Grant: Engage Grants Program

Gold is one of the most expensive precious metals that are widely used not only as traditional jewelleries but also as useful components in a variety of well known advanced materials. Mining companies produce gold from ore by leaching followed by adsorption onto activated carbon. However, activated carbon is not selective to gold as they co-adsorb other metals and further refining is necessary to produce pure gold. Moreover, elution of gold from activated carbon is very difficult as physical adsorption takes place where gold is trapped inside the micro-pore of carbon particles. Activated carbon is also expensive. To overcome this problem, in this industrial research a cost-effective efficient process will be developed to recover pure gold using adsorbents derived from lignin and/or black liquor. Lignin and black liquor is a by-product of the process that transforms wood into pulp to make paper. Black liquor is a thick, dark liquid and one of the main ingredients in black liquor is lignin, which is the material in trees that binds wood fibres together and makes them rigid, and which must be removed from wood fibres to create paper. Typically a pulp mill produces 250-400 gallons of black liquor per ton of pulp, which is mostly burned onsite. It was found that wood lignin can adsorb gold selectively. Since the pulp and paper mill generates lignin/black liquor as a by-product, in the proposed research we will use that lignin/black liquor to produce adsorbents. With this innovative industrial research, kraft mill lignin/black liquor can be effectively used to produce new and value added products for the mining/metallurgical industries. This research will drastically increase the value of lignin, especially for the recovery of very expensive precious metals such as gold (~$1,700/oz). There is a huge possibility of creating new business in this area for the production of such adsorbents to sell in the local and global markets. This will generate extra revenue for the pulp and paper mill. Therefore, a Canadian kraft mill named Kruger Inc., will collaborate in this project. Both gold mining companies and the pulp and paper mills will benefit from this research.