Water, Air, and Soil Pollution

, Volume 169, Issue 1–4, pp 221–238 | Cite as

Solubility and Stability of Calcium Arsenates at 25C

  • Y. N. Zhu
  • X. H. Zhang
  • Q. L. Xie
  • D. Q. Wang
  • G. W. Cheng
Article

Abstract

The solubility and stability of calcium arsenates at 25 C was determined by both precipitation and dissolution experiments. Ca3(AsO4)2⋅ 3H2O(c), Ca3(AsO4)2⋅ 21/4H2O(c), Ca5(AsO4)3(OH)(c) and Ca4(OH)2(AsO4)2⋅ 4H2O(c) were identified in our experiment over a wide range of pH and for Ca/As molar ratios between 1.25 and 4.0. The solids precipitated at pH = 3 ∼ 7 and Ca/As = 1.5 were phase-pure and well-crystallized Ca3(AsO4)2⋅ xH2O(c) and had relatively larger grain size than those formed at pH > 7. Based on the analytical results and using the computer program PHREEQC, the solubility products for Ca3(AsO4)2⋅ 3H2O(c), Ca3(AsO4)2⋅ 21/4H2O(c), Ca5(AsO4)3(OH)(c) and Ca4(OH)2(AsO4)2⋅ 4H2O(c) were calculated as Ksp of 10− 21.14(10− 20.01 ∼ 10− 22.02), 10− 21.40(10− 20.08 ∼ 10− 21.98), 10− 40.12(10− 37.53 ∼ 10− 42.72) and 10− 27.49(10− 26.10 ∼ 10− 28.91), respectively. Correspondingly, the free energies of forming (Δ Gfo) of these calcium arsenates were calculated to be −3787.87 kJ/mol, −3611.50 kJ/mol, −5096.47 kJ/mol and −4928.86 kJ/mol.

