総説（特集）
重希土類資源としてのアパタイトの可能性
2020 年 54 巻 1 号 p. 29-59
詳細
2020 年 54 巻 1 号 p. 29-59
Phosphorous is one of the three major nutrients (N, K, P) required by plants and about 80 of phosphate mined in the world is used to produce chemical fertilizers. “Phosphate rock” is the term generally used in industry to describe mineral assemblages with a high concentration of phosphate minerals, consisting commonly of francolite (Ca5(PO4, CO3)3(OH, F, Cl)) - apatite (Ca5(PO4)3(OH, F, Cl)) series.
Apatites contain a variety of REE concentrations from several thousands ppm to several wt.%. They are generally enriched in LREE, however, some apatites are rich in HREE: apatites in sedimentary phosphate rocks and deep sea mud, and igneous rocks. In addition, both Th and U contents in apatite are relatively low, compared with common REE minerals such as monazite and xenotime. Thus, the extraction of REE from apatite as by-products in the existing plants for phosphate fertilizer would be highly economically efficient and feasible compared with the development of new REE deposits.
This paper reviews firstly REE and actinide substitution mechanism of apatite and apatite-group minerals, and secondarily the classification and variety of apatite deposit types by focusing on REE resource (especially HREE).I finally present the studies concerning precipitation, solvent extraction and adsorption for REE in the process of phosphoric acid production.
