Research article
Study of a tropical soil in order to use it to retain aluminum, iron, manganese and fluoride from acid mine drainage

https://doi.org/10.1016/j.jenvman.2017.09.024Get rights and content

Highlights

  • Column test was performed using a tropical soil and acid water as contaminant.

  • Soil was subjected to geotechnical, chemical and mineralogical tests.

  • Formation of insoluble Al-F complexes in the soil occurred at pH below 6.0.

  • Release of aluminum and fluoride in free form occurred at pH greater than 6.0.

  • Mn and Fe concentrations were higher than the allowed by the Brazilian legislation.

Abstract

The Ore Treatment Unit (UTM-Caldas), in the city of Caldas, Minas Gerais, Brazil, nowadays in decommissioning stage, was the first uranium extraction mine in Brazil. Several negative environmental impacts in the area have occurred, because of mining, treatment and beneficiation processes. Waste rock pile 4 (WRP-4) generates acid mine drainage (AMD), which is discharged in the Nestor Figueiredo retention pond (NFP). However, leakage of acid water by the NFP dam foundation has been constantly observed. Therefore, this research aimed to investigate a typical tropical soil, in order to use it as mineral liner for the NFP to minimize the leakage of acid water through the dam foundation and to retain predominant chemical species. Geotechnical, chemical and mineralogical tests were performed to characterize the soil and a column test was carried out using the acid mine drainage as contaminant, which contained aluminum (Al), manganese (Mn), iron (Fe) and fluoride (F). The soil presented micro aggregation, acid pH, and low values of organic matter content and cation exchange capacity, which are characteristics of highly weathered soils. Diffusion was the predominant transport mechanism in the column test. Effluent solutions with pH less than 6.0 indicated the formation of insoluble Al-F complexes in the soil and desorption of iron and manganese at concentrations above those allowed by the Brazilian legislation. At pH greater than 6.0, the desorption of iron and manganese and release of aluminum and fluoride in the free form occurred, with concentrations also higher than the allowed by the Brazilian legislation.

Introduction

Acid mine drainage (AMD) is a persistent environmental problem that directly affects the mining industry. Many researchers have studied environmental problems arising from AMD in Brazil and in the world (Singh and Rawat, 1985, Fernandes et al., 1998, Diz et al., 1999, Ladeira and Gonçalves, 2007, Motsi et al., 2009, Vazquez et al., 2010, Campos et al., 2011, Kwon et al., 2016, Rakotonimaro et al., 2017, Godoi et al., 2017). AMD is very acidic (pH < 3.0) and contains iron, aluminum, sulfate and heavy metals such as lead, mercury, cadmium and arsenic (Kwon et al., 2016).

The oxidation of sulfide minerals is the main cause of acid drainage from mining tailings. In the case of the uranium mine of Caldas Mineral Treatment Unit (UTM-Caldas), pyrite (FeS2) is the sulfide responsible for the occurrence of acid drainage (Franklin, 2007). UTM-Caldas was inaugurated in 1982, being the first Brazilian uranium mine. In 1996 it finished its operations and is currently in decommissioning stage. UTM-Caldas is located in the municipality of Caldas, in the plateau of Poços de Caldas, Southwest region of the State of Minas Gerais, Brazil. The average annual rainfall is 1750 mm and the average annual temperature is 17 °C.

According to Sicupira et al. (2015), the AMD generated in the mining region of Poços de Caldas contains radionuclides (U, Th, among others) as well as species of Mn, Zn, Fe, and F ions at concentration levels above those permitted by Brazilian law regarding their discharge into the environment.

The solid waste from the mine (waste rock) was defined as material with less than 170 mg kg−1 of uranium in the ore. This material was disposed in the so-called Waste Rock Piles (WRP). The waste rock pile number 4 (WRP-4) is the main type in the UTM-Caldas, occupies an area of 56.9 ha and contains 12.4 × 103 m3 of waste rocks, slope height of 90 m and slope of 70°. The waste rocks present a tinguatic texture, constantly impregnated by pyrite, fluorite, uranium, molybdenum and zirconium minerals (Cipriani, 2002). WRP-4 was formed by the disposal of waste rocks over the valley and bed of the Consulta Creek, without any compaction control, allowing waste rocks of higher particle size formed drainage channels in the base.

