Characterization and pH neutralization products of efflorescent salts from mine tailings of (semi-)arid zones

Alan U. Loredo-Jasso*, Mario Villalobos, Daniela B. Ponce-Pérez, Teresa Pi-Puig, Diana Meza-Figueroa, Rafael del Rio-Salas, Lucas Ochoa-Landín

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Acidic water-soluble efflorescent salts in mining residues commonly form from sulfide oxidation and are particularly prevalent in semi-arid to arid environments. These salts are easily carried by winds and may contaminate the environment and affect human health, especially because they contain potentially toxic metals and have high solubilities. In this work, efflorescent salts from four mining sites in Mexico were characterized by X-ray diffraction and chemical analysis. They produced acidic pH values upon dissolution, and were found to be composed mostly of soluble sulfates of Ca(II), Mg(II), Zn(II) and/or Cu(II), and to a lesser extent of Fe(II/III) and/or Al, of variable stoichiometries, crystal water contents and crystallinity. Their physical and chemical characteristics varied highly depending on the underlying geochemical matrix and on the composition of the original mining residues, but gypsum was present in all samples. Two selected samples were dissolved and the solution neutralized, causing substantial precipitation of solids. The precipitates, at pH 7 were found to contain the Cu and/or Zn - rich hydroxysulfates: lahnsteinite [Zn4(OH)6SO4·3H2O], or schulenbergite [Cu3Zn4(OH)10(SO4)2]. Solubility product constants were determined on these, and on other solids produced in the absence of certain major components [such as sulfate or Zn(II)], by a combination of chemical measurements and geochemical code calculations to speciate some of the components found. These results should enhance thermodynamic properties of databases and help to predict what phases form if pH neutralization occurs or is used for remediation purposes.

Original languageEnglish
Article number120370
JournalChemical Geology
Volume580
DOIs
StatePublished - 5 Oct 2021

Bibliographical note

Funding Information:
The authors thank Adriana Guzmán Cruz for the samples from the mine tailings in Taxco; Juanita Sierra Salamanca for her assistance in the design of the map using the ArcGIS program, and Luis Palomino from the Universidad de Sonora for granting access to sampling at the La Caridad mine tailings site. A.U. L.-J. is thankful to the CONACyT for the Master's fellowship received. This research was funded by the Consortium for Arizona-Mexico Arid Environments (CAZMEX) with participation from CONACyT , and from the project CONACyT-Ciencia Basica 2016 283416 . Funds for the general functioning of the lab were obtained by support to the LANGEM from CONACyT as well. Finally, we are grateful for the extensive comments of two anonymous reviewers, who helped to considerably improve the writing of the manuscript text.

Funding Information:
The authors thank Adriana Guzm?n Cruz for the samples from the mine tailings in Taxco; Juanita Sierra Salamanca for her assistance in the design of the map using the ArcGIS program, and Luis Palomino from the Universidad de Sonora for granting access to sampling at the La Caridad mine tailings site. A.U. L.-J. is thankful to the CONACyT for the Master's fellowship received. This research was funded by the Consortium for Arizona-Mexico Arid Environments (CAZMEX) with participation from CONACyT, and from the project CONACyT-Ciencia Basica 2016 283416. Funds for the general functioning of the lab were obtained by support to the LANGEM from CONACyT as well. Finally, we are grateful for the extensive comments of two anonymous reviewers, who helped to considerably improve the writing of the manuscript text.

Publisher Copyright:
© 2021 Elsevier B.V.

Keywords

  • Efflorescent salts
  • Hydroxysulfates
  • Lahnsteinite
  • Schulenbergite
  • Solubility product constant

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