Preliminary study on desorption of gold Ions on self- flocculating microalga and its regeneration potential

Abstract

Microalga, possessing high binding affinity to different metals, has been considered as a promising biosorbent. Precious metals recovery and adsorbent regeneration are important for the financial competitiveness of biosorption with other processes. In this study, the desorbing agent thiourea was studied at different concentrations, contact time, pH and temperatures to optimize gold elution from the self-flocculating microalgae Scenedesmus obliquus AS-6-1. The variation in desorption performance with the adsorption time was also investigated. The gold-loaded biomass of S. obliquus AS-6-1 was regenerated efficiently by 0.2 M of thiourea at 25 ℃ and pH of 1.0 within 15 minutes. The adsorption time had significant effect on subsequent desorption, with a decrease in desorption efficiency with an increase in adsorption time. S. obliquus AS-6-1 as biosorbent remained efficient biosorption and desorption potential for gold(III) recovery in the first two adsorption/desorption cycles. The microalga cells could be harvested/separated from solutions by their gravity sedimentation. However, more studies are still required to enhance the regeneration of S. obliquus AS-6-1 by improving its flocculating property.