Laboratory Study on the Effectiveness of Limestone and Cementitious Industrial Products for Acid Mine Drainage Remediation

Abdellatif Elghali,Hassan Bouzahzah,Bruno Bussière,Mostafa Benzaazoua

doi:10.3390/min11040413

Abstract

Acid mine tailings may affect several environmental matrices. Here, we aimed to stabilize acid-generated mine tailings using several alkaline and cementitious amendments, which were tested in columns for 361 days. The alkaline amendments consisted of 10 and 20 wt.% limestone, while the cementitious amendments consisted of different binders at a total dosage of 5 wt.% binder. The different formulations for the cementitious amendments were: 50% Kruger fly ash and 50% class F fly ash; 20% ordinary Portland cement, 40% Kruger fly ash, and 40% class F fly ash; 80% ordinary Portland cement and 20% Kruger fly ash; and 20% ordinary Portland cement, 40% Kruger fly ash, and 40% fly ash. Kinetic testing on the amendment formulations showed that the pH values increased from <2.5 to circumneutral values (~7.5). The mobility of various chemical species was greatly reduced. Cumulative Fe released from the unamended tailings was ~342.5 mg/kg, and was <22 mg/kg for the amended tailings. The main mechanisms responsible for metal(loid) immobilization were the precipitation of secondary phases, such as Fe-oxyhydroxides, physical trapping, and tailing impermeabilization.

Highlights

Mining activities generate large quantities of solid wastes such as waste rocks and tailings
Sulfide oxidation increases the acidity of leachate waters, which can lead to the formation of acid mine drainage (AMD)
The D90 values, which correspond to the diameter at which 90% of particles pass on the cumulative grain-size distribution curve, were about 30.4, 4500, 46.7, 1500, 104.2, and 89.1 μm for the mine tailings, LS, ordinary Portland cement (OPC), fly ash (FA), CVK, and FAF, respectively

Summary

Introduction

Mining activities generate large quantities of solid wastes such as waste rocks and tailings. Tailings are generated after ore treatment and processing, and are characterized by fine grain-size distributions and high specific surface areas [1,2,3]. Mine tailings often contain non-negligible amounts of iron sulfide minerals such as pyrite and pyrrhotite [4,5,6]. The oxidation of sulfide minerals occurs when they are exposed to water and oxygen, both in the presence or absence of microorganisms [5]. Sulfide oxidation can involve various and complex processes, including chemical, biological, and electrochemical reactions [7]. The overall reaction of pyrite oxidation result produces four moles of H+ (Equation (1))

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Conclusion