Cyanogenic Plants to Extract Gold: an Alternative for Artisanal MIners

在世界范围内，70多个国家的手工黄金开采每年生产380-450吨黄金，涉及约1600万人。这些矿工使用的主要方法是基本的汞齐技术，每年消耗1400吨元素汞，而且还在增加。这是世界上最大的人为汞污染源。合并的主要替代方法是氰化，但许多矿商没有足够的管理技能或资本，甚至无法获得氰化物。手工矿工使用的加工技术的改变意味着对矿工的教育和组织。技术本身并不是对贫困和污染这一戏剧性图景的唯一应对措施，但替代汞和改善黄金回收的负担得起的简单技术已列入所有国际机构、政府、非政府组织和学者的议程。如果矿工们学到了简单而实惠的方法，可以比汞并法(通常提取30%的金)更有效地提取黄金，他们肯定会采用这些技术。2000多种蔬菜含有糖苷，可以通过水解转化为氰化物。竹子、高粱和木薯是热带和亚热带地区广泛种植的主要产氰植物。木薯是世界上超过5亿人的点缀食物，意外食用苦木薯，超过2000毫克CN/公斤，每年夺走大约2000人的生命，数十万人因食用这种氰根而遭受称为kopnzo的毁灭性运动神经损伤。利用苦木薯和其他产氰植物作为黄金回收过程中氰化物的来源，是在手工金矿中取代汞的一种潜在选择。UBC的初步研究是在植物系和土地与食品系统学院的协助下进行的，并与巴西EMBRAPA密切合作，从一个黄金浮选精矿中提取了30%的金。关于使用氰化物提金的过程，我们的知识有很多空白。必须进一步研究pH、温度、时间、溶解氧和其他催化剂的影响，才能产生一种简单的提金方法。这个想法是在实验室测试使用氰化植物从精矿中提取黄金的最佳条件，然后将其应用于哥伦比亚(或其他面临年度汞问题的国家)的现场试点研究。预可行性研究将完成一个使用当地蔬菜清洁生产黄金的简单工厂的工程设计。

Worldwide, artisanal gold mining (AGM), in more than 70 countries, involves approximately 16 million people to produce 380-450 tonnes of gold annually. The main method used by these miners is the rudimentary amalgamation technique that consumes 1400 tonnes/a of elemental mercury and increasing. This is the world's largest source of man-made mercury pollution. The main alternative to amalgamation is cyanidation but many miners do not have adequate management skills or capital or even access to cyanide. A change in processing techniques used by artisanal miners implies in education and organization of the miners. Technology alone is not the only response to this dramatic picture of poverty and pollution, but affordable and simple techniques to replace mercury and Improve gold recovery is in the agenda of all International Agencies, Governments, NGOs and academics. If miners learn simple and affordable methods to extract gold with more efficiency than amalgamation (which usually extracts <30% of Au ), definitely they will adopt these techniques. More than 2000 vegetables contain glucosides that can be converted to cyanide by hydrolysis. Bamboo, sorghum and cassava are the main cyanogenic plants extensively cultivated in tropical and subtropical regions. Cassava is the stipple food of more than 0.5 billion people in the world and the accidental consumption of bitter cassava, with more than 2000 mg CN/kg, takes the lives of approximately 2000 people annually and hundreds of thousands suffer a devastating motor neurological damage called "kopnzo" due to the consumption of this cyanogenic root. Using bitter cassava and other cyanogenic plants as a source of cyanide for gold recovery process is a potential option to replace mercury in artisanal gold mines. The preliminary studies at UBC, being conducted with assistance of the Dept of Botany and Faculty of Land and Food Systems, as well as in close collaboration with the EMBRAPA, Brazil, resulted in extractions of 30% of gold from a gold flotation concentrate. There are many gaps in our knowledge about the gold extraction process using glycocyanide. The effect of pH, temperature, time, dissolved oxygen, and other catalysts must be further investigated generating a simple method to extract gold. The idea is to test in the lab the best conditions to extract gold from concentrates using cyanogenic plants and then apply this in a pilot study in the field in Colombia (or other country facing problems with Hg from AGM). A pre-feasibility study will complete the engineer design of a simple plant for cleaner production of gold using local vegetables.