在某些表面活性剂存在下二水硫酸钙的晶型转变

Crystal modification of calcium sulfate dihydrate in the presence of some surface-active agents.

作者信息

Mahmoud M H H, Rashad M M, Ibrahim I A, Abdel-Aal E A

机构信息

Central Metallurgical R&D Institute, P.O. Box 87, Helwan, Cairo, Egypt.

出版信息

J Colloid Interface Sci. 2004 Feb 1;270(1):99-105. doi: 10.1016/j.jcis.2003.09.023.

DOI:10.1016/j.jcis.2003.09.023

PMID:14693140

Abstract

The effect of surface-active agents (surfactants), as additives, on the crystallization of gypsum was studied under conditions of the simulated dihydrate process of phosphoric acid production. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80 degrees C, and the turbidity of the reaction mixture was measured at different time periods to determine the induction time of gypsum crystal formation. Two types of surfactants, namely, cetyltrimethylammonium bromide (CTAB) as a cationic surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant were added to investigate their effects on the crystallization of gypsum. Addition of CTAB decreased the induction time and increased the growth efficiency, while addition of SDS increased the induction time and decreased the growth efficiency compared with the baseline (without additives). The surface energy increased with CTAB and decreased with SDS compared with the baseline. The percentage of fine crystals decreased in the presence of CTAB and increased in the presence of SDS compared with the baseline. Gypsum morphology changed from needle-like in the absence of additives to tabular in the presence of CTAB.

摘要

在磷酸生产二水合物模拟过程的条件下，研究了作为添加剂的表面活性剂对石膏结晶的影响。在80℃下，将磷酸二氢钙和硫酸与稀磷酸混合，并在不同时间段测量反应混合物的浊度，以确定石膏晶体形成的诱导时间。添加了两种类型的表面活性剂，即作为阳离子表面活性剂的十六烷基三甲基溴化铵（CTAB）和作为阴离子表面活性剂的十二烷基硫酸钠（SDS），以研究它们对石膏结晶的影响。与基线（无添加剂）相比，添加CTAB缩短了诱导时间并提高了生长效率，而添加SDS则延长了诱导时间并降低了生长效率。与基线相比，表面能随CTAB增加而随SDS降低。与基线相比，在CTAB存在下细晶百分比降低，在SDS存在下细晶百分比增加。石膏形态从无添加剂时的针状变为CTAB存在时的板状。