Wan Linsheng, Zhao Lifu, Cao Caifang, Gong Dandan, Zeng Xuepin, Yang Liang
Jiangxi University of Science and Technology, Ganzhou, Jiangxi, China.
Front Chem. 2023 Sep 12;11:1238644. doi: 10.3389/fchem.2023.1238644. eCollection 2023.
The waste water generated from the sodium tungstate ion exchange process of scheelite hydrometallurgical extraction contains a certain concentration of fluorine ion, which caused environmental pollution and harmed human health. In this study, a new method for removing fluorine from the wastewater by precipitation with addition of lanthanum chloride was proposed. In the process, fluorine was removed by from the solution as insoluble lanthanum fluoride precipitates. To explore the favourable conditions for the formation of lanthanum fluoride, thermodynamic analysis of the La-F-HO system was conducted. Results show that lanthanum fluoride is stable when the solution pH value is between 1.0 and 10.0, and the lanthanum fluoride is gradually converted into lanthana hydroxide when the pH value is more than 10.0 at 298K. The effects of various parameters on the fluorine removal were studied, and the optimum process parameters were determined. More than 92% of the fluorine can be removed when the concentration of fluorine in the solution ranged from 60 to 400 mg/L, the dosage of lanthanum chloride was 1.3 times of the theoretical amount, the pH value was 8.0 at 60°C for 30 min. After removing fluorine from the solution, the resiual fluorine concentrtion was lower than 10 mg/L, which could meet the requirement of national wastewater discharge.
白钨矿湿法冶金提取的钨酸钠离子交换过程产生的废水中含有一定浓度的氟离子，这造成了环境污染并危害人体健康。本研究提出了一种通过添加氯化镧沉淀法从废水中去除氟的新方法。在此过程中，氟以不溶性氟化镧沉淀的形式从溶液中去除。为了探索形成氟化镧的有利条件，对La-F-H₂O体系进行了热力学分析。结果表明，在298K时，当溶液pH值在1.0至10.0之间时，氟化镧是稳定的，而当pH值大于10.0时，氟化镧会逐渐转化为氢氧化镧。研究了各种参数对除氟的影响，并确定了最佳工艺参数。当溶液中氟浓度在60至400mg/L范围内，氯化镧用量为理论量的1.3倍，在60°C下pH值为8.0反应30min时，氟去除率可达92%以上。溶液除氟后，残留氟浓度低于10mg/L，可达到国家废水排放标准要求。
