Effects of bioleaching on the chemical, mineralogical and morphological properties of natural and waste-derived alkaline materials

Abstract

Bioleaching is a potential route for the valorisation of low value natural and waste alkaline materials. It may serve as a pre-treatment stage to mineral carbonation and sorbent synthesis processes by increasing the surface area and altering the mineralogy of the solid material and by generating an alkaline rich (Ca and Mg) aqueous stream. It may also aid the extraction of high value metals from these materials (e.g. Ni), transforming them into valuable ore reserves. The bioleaching potential of several bacteria (Bacillus circulans, Bacillus licheniformis, Bacillus mucilaginosus, Sporosarcina ureae) and fungi (Aspergillus niger, Humicola grisea, Penicillium chrysogenum) towards the alteration of chemical, mineralogical and morphological properties of pure alkaline materials (wollastonite and olivine) and alkaline waste residues (AOD and BOF steel slags, and MSWI boiler fly ash) at natural pH (neutral to basic) was assessed. Bioleaching was conducted using one-step and two-step methodologies. Increased solubilisation of alkaline earth metals and nickel were verified. Alteration in basicity was accompanied by alteration of mineralogy. AOD slag experienced solubilisation-precipitation mechanism, as evidenced by the decline of primary phases (such as dicalcium-silicate, bredigite and periclase) and the augmentation of secondary phases (e.g. merwinite and calcite). Nickel-bearing minerals of olivine (clinochlore, lizardite, nimite and willemseite) significantly diminished in quantity after bioleaching. Altered mineralogy resulted in morphological changes of the solid materials and, in particular, in increased specific surface areas. The bioleaching effect can be attributed to the production of organic acids (principally gluconic acid) and exopolysaccharides (EPSs) by the microorganisms. The similarities between fungal and bacterial mediated bioleaching suggest that biogenic substances contribute mostly to its effects, as opposed to bioaccumulation or other direct action of living cells.

Optimization of As Bioleaching by Herbaspirillum sp. GW103 Coupled with Coconut Oil Cake

“…Several bacterial isolates belonging to the genera Acidothiobacillus, Acetobacter, Acidophilum, Arthrobacter, Pseudomonas, and Bacillus have been reported as efficient bioleachers (Mulligan and Cloutier, 2003;Deng et al, 2012;Chiang et al, 2013).…”

Chemoorganotrophic Bioleaching of Olivine for Nickel Recovery

“…The increasing demand and diminishing availability of raw materials requires us to look beyond conventional resources; particularly, the importance of low-grade ores is expected to increase in the near future [1]. An example is the depletion of accessible high-grade sulfidic ores, which makes it necessary to seek more abundant but lower grade ores, often rich in siliceous mafic minerals (olivine, pyroxene, amphibole and biotite).…”

“…An alternative, potentially more sustainable approach is the application of biohydrometallugy, wherein microorganisms act as renewable chemical producers [1] of substances that deteriorate and dissolve minerals, thereby liberating the immobilized metals into solution (leachate). Biogenic substances produced include not only organic acids [2], but also chelates, mineral acids, and for certain bacteria, ammonia or amines [3].…”

“…These will influence both the growth of the microorganisms as well as their leaching behavior [1,[7][8][9]. Most importantly, the microorganism must be able to leach the material, and also be resistant to the metals that are leached out.…”

“…The microorganisms utilized were the bacterium Paenibacillus mucilaginosus, and the fungi Aspergillus niger, Penicillium chrysogenum and Humicola grisea. These microorganisms were selected based on the prior work of Chiang et al [1], who screened several bacteria and fungi for bioleaching of various alkaline materials. In that study, the bioleaching performance of fungi was more comparable, hence three fungi and one bacteria were selected for the present study.…”