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

这项发现赠款提案的重点是促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。包括：(1)高温下金的活动性控制；(2)含可溶氯化物的难处理碳质金矿的酸压处理；(2)废水除硒和固体硒稳定化；(3)甲烷磺酸溶液中电积铅的阳极开发和阳极化学控制；(4)混合非氰化浸金剂的使用。*难选硫化金矿和精矿通常在210-230°C的高压灭菌器中被氧化，以在氰化之前破坏黄铁矿和毒砂。该技术的局限性之一出现在金矿也含有有机物，而高压灭菌液含有少量氯化物(通常为10-50ppm)的情况下。已经初步确定了一种化学体系，有望使氯化物沉淀并防止这种金损失的机制。在受矿山影响的废水中，硒通常以亚硒酸盐(IV)和亚硒酸盐(VI)的形式存在。亚硒酸盐的沉淀是通过与氢氧化铁共沉淀完成的。从废水中去除硒的难度要大得多，由于化学成分与通常存在的高浓度硫酸盐相似，所以难度更大。废水中除硒的目标水平为1 ppb。已经确定了一种无机层状双氢氧化物吸附剂，它具有将硒吸附到固体基质结构中的能力。这是非常有希望的，但有必要研究层状双氢氧化物的溶解度，因为这将影响载硒吸附剂的长期储存。一种溶剂萃取系统对废水中的硒酸盐比硫酸盐有一定的选择性。莱茵集团开发了三种利用甲烷磺酸溶液化学方法回收铅或精炼铅的工艺。这一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体系的阳极电化学，以确定避免形成二氧化铅并再生酸浸出的阳极体系和电解液化学。世界范围内正在研究使用非氰化物浸出剂来浸金，以提供使用氰化物浸金和浸银的替代方案。阻碍更广泛采用氰化浸出替代品的障碍有很多，包括试剂消耗高、浸金动力学缓慢、难以从浸出液中回收金等。在许多情况下，人们认为可以通过引入混合浸出剂系统来克服其中一些困难。*****

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 210-230°C 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. *****