柠檬酸对石膏结晶特性的影响

Effect of citric acid on crystallization properties of gypsum

通过石膏成核试验和晶体生长试验,探索柠檬酸对脱硫石膏晶体品质的影响原理,有利于脱硫石膏高品质资源化利用。石膏晶体成核试验表明,柠檬酸延长结晶诱导时间,抑制了成核速率。空白工况下过饱和比为2.3时诱导时间为38 min,过饱和比越小,柠檬酸对诱导时间的延长作用越明显,柠檬酸的成核抑制指数越大。不同过饱和比下,柠檬酸导致石膏结晶诱导时间延长4.8~6.9倍,石膏结晶成核抑制指数分布在76.1%~89.6%。柠檬酸抑制石膏晶体的成核过程。脱硫石膏晶体生长试验表明,空白工况下石膏晶体的中值粒径为39.738μm,添加柠檬酸工况,石膏粒径增大了79.28%。同时添加柠檬酸和晶种工况,石膏粒径比空白工况样品增大了288.66%。形貌分析表明,添加柠檬酸后,石膏晶体长度减小,宽度增加,石膏呈现短柱状。同时添加晶种和柠檬酸时,石膏晶体生长更粗壮,出现叠层状结构。柠檬酸中的羧基基团对Ca^(2+)的吸附作用,使石膏由细针状转化为短柱状。因此,柠檬酸抑制石膏晶体成核过程,促进石膏晶体短柱状生长,提高了石膏品质。

The nucleation experiment and crystal growth experiment of gypsum were carried out in this study to explore the principle of the influence of citric acid on the crystal quality of desulfurized gypsum,which was conducive to the high quality resource utilization of desulfurized gypsum.The nucleation experiment of gypsum crystals show that citric acid prolongs the crystallization induction time and inhibites the nucleation rate.In blank condition,the induction time is 38 min when the suoversaturation ratio is 2.3.The smaller the suoversaturation ratio is,the more obvious the prolonging effect of citric acid on induction time is,and the larger the nucleation inhibition index of citric acid is.With different suoversaturation ratio,citric acid can prolong the crystallization induction time by 4.8-6.9 times,and the inhibition index of gypsum crystallization nucleation is 76.1%-89.6%.Citric acid inhibits the nucleation of gypsum crystals.The growth experiment of desulfurized gypsum crystal show that the median particle sizeof gypsum crystal is 39.738μm in blank condition,and the particle size of gypsum crystal increases by 79.28%when citric acid is added.When citric acid and seed are added at the same time,the particle size of gypsum is increased by 288.66%compared with the blank condition.Morphology analysis show that the length of gypsum crystal decreases and the width increases after citric acid is added.When seed crystals and citric acid are added at the same time,the gypsum crystals grows stronger and showed lamellar structure.The adsorption of Ca^(2+)by carboxyl groups in citric acid transforms gypsum from fine needle to short column.Therefore,citric acid inhibits the nucleation process of gypsum crystals,promotes the short columnar growth of gypsum crystals and improves the quality of gypsum.