(南昌大學稀土工程研究中心， 南昌 330047)
摘 要: 連續(xù)測定了碳酸稀土的形成過程及其結晶過程中平衡溶液的pH值， 發(fā)現(xiàn)碳酸稀土的結晶過程與溶液pH的下降有對應關系， 其下降幅度和速度與結晶物料量和結晶速度相關， 表明可根據(jù)pH值變化來評價碳酸稀土的結晶化特征。 提出了確定碳酸稀土結晶活性及結晶區(qū)域的實驗方法， 根據(jù)它們的結晶活性可將碳酸稀土分為易結晶、 可結晶和難結晶三大類； 結果表明鈰和釔在常溫下均為易結晶的， 只是鈰的結晶活性區(qū)域在低摩爾比區(qū)域([NH4HCO3]/[Ce3+]=1.4～2.8)， 而釔在高摩爾比區(qū)域(4.5～6.0)。 同時， 還對碳酸氫銨沉淀稀土的一般反應和結晶過程的反應機理進行了探討， 提出了相應的反應方程式。
關鍵字: 碳酸稀土 沉淀 結晶
OF RARE EARTH CARBONATE
（Rare Earth Technology Research Centre, Nanchang University, Nanchang 330047, P. R. China）
Abstract:The pH values of equilibrium solution in which the rare earth carbonate is formed with ammonium bicarbonate as precipitant and aged were determined continuously. It was found that the crystallization process of rare earth carbonate is always related to a descent of solution pH value which is associated with the amount of rare earth carbonate crystallized, and the time needed for crystallization is the reflection of crystalline rate. These relations can be used for the crystallization process studying. Some experimental methods for characterizing crystalline activity and crystalline district of different rare earth carbonates were established. Based on their crystalline activity, rare earth carbonates may be divided into three categories: easy to crystallize, capable to crystallize and difficult to crystallize. Although cerium and yttrium carbonate are all easy to crystallize at room temperature, their crystalline districts are particularly different, which expressed with molar ratio of NH4HCO3 to rare earth ion are 1.4～2.8 for cerium and 4.5～6 for yttrium. At the same time, the general precipitation reaction of rare earth with ammonium bicarbonate and the crystallization mechanism of rare earth carbonate were discussed and the corresponding reaction equations were proposed.
Key words: rare earth carbonate precipitation crystallization
