Clays and Clay Minerals

, Volume 44, Issue 2, pp 286–296 | Cite as

Goethite Dispersibility in Solutions of Variable Ionic Strength and Soluble Organic Matter Content

  • A. C. Herrera Ramos
  • M. B. McBride


The degree of flocculation of aqueous suspensions of microcrystalline goethite was measured in salts of monovalent, divalent and trivalent cations at pH 6.0–6.5 over a range of ionic strengths using light scattering measurements at 650 nm. Varying concentrations of soluble humic material as well as the organic ligands, salicylate and citrate, were tested for their effect on flocculation. It was found that KCl and NaCl induced flocculation at lower ionic strength than CaCl2, while AlCl3 favored dispersion at all ionic strengths tested. The simple organic ligands promoted flocculation at low concentration, with citrate having a more pronounced effect than salicylate. At higher concentrations, these ligands reversed their effect, inducing a more dispersed state of the oxide. The organic ligand effect on dispersibility was modified by the particular metal cation present, with Ca2+ being more conducive to flocculation than K+. Soluble humic materials affected goethite flocculation in a qualitatively similar way to that of the simple organic ligands, that is low concentrations favored flocculation while high concentrations induced dispersion. This dispersing effect was partially suppressed by the presence of Ca2+, and completely suppressed by Al3+. Thus, soluble humic substances at relatively high concentrations appear to have a marked dispersing effect on goethite in the absence of polyvalent cations, and a strongly flocculating effect in their presence.

The results can be explained qualitatively by a simple oxide surface charge model, in which chemi-sorption of multivalent cations or organic ligands alters the surface charge. Reactions that increase the magnitude of positive or negative surface charge favor dispersion, while those that reduce the magnitude of charge favor flocculation.

Key Words

Citrate Dispersion Flocculation Goethite Humic Acid Light Scattering Salicylate Soluble Organic Matter 


