Neutralization/prevention of acid rock drainage using mixtures of alkaline by-products and sulfidic mine wastes

Abstract

Backfilling of open pit with sulfidic waste rock followed by inundation is a common method for reducing sulfide oxidation after mine closure. This approach can be complemented by mixing the waste rock with alkaline materials from pulp and steel mills to increase the system's neutralization potential. Leachates from 1 m3 tanks containing sulfide-rich (ca.30 wt %) waste rock formed under dry and water saturated conditions under laboratory conditions were characterized and compared to those formed from mixtures. The waste rock leachate produced an acidic leachate (pH<2) with high concentrations of As (65 mg/L), Cu (6 mg/L), and Zn (150 mg/L) after 258 days. The leachate from water-saturated waste rock had lower concentrations of As and Cu (<2 μg/L), Pb and Zn (20 μg/L and 5 mg/L), respectively, and its pH was around 6. Crushed (<6 mm) waste rock mixed with different fractions (1-5 wt %) of green liquid dregs, fly ash, mesa lime, and argon oxygen decarburization (AOD) slag was leached on a small scale for 65 day, and showed near-neutral pH values, except for mixtures of waste rock with AOD slag and fly ash (5% w/w) which were more basic (pH>9). The decrease of elemental concentration in the leachate was most pronounced for Pb and Zn, while Al and S were relatively high. Overall, the results obtained were promising and suggest that alkaline by-products could be useful additives for minimizing ARD formation.

The effect of magnesium on partial sulphate removal from mine water as gypsum

“…Chemical precipitation with lime is the traditional treatment method for mine water although by-products as alternatives for lime have also been investigated (Mackie et al, 2010a(Mackie et al, , 2010bMackie and Walsh, 2012;Alakangas et al, 2013;Tolonen et al, 2014). With lime precipitation sulphate removal occurs via precipitation of gypsum.…”

Experimental Study on the Optimum Preparation of Bentonite–Steel Slag Composite Particles

“…Sustainability 2020, 12, 18 2 of 27 Current techniques for treating AMD containing heavy metals include the neutralization precipitation [11], electrochemical [12], membrane separation [13-15], microbial [16,17], constructed wetland [18], and adsorption [19,20] methods. Neutralization precipitation and adsorption are widely used [21,22]. However, neutralization precipitation requires a large amount of chemical agents, such as neutralizer and flocculent [23,24], which leads to difficulties in solid-liquid separation and high processing costs [25,26].…”

Basic Characteristics and Effective Control of Gangue Piles in Mining Areas: A Case Study

“…Gangue is mainly dealt with surface deposition. The number of gangue piles has also been increasing; lots of arable land and natural vegetation have been lost, causing a waste of land resources [13]. The environment around mining areas is therefore degraded [14].…”