The bio-treatment of double refractory gold ores (DRGO) to reduce preg-robbing needs to account for the heterogeneity of the ore so as to acquire a much more complete picture of the system. To this end, the effects of ferrous ion additives on the degradation of powdered activated carbon (PAC) by cell-free spent medium (CFSM) was studied. Au(CN)2- adsorption and Raman spectrometric results suggest that the ferrous salt could have possibly reacted with some biogenic hydrogen peroxide to aid in the degradation of PAC. The bio-treatment produced mixed solid residues containing some partially degraded aromatic compounds which were soluble in alkaline solutions. Ultimately, biodegradation of PAC using CFSM in the presence of 50 µM FeSO4.7H2 O for 7 days followed by washing with 3 mM NaOH reduced Au(CN)2- uptake by 80%.