Reaction mechanism of fluoride conversion into BF4-during sulphuric acid leaching of roasted bastnaesite

• 作者: Hongcheng Zhang Dairui Xie Heng Zhang Meng Jiang Hao Huang Yu Wan Yang Liao Shilin Zhao
• 来源期刊: 稀土学报（英文版）
• 年，卷（期）: 2021,（2）
• 所属期刊栏目: CHEMISTRY AND HYDROMETALLURGY
• 页码范围: 186-193
• 页数: 8页
• 语种: 英文

摘要

The bastnaesite used in hydrometallurgy usually contains 7％-11％fluorine,and the conversion of fluo-rine into high-value products is the key to achieving green production of rare earths and improving the comprehensive utilization of bastnaesite.In order to recover fluorine from bastnaesite in the form of KBF4,the mechanism of F-conversion to BF4 in sulphuric acid leaching solution of roasted bastnaesite was studied by using Eh-pH diagram and simulation experiment.It shows that the formation of BF-4 is affected by pH in the absence of rare earths.BF4-is hydrolyzed to BF3OH-and F-when the pH is greater than 3.9,and part of F-exists as HF2-when pH is lower than 2.In the presence of La3+,the formation of BF4-is mainly affected by LaF3 when pH is greater than 0,and in the case that the pH is lower than 2,it is mainly affected by HF2-.When Ce4+is present in solution,CeF22+can exist stably in sulphuric acid so-lution.Bringing down the pH can reduce the stability of CeF22+and increase the BF4 conversion rate.Based on these results,KBF4 was prepared in the alkaline solution of bastnaesite,and the conversion of BF4-is 84.31％.This provides a theoretical basis for the recovery of fluorine from bastnaesite in the form of KBF4.