Removal of Heavy Metals from Industrial Wastewater Using Microbial Fuel Cell

Abstract

The development in science and technology has resulted in a steady increase in the growth rate of several industries, thereby resulting in an increased demand of precious metals as well, such as gold and platinum. This also results in the selling prices for these metals to increase. Hence, recovery of such metals from low grade ores and scraps plays an important role. Conventional methods of recovery of gold can result in the pollution of environment. Additionally, despite low concentrations of gold being released into the environment, the recovery of this metal can provide additional profit and help to reduce operating costs. The objective of this work is to use Microbial Fuel Cells (MFC) as an alternative green technology to simultaneously remove heavy metals and recover remaining gold found in the effluent samples taken from one of the gold refinery industries in the UAE. Removal efficiency of pure tetrachloroaurate ions was investigated first to ensure the feasibility of MFC in terms of removing gold ions and determining the optimum conditions for removal efficiency in terms of catholyte solution, as well as initial gold concentrations. Next, the effect of copper ions on the removal efficiency of the gold ions was investigated due to their high presence in the actual wastewater samples. Later, the gold removal efficiency was evaluated from the industrial effluent. The effect of pH and initial biomass concentration on the gold removal efficiency was also determined. Based on the successful results, after 5 hours, 95% of gold removal efficiency from the wastewater containing 250 ppm of initial gold ions at ambient temperature with the 80g/L yeast concentration was achieved. After 48 hours of the cell’s operation under the same condition, 98.86% of AuCl₄ˉ ions were successfully removed from the solution. Based on the investigation of the effect of different factors, 100% removal efficiency of the gold was achieved at a pH of 2, initial yeast concentration of 80 g/L and the initial gold concentration in the waste solution being 250 ppm. On the other hand, the most suitable condition in terms of copper removal was found at a pH of 5.2 where 53% removal efficiency from the waste solution was accomplished.