Keywords

calcium arsenates free energies of forming solubility products stability 

References

  1. Bothe, J. V. and Brown P. W.: 1999a, ‘Arsenic immobilization by calcium arsenate formation’, Environ. Sci. Technol. 33, 3806–3811.CrossRefGoogle Scholar
  2. Bothe, J. V., and Brown, P. W.: 1999b, ‘The stabilities of calcium arsenates at 23±1C’, J. Hazard. Mater. B69, 197–207.Google Scholar
  3. Chukhlantsev, V.: 1956, ‘Solubility products of arsenates’, Zhurnal Neorganicheskoi Khmii (J. Inorg. Chem.-USSR) 1, 1975–1982.Google Scholar
  4. Donahue, R. and Hendry, M. J.: 2003, ‘Geochemistry of arsenic in uranium mine mill tailings, Saskatchewan, Canada’, Appl. Geochem. 18, 1733–1750.CrossRefGoogle Scholar
  5. Essington, M. E.: 1988, ‘Solubility of barium arsenate’, Soil Sci. Soc. Am. J. 52, 1566–1570.Google Scholar
  6. Fulladosa, E., Murat, J. C., Martinez, M. and Villaescusal, I.: 2004, ‘Effect of pH on arsenate and arsenite toxicity to luminescent bacteria (Vibrio fischeri)’, Arch. Environ. Contam. Toxicol. 46, 176–182.Google Scholar
  7. Karagas, M. R., Le, C. X., Morris, S., Blum, J., Lu, X., Spate, V.: 2001 ‘Markers of low level arsenic exposure for evaluating human cancer risks in the US population’, Int. J. Occup. Med. Environ. Health 14, 171–175.Google Scholar
  8. Kittrick, J. A., and F. J. Peryea.: 1986, ‘Determination of the Gibbs free energy of formation of magnesite by solubility methods’, Soil Sci. Soc. Am. J. 50, 243–247.CrossRefGoogle Scholar
  9. Magalhães, M. C. F.: 2002, ‘Arsenic - An environmental problem limited by solubility’, Pure Appl. Chem. 74, 1843–1850.Google Scholar
  10. Mahapatra, P. P., Mahapatra, L. M. and Mishra, B.: 1986, ‘Solubility of calcium hydrogen arsenate in aqueous medium’, Indian. J. Chem. 25A, 647–9.Google Scholar
  11. Mihaljevic, M., Ponavic, M., Ettler, V. and Šebek, O.: 2003, ‘A comparison of sequential extraction techniques for determining arsenic fractionation in synthetic mineral mixtures’, Anal. Bioanal. Chem. 377, 723–729.CrossRefGoogle Scholar
  12. Nishimura, T. and Robins, R. G.: 1998, ‘A re-evaluation of the solubility and stability regions of calcium arsenites and calcium arsenates in aqueous solution at 25C’, Mineral Proc. and Extr. Met. Reviews 18, 283–308.Google Scholar
  13. Nishimura, T. and Tozawa, K.: 1978, ‘On the solubility products of ferric, calcium and magnesium arsenates’, Bull. Res. Inst. Min. Dress. Metall. Tohoku Univ. 34(1), 19–26.Google Scholar
  14. Nishimura, T. and Tozawa, K.: 1984, ‘The reaction for the removal of As(III) and As(V) from aqueous solutions by adding calcium hydroxide’, J. Min. Met. Inst. Japan 100, 1085–1091.Google Scholar
  15. Nishimura, T. and Tozawa, K.: 1985, ‘Removal of arsenic from waste water by addition of calcium hydroxide and stabilization of arsenic-bearing precipitate by calcination’, In A. J. Oliver (ed.), Impurity Control Disposal, Canadian Institute of Mining, Metallurgy and Petroleum, Montreal, Canada, pp.3/1–3/18.Google Scholar
  16. Nishimura, T., Tozawa, K. and Robins, R. G.: 1983, ‘The calcium-arsenic-water system’, proceedings MMIJ/Aus.IMM Joint Symposium, Sendai, Japan. Paper JD-2-1, 105–120.Google Scholar
  17. Parkhurst, D. L., and Appelo, C. A. J.: 1999, ‘User's guide to PHREEQC (Version2) - A computer program for speciation, reaction-path, advective-transport, and inverse geochemical calculations’, USGS Water-Resources Investigations Report 99-4259.Google Scholar
  18. Robins, R. G.: 1981, ‘The solubility of metal arsenates’, Metallurgical Transactions 12B, 103–109.Google Scholar
  19. Robins, R. G.: 1985, ‘The solubility of barium arsenates: Sherritt's barium arsenate process’, Metallurgical Transactions 16B, 404–406.Google Scholar
  20. Smedley, P. L., and Kinniburg, D. G.: 2002, ‘A review of the source, behaviour and distribution of arsenic in natural waters’, Appl. Geochem. 17, 517–568.Google Scholar
  21. Stefanakis M. and Kontopoulos A.: 1988, ‘Production of environmentally acceptable arsenites-arsenates from solid arsenic trioxide’, In R. G. Reddy, J. L. Hendrix and P. B. Queneau (eds), Arsenic Metallurgy Fundamentals and Applications, The Minerals, Metals and Materials Society, Warrendale, PA, U.S.A., pp. 287–304.Google Scholar
  22. Swash, P. M. and Monhemius, A. J.: 1995, ‘Synthesis, characterisation and solubility testing of solids in the Ca-Fe-AsO4 system’, Paper presented at Sudbury'95, Conference on Mining and the Environment, Sudbury, Ontario, 28 May – 1 June.Google Scholar
  23. US EPA: 1998, ‘Locating and estimating air emissions from sources of arsenic and arsenic compounds’, EPA-454-R98-013, Office of Air Quality Planning and Standards. Valenzuela, A.: 2000, ‘Arsenic management in the metallurgical industry’, M. Sc. Thesis, University of Laval, Department of mines and metallurgy, Quebec, Canada./Sc.Google Scholar

Copyright information

© Springer Science + Business Media, Inc. 2006

Authors and Affiliations

  • Y. N. Zhu
    • 1
  • X. H. Zhang
    • 1
  • Q. L. Xie
    • 1
  • D. Q. Wang
    • 1
  • G. W. Cheng
    • 1
  1. 1.Department of Resources and Environmental EngineeringGuilin University of TechnologyGuilinP.R. China

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