LAUSR

Abstract This work describes the mechanistic aspects of Au(III) sorption by Aspergillus terreus SRD49. Under experimental setup studied, Au(III) sorption by SRD49 was independent of system between pH 1.5 and 5.5. This suggested covalent boding that may be playing a role. Under optimum conditions, the maximum Au(III) sorption capacity of SRD49 was 0.755 mM/g of biomass. The sorption data followed Langmuir model rather than a Freundlich model, which suggested a monolayer type of interaction between SRD49 biomass and Au(III) species. Thermodynamic studies suggested that ∆G was negative; while, ∆H and ∆S were positive. SEM analysis indicated smoothening of the surface texture, that was attributed to deposition of Au(III) on the SRD49 surface. EDX analysis showed absence of K peaks and addition of Au peaks. The sorption process was accompanied by reduction of Au(III) to elemental Au. This was confirmed by visual observation, UV–vis spectroscopic study of surface plasmon as well as SEM analysis. Desorption studies revealed that thiourea was a better desorbent than NaOH. Au(III) sorption by SRD49 was a reversible process.