采用碳酸氢铵-氨水混合沉淀剂制备碳酸镧的研究

Study on Preparation of Lanthanum Carbonate with Mixed Precipitation Agent of Ammonium Bicarbonate and Ammonia

以碳酸氢铵-氨水作为混合沉淀剂,氯化镧溶液为料液,采用并流沉淀法制备碳酸镧产品,考察了底液中稀土浓度、反应时间及沉淀废水回用对产品质量的影响,并对产品物相结构和形貌进行了表征,最后与采用碳酸氢铵作为沉淀剂的工艺进行了技术指标对比。结果表明,在控制底液中稀土浓度为30g/L,反应时间为7h,沉淀废水回用的条件下,产品的主要成分为La_2(CO_3)3·8H_2O,Cl^-含量<0.07%,稀土总量≥45%。沉淀1t稀土氧化物产出5.9m^3沉淀废水,废水中氯化铵含量为169g/L。与采用碳酸氢铵作为沉淀剂的工艺相比,采用混合沉淀剂一方面大幅降低了废水的产出量,进而减少了废水的治理成本;另一方面有效利用了C元素,从而降低了温室气体CO_2的排放量和碳酸氢铵的使用量,具有良好的经济和环境效益。

Lanthanum carbonate was prepared by merging precipitation with ammonium bicarbonate and ammonia as the mixed precipitant and lanthanum chloride solution as the material. The effects were inves- tigated of rare earth concentration in base solution,reaction time and reuse of precipitation wastewater on product quality. Phase structure and morphology of the product were analyzed, and technical indexes were compared between the above process and the existing process with ammonium bicarbonate as the precipita- tion agent. The results show that the main component of lanthanum carbonate product is La2 （CO3）3 · 8H2O with〉0.07% Cl- and ≥45% REO under the conditions as follows ： rare earth concentration in base solution of 30 g/L,reaction time of 7 h and reusing precipitation wastewater. At the same time,5.9 m3 pre- cipitation wastewater is generated for 1 t REO with ammonium chloride content of 169 g/L. Compared with the existing process with ammonium bicarbonate as the precipitation agent,the use of mixed precipi- tants significantly reduces the output of wastewater and its treatment cost,and effective use of carbon re- duces the emission of CO2 and dosage of NH4 HCO3 ,with good economic and environmental benefits.