Currently, the acid drainage of the WRP-4 is discharged in the Nestor Figueiredo retention pond (NFP), with an approximate area of 2170.5 m2, which was constructed to capture almost all the water that percolates through WRP-4, besides receiving part of the run-off from the same pile. The pH of WRP-4 effluent water ranges from 3.0 to 4.0 and has high concentration of chemical elements and ions such as aluminum, manganese, iron, fluoride among others, and radioactive elements such as uranium, radium and thorium. The surplus water from the NFP flows through a channel located on the left bank of the Consulta Creek, which discharges the water downstream from its dam. However, leaking acid water by the NFP dam foundation has been observed frequently.

As there are no reports of the construction of a liner system at the NFP bottom, this research aimed to investigate a typical tropical soil, located in the UTM-Caldas area, in order to use it as a mineral liner for the NFP. It is intended to minimize the leakage of acid waters by the dam foundation and to retain the predominant elements in those waters (aluminum, iron, manganese and fluoride). In this study, we present the geotechnical and chemical-mineralogical characterization of the tropical soil and the performance and analysis of a column test using this soil and the acid water from the WRP-4 as a percolating solution.

Section snippets

Contaminant transport

The transport of contaminants refers to the transport of mass in porous medium in which the mass moves with the water between the voids of the soil in unsaturated and saturated zones. The main mechanisms of contaminant transport are advection, diffusion and hydrodynamic dispersion.

Advection is a physical process whereby the contaminant is carried by the water in a flow generated in the medium, where the rate of transport is directly proportional to the velocity, as a consequence of a gradient

Material and methods

The sampling site was the ground adjacent to the Nestor Figueiredo pond (NFP) at a level corresponding to the pond bottom. The geographical coordinates of the collection point were: Latitude (S) 21°56′24.72″; Longitude (W) 46°29′24.13″. The UTM coordinates were: N (m): 7573066.488 and E (m): 346123.741.

An undisturbed soil sample was collected by carefully crimping a beveled cylindrical polyethylene mold with an internal diameter of approximately 20 cm and a height of about 30 cm. Part of the

Characterization tests

The particle size curves of the soil sample with the use of deflocculant (WD) and without deflocculant (ND) is shown in Fig. 1. The results of the geotechnical and chemical characterization tests of the soil sample are presented in Table 1, Table 2.

The soil sample was classified as silty clay with the use of the deflocculant, and as sand-clayey silt, without it, and the result was the micro aggregation of particles, typical of tropical soils (Gidigasu, 1976, Committee on Tropical Soils of

Conclusion

The tropical soil located in the area of the Caldas Mineral Treatment Unit (UTM-Caldas) – characterized to be used as a mineral liner base for the NFB pond (NFP) that receives the acid drainage from the WRP-4 – was not suitable for retaining the main chemical species present. The soil has micro aggregation, acid pH, low values of organic matter content and cation exchange capacity, typical characteristics of highly weathered tropical soils. The estimated point of zero charge was 3.5, below the

Acknowledgments

The authors would like to thank the National Nuclear Energy Commission (CNEN) and the Nuclear Industries of Brazil SA (INB) for the support given to the research, and the National Council for Scientific and Technological Development (CNPq) for granting master's scholarship (process number 300789/2011-4).

References (49)

  • T. Yokoyama et al.

    Evaluation of the coprecipitation of incompatible trace elements with fluoride during silicate rock dissolution by acid digestion

    Chem. Geol.

    (1999)
  • APHA

    Standard Methods for the Examination of Water and Wastewater

    (2005)
  • A.K.M. Arnesen et al.

    Sorption and desorption of fluoride in soil

    Water Air Soil Poll.

    (1998)
  • ASTM D 422–463

    Standard Test Method for Particle-size Analysis of Soils

    (2007)
  • ASTM D 4318–10

    Standard Test Method for Liquid Limit, Plastic Limit and Plasticity Index of Soils

    (2010)
  • ASTM D 854–14

    Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer

    (2014)
  • M. Balintova et al.

    Study of pH influence on selective precipitation of heavy metals from acid mine drainage

    Chem. Eng. Trans.

    (2011)
  • R.P. Barreto

    Diffusion of Al, Fe, Mn and F by a Lateritic Soil Aiming at the Application as a Liner for the Drainage Basin Acid Drainage Generated by the Waste Rock Pile 4 of the UTM-Caldas

    (2011)
  • J. Bear

    Dynamics of Fluid in Porous Media

    (1972)
  • R. Buamah et al.

