Abstract
Weathering cell test, designed specifically to overcome material-limited constraints, yields prompt and efficient experimental assessment during the development stages of mining projects. However, it has barely benefited from geochemical modeling tools despite their ease of use. Accordingly, this paper aims to strengthen the upstream geochemical assessment via parametric analysis that simulates the effect of various mineral assemblages on leachate quality recovered from weathering cells. The main objective is to simulate the pH in presence of silicate neutralizing minerals and Mn release from carbonates based upon minimal characterization data. The public domain code PHREEQC was used for geochemical kinetic modeling of four weathering cells. The kinetic model utilized a water film concept to simulate diffusion of chemical elements from mineral surfaces to the pore water. The obtained results suggest that the presence of the silicate neutralizing minerals slightly affects the Mn release from carbonates. Furthermore, plagioclases could supply a significant neutralization potential when they predominate the mineral assemblage. Finally, coupling weathering cell test and parametric analyses illuminate the pH evolution for various mineral proportion scenarios.
Highlights
This study aims to (i) simulate weathering cells designed for the upstream stage, and (ii) introduce a straightforward geochemical screening tool that expands the geochemical assessment from the interpretation of experimental results to parametric analysis throughout the development stage
A residence time of 100 days kinetically controlled reactions occurring in four weathering cells using a film diffusion produced leachate with pH = 3.66, 20.03 mg/L sulfate, and 5.91 mg/L Fe after a simulation model implemented in PHREEQC
Iron concentrations were as high as 73 mg/L in pores with extremely slowusing PHREEQC exhibited a good agreement with weathering cell data
Summary
Atmospheric oxygen and through-flowing water trigger oxidation of sulphides such as pyrite and pyrrhotite, resulting in potentially contaminated effluents. This naturally occurring phenomenon has aroused growing interest and is termed acid mine drainage (AMD) or contaminated neutral drainage (CND), depending on the neutralizing potential [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. Sulphide oxidation and the subsequent effluent result in water quality exceedances in terms of metals and oxyanions concentrations as well as low pH in the case of AMD. Research endeavors adopted by governments, the mining industry, universities, and research establishments focus on assessment, prevention, and treatment of AMD and CND to safeguard ecosystems neighboring mine facilities [24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42]
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