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  1. Atkinson RJ, Posner AM, Quirk JP. 1967. Adsorption of potential-determining ions at the ferric oxide-aqueous electrolyte interface. J Phys Chem 71:550–555.CrossRefGoogle Scholar
  2. Bartoli F, Burtin G, Guerif J. 1992. Influence of organic matter on aggregation in Oxisols rich in gibbsite or in goethite. II. Clay dispersion, aggregation strength, and water-stability. Geoderma 54:259–274.CrossRefGoogle Scholar
  3. Biber MV, Stumm W. 1994. An in-situ ATR-FTIR study, the surface coordination of salicylic acid on aluminum and iron (III) oxides. Environ Sci Technol 28:763–768.CrossRefGoogle Scholar
  4. Cornell RM, Schindler PW. 1980. Infrared study of the adsorption of hydroxycarboxylic acids on α-FeOOH and amorphous Fe(III) hydroxide. Colloid & Polymer Sci 258: 1171–1175.CrossRefGoogle Scholar
  5. Davis JA. 1982. Adsorption of natural dissolved organic matter at the oxide/water interface. Geochim et Cosmochim Acta 46:2381–2393.CrossRefGoogle Scholar
  6. Fontes MPF, Alvarenga RC, Gjorup GB, Nascif PS. 1992a. Influence of calcium salts and mechanical stresses in the water dispersible clay (WDC) of Brazilian oxisols. Agron Abstr p. 370.Google Scholar
  7. Fontes MR, Weed SB, Bowen LH. 1992b. Association of microcrystalline goethite and humic acid in some oxisols from Brazil. Soil Sci Soc Am J 56:982–990.CrossRefGoogle Scholar
  8. Greenberg AE, Trussell RR, Clesceri LS. 1992. Standard methods for the examination of water and wastewater, including bottom sediment and sludges. American Public Health Association, American Water Works Association. New York: Water Pollution Central Federation, p. 16.Google Scholar
  9. Gu B, Doner HE. 1993. Dispersion and aggregation of soils as influenced by organic and inorganic polymers. Soil Sci Soc Am J 57:709–716.CrossRefGoogle Scholar
  10. Gu B, Schmidt J, Chen Z, Liang L, McCarthy JF. 1994. Adsorption and desorption of natural organic matter on iron oxide, mechanisms and models. Environ Sci Technol 28: 38–46.CrossRefGoogle Scholar
  11. Huang CP, Stumm W. 1973. Specific adsorption of cations on hydrous γ-Al2O3. J Colloid Int Sci 43:409–420.CrossRefGoogle Scholar
  12. Liang L, Morgan JJ. 1990. Chemical aspects of iron oxide coagulation in water, laboratory studies and implications for natural systems. Aquatic Sci 52:32–55.CrossRefGoogle Scholar
  13. Lumsdon DG, Evans LJ. 1994. Surface complexation model parameters for goethite (α-FeOOH). J Colloid Int Sci 164: 119–125.CrossRefGoogle Scholar
  14. Muneer M, Oades JM. 1989. The role of Ca-organic interactions in soil aggregate stability. III. Mechanisms and models. Australian J Soil Research 27:411–423.CrossRefGoogle Scholar
  15. Oades JM. 1989. An introduction to organic matter in mineral soils. In:Dixon JB, Weed SB, editors. Minerals In Soil Environments. 2nd ed. Madison, WI: Soil Sci Soc Am. p.89–159.Google Scholar
  16. O’Melia CR. 1987. Particle-particle interactions. In: Stumm W, editor. Aquatic Surface Chemistry. New York: John Wiley and Sons. p. 385–403Google Scholar
  17. Ong HL, Bisque RE. 1968. Coagulation of humic colloids by metal ions. Soil Sci 106:220–224.CrossRefGoogle Scholar
  18. Peng FF, Di P. 1994. Effect of multivalent salts-calcium and aluminum on the flocculation of kaolin suspension with anionic Polyacrylamide. J Colloid Int Sci 164:229–237.CrossRefGoogle Scholar
  19. Quirk JP, Aylmore LAG. 1971. Domains and quasi-crystalline regions in clay systems. Soil Sci Soc Am Proc 35:652–654.CrossRefGoogle Scholar
  20. Sholkovitz ER. 1976. Flocculation of dissolved organic and inorganic matter during the mixing of river water and seawater. Geochim Cosmochim Acta 40:831.CrossRefGoogle Scholar
  21. Sletten RS, Benjamin MM. 1994. Mobilization of Fe- and Al-hydroxides by fulvic and humic acids. Agron Abstr p. 256.Google Scholar
  22. Steel RGD, Torrie JH. 1980. Principles and Procedures of Statistics. 2nd ed. New York: McGraw-Hill. 633p.Google Scholar
  23. Stumm W, Kummert R, Sigg L. 1980. A ligand exchange model for the adsorption of inorganic and organic ligands at hydrous oxide interfaces. Croatica Chem Acta 53:291–312.Google Scholar
  24. Stumm W. 1992. Chemistry of the Solid-Water Interface, Processes at the Mineral-Water and Particle-Water Interface in Natural Systems. New York: J. Wiley and Sons. 428p.Google Scholar
  25. Tipping E, Higgins DC. 1982. The effect of adsorbed humic substances on the colloid stability of haematite particles. Colloids & Surfaces 5:85–92.CrossRefGoogle Scholar
  26. van der Marel HW, Beutelspacher H. 1976. Atlas of Infrared Spectroscopy of Clay Minerals and their Admixtures. Amsterdam: Elsevier. 396p.Google Scholar
  27. van Olphen H. 1977. An Introduction to Clay Colloid Chemistry. 2nd edition. New York: John Wiley and Sons. 318p.Google Scholar
  28. Wilson MJ. 1987. A Handbook of Determinative Methods in Clay Mineralogy. New York: Chapman and Hall. 320p.Google Scholar
  29. Yost EC, Tejedor-Tejedor MI, Anderson MA. 1990. In situ CIR-FTIR characterization of salicylate complexes at the goethite/aqueous solution interface. Environ Sci Technol 24:822–828.CrossRefGoogle Scholar

Copyright information

© The Clay Minerals Society 1996

Authors and Affiliations

  • A. C. Herrera Ramos
    • 1
  • M. B. McBride
    • 1
  1. 1.Department of Soil, Crop & Atmospheric SciencesCornell UniversityIthacaUSA

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