Carbonation, Cementation, and Stabilization of Ultramafic Mine Tailings

Abstract

Tailings dam failures can cause devastation to the environment, loss of human life, and require expensive remediation. A promising approach for de-risking brucite-bearing ultramafic tailings is in situ cementation via carbon dioxide (CO 2 ) mineralization, which also sequesters this greenhouse gas within carbonate minerals. In cylindrical test experiments, brucite [Mg(OH) 2 ] carbonation was accelerated by coupling organic and inorganic carbon cycling. Waste organics generated CO 2 concentrations similar to that of flue gas (up to 19%). The abundance of brucite (2−10 wt %) had the greatest influence on tailings cementation as evidenced by the increase in total inorganic carbon (TIC; +0.17−0.84%). Brucite consumption ranged from 64−84% of its initial abundance and was mainly influenced by water availability. Higher moisture contents (e.g., 80% saturation) and finer grain sizes (e.g., clay-silt) that allowed for a better distribution of water resulted in greater brucite carbonation. Furthermore, pore clogging and surface passivation by Mg-carbonates may have slowed brucite carbonation over the 10 weeks. Unconfined compressive strengths ranged from 0.4−6.9 MPa and would be sufficient in most scenarios to adequately stabilize tailings. Our study demonstrates the potential for stabilizing brucite-bearing mine tailings through in situ cementation while sequestering CO 2 .

The mechanisms and drivers of lithification in slag‐dominated artificial ground

“…Such artificial ground can pose various challenges, ranging from pollution to ground instability. Precipitation of a calcite cement has been shown to stabilise soils and sediments (Power et al, 2021; Stocks‐Fischer et al, 1999), and therefore, the occurrence of this process in unstable slag heaps can be important in reducing the risk of failure and harm to humans. Precipitated calcite can also immobilise potentially toxic metals (Merrikhpour & Jalali, 2012; Olsson et al, 2014a, 2014b), which are likely to be present in higher concentrations in artificial ground than in the natural environment.…”

“…While lithification is a natural process, it can be anthropogenically induced in soils/sediments. Laboratory experiments indicate that injection of CO 2 into certain types of artificial ground deposits (ultramafic mine tailings) can lead to cementation and stabilisation (Power et al, 2021). While not strictly lithification, microbially induced calcite precipitation (MICP) through harnessing of soil bacteria can be used to stabilise soils and sediments and improve their geochemical properties (Liu et al, 2021; Moravej et al, 2018; Tiwari et al, 2021).…”

Constraining the Capacity of Global Croplands to CO2 Drawdown via Mineral Weathering

“…In this perspective, we have assumed global availability of each of the minerals exemplified because we aimed to highlight the effects of cropland soil pH and temperature rather than mineral availability, but this is certainly an assumption that should be reviewed on a case-by-case (i.e., region-by-region) basis. We selected wollastonite (CaSiO 3 ), forsterite (Mg 2 SiO 4 ), and lizardite [Mg 3 (Si 2 O 5 )­(OH) 4 ] for our analysis as these represent minerals with both demonstrated suitability for ERW in crop soils ,− and mine tailings ,, scenarios and a diverse set of comparatively fast, moderate, and slow weathering rates (Figure ), respectively. Anorthite, a common constituent of basalt, was not selected because it was aforementioned that its data in Figure is less reliable.…”

Status of Ecosystem Services in Abandoned Mining Areas in the Iberian Peninsula: Management Proposal

“…Assessing the degree of contamination of an environment and the mobility patterns of toxic elements present is vital to establish the risks of dispersion of contaminants through the ecosystem and, when these risks are known, to allow sludge slope stabilization or soil remediation and encapsulation to be undertaken [ 45 , 46 ]. This study refers to various techniques are referred: (i) the formation of a hardpan to facilitate both geochemical reactions and the precipitation of secondary minerals to increase the physical and chemical stability of the sludge [ 47 , 48 ]; (ii) revegetation to reduce water and wind erosion and physically stabilize the sludge [ 49 ]; (iii) the application of carbonation and cementation techniques to achieve the physical stabilization and immobilization of released metals [ 50 , 51 , 52 ] and (iv) the addition of organics, including biochar, compost, biosolids, and organic-rich sludge, to achieve phytostabilization and remediation through the formation of technosoils [ 53 , 54 , 55 , 56 , 57 , 58 ].…”