Continuous culture of sulphur-oxidizing microorganisms for metal recovery

Abstract

Nowadays heavy metal contamination has become a global problem. So, it is necessary to find a way to remove heavy metals and biological extraction can be a good alternative from physical or chemical. Biological extraction ahs low energy demand and it is considered a green and environment friendlier technique. The most commonly biological method used in metal recovery is called bioleaching. An example of bioleaching could be use sulphur oxidizing bacteria (SOB) to oxidized elemental sulphur to sulphuric acid, lowering pH and improving heavy metals solubilization. The present work aims to study copper recovery and to enrich sulphur oxidizing microorganisms in a reactor to obtain an effluent to be able to carry out the bioleaching process. A continuous stirred tank reactor with mixed of Acidithiobacillus thiooxidans and sulphur-oxidizing microorganisms to achieved the effluent, had been tested. Also, a bioleaching Jar-Test in order to assess copper solubilization as a function of sulphuric acid dose, total solids content and stirring time. After activating the microorganisms, the reactor was able to start up properly, achieving an effluent with a 0.06 M of sulphuric acid concentration. In addition, Jar-Test was reached a copper solubilization between 148.25 mg Cu/kg sludge and 203.86 mg Cu/kg sludge. The factor combination that obtained the best copper solubilization was: 2% total solids content, 6 days of stirring time and 3 g S°/L transformed in sulphuric acid dose.