摘要
采用反应结晶的实验方法,结合地球化学模拟软件PHREEQC计算获得的离子活度积、溶度积以及过饱和指数等热力学参数,对二水硫酸钙结晶的主要影响因素进行了研究.结果表明:实验条件下,温度、nCa2+/nSO42-、反应物浓度是影响二水硫酸钙结晶的关键因素,而反应溶液pH的影响不明显.温度升高会大大缩短结晶诱导时间,且较高温度下(55℃)晶体生长得更为粗壮和均匀;nCa2+/nSO42-和反应物浓度的改变使得溶液的离子活度积、过饱和度发生变化,从而影响结晶诱导时间和晶体形貌.适中的过饱和条件(S≈2.19)更有利于形成饱满且尺寸分布均匀的晶体;较低过饱和度条件下,适当地增大溶液nCa2+/nSO42-,不仅可以缩短结晶诱导时间,还可以促进晶体在b轴方向的生长.
The thermodynamic parameters of the crystallization of calcium sulfate dihydrate such as ion activity product（IAP） 、solubility product（Ksp） and supersaturation index（SI） under different crystallization conditions were obtained with a geochemical aqueous model program,PHREEQC 2.12.With reactive crystallization of calcium chloride and sodium sulfate,we found that temperature、n Ca^2＋ / n SO4^2-and concentration of reactants were the key factors influencing the dihydrate calcium sulphate crystallization,and the influence of pH was not obvious.With the increase of temperature,the induction time was shortened,and higher temperature（i.g.55 ℃） was more advantageous to the growth of more uniform and larger crystals.The change of n Ca2＋ / n SO42-and concentration of reactants causes variation of the ion activity product and the degree of supersaturation of the reaction solution,thus affecting the crystallization induction time and crystal morphology.Moderate degree of supersaturation（S≈2.19） favor the formation of uniform and larger crystals.the appropriate change of n Ca^2＋ / n SO4^2-could promote the growth of crystals in b-axis direction and shorten the induction time.
出处
《湘潭大学自然科学学报》
CAS
北大核心
2014年第3期60-66,共7页
Natural Science Journal of Xiangtan University
基金
浙江省工业锅炉炉窑烟气污染控制工程技术研究中心开放基金课题
关键词
二水硫酸钙
结晶
诱导时间
PHREEQC
calcium sulfate dihydrate
crystallization
induction time
PHREEQC Program
