Defining the applicable pathway of laccase pre-treatment in the bio-mineral processing of double refractory gold ores based on carbonaceous matter characterization.

Enzymes application in mineral processing is a novel alternative to oxidize carbonaceous matter in double refractory gold ores (DRGOs) and reduce Au(CN) 2 ^- adsorption during cyanidation. In this work, contrasting flotation concentrates from DRGOs with different Au(CN) 2 ^- affinities were sequentially treated to improve Au cyanidation. Sequential pre-treatment comprised sulfide decomposition and carbonaceous matter degradation through laccase-mediator system (LMS). In addition, carbonaceous matter was characterized from various aspects using Raman spectroscopy, 3D-fluorescence spectrometry, preg-robbing test, and gas chromatography-mass spectrometry (GC-MS). The characterization of the original ores showed that Au(CN) 2 ^- adsorption densities were positively correlated with the relative intensities of defective carbon to graphitic carbon obtained in Raman spectra. Degradation of carbonaceous matter through LMS was inhibited by the presence of biopolymers formed during extensive bio-oxidation, thus reconsidering the appropriate sulfide decomposition step. When FeCl 3 leaching to decompose sulfides proceeded enzymatic treatment, mass spectra of extracted intermediates from carbonaceous matter suggest the presence of alcohols, fatty acids and aliphatic hydrocarbon moieties, mainly on the most polar solvent fractions. This suggests that enzymatic degradation went through the indirect disturbance of the aromatic planes, making the surface more hydrophilic due to the inclusion of oxygen-containing functional groups, thus improving Au extraction. Finally, the current findings provide a general panorama for selecting the appropriate pre-treatments to maximize gold extraction on DRGOs when using LMS. [Display omitted] • Raman spectroscopy and Au(CN 2)^- adsorption test predict carbon preg-robbing ability. • Mass-spectra similar to benzene aromatic moieties were observed in the high pre-robbing gold concentrate. • Biopolymers produced after bio-oxidation interferes with carbonaceous matter enzymatic degradation. • FeCl 3 leaching before enzymatic treatment is recommended for high preg-robbing gold concentrates. • GC-MS suggested carbonaceous matter surface is more hydrophilic after laccase-mediator treatment. [ABSTRACT FROM AUTHOR]