【作者】 王锦华；

【导师】 陈文；

【作者基本信息】 武汉理工大学 ， 材料物理与化学， 2008， 博士

【摘要】 我国天然无水硫酸钙（硬石膏）矿产资源丰富,但由于水化活性差,利用率很低。随着国民经济的高速发展,对石膏产品需求日益加大,解决天然硬石膏水化活性低的问题越来越迫切。因此针对无水硫酸钙水化理论中存在的问题,如复盐生成与分解、激发剂阳离子的z/r参数的作用、同离子效应等开展研究,揭示盐类激发剂对硬石膏水化激发作用机理,探寻激发硬石膏水化的规律,对促进天然石膏矿产的开发具有重要的理论意义与现实意义。本论文从硫酸钙复盐的合成入手,深入开展了硫酸钙复盐的生成条件、热学性质、光谱学表征、水溶特性等方面的研究;对可溶性硫酸盐对无水硫酸钙水化激发效果进行了系统的分析研究;揭示了可溶性硫酸盐对无水硫酸钙的水化激发机理,探讨了盐类激发剂对不同产地天然硬石膏的适应性。主要内容和研究成果如下:1、通过应用溶液合成和高温淬冷合成两种方法,对可溶性硫酸盐与无水硫酸钙合成复盐的条件及规律进行了系统研究,优化了复盐的合成工艺参数,并对水溶液合成法中反应温度、反应时间与溶剂量对复盐合成的影响进行了探讨。结果显示,虽然无水硫酸钙具有络合性,但在常温常压水溶液中,仅一价硫酸盐（除Li外）能合成复盐,I族元素从上到下随原子序数增加,与硫酸钙形成复盐的难度逐渐降低,其中钾盐合成复盐速度最快。水溶液合成复盐的影响因素主要为合成温度和溶剂量。硫酸钙复盐的高温合成是一个渐进的过程,受温度影响较大,且与反应物熔点高低密切相关;硫酸钙复盐的高温合成动力学可以用二维扩散反应方程（（1.α）ln（1-α）+α=kt）和Ginstling-Brounshtein方程(1-2α/3-（1-α）^2/3=kt)来描述,反应受扩散控制。2、对硫酸钙复盐的晶体结构、谱学性质及热稳定性进行了研究分析,建立了热学与谱学档案。高温淬冷合成的硫酸钙复盐有较好的热学稳定性,但水合复盐随着温度的升高,复盐的物相组成变化较复杂。受硫酸钙复盐中阳离子数量与种类的影响,SO₄^2-阴离子基团的振动光谱出现变化,复盐中阳离子种类越多,其谱峰分裂越明显。3、对合成的硫酸钙复盐水溶特性进行研究,对复盐的水化历程、影响因素进行了分析讨论。硫酸钙复盐水溶特性较复杂,但具有一定的相似性。其水化分解主要受水量和水化时间的影响,水合复盐在水量较少的情况下不易分解,在0.3-10L/mol水量范围内含钾硫酸钙水合复盐存在可逆转化。复盐在高水量时溶解非常快,受扩散过程控制。两种水合复盐溶解性能相似,溶解方程级数在1.1左右。而高温复盐的溶解动力学级数则在1.5-1.8范围内,动力学常数比水合复盐低一个数量级,其大小呈现以第三周期元素为中心向两边增大的趋势。结晶阶段为CaSO₄·2H₂O相的析出,其结晶Stumm动力学方程级数为1.07。4、通过对CaSO₄在Na₂SO₄、K₂SO₄、Rb₂SO₄、Cs₂SO₄、（NH₄）₂SO₄溶液中水化过程,以及CaSO₄·2H₂O、CaSO₄与以上硫酸盐反应速度、产物的研究,结合复盐合成与水化过程研究结果分析,明确了无水硫酸钙水化不可能按照布德尼科夫的复盐理论进行;CaSO₄在其它种类的可溶性硫酸盐溶液中水化研究表明,无水硫酸钙水化过程中受硫酸盐水合物的析晶过程影响,与激发剂阳离子z/r值大小无关,阳离子的z/r参数影响水化率的规律并不存在;5、无水硫酸钙在可溶性硫酸盐中的水化按照溶解-成核-生长理论进行。CaSO₄达到溶解平衡时,Ca²⁺的浓度大于CaSO₄·2H₂O溶解平衡的Ca²⁺的浓度,CaSO₄·2H₂O获得结晶的驱动力;可溶性硫酸盐激发作用在于异向晶核的形成:水化过程与CaSO₄生成复盐或析出水合物所形成的细小物相,作为异质微粒使母相中存在不均匀性,这些不均匀性有效地降低成核时的表面能位垒,使CaSO₄·2H₂O晶核优先地在这些不均匀的地方形成,因此这些物质起成核催化剂作用。引入外来离子,降低了成核的表面能势垒,使CaSO₄·2H₂O更容易结晶。6、选用四种不同产地与地质成因的天然硬石膏研究盐类激发剂的适应性,并对加水量与环境温度对水化的影响进行了探讨。天然硬石膏由于其地质成因与所处地质环境不同,在物相组成、碱金属离子等杂质含量、晶体生长状态等多方面存在明显差异,因此不同产地硬石膏对激发剂种类具有选择性,但水化激发机理一致。在有杂质存在的天然硬石膏中,FeSO₄表现出了良好的适应性,其水化激发效果高于在分析纯无水硫酸钙中的效果。温度与水量对无水硫酸钙的水化有重要影响,硬石膏胶结料及其制品在生产过程中环境温度宜控制在30℃以内。更多还原

