Concentration and enrichment of heavy metals in efflorescence secondary sulfate minerals and mine drainage of the Rahatabad kaolin mine, Isfahan province

Authors

Department of Geology, University of Isfahan

Abstract

The abandoned kaolin mine under study is situated near Rahatabad village in the southwest of Naein county, Isfahan province, Iran. Samples were collected from the brine and efflorescent salts of two ponds formed by excavation in the mine, and the pH, Eh, and heavy metals concentration in the samples were determined. Efflorescent salts were identified via XRD analysis after being separated by color. Minerals found in the efflorescent salt samples include tamarugite, rhomboclase, szomolnokite, metasideronatrite, gypsum, ferricopiapite, magnesiocopiapite, bloedite, and konyaite. Cu, Mn, Ni, and Co are concentrated in bloedite and konyaite minerals, Cu, Mn, and Zn in kopiapite group minerals, Cu, Mn, and Co in szomolnokite, Pb and Zn in gypsum, and Zn and Mn in rhomboclase. Enrichment factor calculations indicate that Cu has extremely high enrichment, Co and Ni have high enrichment, while Pb, Mn, Zn, and Cd have low enrichment in the efflorescent salts. Moreover, all heavy metals exhibit very high enrichment in the efflorescent salts compared to the brine. With regards to the Pollution Load Index (PLI) in the efflorescent salts, the yellow and gray efflorescent salts are categorized as contaminated, while the other samples are non-contaminated. The Geoaccumulation Index (Igeo) categorizes the samples as highly to heavily contaminated for Cu, slightly contaminated for Co, not contaminated to slightly contaminated for Ni, and non-contaminated for the other heavy metals.

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