Enhancement of gold-cyanide biosorption by L-cysteine

The presence of L-cysteine increased gold-cyanide biosorption by protonated Bacillus subtilis, Penicillium chrysogenum and Sargassum fluitans biomass at pH 2 by (148 similar to 250)%. The respective Au uptake by these biomass types was 20.5 mu mol/g,14.2 mu mol/g and 4.7 mu mol/g of Au. Au-loaded biomass can be eluted with 0.1M NaOH. The elution efficiencies exceeded 90% at pH 5.0 with the Solid-to-Liquid ratio S/L = 4. Biosorption of anionic AuCN2- complex involved ionizable protonated cysteine-loaded biomass functional groups. An adverse effect of increasing solution ionic strength (NaNO3) was explained by a triple layer surface complexation mechanism. The NO3- anion competed with AuCN2-. Results confirmed that certain waste microbial biomaterials are capable of effectively removing and concentrating gold from solutions containing residual cyanide.