    Adsorption of fluoride form aqueous solution using a low cost adsorbent

    J. Water Sci. Tech. Water Supply

    (2013)
  • O.A. Camargo et al.

    Methods of Chemical, Mineralogical and Soil Analysis of the Agronomic Institute of Campinas

    (2009)
  • M.B. Campos et al.

    Environmental assessment of water from a uranium mine (Caldas, Minas Gerais State, Brazil) in a decommissioning operation

    Environ. Earth Sci.

    (2011)
  • M. Cipriani

    Mitigation of Social and Environmental Impacts Due to the Definitive Closure of Uranium Mines

    (2002)
  • V.E. Crooks et al.

    Saline leachate migration through clay: a comparative laboratory and field investigation

    Can. Geotech. J.

    (1984)
  • Cited by (20)

    • Integrated bacteria-algal bioreactor for removal of toxic metals in acid mine drainage from iron ore mines

      2020, Bioresource Technology Reports
      Citation Excerpt :

      AMD is characterized with low pH, high concentration of heavy metals, sulfate, iron, manganese, and multiple toxic elements which pose threat to aquatic organisms, plant communities and human health. Chemical and mineralogical evidences reveal that AMD sources were mostly contaminated with manganese (Mn), sulfate, fluoride (F−), iron (Fe), aluminum (Al) and many heavy metals (lead, mercury, cadmium, arsenic) (Kwon et al., 2016; Miguel et al., 2017). Further, rampant discharge of AMD causes negative influence on physico-chemical characteristics of soil, aquatic systems, air due to production of hydrogen sulfide (Yang et al., 2015).

    • Mechanism of simultaneous removal of aluminum and fluoride from aqueous solution by La/Mg/Si-activated carbon

      2020, Chemosphere
      Citation Excerpt :

      Fluoride has been used in the production processes in many industries such as metal plating, semiconductor production, and coal mining for many years (Yu et al., 2015). Moreover, high level of aluminum and floride leached from mines and associated mine drainage, wastes or tailing piles (Miguel et al., 2017; Rakotonimaro et al., 2017; Godoi et al., 2017; Kwon et al., 2016). Therefore, the production and discharge of a large amount of aluminum and fluoride have led to the continuous increase of these ions in water.

    • Water defluorination using granular composite synthesized via hydrothermal treatment of polyaluminum chloride (PAC) sludge

      2020, Chemosphere
      Citation Excerpt :

      However, contamination of F− in surface- and groundwater at excessive level has become a major problem in the environment because the excessive amount can threaten the human health (skeletal fluorosis and diffuse osteosclerosis) (Gao et al., 2020). Recently, high level of F− (ppm level) has been also detected in the mine drainage in China, Brazil, and United States (US) (Alsaiari and Tang, 2018; Feng et al., 2014; Miguel et al., 2017). Thus, the standard limits for F- in drinking water (the maximum contaminant level, MCL) are regulated below 1.5 mg L−1 by the World Health Organization (WHO) (Bhatnagar et al., 2011) and 4 mg L−1 by United States Environmental Protection Agency (US EPA) (Yadav et al., 2019), respectively.

    • Phytoremediation of mine tailings by Brassica juncea inoculated with plant growth-promoting bacteria

      2019, Microbiological Research
      Citation Excerpt :

      The metal with higher accumulation in the presence of bacteria was Al, for it can be available, which can be corroborated by XRD, helping to perform a phytoextraction of Al to recover it, which coincides with the studies performed for bioremediation systems using enzymes such as Trametes versicolor (Wu et al., 2006) and Aspergillus niger (accumulation), which due to the production of citric exudates such as the citric, oxalic and gluconic, are capable of contributing to the extraction and mobility of Al in polluted soils (Boriov et al., 2016). On the other hand, the mobility of Al depends on the soil pH, where this element is normally static at values below 6 (Gonalves et al., 2017), but for our system, the pH values are above 6 and then, soluble compounds of this element are formed, thus favoring the phytoextraction process. The SEM results confirmed that the bacteria not only colonized the external part of the roots, but also colonized them inside, working as endophytic bacteria, where Enterobacter MC156 was the strain with higher colonization, followed by Serratia K120, which favored the accumulation of metals in Brassica juncea L., promoting its growth by diminishing the stress caused by the high concentrations of metals.

    View all citing articles on Scopus
    View full text