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Interaction of gypsum with As(V)-bearing aqueous solutions: Surface precipitation of guerinite, sainfeldite, and Ca2NaH(AsO4)2·6H2O, a synthetic arsenate

  • Juan D. Rodríguez , Amalia Jiménez EMAIL logo , Manuel Prieto , Laura Torre and Santiago García-Granda
Published/Copyright: April 1, 2015
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American Mineralogist
From the journal American Mineralogist Volume 93 Issue 5-6

Abstract

The interaction of arsenate-bearing aqueous solutions with gypsum at a starting pH of 9 and 25 °C results in surface precipitation of guerinite, Ca5(HAsO4)2(AsO4)2·9H2O, sainfeldite, Ca5(HAsO4)2(AsO4)2·4H2O, and occasionally Ca2Na(HAsO4)(AsO4)·6H2O, a new arsenate. These three solid phases are characterized by the simultaneous presence of HAsO42- and AsO43- groups in their structure, which is explainable since crystallization occurs within a pH range in which both HAsO42- and AsO43- are available in the aqueous solution. The interaction leads to a decrease in the As(V) concentration in the aqueous phase to reach values controlled by the solubility of these solid phases. The study combines several macroscopic experiments, in which changes in the solution chemistry are monitored as a function of time, with the characterization of solid phases by SEM-EDS and XRD. The crystal morphologies of the precipitating phases are interpreted on the basis of their respective structures. The thermodynamic solubility products of both guerinite and the new arsenate have been determined, being 10-31.17±0.05 and 10-13.83±0.03, respectively. The reaction paths followed by the system and the equilibrium endpoints have been modeled using the geochemical code PHREEQC.

Keywords: Crystal growth; calcium arsenate; analysis chemical; sainfeldite; phase equilibrium; guerinite; gypsum
Received: 2007-7-16
Accepted: 2007-12-27
Published Online: 2015-4-1
Published in Print: 2008-5-1

© 2015 by Walter de Gruyter Berlin/Boston

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  1. The crystal structure of vurroite, Pb20Sn2(Bi,As)22S54Cl6: OD-character, polytypism, twinning, and modular description
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  22. Birchite, a new mineral from Broken Hill, New South Wales, Australia: Description and structure refinement
  23. Crystal structure of synthetic Al4B2O9: A member of the mullite family closely related to boralsilite
  24. Interaction of gypsum with As(V)-bearing aqueous solutions: Surface precipitation of guerinite, sainfeldite, and Ca2NaH(AsO4)2·6H2O, a synthetic arsenate
  25. Jahnsite-(NaFeMg), a new mineral from the Tip Top mine, Custer County, South Dakota: Description and crystal structure
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https://doi.org/10.2138/am.2008.2750
Keywords for this article
Crystal growth; calcium arsenate; analysis chemical; sainfeldite; phase equilibrium; guerinite; gypsum

Articles in the same Issue

  1. The crystal structure of vurroite, Pb20Sn2(Bi,As)22S54Cl6: OD-character, polytypism, twinning, and modular description
  2. Mineralogy of the Paso Robles soils on Mars
  3. Dingdaohengite-(Ce) from the Bayan Obo REE-Nb-Fe Mine, China: Both a true polymorph of perrierite-(Ce) and a titanic analog at the C1 site of chevkinite subgroup
  4. Thermal equation of state of CaGeO3 perovskite
  5. Quantitative absorbance spectroscopy with unpolarized light: Part I. Physical and mathematical development
  6. Quantitative absorbance spectroscopy with unpolarized light: Part II. Experimental evaluation and development of a protocol for quantitative analysis of mineral IR spectra
  7. Oxide-melt solution calorimetry of selenides: Enthalpy of formation of zinc, cadmium, and lead selenide
  8. Precise dating of biotite in distal volcanic ash: Isolating subtle alteration using 40Ar/39Ar laser incremental heating and electron microprobe techniques
  9. Rationale for the existence of four- and eight-reversals in antigorite
  10. Structural relaxation around substitutional Cr3+ in pyrope garnet
  11. Metasomatic thorite and uraninite inclusions in xenotime and monazite from granitic pegmatites, Hidra anorthosite massif, southwestern Norway: Mechanics and fluid chemistry
  12. Interlayer potassium and its neighboring atoms in micas: Crystal-chemical modeling and XANES spectroscopy
  13. Effect of chemical environment on the hydrogen-related defect chemistry in wadsleyite
  14. Fracture toughness, hardness, and elastic modulus of kyanite investigated by a depth-sensing indentation technique
  15. Crystal chemistry of the natrojarosite-jarosite and natrojarosite-hydronium jarosite solid-solution series: A synthetic study with full Fe site occupancy
  16. A new experimental thin film approach to study mobility and partitioning of elements in grain boundaries: Fe-Mg exchange between olivines mediated by transport through an inert grain boundary
  17. Titanium as a cathodoluminescence activator in alkali feldspars
  18. Biogenic vs. abiogenic magnetite nanoparticles: A XMCD study
  19. Solubility of andradite, Ca3Fe2Si3O12, in a 10 mol% NaCl solution at 800 °C and 10 kbar: Implications for the metasomatic origin of grandite garnet in calc-silicate granulites
  20. A 3D reconstruction of plagioclase crystals in a synthetic basalt
  21. Rudashevskyite, the Fe-dominant analogue of sphalerite, a new mineral: Description and crystal structure
  22. Birchite, a new mineral from Broken Hill, New South Wales, Australia: Description and structure refinement
  23. Crystal structure of synthetic Al4B2O9: A member of the mullite family closely related to boralsilite
  24. Interaction of gypsum with As(V)-bearing aqueous solutions: Surface precipitation of guerinite, sainfeldite, and Ca2NaH(AsO4)2·6H2O, a synthetic arsenate
  25. Jahnsite-(NaFeMg), a new mineral from the Tip Top mine, Custer County, South Dakota: Description and crystal structure
  26. Evidence for anomalously large degree of polymerization in Mg2SiO4 glass and melt
  27. Theoretical infrared absorption coefficient of OH groups in minerals
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