control of hundreds of extraction stages.