EAGER: GOALI: Novel Anaerobic Nitrogen Transformations in Gold-Cyanide Metallurgical Processing Tailings

EAGER：GOALI：金氰化冶金加工尾矿中的新型厌氧氮转化

• 批准号: 1464496
• 负责人: Linda Figueroa
• 金额: $ 6.3万
• 依托单位: Colorado School of Mines
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-02-15 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1464496&HistoricalAwards=false
• 关键词: EAGER; GOALI; Novel; Anaerobic; Nitrogen

1464496LandkamerEAGER: GOALI: Novel anaerobic nitrogen transformations in gold-cyanide metallurgical processing tailingsHarnessing anaerobic microbial processes for control of cyanide release from heap-leach, milling and other industrial operations would transform how waste cyanide material is managed. Anaerobic incubations of sediment and water collected from gold-cyanide heap-leach and milling operations containing cyanide, nitrate and sulfate produced data that suggest a previously undocumented transformation of cyanide and denitrification mechanism. Two important nitrogen transformations are hypothesized for the observed transformations in the microcosms. The native heap-leach bacteria appeared to convert cyanide to formate and ammonia and subsequently consume the formate under anaerobic conditions in the absence of added carbon. Secondly, nitrate was reduced in the absence of added organic carbon. Reduced iron minerals present in the mill residues (waste rock) may have acted as electron donors for nitrate reduction along with the formate produced from cyanide degradation. Harnessing these novel anaerobic nitrogen transformations in the management of cyanide at mining ore processing operations has the potential to significantly reduce treatment cost. The utilization of autotrophic anaerobic cyanide degradation to prevent environmental cyanide releases at gold mining ore processing sites represents the potential for significant monetary savings because there are no (or minimal) chemical or aeration requirements. Total nitrogen discharge limits also result in expensive treatment scenarios that could be replaced by inexpensive in-situ autotrophic denitrification. This university/ industry partnership will facilitate the applicability and dissemination of the research outcomes to the industrial community.Autotrophic (no added organic carbon) anaerobic cyanide biodegradation has not been documented previously. To find an organism(s) that can utilize cyanide as both an electron donor and a carbon source in the absence of oxygen would represent an entirely new metabolic pathway for supporting microbial growth that has not been explored. Secondly, denitrification driven by solid phase reduced iron as an electron donor has not been investigated in mining site environments such as heap leach operations. Accordingly, the effect of pH, temperature on these microbes and associated metabolisms will also represent new knowledge. Experiments that control for potentially competing reactions are required to provide clearer evidence for these transformations. Planned work involves anaerobic, autotrophic microcosm studies to validate the hypothesized mechanisms. Experimental variables will include pH, temperature and nitrate concentration to elucidate their effect on cyanide degradation and denitrification. This will be accomplished by incubating anaerobic batch microcosms containing heap leach residues, cyanide and sulfate at different pH and temperatures in the presence and absence of nitrate. Liquid samples will be withdrawn from the microcosms periodically and analyzed for cyanide species, sulfate, sulfide, nitrate, nitrite and ammonia. Headspace gas phase samples will be analyzed for the appearance of nitrogen gas. Additionally, microbial DNA from key microcosms will be sequenced to identify members of the microbial consortium responsible for the transformations. The role of solid phase reduced iron in denitrification will also be studied by including microcosms that contain a chemically pure reduced iron solid phase rather than heap leach residues.

1464496LandkamerEAGER: goal：金氰化冶金工艺尾矿中的新型厌氧氮转化利用厌氧微生物工艺来控制堆浸、磨矿和其他工业操作中的氰化物释放，将改变废氰化物的管理方式。从含氰化物、硝酸盐和硫酸盐的金氰化物堆浸和磨矿作业中收集的沉积物和水进行厌氧培养产生的数据表明，以前没有记录的氰化物转化和反硝化机制。对于微观世界中观察到的转化，假设了两个重要的氮转化。原生堆浸细菌似乎将氰化物转化为甲酸盐和氨，随后在无添加碳的厌氧条件下消耗甲酸盐。其次，在不添加有机碳的情况下，硝酸盐被还原。存在于磨渣（废石）中的还原性铁矿物可能与氰化物降解产生的甲酸一起充当了硝酸盐还原的电子供体。利用这些新的厌氧氮转化管理氰化物在采矿矿石加工操作有可能显著降低处理成本。利用自养厌氧氰化物降解来防止金矿矿石加工场所的环境氰化物释放，可能会节省大量资金，因为没有（或很少）化学或曝气要求。总氮排放限制也导致昂贵的处理方案，可以由廉价的原位自养反硝化取代。这项大学与工业界的伙伴关系将促进研究成果在工业界的应用和传播。自养（不添加有机碳）厌氧氰化物生物降解以前没有记录。在没有氧气的情况下，寻找一种既能利用氰化物作为电子供体又能利用氰化物作为碳源的生物，将为支持微生物生长提供一种全新的代谢途径，这一途径尚未被探索过。其次，固相还原铁作为电子供体驱动的脱硝尚未在堆浸作业等矿山现场环境中进行过研究。因此，pH、温度对这些微生物及其相关代谢的影响也将代表新的知识。控制潜在竞争反应的实验需要为这些转化提供更清晰的证据。计划中的工作包括厌氧、自养的微观环境研究，以验证假设的机制。实验变量包括pH、温度和硝酸盐浓度，以阐明它们对氰化物降解和反硝化的影响。这将通过在不同pH值和温度下，在硝酸盐存在和不存在的情况下，培养含有堆浸渣、氰化物和硫酸盐的厌氧间歇式微生物来完成。将定期从微生物中提取液体样品，分析氰化物、硫酸盐、硫化物、硝酸盐、亚硝酸盐和氨。顶空气相样品将分析氮气的外观。此外，将对来自关键微生物群落的微生物DNA进行测序，以确定负责转化的微生物联盟成员。固相还原铁在反硝化中的作用也将通过包括含有化学纯还原铁固相而不是堆浸渣残留物的微观环境来研究。