Lead Mobilization and Speciation in Mining Waste: Experiments and Modeling

Clémentine Drapeau,Denise Blanc,Cécile Delolme,Thomas Baumgartl,Rabei Argane,Rachid Hakkou,Mansour Edraki,Mostafa Benzaazoua,Laurent Lassabatere

doi:10.3390/min11060606

Abstract

Mining produces significant amounts of solid mineral waste. Mine waste storage facilities are often challenging to manage and may cause environmental problems. Mining waste is often linked to contaminated mine drainage, including acidic waters with more or less elevated concentrations of trace metals such as lead. This work presents a study on the mobilization of lead from waste from two typical mining sites: Zeida and Mibladen, two now-closed former Pb–Zn mines in the Moulouya region of Morocco. Our research investigates the mobilization potential of Pb from the waste of these mines. The study involved acid–base neutralization capacity tests (ANC–BNC) combined with geochemical modeling. Experimental data allowed for the quantification of the buffering capacity of the samples and the mobilization rates of lead as a function of pH. The geochemical model was fitted to experimental results with thermodynamic considerations. The geochemical model allowed for the identification of the mineral phases involved in providing the buffering capacity of carbonated mining waste (Mibladen) and the meager buffering capacity of the silicate mining waste (Zeida). These cases are representative of contaminated neutral drainage (CND) and acid mine drainage (AMD), respectively. The results highlight the consistency between the ANC–BNC experimental data and the associated modeling in terms of geochemical behavior, validating the approach and identifying the main mechanisms involved. The modeling approach identifies the dissolution of the main solid phases, which impact the pH and the speciation of lead as a function of the pH. This innovative approach, combining ANC–BNC experiments and geochemical modeling, allowed for the accurate identification of mineral phases and surface complexation phenomena, which control the release of lead and its speciation in drainage solutions, as well as within solid phases, as a function of pH.

Highlights

Open-pit and underground mining operations produce a significant amount of solid mineral waste
PointSpeciation for the neutral zone with water). For all of these modeled points, into 200 increments in the acidic zone, 200 increments in the basic zone, plus 1 point for we provide the of mineral composition of the solid and liquid phases and leadofspeciation, The benefit the modeling approach is fully the provision charthe neutral zone
For the sake of precision, the whole range of pH meshes into 200 increments in the acidic zone, 200 increments in the basic zone, plus 1 point for the neutral zone. For all of these modeled points, we provide the mineral composition of the solid and liquid phases and lead speciation, including lead in solution, lead sorbed onto surface complexation sites or cationic exchange sites, and lead precipitated or associated with lead-bearing minerals (Figure 5)

Summary

Introduction

Open-pit and underground mining operations produce a significant amount of solid mineral waste Whether it is mine waste rock in the form of waste rock piles or concentrator rejects discharged in the form of tailings, above-ground waste storage facilities are difficult to manage and expensive to rehabilitate. Acid mine drainage (AMD) represents the phenomenon of acidification of the environment due to the oxidation of sulfidic mining waste, while contaminated neutral drainage (CND) refers to drainage from mining waste with acidneutralizing capacity and water pH close to neutrality Both water types may have high concentrations of metals, metalloids, and sulfate [3,4]. This sector represents more than 27% of all exports and nearly 6% of gross domestic product [1] This industry has too often ignored the need to rehabilitate mining sites in the past, including tailing storage facilities and waste rock dumps. In addition to the substantial contamination of surface waters and soils, the weathering of this waste triggers the release of some pollutants, including toxic trace metals, e.g., [13,14,15]

Methods

Results

Conclusion