【Abstract】 Natural anhydrous calcium sulfate （anhydrite） is rich in mineral resources in our country, but activity is very low. So its utilization ratio is not high. With the rapid development of national economy, increasing demand for gypsum products, the improvement of natural anhydrite’s low activity has become increasingly pressing. Therefore, in order to aim at the existing problems in anhydrous calcium sulfate hydration theory （eg. the formation and decomposition of double salts, the role of z / r of the activator’s cations, common ion effect etc.）, reveal for the excitation mechanism of the salts to anhydrite hydration, and seek for the law of catalyzing anhydrite hydration, it is greatly theoretical significance and practical significance for promoting the development of natural mineral gypsum.The synthesis of the calcium sulfate double salt was investigated firstly and then researched thoroughly to the formulation condition, thermodynamic properties, spectroscopy characterization and solubility idiosyncrasy of the calcium sulfate double salt. The effect on hydration of the soluble sulfate to the anhydrous calcium sulphate was analyzed systematically, and the mechanism was given. The adaptability of the salts to the different natural anhydrite was also discussed. The main content and research results are as follows:1. By mean of the solution method and the high temperature synthetic method, it was investigated to the reactive law of the soluble sulfate with calcium sulfate and the synthetic condition of the double salts systematically, and optimized the parameters of the preparations. The influence of the reaction temperature, reaction time and solvent amount to the synthesis by the solution method were discussed. The result showed that although the anhydrous calcium sulfate has the complexing, in the normal temperature and the atmospheric pressure solution, only univalent sulfate （except Li） can synthesize the double salt with calcium sulfate. Increasing along with the atomic number, I-group sulfate with the anhydrous calcium sulfate is easy to synthesize. The speed of the sylvite is highest. Main effect factors are synthesis temperature and solvent volume. The transformation by the high temperature synthetic method is tardy. And it is effected by the temperature more and closely related with the reactant melting point. High temperature synthesis dynamics of calcium sulfate double salts can be described by the two-dimensional proliferation response （（1-α）ln（1-α）+α=kt） and Ginstling-Brounshtein Equation (1-2α/3-（1-α）^2/3=kt). The response is controlled by the diffusion.2. Crystal structure, spectroscopy characterization and thermal stability of the double salts were studied in this paper. And their thermodynamic, spectroscopy files were improved. The thermodynamic stability of the calcium sulfate double salts which were quenched is better, while the transformation of the hydration double salts was complicatedly. Influenced by the quantity and type of the positive ions of the double salts, the vibration spectrum of SO₄^2- changed. The type of the positive ion is more and the spectrum peak splits are more obvious.3.The solubility idiosyncrasy of the calcium sulfate double salt was researched systematically. And the process and the influencing factors of double salts’ hydration were discussed. They are complicated, but have certain similarity. The main factors of the solubility transformation were the solvent quantity and the hydration time. The double salts synthesized by the solution method decompose not easily when the water volume is few, and the transformation of potassium calcium sulfate double salts when the water volume is reversible between 0.3 to 10 L/mol. The double salts decompose quickly when the water is enough and it is controlled by the diffusion. Based on that research, the dissolution kinetics and the crystallization kinetics of the double salts were investigated.And the kinetic equations have been obtained. The progressions of the solubility equations of the hydrate double salts were about 1.1, while the quenched double salts’ were about 1.5-1.8. The constants of the kinetics equations were increasing as the center of the third period element. And the CaSO₄·2H₂O phase crystallized in the final stage. Its progression of crystallization kinetic equation was 1.07.4. Through the research on hydration of the anhydrous calcium sulfate in the following sulfate（Na₂SO₄、K₂SO₄、Rb₂SO₄、Cs₂SO₄、（NH₄）₂SO₄）, reaction speed and offspring of the anhydrous calcium sulfate with the previous sulfate, and according to the analytic results of the double salts’ synthesis and the hydrated processes, it is founded that double salt theory is not accurate. Through the experiments on hydration of the anhydrous calcium sulfate in the other sulfate, dissoluble sulfate hydrate origining from hydration process of AH affects its hydrous rate, hydrous rate of the anhydrous calcium sulfate does not connect with z/r of the cation in stimulation, and neither does the theory that z/r affect hydrous rate of the anhydrous calcium sulfate.5. Hydration of the anhydrous calcium sulfate in dissoluble sulfate complies with dissolve-nucleate-grow theory, concentration of Ca²⁺ from dissolving of CaSO₄is higher than one of CaSO₄·2H₂O,CaSO₄·2H₂O gets a motivity of crystallization. Dissoluble sulfate takes the following functions: double-salt or dissoluble sulfate hydrate from hydration of the anhydrous calcium sulfate in it becomes heterogeneous particle and a kind of nucleation catalyzer, and reducing surface barrier when CaSO₄·2H₂O becomes crystal because the crystal of CaSO₄·2H₂O presciently appears in uneven place. Results indicate that hydration of the anhydrous calcium sulfate does not conform to double-salt theory, but it conforms to this mechanism: dissolve-nucleate-grow, formation of CaSO₄·2H₂O is an uneven nucleation and crystallization process.6. It is selected from four kind of different habitats and the geologic origin natural anhydrite, for researching the compatibility of the catalysts. And it is discussed to the influence of the water and the ambient temperature to the hydration. Owing to theirs geologic origin and the geological environment differently, phase composition and foreign inclusions （e.g. alkaline metal ion） and crystal growth condition etc of different kinds of natural anhydrite are discrepant. So the different habitat anhydrite needs different catalyst. But the mechanism is consistent. The effect of FeSO₄ to the natural anhydrite with impurity is better than to analytically pure anhydrous calcium sulfate. The temperature and the water volume have the important effect to the anhydrous calcium sulfate’s hydration. Ambient temperature in the production process of anhydrite cement materials and products should be within 30°C.更多还原