The Extraction, Separation and Recovery of Metals and Contaminants Using Hydrometallurgical Technologies

这项发现拨款提案的重点是推进湿法冶金浸出和分离技术发展的基础科学。已经确定了四个独立的发现项目进行调查。这些包括(1)高温下金迁移率的控制，含可溶性氯化物的难熔碳质金矿的酸蒸釜处理，(2)废水中硒的去除和固体硒的稳定，(3)阳极的开发和阳极化学的控制，用于从甲烷磺酸溶液中电积铅，(4)使用混合的非氰化物浸出剂进行金和银的浸出。******难熔硫化金矿石和精矿通常在210-230℃的高压灭菌器中氧化，以在氰化之前破坏黄铁矿和毒砂。该技术的局限性之一发生在金矿也含有有机物质和高压灭菌器溶液含有少量氯化物（通常为10- 50ppm）的地方。初步确定了一种化学体系，有望使氯化物沉淀，并防止金的这种损失机制。******硒通常以亚硒酸盐（IV）和硒酸盐（VI）的形式存在于矿化废水中。亚硒酸盐的沉淀是通过与氢氧化铁共沉淀法完成的。从废水中去除硒酸盐要困难得多，由于其化学成分与通常存在的高含量硫酸盐相似，因此更加困难。从废水中去除硒的目标水平是1 ppb。发现了一种能将硒酸盐吸附到固体基体结构中的无机层状双氢氧化物吸附剂。这是非常有前途的，但有必要研究层状双氢氧化物的溶解度，因为这将影响硒负载吸附剂的长期储存。一种溶剂萃取系统对废水中硒酸盐有一定的选择性。******我们已经开发了三种使用甲烷磺酸溶液化学回收或精炼铅的工艺。该过程依赖于阴极的铅电积和阳极的析氧和酸再生。必须研究铅- msa系统的阳极电化学，以确定避免二氧化铅形成和再生酸浸出的阳极系统和电解质化学。******世界范围内正在研究使用非氰化物浸出剂浸金，以提供替代氰化物浸出金和银的方法。阻碍更广泛采用氰化浸出替代品的障碍有很多，包括高试剂消耗、金浸出动力学缓慢、难以从浸出溶液中回收金等。在许多情况下，人们相信这些困难中的一些可以通过引入混合溶剂系统来克服。＊＊＊＊＊

The focus of this discovery grant proposal is advancing the fundamental science for the development of hydrometallurgical leaching and separation technologies. Four separate discovery projects have been identified for investigation. These include (1) the control of gold mobility in high temperature, acid autoclave treatment of refractory carbonaceous gold ores containing soluble chloride, (2) selenium removal from waste water and solid selenium stabilization, (3) development of anodes and control of anode chemistry for electrowinning of lead from methane sulfonic acid solutions and (4) the use of mixed, non-cyanide lixiviants for leaching of gold and silver. ******Refractory sulfide gold ores and concentrates are commonly oxidized in autoclaves at 210-230C to destroy pyrite and arsenopyrite prior to cyanidation. One of the limitations of the technology occurs where the gold ore also contains organic matter and the autoclave solutions contain small amounts of chloride (typically 10-50 ppm). A chemical system has tentatively been identified that is expected to precipitate the chloride and prevent this mechanism of gold loss.******Selenium is often present in mine-affected wastewater as selenite (IV) and selenate (VI). The precipitation of selenite is accomplished by co-precipitation with ferric hydroxide. The removal of selenate from wastewater is much more difficult, even more so due to chemical similarity to high levels of sulfate that are often present. The target level for selenium removal from wastewater is 1 ppb. An inorganic layered double hydroxide adsorbent has been identified that has the ability to adsorb selenate into the solid matrix structure. This is very promising but there is a need to study the solubility of the layered double hydroxide, as this will impact the long-term storage of the selenium-loaded adsorbent. A solvent extraction system has also been identified with some selectivity for selenate over sulfate from wastewater.******RWe have developed three processes for lead recovery or refining using methane sulfonic acid solution chemistry. The process is dependent on lead electrowinning at the cathode and oxygen evolution and acid regeneration at the anode. The anode electrochemistry of the lead-MSA system must be studied to identify anode systems and electrolyte chemistries that avoid lead dioxide formation and regenerate acid for leaching.******The use of non-cyanide lixiviants for gold is under worldwide investigation to provide alternatives to the use of cyanide for gold and silver leaching. The obstacles that prevent wider adoption of alternatives to cyanide leaching are numerous including high reagent consumption, slow kinetics of leaching of gold, difficult recovery of gold from the leach solution, etc. In many cases it is believed that some of these difficulties may be overcome by introduction of mixed lixiviant systems. *****