Abstract

Addressing the existing problems in the gold mining industry, two types of high-capacity adsorbents have been developed to improve the economics and efficiency of the industrial gold extraction processes, as well as to reduce their environmental impact. In the first sub-project, high-performance lignin-polyethylene composite adsorbents have been developed for extraction of solubilized gold complexes from gold mill leaching solutions that show fast, high selectivity gold capturing from very low concentration of gold leachate solutions. In the second sub-project, high-capacity Mg─Fe layered double hydroxide-graphene oxide (LDH-GO) nanocomposite adsorbents have been developed to remove arsenic as a most toxic and carcinogenic element often present in gold sulfide ores, from gold mill effluent streams, to reduce both the adverse environmental impact of the gold mining activities and the environmental impact of the mining operations.
In our design of both types of composite adsorbents, we employ cost-effective active materials (lignin and magnesium/iron-based LDHs, respectively) of high adsorption capacity towards gold and arsenic species, respectively. Meanwhile, robust support/matrix materials (polyethylene and graphene oxide, respectively) are employed for the effective loading/encapsulation of the active materials. The composition and structure of both classes of composite adsorbents are tuned to achieve optimum adsorption performance. The adsorption properties of the composites have been evaluated towards the adsorption of gold and arsenic, respectively, from simulated waters under different conditions such as pH, contact time and initial concentration in batch process. The results show that the composites are highly effective in removing arsenic and capturing gold. The success of this research is expected to improve the economics and efficiency of the industrial gold extraction processes, and meanwhile make them safer and more environmentally responsible.