Degradation of powder activated carbon by laccase-mediator system: Model experiments for the improvement of gold recovery from carbonaceous gold ore

Abstract

Several efforts are made to find various green alternatives for carbonaceous matter (CM) degradation in carbonaceous gold ores. The deleterious effect of CM is observed during cyanidation, where CM adsorbs Au(CN)2- behaving like activated carbon, an effect called pre-robbing. Thus, biotechnological approaches like enzyme degradation of CM to reduce Au(CN)2- adsorption are currently being studied. In the present work, the potential of CM degradation and gold preg-robbing reduction by laccase-mediator system (LMS) oxidation was evaluated using powder activated carbon (PAC) as CM surrogate material through model experiments. Based upon gas chromatography-mass spectrometry (GC-MS) analysis of extracted by-products from bio-treated PAC, LMS treatment after seven days physically and chemically altered the surface of PAC by the reduction of specific surface area and pore volume, the disruption of aromatic moieties into aliphatic compounds, and the formation of oxygen-containing functional groups. Subsequently, under the studied condition, the adsorption capacity of Au(CN)2- on the surface-degraded PAC was dramatically decreased from 46 μmol/g to 7.36 μmol/g. The present findings provide a new outlook of an alternative pre-treatment process of carbonaceous gold ore in mineral processing.