Use of natural zeolite-rich tuff and siliceous sand for mine water treatment from abandoned gold mine tailings

Abstract

Tailings facilities and associated waters often generate major environmental concerns due to the contaminant potential of the solids and the resulting acid mine drainage. The present study is focused on an area with mining tradition in the department of Santander, Cordillera Oriental - Colombia, where the evolution of mine tailings from gold exploitation resulted in acid mine drainage. An integrated approach led to a global characterization to the tailings and associated waters, including petrography, mineralogy, geochemistry, and hydrogeochemistry methods. The obtained results indicated that mine tailings are composed of sulfides (primarily pyrite with minor chalcopyrite, sphalerite, molybdenite, and galena), barite, silver, goethite, rare earths elements minerals, iron and titanium oxides, associated with quartz, muscovite and feldspar. The mine tailings are mainly in the silty range, and fire tests emphasized their compositional heterogeneity, namely for gold and silver, with the spatial distribution throughout the facility remaining unknown. Geochemical static tests, such as neutralization potential and acidity potential, allow the classification of these mine tailings as acid generators, as per the physical-chemical properties of the water samples. These samples were characterized before and after treatment with natural zeolite-rich tuff and siliceous sand with different weight ratios and days of duration of the experiment. Initially, chemical analyzes in the water showed an acidic pH of 2.96, high concentrations of sulfides (162 mg S−2/L) and Fe (10.41 mg Fe/L), being classified as high-acid, high-metal water. The column experiments revealed that the best relationship for remediation of this contaminated water was the one with the highest zeolite content, obtaining neutral pH values close to 7 and iron values on average < 0.07 mg/L for the different days of the experiment. The results obtained in this study indicate the efficiency of the low-cost natural zeolite-rich tuff for cost-effective treatment of acid mine drainage.