Sequential process of sorption and incineration for recovery of gold from cyanide solutions: Comparison of ion exchange resin, activated carbon and biosorbent

This study evaluated the gold(I) sorption capacities of various types of sorbents such as ion exchange resin, granular activated carbon, and chemically modified biosorbent. The gold(I)-loaded sorbents were incinerated and the purity of gold in the ashes was compared. As a biosorbent, polyethylenimine modified biomass (PEIB) was prepared by cross-linking the biomass of Corynebacterium glutamicum with polyethylenimine. The sorption capacity of the sorbents of gold(I) ion from the gold(I)-cyanide complex solution were examined by the pH edge and isotherm experiments. The maximum uptakes of gold by ion exchange resin (Amberjet™ 4400), activated carbon, and PEIB were 427.77, 170.64 and 361.76mgg^-1, respectively. To recover gold as a metallic form, the gold(I) sorbed sorbents were incinerated. The recovery efficiency of incineration process and purity of gold in the ash were estimated to be higher than 85.6% and 97.72% for the PEIB, 97.23% and 94.57% for activated carbon and 92.72% and 96.56% for the Amberjet™ 4400, respectively. These sorbent constituents could be burnt out and at the same time, the sorbed Au⁺ could be reduced to Au⁰. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicated that the remaining ash contained metallic form of zero-valent gold. These results support that the sequential process comprising of sorption of gold ions followed by incineration of the loaded sorbents could be an alternative method for recovery of metallic zero-valent gold from gold-cyanide complex solution.