【作者】 李骞；

【导师】 邱冠周； 姜涛；

【作者基本信息】 中南大学 ， 矿物加工工程， 2007， 博士

【摘要】 我国含砷金矿资源比较丰富,分布广泛。生物预氧化一氰化浸金法由于其金回收率高、成本低、无环境污染,越来越得到重视。但由于其周期长,加之某些重要环节的机理还未完全查清,影响了生物预氧化法的大规模工业应用。本论文运用电化学方法研究了砷黄铁矿在无菌和有菌体系下氧化的行为及腐蚀机理;在此基础上进行了生物氧化As（Ⅲ）和砷黄铁矿动力学的研究;并以含砷锑金精矿为对象,详细研究了生物预氧化一氰化浸出法提金过程。采用矿物粉末电极,运用线性极化和交流阻抗等电化学测试手段,模拟生物氧化体系,详细研究了砷黄铁矿氧化的电化学行为。研究发现砷黄铁矿在酸性溶液中,在0.2～0.3V处被氧化为As₂S₂,覆盖于电极表面,使电极表面发生钝化;随着电位的继续升高,As₂S₂被氧化生成亚砷酸,在0.8v以上,亚砷酸被氧化为砷酸,揭示了砷黄铁矿在酸性溶液中氧化的机理。添加细菌降低了砷黄铁矿氧化的静止电位以及腐蚀电位,且在细菌的作用下砷黄铁矿直接氧化为亚砷酸,消除了由于As₂S₂生成导致的电极表面钝化现象,证明细菌直接作用于矿物表面。在有菌外加三价铁体系中生物氧化的机理与酸性体系下的比较没发生变化,钝化物膜为As₂S₂,揭示了生物氧化钝化的机理;腐蚀速度是有菌时腐蚀速度的2倍,证实在三价铁存在时砷黄铁矿的生物氧化主要为铁离子的化学氧化作用。交流阻抗研究的结果与砷黄铁矿阳极氧化的结果一致,As₂S₂钝化膜的形成是阻碍砷黄铁矿继续氧化的主要原因,要使氧化过程中不形成钝化物就必须使体系电位大于0.3v（vsSHE）,然而在0.3V（vsSHE）至0.8V（vsSHE）的范围内,砷主要以As（Ⅲ）的形态存在,这对细菌的存活是一大考验。溶液中三价砷的氧化行为动力学研究发现:随着As（Ⅲ）浓度的升高,细菌的活性逐渐降低,控制溶液中As（Ⅲ）的浓度是生物预氧化含砷金矿能否顺利进行的关键;Fe（Ⅲ）可以氧化As（Ⅲ）,添加Fe（Ⅲ）后,在氧化的初期,As（Ⅲ）的氧化主要是作为添加剂的Fe（Ⅲ）的作用,从而降低溶液中As（Ⅲ）的浓度,为细菌的繁殖提供必须的条件,待细菌大量繁殖后主要是细菌氧化的间接作用使As（Ⅲ）向As（Ⅴ）转化;As（Ⅲ）的生物氧化与溶液中As（Ⅲ）的浓度、Fe（Ⅱ）、Fe（Ⅲ）离子浓度有相关关系,铁砷摩尔比高,则As（Ⅲ）的氧化率就高,所以控制溶液中铁离子的含量,防止沉铁反应可以强化As（Ⅲ）的氧化。生物氧化砷黄铁矿的矿浆电位为0.5v左右,避免了As₂S₂钝化膜的生成,但溶液中砷主要以As（Ⅲ）的形态存在,影响细菌的活性,从而影响砷黄铁矿的氧化;Fe（Ⅲ）离子优先氧化比较活泼的砷黄铁矿而非As（Ⅲ）;添加黄铁矿后,由于其提供营养源以及形成原电池的作用强化了砷黄铁矿的氧化;控制合理的pH,温度以及转速等有利于砷黄铁矿的生物氧化。砷黄铁矿生物氧化理论研究结果可以指导实际含砷金矿的生物预氧化;对含砷为10.37%的锑金矿,未经生物氧化预处理时,金浸出率仅为41%;经生物氧化预处理12天后,金的浸出率达76.55%,提高了35.62个百分点;生物预氧化大大强化了含砷锑金矿的氰化浸出。另外,金的浸出率与脱砷率成正比关系,而且只需脱除部分砷就可以获得较高的金浸出率,脱砷率为60%时,金的浸出率可达90%以上。本论文的研究为含砷难处理矿的生物预氧化一氰化浸出提供了理论和技术上的指导。本论文得到国家自然科学基金创新研究群体项目（50321402）和国家重点基础研究发展生物973项目（2004CB619204）的资助。更多还原

