有机酸对α半水脱硫石膏晶体生长习性的影响与调晶机理

Effect of Organic Acid on Crystalline Habit of α-Hemihydrate Desulfurization Gypsum and its Crystal Modification Mechanism

研究了有机酸的吸附特性、有机酸对α半水石膏晶体生长习性和形貌的影响,从α半水脱硫石膏晶体生长角度对有机酸调晶机理进行了分析。结果表明:有机酸改变了α半水石膏晶体生长习性,长轴生长被抑制,晶形由长棒状转变为短柱状,且晶粒尺寸增大;控制pH值和有机酸掺量,可制备长径比1:1的短柱状α半水石膏晶体;有机酸通过与Ca2+发生络合作用,在α半水脱硫石膏晶体表面形成环状有机酸钙络合物,阻碍离子扩散与晶面叠合,使α半水石膏晶体生长速率降低,晶体发育更充分,晶体尺寸更大;有机酸优先选择吸附在α半水石膏晶体(111)面,抑制其c轴方向生长,使晶面沿c轴生长速率的比较优势被削弱甚至逆转,导致α半水石膏晶体生长习性和晶体形状发生改变。

The adsorption characteristic of organic acid and its effect on the crystalline habit and morphology of ct-hemihydrate desulfurization gypsum were investigated. The crystal modification mechanism of organic acids was analyzed by means of adsorption and crystal growth. The results show that organic acid evidently changes the crystalline habit of dihydrate, leading to a large crystal size and transformation of crystal shape from long clavate-like to short columnar-shaped. The short columnar-shaped ct-hemihydrate desulfurization gypsum crystals with a length-diameter ratio of 1：1 could be prepared by controlling the dosage of organic acid. Organic acid complexes with Ca2＋, and organic acid calcium complex compounds were formed on the crystal nucleus of ct-hemihydrate desulfurization gypsum, which hindered Ca2＋ diffusion and crystal growth, and decreased the growth rate of ct-hemihydrate desulfuri- zation gypsum crystals. The crystals could thus have time enough to grow up, and as a result, the size of dihydrate crystals became coarser. Organic acid was selectively chemisorbed on the （111） face of gypsum crystal, which inhibited the growth of c axis and altered the relative growth rate of crystal faces in different axis directions, consequently leading to the transformation of crystalline habit and crystal morphology of dihydrate gypsum.