【摘要】：鎂是工業(yè)發(fā)展的重要資源。世界所利用的鎂礦石資源主要是菱鎂礦,隨著菱鎂礦的不斷開發(fā),開采及煅燒過程中鎂粉塵對(duì)土壤造成的污染也日漸引起人們的重視。本文針對(duì)遼寧省海城市菱鎂礦區(qū)鎂粉塵污染土壤為研究對(duì)象,進(jìn)行室內(nèi)模擬結(jié)皮形成過程,對(duì)土壤結(jié)皮的動(dòng)態(tài)形成過程進(jìn)行了研究,為菱鎂礦區(qū)污染土壤修復(fù)提供了理論依據(jù)。通過實(shí)驗(yàn)室模擬鎂粉塵沉降與降雨條件,研究不同組成鎂粉塵對(duì)結(jié)皮形成的影響,通過X射線粉末衍射和掃描電鏡兩種檢測(cè)手段對(duì)土壤結(jié)皮形貌及物相組成分析,證明了MgO的存在是形成堅(jiān)硬結(jié)皮的最主要因素。MgO所占比例越小,形成結(jié)皮的主要物質(zhì)堿式碳酸鎂越少。單獨(dú)施加輕燒氧化鎂粉塵,進(jìn)行為期八周的結(jié)皮形成模擬實(shí)驗(yàn)的結(jié)果表明:在結(jié)皮形成的前兩周主要反應(yīng)為:氧化鎂與雨水反應(yīng)生成氫氧化鎂,以及氧化鎂和空氣中的CO2反應(yīng)生成碳酸鎂的過程。而在結(jié)皮形成的第三周,結(jié)皮中出現(xiàn)不穩(wěn)定的堿式碳酸鎂,在第四、五周不穩(wěn)定的堿式碳酸鎂消失,形成較穩(wěn)定的堿式碳酸鎂,并在這兩周出現(xiàn)了水泥物質(zhì)硫氧鎂水合物(3Mg(OH)2?MgSO4?8H2O)和硫鎂水合物(MgSO4·6H2O)。在結(jié)皮形成的6-8周,結(jié)皮中硫氧鎂水合物3Mg(OH)2?MgSO4?8H2O消失,硫鎂水合物(MgSO4·6H2O)和堿式碳酸鎂不斷增加,結(jié)皮更見緊密堅(jiān)硬。通過熱力學(xué)計(jì)算結(jié)皮中可能發(fā)生的反應(yīng),熱力學(xué)計(jì)算結(jié)果進(jìn)一步驗(yàn)證了結(jié)皮形成的動(dòng)態(tài)過程,MgO生成Mg(OH)2和MgCO3的反應(yīng)更易在室溫下進(jìn)行。這兩種物質(zhì)的生成促進(jìn)了水纖菱鎂礦的生成。隨著放熱反應(yīng)的進(jìn)行,體系溫度升高促進(jìn)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.
【學(xué)位授予單位】：遼寧科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X53;X753

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