菱镁矿区土壤结皮形成过程研究

发布时间：2018-12-18 05:20

【摘要】：镁是工业发展的重要资源。世界所利用的镁矿石资源主要是菱镁矿,随着菱镁矿的不断开发,开采及煅烧过程中镁粉尘对土壤造成的污染也日渐引起人们的重视。本文针对辽宁省海城市菱镁矿区镁粉尘污染土壤为研究对象,进行室内模拟结皮形成过程,对土壤结皮的动态形成过程进行了研究,为菱镁矿区污染土壤修复提供了理论依据。通过实验室模拟镁粉尘沉降与降雨条件,研究不同组成镁粉尘对结皮形成的影响,通过X射线粉末衍射和扫描电镜两种检测手段对土壤结皮形貌及物相组成分析,证明了MgO的存在是形成坚硬结皮的最主要因素。MgO所占比例越小,形成结皮的主要物质碱式碳酸镁越少。单独施加轻烧氧化镁粉尘,进行为期八周的结皮形成模拟实验的结果表明:在结皮形成的前两周主要反应为:氧化镁与雨水反应生成氢氧化镁,以及氧化镁和空气中的CO2反应生成碳酸镁的过程。而在结皮形成的第三周,结皮中出现不稳定的碱式碳酸镁,在第四、五周不稳定的碱式碳酸镁消失,形成较稳定的碱式碳酸镁,并在这两周出现了水泥物质硫氧镁水合物(3Mg(OH)2?MgSO4?8H2O)和硫镁水合物(MgSO4·6H2O)。在结皮形成的6-8周,结皮中硫氧镁水合物3Mg(OH)2?MgSO4?8H2O消失,硫镁水合物(MgSO4·6H2O)和碱式碳酸镁不断增加,结皮更见紧密坚硬。通过热力学计算结皮中可能发生的反应,热力学计算结果进一步验证了结皮形成的动态过程,MgO生成Mg(OH)2和MgCO3的反应更易在室温下进行。这两种物质的生成促进了水纤菱镁矿的生成。随着放热反应的进行,体系温度升高促进了MgSO4·6H2O的生成。
[Abstract]:Magnesium is an important resource for industrial development. Magnesite is the main resource used in the world. With the continuous development of magnesite, the pollution of soil caused by magnesium dust in the process of mining and calcining has been paid more and more attention. Based on magnesium-dust contaminated soil in magnesite mine area of Haicheng City, Liaoning Province, the formation process of soil crust was simulated in laboratory, and the dynamic formation process of soil crust was studied, which provided a theoretical basis for remediation of contaminated soil in magnesite mine area. The effects of different composition of magnesium dust on the formation of crust were studied by simulating the precipitation and rainfall conditions of magnesium dust in laboratory. The morphology and phase composition of soil crust were analyzed by means of X-ray powder diffraction and scanning electron microscope. It is proved that the existence of MgO is the most important factor in the formation of hard crust, and the smaller the proportion of MgO is, the less the base magnesium carbonate is. The results showed that in the first two weeks of crust formation, the main reaction was that magnesium oxide reacted with Rain Water to form magnesium hydroxide. And the reaction of magnesium oxide with CO2 in air to form magnesium carbonate. In the third week of the formation of crusts, unstable basic magnesium carbonate appeared in the crust, and the unstable basic magnesium carbonate disappeared in the fourth and fifth weeks, resulting in the formation of more stable basic magnesium carbonate. In these two weeks, the cement materials, magnesium sulfide hydrate (3Mg (OH) 2?MgSO4?8H2O) and magnesium sulfide hydrate (MgSO4 6H2O) were found. During the 6-8 weeks of crusts formation, the 3Mg (OH) 2?MgSO4?8H2O of magnesium sulfate hydrate disappeared, the MgSO4 6H2O and basic magnesium carbonate increased continuously, and the crust became more compact and hard. The possible reactions in the crusts were calculated by thermodynamics. The thermodynamic calculation results further verified the dynamic process of the formation of severed skins. The reaction of MgO to Mg (OH) _ 2 and MgCO3 was easier to take place at room temperature. The formation of these two substances promotes the formation of water fiber magnesite. With the exothermic reaction, the temperature of the system increased to promote the formation of MgSO4 6H2O.
【学位授予单位】：辽宁科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53;X753

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