New Environment-Friendly Approach for Bastnasite Metallurgic Treatment （Ⅰ）： Extraction of Tetravalent Cerium from Sulphuric Acid Medium with Di（2-ethylhexyl） Phosphoric Acid

The extraction of cerium （Ⅳ) from sulphuric acid medium with Di(2-ethylhexyl) phosphoric acid (DEHPA) was studied. The influence of sulphate ion, acidity, extractant concentration as well as the presence of fluoride ion on the extraction of Ce(Ⅳ) was investigated, and the extraction mechanism was also discussed. The results show that sulphate ion can inhibit the extraction of Ce(Ⅳ) significantly due to its complexation with Ce(Ⅳ). Fluoride ion can enhance Ce(Ⅳ) extraction dramatically by the formation of CeF2^2 and less amount of CeF^3 which can almost be extracted completely. Nevertheless, in the case as F/Ce(mole ratio) in the initial aqueous phase is approximately more than 1.5, the precipitate will be formed and the extraction can not be progressed smoothly.