【Abstract】 The arsenic bearing gold ores is abundance and distributing abroad in China.The bio-pretreatment—cyanidation technique has advantage of higher leaching,lower cost and no pollution,so it is gradually a hot research subject.Howerever,it has long periods and there are still very important unknown mechanisms,which affects its large scale application. In this research,electro-methods were used to investigat the bio-oxidation action and corrosion mechanism with or without bacteria in acidic solution.Based on the electrochemical results,the solution chemistry of bio-oxidation As（Ⅲ）to As（Ⅴ）and arsenopyrite oxidation kinetics were studied.At the same time,the process of bio-pretreatment—cyanidation leaching was investigated with arsenical antimony concentrates.The arsenopyrite oxidation action was investigated by various methods of electrochemistry（such as Tafel,liner polarization,AC impedance）and using Carbon- Paste-Electrode simulating the bacteria leaching system.In the acdic solution without bacteria,arsenopyrite was fistlly oxidated to As₂S₂ at the potential of 0.2～0.3v（vsSHE）,which covered the electrode and blocked the process continuesly,and At higher potential,As₂S₂ was oxidated to H₃AsO₃,when the potential is over 0.8v （vsSHE）,H₃AsO₃ was then oxidated to H₃AsO₄.The results showed the mechanism of arsenopyrite oxidation in acidic solution.Adding bateria in the system,the electrostatic potential of arsenopyrite was reduced,and arsenopyrite was dedirectly oxidated to H₃AsO₃ and no intermediate product As₂S₂,which tesitified that bacteria is directly action on the surface of the ore.The mechanism of adding bacteria and irons is the same as acidic solution without bacteria,the pasivation film is As₂S₂, which discovered the mechanism of biooxidation passivation.The current density is two times of the biooxidation,which shown that iron is the main oxidants to oxidate arsenopyrite.The result of AC impedance is the same as that of liner polarization,which made sure that As₂S₂ passivation film was the main matter to block the arsenopyrite to be further oxidated. In order to avoild to form As₂S₂,the potential must be higher than 0.3v（vsSHE）,however,in the range of 0.3V to 0.8V（vsSHE）,arsenic is mainly as As（Ⅲ）in the solution,which would lead bacteria to death.The results of kinetics of bio-oxidation As（Ⅲ）to As（Ⅴ）indicated that the bacteria activity decrease with As（Ⅲ）concentratin increasing. Fe（Ⅲ）can oxidate As（Ⅲ）to As（Ⅴ）,but the oxidation rate is very solly and the activity of bacteria decreased with As（Ⅲ）concentration increasing.As（Ⅲ）is mainly oxidated by Fe（Ⅲ）on the early stage when adding Fe（Ⅲ）,When bacteria survive,As（Ⅲ）is oxidated by inderect mechanism.There were relationship between As（Ⅲ）oxidation and initial As（Ⅲ）concentration,Fe（Ⅱ）and Fe（Ⅲ）concentration in the solution. Keeping iron concentration and avoilding iron deposition can intensify As（Ⅲ）oxidation.The results of arsenopyrite oxidation kinetics showed that in the bio-oxidation system the solution potential is 0.5v or so,avoiding the As₂S₂ passivation but arsenic is mainly the As（Ⅲ）form,which can lead bacteria to death and affect arsenopyrit to oxide.Fe（Ⅲ）firstly oxidized arsenopyrite.Suitable amount of pyrite will form galvanic cell and also supply nutrient source,which could intensify the bio-oxidation of arsenopyrite.when pH is over 2.0,The passivation film is jarrosite which would affect the arsenopyrite to be further oxidated.Suitable temperature and shaking table speed is advantageous for biooxidation.The theory of bioxidation arsenopyrite kinetics can direct the bio-oxidation arsenic bearing gold ores.If the ore,of which contain 10.37%arsenic,is not pretreatment,gold leaching is about 41%,after 12days oxidation,the result is about 76.55%,which improved about 35.62 points.The bio-pretreatment greatly intensified the cynidation of arsenic bearing gold ores.The raelationship between gold leaching and arsenic oxidation is direct proportion,furthermore,it needs only partly oxidateand higher gold leaching could be get,for example,gold leaching is over 90%when asenic oxidation is 60%.This investigation provided new theory and technique for the bio-pretreatment—cyanidation leaching technology.The research is supported by the National Natural Science Foundation of China（50321402）and Major State Basic Research Development Program of China（2004CB619204）.更多还原