Recovery of gold from industrial wastewater by extracellular proteins obtained from a thermophilic bacterium Tepidimonas fonticaldi AT-A2

Biosorption has emerged as a promising alternative approach for treating wastewater with dilute metal contents in a green and cost effective way. In this study, extracellular proteins of an isolated thermophilic bacterium (Tepidimonas fonticaldi AT-A2) were used as biosorbent to recover precious metal (i.e., Au) from wastewater. The Au (III) adsorption capacity on the T. fonticaldi AT-A2 proteins was the highest when the pH was set at about 4.0-5.0. The adsorption capacity increased with increasing temperature from 15 to 70 degrees C. Adsorption isotherm studies show that both Langmuir and Freundrich models could describe the adsorption equilibrium. The maximum adsorption capacity of Au ( III) at 50 degrees C and pH 5 could reach 9.7 mg Au/mg protein. The protein-based biosorbent was also used for the recovery of Au from a wastewater containing 15 mg/L of Au, achieving a high adsorption capacity of 1.45 mg Au/mg protein and a removal efficiency of 71%. (C) 2017 Elsevier Ltd. All rights reserved.