Source control on the acid mine drainage produced by the oxidation of pyrite and sulfur-containing uranium tailings based on the microbially induced carbonate precipitation technology

Abstract

Large quantities of acid mine drainage (AMD) generated through the oxidation of sulfide-bearing minerals, particularly pyrite, pose a significant global environmental challenge. The implementation of efficient and fundamental governance methods is crucial as current conventional approaches fail to address the root cause of this problem. To investigate the technique of controlling AMD at its source, a 10-day static experiment was conducted in order to examine the inhibitory effect of Sporosarcina pasteurii (S. pasteurii) on oxidative acid production from pyrite under varying redox potentials (Eh) and Ca2+ concentrations. Additionally, a 180-day dynamic column experiment was carried out to assess the long-term stability of its inhibition and heavy metal fixation. The results of both short-term and long-term analysis indicate that the metabolic activity of S. pasteurii has beneficial effects on the control of AMD through sulfur oxidation, even in the presence of strong oxidants such as H2O2 and FeCl3. 1. It stabilizes pH within the neutral to alkaline range; 2. It maintains Eh at a low potential reducing environment; 3. It promotes an increase in SO42− concentration, followed by a decline and stabilization at lower concentrations; 4. It supplies carbonate for pyrite oxidation, maintaining a balance between acid production and consumption. Additionally, SEM, XRD, and XPS results demonstrated that the mineral surface appeared flat without prominent characteristic peaks of oxidation products, indicating effective inhibition of pyrite oxidation by S. pasteurii. The immobilization experiments for heavy metals showed that Cd exhibited the highest fixation effect with a rate of 94%; Mn, Cu, Zn, and Co had the second best fixation effect with ion concentrations decreasing by 82%, 83%, 87%, and 88% respectively; Ni and U(VI) decreased by rates of 75% and 69% respectively. These experimental findings suggest that S.pasteurii can effectively inhibit pyrite oxidation as well as sulfur-containing uranium waste rock oxidation while providing long-term stabilization for heavy metal immobilization.