Graphene could be used to recover gold, silver from tailings

“Functionalized graphene composite-based adsorbents for the removal of precious metals, oils and PFAS contaminants have been explored and developed by the Sparc team as part of its drive to develop technologies that can enhance large scale industrial markets and provide a solution for previously uneconomic or environmentally hazardous scenarios,” the Australian company said.

The preliminary study was undertaken together with The University of Adelaide and consisted of selecting eight available adsorbents whose foundation was graphene-based composites designed and developed for the adsorption of heavy metals and their applicability for precious metals Au, Ag and rare metals. 

Two different types of industry-standard commercial adsorbents, activated carbon and biochar, were used as control adsorbents to compare efficiency and enhancements. 

According to Sparc, the adsorption study for removal of precious metals was performed using model water solutions with a known concentration of Au (III) 1.2 mg L-1 (1.2 ppm) and Ag (I) 4.4 mg L-1 (4.4 pm) using common adsorption conditions for these metals and room temperature. Ag (I) and Au (III) ions were prepared from their stock solutions, silver (I) nitrate and chloroauric acid, respectively. 

“Among the in-house developed adsorbents, proprietary testing samples S8 and S9 outperformed all the tested adsorbents including the commercial adsorbents with 96.98% and 91.89% removal efficiency attained for Au (III) ions adsorption respectively,” the release reads. “In terms of Ag (I) ion adsorption, sample S5 outperformed all the adsorbents with 97.82% adsorption efficiency attained.”

The Melbourne-based firm said that following these results, the plan is to test its graphene adsorbents against a wider range of commercially available adsorbents, progressing to live field trials targeting the extraction of actual gold (Au) and silver (Ag) metals in tailings from mine sites.