Biosorption of gold from alkaline solution using biomass wastes.

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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 such as electrical and electronic devices, catalysts and medical instruments. On one hand the availability of gold is very limited; on the other hand, a substantial proportion of this valuable metal is generally discarded in the form of aqueous by-products during metal refining as well as the disposal of obsolete electronic devices. Thus, effective and economical recovery processes related to gold extraction/recycling from primary and secondary resources require urgent development. Recently, sorption processes based on low cost and widely available biomass materials is considered one of the most promising sustainable technologies that can be used for the recovery of gold from dilute solutions. In the last 3 years, we have made major advancements in our biosorption research, publishing more than 30 papers in refereed high impact-factored international journals, such as Bioressource Technology, Chemical Engineering Journal, Industrial & Engineering Chemistry Research, Green Chemistry, Journal of Chemical & Engineering Data, Journal of Hazardous Materials, Hydrometallurgy, Solvent Extraction and Ion Exchange, RSC Advances, etc. We have also published over 10 refereed conference proceeding papers related to this research in world-class conferences such as TMS, CIM/MetSoc, IEX, ALTA, etc. With this tremendous progress made in biosorption research within the last 3 years, we are now well prepared to move forward to extend our research in this field of hydrometallurgy.The objectives of the proposed research program would be to lay a scientific foundation for the development of cost-effective, sustainable and efficient recovery processes for extracting gold from dilute solution using biomaterials prepared from biomass wastes. The currently most adopted technique for leaching gold from gold ore remains leaching in aqueous alkaline cyanide solutions. Recently, Barrick Gold Corporation adopted alkaline thiosulphate processing of gold in their successful demo-plant operation, although thiosulphate cannot completely replace cyanide, it could provide an alternative to cyanide. Following our successful research work on gold recovery from acidic solution through our previous Discovery Grant, in our proposed research we plan to extend our work to the recovery of gold from alkaline solutions of cyanide and thiosulphate, in order to meet industry’s urgent needs. In this research, gold will be recovered from a dilute alkaline solution in a batch reactor using chemically modified cellulosic biomaterials. Initially commercially available pure cellulose, after pre-treatment with sulphuric acid followed by grafting unique functional groups, will be used to develop a kinetic and adsorption isotherm model. Later bioadsorbents will be prepared from cellulosic biomass wastes such as waste paper, waste cotton and waste wood/saw dust that will be tested for gold sorption from real solution. Those biomass wastes are abundantly available and will be a cheap source of raw materials for making bioadsorbents. Proper use of such biomass wastes as value-added products will not only reduce the volume of wastes being generated every day, but will also have high end value to the gold mining industry as this cheap bioadsorbent will have superior performance over the traditionally used activated carbon. Both mining and waste management companies will benefit from this research. The proposed research program will train 4 M.Sc., 1 Ph.D., 5 post-docs and 4 undergraduate students in the area of extractive metallurgy.