(Bio)leaching Behavior of Chromite Tailings

Abstract

Chromite beneficiation operations in Sukinda valley (India) produce large amounts of tailings, which are stored in open air. In this study, bioleaching experiments were carried out in batch reactors with Acidithiobacillus thiooxidans or Pseudomonas putida in order to determine the potential leachability of metals contained in these tailings due to biological activity. Acidic and alkaline pH resulted from the incubation of tailings with A. thiooxidans and P. putida, respectively. Tailings were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM), and chemical extraction of Cr(VI) with KH 2 PO 4 was performed. Mineralogical investigations showed that tailings are mainly composed of chromite, hematite, lizardite, chlorite, and goethite, which are all known as Cr-bearing phases. During the leaching with A. thiooxidans and P. putida, total Cr was initially extracted as Cr(VI) due to the presence of phosphates in the medium, and subsequently decreased because of Cr(VI) adsorption and reduction to Cr(III). Reduction was associated with bacterial activity, but also with the presence of ferrous iron. Despite the occurrence of siderophores in the tailings after incubation with P. putida, under acidic conditions, Fe extracted remained higher. Extracted Ni, Mn, and Al concentrations also increased over time. Given the significant amount of chromite tailings produced every year, this study shows that tailings storage and leachability represent a potential source of chromium. However, our findings suggest that the presence of bacterial communities, as well as physicochemical processes, favor Cr(VI) reduction.

A review on the bioleaching of toxic metal(loid)s from contaminated soil: Insight into the mechanism of action and the role of influencing factors

“…In a batch reactor, the impact of varied mineral pulp densities of 5, 10, and 30 g/L on bacterial activity was studied. The pH of A. thiooxidans increased as the pulp density increased, but the pH of P. putida did not alter as the pulp density increased ( Bolaños-Benítez et al, 2018 ). High pulp density is expected to restrict microbial activity, hence a pulp density of 15% had a significant effect on the leaching of copper and Zinc ( Guo et al, 2010 ).…”

The Strategies of Chromite Terrace in Sukinda Valley, India: An Appraisal

“…Outcrop of chromite ore in either powdery or friable form is underlain at a depth of 3 to 10m soft latosol or alluvial overburden, excavated, scrapped, and carried mainly to chrome steel or ferrochrome industries. Tailings on weathering convert Cr (III) to Cr (VI) in the SUZ, which can be reduced using bio-remediation technology in the dead and active mines area that is polluted, and the chrome VI in the air induces cancer of the lungs, [38,39,40].…”

Progress, Challenges, and Perspectives of Bioleaching for Recovering Heavy Metals from Mine Tailings

“…Chromium-containing tailings are abundant in the Sukinda Valley, India. In a study on bioleaching of chromium, during the bioleaching process, the total chromium was initially extracted in the form of hexavalent chromium due to phosphate in the medium and was subsequently reduced due to hexavalent chromium adsorption and reduction to trivalent chromium [41].…”

“…The effects of mineral pulp densities of 5, 10, and 30 g/L on bacterial activity for different bacteria were investigated in a batch reactor. For A. thiooxidans, the higher the pulp density, the higher the pH, while for P. putida, the change in pulp density had no effect on the pH [41]. Because a high pulp density significantly inhibits microbial activity, when the pulp density was greater than 15%, it had a great influence on the leaching rate of copper and zinc [35, 42].…”