Sustainable Recovery of Gold using Biomass Wastes in an Alkaline-Acidic Hybrid System

在碱性-酸性混合系统中利用生物质废物可持续回收黄金

• 批准号: RGPIN-2020-06989
• 负责人: Alam, Shafiq
• 金额: $ 2.4万
• 依托单位: University of Saskatchewan
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=718598
• 关键词: Sustainable; Recovery; Gold; using; Biomass

The gold processing industry extracts gold by leaching ore in cyanide solution followed by adsorption on activated carbon and electrowinning. However, both cyanidation and carbon adsorption have some major problems. Since cyanide is very toxic, gold plants are forced to destroy the cyanide in effluent that results in loss of expensive cyanide and increase in the overall operating cost. On the other hand, activated carbon, which is manufactured at 600-1200 oC, is expensive and it is not selective to gold only, hence further refining is necessary to produce pure gold. Also, during adsorption, gold is trapped inside the micro-pore of activated carbon that requires high temperature elution to reactivate the carbon. As a result, manufacturing and regenerating of activated carbon represents a major portion of the operating cost in a mining operation. Also, it releases greenhouse gases to the environment. To overcome these problems, in 2011, I started my NSERC Discovery research program to develop an innovative and sustainable gold recovery technology. In our process, gold was recovered from aqueous solution by biosorption on our adsorbents having novel functional groups. These adsorbents were prepared in a very simple process by crosslinking different biomass wastes with sulphuric acid at 100 oC. Biosorption is a new field in hydrometallurgical research, and since 2011, we made tremendous advancement in this area, generating 67 publications in high quality journals and in world-class conference proceedings. From this research, we found some remarkable results, such as: 1) unlike activated carbon, only gold is adsorbed on our novel bioadsorbents, hence no further treatment is necessary for impurity removal; and 2) when gold is adsorbed on our novel bioadsorbent, it is simultaneously reduced to metallic gold. These ground-breaking findings will make gold recovery much simpler, more cost-effective and energy efficient because no stripping, high temperature elution, and electrowinning are necessary. However, we observed that simultaneous adsorption-reduction of gold on our novel bio-adsorbents only takes place in acidic chloride media but not in alkaline cyanide solutions. Considering the urgent need to improve the gold cyanidation process, in the proposed research, I plan to recover gold using our novel bioadsorbents in an alkaline-acidic hybrid system where gold will be leached in an alkaline cyanide solution followed by acidification to recycle cyanide back to the leaching plant leaving behind gold in an acidic chloride media for simultaneous biosorption-bioreduction to produce pure gold. Our proposed biosorption process with recycling of toxic cyanide will ensure zero emission to the environment. This will eliminate the current practice of destruction of expensive cyanide in the effluent and result in huge cost savings for the industry and minimization of greenhouse gas emissions. Canadian mining companies will benefit from this innovative research.

黄金加工行业通过在氰化液中浸出矿石，然后在活性碳上吸附和电积来提取金。然而，氰化和碳吸附都存在一些主要问题。由于氰化物具有很强的毒性，黄金工厂被迫销毁废水中的氰化物，从而导致昂贵的氰化物的损失，并增加了整体运营成本。另一方面，在600-1200oC的温度下生产的活性碳价格昂贵，而且不仅对金具有选择性，因此需要进一步精炼才能生产纯金。此外，在吸附过程中，金被困在活性碳的微孔中，需要高温洗脱才能重新激活碳。因此，在采矿作业中，活性碳的制造和再生是运营成本的主要部分。此外，它还会向环境中释放温室气体。 为了克服这些问题，2011年，我启动了我的NSERC发现研究项目，以开发一种创新的、可持续的黄金回收技术。在我们的过程中，通过我们的具有新官能团的吸附剂的生物吸附从水溶液中回收金。这些吸附剂是用100oC的硫酸将不同的生物质废弃物交联而成的，过程非常简单。生物吸附是湿法冶金研究的一个新领域，自2011年以来，我们在这一领域取得了巨大进展，在高质量期刊和世界级会议记录上发表了67篇论文。从这项研究中，我们发现了一些显著的结果，例如：1)与活性碳不同，我们的新型生物吸附材料只吸附了金，因此不需要进一步的处理来去除杂质；2)当金被我们的新型生物吸附材料吸附时，它同时被还原为金属金。这些突破性的发现将使黄金回收变得更加简单、更具成本效益和能源效率，因为不需要反萃、高温洗脱和电积。然而，我们观察到我们的新型生物吸附剂对金的同时吸附-还原只在酸性氯化物介质中发生，而在碱性氰化物溶液中不发生。 考虑到迫切需要改进金的氰化过程，在拟议的研究中，我计划在碱性-酸性混合体系中使用我们的新型生物吸附剂回收金，在碱性氰化液中浸出金，然后进行酸化，将氰化物循环回浸出厂，将金留在酸性氯化物介质中，同时进行生物吸附-生物还原以生产纯金。我们建议的回收有毒氰化物的生物吸附工艺将确保对环境的零排放。这将消除目前销毁污水中昂贵的氰化物的做法，为该行业节省大量成本，并将温室气体排放降至最低。加拿大矿业公司将从这项创新研究中受益。