Morphology and Size Distribution of Calcium Sulfate Dihydrate Crystals Precipitated from Simulated Acidic Wastewater by Lime
石灰乳中和模拟酸性废水形成的二水硫酸钙的晶粒形貌与粒度分布

The effects of process parameters and addition of Mg2+ and Fe3+ ions on the morphology and size distribution of calcium sulfate dihydrate (gypsum) particles produced by the reactive crystallization between simulated acidic wastewater and lime were investigated. Compared with the stirring speed, addition rate of lime slurry and concentration of Ca(OH)2, reaction temperature significantly affected the morphology and particle size distribution of calcium sulfate dihydrate. The morphology of precipitated crystals evolved from platelet-like and needle-like shapes to rod-like shape when the temperature increased from 25 to 70℃. And the crystallization of gypsum slowed significantly in the presence of Mg2+ and Fe3+ ions in the solution. Moreover, the morphology of gypsum was transformed from platelet-like to rod-like shape with over 1945 mg/L Mg2+ concentration in the solution. The simulated industrial acidic wastewater containing heavy metals was efficiently purified by the two-stage neutralization technology, and highly agglomerated gypsum precipitates with rod-like shape were obtained.