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Prccipitation phenomena of calcite and research for apparatus and operational conditions

方解石的沉淀现象及装置和操作条件的研究

基本信息

批准号：
07455316
负责人：
TOYOKURA Ken
金额：
$ 4.29万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Calcium carbonate precipitated by the reaction between calcium chloride solution and sodium carbonate solution was studied. In this reaction calcium carbonate intermediate was came out in the initial reaction step, and then transformed to mixture of calcite and vaterite in the reacting solution, and transformation of intermediate was focused in this study. Sodium chloride crystal was added to reacting slurry in which intermediate was coexisted, calcite was precipitated dominantly. Crystal size and precipitated number of calcite was affected by the crystal size of added sodium chloride crystal and crystal growth rate of calcite was obtained in the reacting slurry which intermediate was coexisted. On the other hand, calcite precipitated dominantly by reaction between calcium chloride solution and sodium bicarbonate solution. In this reaction, precipitated number of calcite was correlated with the amount of sodium bicarbonate and it was considered that transformation of intermediate to calcite was promoted by decomposition of bicarbonate ions.In the case of double jet reactive crystallization method wihch is applied for precipitation of silver halide industry, precipitated calcium carbonate was mixture of calcite and vaterite and it was not found the operational conditions which calcite precipitated dominantly. Therefore nucleating agent were considered to be necessary in this system.Crystallization phenomena of calcite in the stationary solution was studied. It was found that mixture of calcite and vaterite was precipitated within the range of average supersaturation which was calculate by the values of pH from 100 to 250. But the calcite was precipitated in the range of average supersaturation under 50 or over 280.

研究了氯化钙溶液与碳酸钠溶液反应生成碳酸钙的过程。在该反应中，碳酸钙中间体在初始反应阶段析出，然后在反应溶液中转化为方解石和钒石的混合物，本研究的重点是中间体的转化。反应浆中加入氯化钠晶体，中间物共存，方解石以析出为主。添加的氯化钠晶体的晶粒大小影响方解石的晶粒大小和析出数，并且在中间体共存的反应浆中得到方解石的晶体生长速率。另一方面，方解石主要通过氯化钙溶液和碳酸氢钠溶液的反应析出。在此反应中，方解石的析出数与碳酸氢钠的用量相关，认为碳酸氢钠离子的分解促进了中间体向方解石的转化。应用于卤化银工业沉淀的双射流反应结晶法，沉淀的碳酸钙是方解石和水晶石的混合物，没有找到方解石为主沉淀的操作条件。因此，在该体系中必须加入成核剂。研究了方解石在固定溶液中的结晶现象。在pH值为100 ~ 250的平均过饱和范围内，方解石和钙矾石的混合物析出。而方解石在50℃以下和280℃以上的平均过饱和范围内析出。