Recovery of gold from solutions using Cladosporium cladosporioides biomass beads

A fungal isolate, Cladosporium cladosporioides was used for biosorption of gold from solutions. The fungal biomass was granulated by mixing it with a matrix derived from keratinous material of natural origin. The resulting biosorbent beads adsorbed 100 mg gold per gram from a solution of gold. Maximum biosorption of gold (80%) occurred under acidic pH conditions (pH 1–5). The contact time required for 80% biosorption of gold could be reduced to 20 min by pre-soaking the beads in deionized distilled water. Gold uptake by the beads was found to increase linearly as a function of metal concentration. The data could be fitted into Freundlich model of adsorption isotherms. A column packed with 3 g biosorbent beads was used for continuous adsorption of gold. The gold loading capacity obtained in the system was to the tune of 110 mg g −1. Gold was removed from an electroplating unit effluent with 55% efficiency in batch experiment and the loading capacity was 36 mg g −1. It was found that gold could be removed from solutions in the presence of carbonate and complexing agents like citrate, sulfite and thiosulfate albeit with less efficiency. The beads were found to biodegrade in soil in about 140 days. The process, thus, has the prospect of becoming an efficient and environmental friendly method to recover gold from aqueous solutions.