Removal of arsenic from gold processing circuits by use of novel magnetic nanoparticles

Abstract

ABSTRACTArsenic adversely affects gold mining operations by interfering with the extraction of gold, as well as posing a significant health and environmental hazard. While a number of technologies are available for removing arsenic, none of them is effective under all conditions. Although adsorption is a promising approach, most methods focus on the purification of water under neutral or acidic conditions and tend to be less effective in gold mining process waters, operating under highly alkaline conditions. In this study, the removal of As(III) and As(V) from both arsenic-only solutions and simulated process waters using composite magnetic nanoparticles was investigated. The nanoparticles consisted of magnetite (Fe3O4) or maghemite (γ-Fe2O3) cores covered by various metal oxides with Langmuir adsorption capacities of As(III) and As(V) ranging from 31.4 to 79.1 mg g−1 and 10.2 to 25.5 mg g−1, respectively, in arsenic-only solutions at pH 9. The adsorption capacities were further characterised by adsorption tests conducted in simulated process waters. The ability to remove As(III) is of particular importance as it is harder to remove it from alkaline solutions than As(V). The magnetic cores allow simple and efficient magnetic recovery of the As-loaded nanoparticles.