基于无机盐调控的脱硫石膏晶须水热生长机理

It is a green technology of the comprehensive utilization of flue-gas desulfurization (FGD) gypsum that calcium sulfate whiskers (CSWs) were prepared via hydrothermal method from FGD gypsum. Reported literatures and our previous investigations showed that the addition of inorganic salt had significant effects on the crystal morphology, diameter and aspect ratio of CSWs. While with the change of the type of inorganic salt, its dosage and effects were very different. However, the crystal mechanism of CSWs prepared from FGD gypsum had not been explained well when an inorganic salt was added into the hydrothermal solution. Therefore, in the process of the preparation of CSWs via hydrothermal method, it is very interesting to explore the function of inorganic salts. Namely, in the reaction solutions at the presence of inorganic salts, the dissolution characteristics of FGD gypsum, the reaction solution composition and its dissociation equilibrium, the interaction between ions of inorganic salts and surface lattice ions of CSWs and the nucleation and growth mechanism of whiskers will be systematically investigated. Simultaneously, the balance quality of system before and after reaction and the growth kinetics of CSWs will be calculated to explore the function of inorganic salts and crystal mechanism of CSWs. On this basis, the natural relationship of process parameters and quality parameters, and the principium how to select inorganic salts will be probed, which contributes to enhance the theories on CSWs prepared from FGD gypsum by hydrothermal method and realize their industrial production.

以脱硫石膏为原料，采用水热法制备脱硫石膏晶须是脱硫石膏资源化的一种绿色新工艺。已有研究和本课题组的前期探索研究表明：加入无机盐对晶须的结晶形貌、直径、长径比等有重要影响；且无机盐种类不同，其用量和作用效果差异很大，但对无机盐调控下晶须的水热生长机理仍缺乏深入而恰当的解释。本项目拟深入研究水热法制备脱硫石膏晶须过程中，无机盐作用下反应溶液体系中脱硫石膏的溶解特性、溶液组成及其解离平衡、无机盐阴阳离子与晶须晶格表面离子相互作用、晶须的形核与生长等内容；通过反应前后物料质量平衡计算和晶须生长动力学计算，揭示无机盐作用下晶须的生长机理，同时建立脱硫石膏晶须水热制备过程中无机盐调控剂的筛选准则，探索晶须制备宏观工艺参数和晶须品质参数之间的内在联系规律，为水热法制备高品质脱硫石膏晶须奠定理论基础，从而实现脱硫石膏晶须的工业化生产。

开发了脱硫石膏晶须制备与调控技术，制备的晶须结晶良好，长径比可控。揭示了无机盐作用下脱硫石膏溶解度和溶液组成变化规律，提出了复杂溶液环境中SO42-测定的新方法。建立了水热环境参数与晶须品质参数之间的定量关系模型，通过遗传算法确定的最佳工艺参数是：温度122.6℃，时间57.4min，H2SO4浓度0.99mmol/L，CuCl2用量1.4wt.%。以化学反应自催化模型为基础，构建了晶须结晶动力学方程，其转化动力学受水热环境温度、H2SO4浓度及CuCl2用量的影响。制备的晶须晶体结构中Ca-O多面体为12面体，沿c轴方向H2O通道由Y型变为O型，Ca-O-S键长呈4.4731 (7) Å（本文晶须）＞4.0045(9) Å（六方）＞3.879(9) Å（单斜）的变化，并从晶体结构上揭示了DH到HH脱水微观过程。揭示了无机盐阴阳离子的作用机理，阳离子主要吸附在晶须表面，少量进入晶格。SO42-阻碍FGD溶解，同离子效应起主导作用；Cl-、NO3-促进FGD溶解，盐效应起主导作用。无机盐对晶须品质的影响呈化学稳定性＞同离子效应＞阴离子结构＞非水合游离阳离子数量的规律。