【作者】 郑粟；

【导师】 柴立元；

【作者基本信息】 中南大学 ， 冶金环境工程， 2006， 博士

【摘要】 自1941年首次报道硫脲溶金以来，由于其清洁、高效等特点，成为浸金领域中倍受关注的热点，世界各国对硫脲浸金的理论及工艺开展了广泛的研究，但仅局限于酸性介质。酸性硫脲法存在溶金过程中硫脲过多消耗、酸性溶液引起设备严重腐蚀、伴生金属大量溶解致使溶液再生和净化工序复杂等一系列问题，这都是传统酸性硫脲法没能得到广泛工业应用的重要原因。为克服酸性硫脲浸金过程存在的缺点，人们试图采用碱性硫脲溶液浸金。然而，硫脲在碱性介质中不稳定，因此解决碱性介质中硫脲的稳定性便成了碱性硫脲法浸金得以工业应用的首要问题。本课题在国家自然科学基金的资助下，对碱性硫脲的稳定性及其清洁提金的相关理论基础进行了比较系统的创新性研究，得出如下主要结论。 依据分子力学理论，采用HYPERCHEM 6.0化学计算软件，结合红外光谱等现代测试技术，研究了硫脲分子的结构稳定性，建立了已发现稳定剂亚硫酸钠的结构与碱性硫脲稳定性之间的“构效关系”。水溶液中硫脲易产生同分异构体而存在碳氮双键。酸性介质中，硫脲分子易与氢形成硫氢键，降低了硫原子的最高占据分子轨道（HOMO）能量，使其较为稳定；而在碱性介质中，硫脲分子不易形成硫氢键，硫原子的HOMO值明显高于酸性介质中相应值，硫脲则不稳定。亚硫酸根的加入，通过氢键与碱性硫脲分子粘接，形成稳定的环状结构，降低了硫脲分子中硫原子的HOMO值，增加了硫脲的稳定性。由此推断，碱性硫脲的高效稳定剂从分子力场的角度必须能降低硫原子的HOMO的能量，即要满足两个条件：其一，在碱性介质中易与硫脲分子形成硫氢键；其二，与硫脲分子形成稳定的环状结构。 在“构效关系”理论的指导下，分析与Na₂SO₃结构类似的物质Na₂SeO₃、Na₂SiO₃作为稳定剂的微观结构，借助电化学测试技术，优选比Na₂SO₃更高效的稳定剂，并考察了稳定剂对碱性介质中硫脲稳定性（分解率）的影响，系统研究了稳定剂对碱性硫脲浸金的促进作用。稳定剂Na₂SO₃和Na₂SiO₃大大降低了碱性硫脲的分解率，随稳定剂浓度的增大，硫脲分解率逐渐降低，而且Na₂SiO₃对碱性硫脲的稳定效果明显优于Na₂SO₃，而Na₂SO₃在所研究的电势范围内发生了氧化反应，作为稳定剂会造成其本身的过多消耗。当Na₂SiO₃浓度为更多还原

【Abstract】 Dissolution of gold in thiourea solution was reported firstly in 1941, and then the theory and process of gold leaching in thiourea solution have been most widely studied throughout the world mainly because thiourea is not detrimental to the environment, non-toxic to humans, and the dissolution of gold in thiourea solutions is much faster than in cyanide solutions, however, which is limited to acidic media. There exist some problems in acidic thiourea solution, such as, higher consumption of thiourea during gold dissolution, serious corrosion of equipments in acidic solution, no selectivity of gold leaching, complicated regeneration and purify procedures of lixiviums, which are the important reasons that acidic thiourea had not been widely applied industrially. In order to overcome the above disadvantages of acidic thiourea solution, gold leaching in alkaline thiourea solution was proposed, and accordingly some research works were carried out. However, thiourea is less unstable in alkaline media than in acidic one, so resolving the stability of thiourea in alkaline media has become the first item to apply it to industry. Since gold leaching in the alkaline thiourea solution is still at the developmental stage, a better understanding of the thermodynamics, a more comprehensive summarization of the research status, and a proper discussion of prospect should be put forward. Under the financial support of the National Natural Science Foundation of China (Grant No.50004009), the stability of the alkaline thiourea system and the concerned fundamentals of green process of gold leaching were carried out. the objective of this dissertation is to offer theories for industrial application of gold leaching in alkaline thiourea solution, to insure continuous and harmonious development of gold industry through studying the fundamental and the key scientific problems of gold leaching in alkaline solution, and accordingly some innovative conclusions were obtained as follows:Based on theory of molecular mechanics (MM), a structure-property relationship between the stability of alkaline thiourea and the structure of thiourea and sodium sulfite was built by a combination of software calculation of HYPERCHEM6.0 with the experiment of infrared spectrum. A double bond between carbon and nitrogen exists in aqueous thiourea because of isomer. Hydrogen-sulfur bond formed easily decreases the energy of HOMO of thiourea molecular, resulting更多还原