Journal of the Mineralogical Society of Korea (한국광물학회지)

The Mineralogical Society of Korea (한국광물학회)
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Surface Chemical Properties of Aqueous Kaolinite and Halloysite: Surface Complexation Modeling

수용액 내 캐올리나이트와 할로이사이트의 표면화학 특성: 표면복합반응 모델링

  • 장세정 (서울대학교 지구환경과학부) ;
  • 김수진 (서울대학교 지구환경과학부)
  • Published : 2004.06.01
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Abstract

The surface chemical properties of aqueous kaolinite and halloysite were studied using a potentiometric titration experiment and a computer program FITEQL3.2. Among the surface complexation models a constant capacitance model was selected for this study. The 2 sites - 3 p $K_{a}$ s model, in which the surfaces were assumed to have tetrahedral and octahedral sites, was reasonable for the description of the experimental data. The surface charges of both minerals were negative above pH of 4. The higher the pH, the lower the proton surface charge densities of both minerals. The ≡ $SiO^{[-10]}$ site played an important role in cation adsorption in acid and neutral pH range; whereas the ≡ Al $O^{[-10]}$ site was in an alkaline pH range. The optimized intrinsic constants of kaolinite, p $K_{a2(Si)}$$^{int}$, p $K_{al(Al)}$$^{int}$ and p $K_{a2(Al)}$$^{int}$ were 4.436, 4.564, and 8.461 respectively, and those of halloysite were 7.852, 3.885, and 7.084, respectively. The total Si and Al surface sites concentrations of kaolinite were 0.215 and 0.148 mM, and those of halloysite were 0.357 and 0.246 mM. The ratio of Si and Al surface site densities ([≡SiOH]:[≡AlOH]) of both minerals was 1 : 0.69. The total surface site density of kaolinite, 3.774 sites/n $m^2$, was 1.6 times larger than that of halloysite, 2.292 sites/n $m^2$./TEX>.

수용액 내 캐올리나이트와 할로이사이트의 표면화학 특성을 전위차 적정 실험과 FITEQL3.2 프로그램을 이용하여 연구하였다. 표면복합반응 모델 중 일정용량 모델을 적용하였으며, 표면을 사면체 자리와 팔면체 자리로 나누어 설정한 2 sites - 3 $pK_{a/s}$ 모델은 캐올리나이트와 할로이사이트의 표면화학 특성을 설명하는데 적합하였다. 두 점토광물 표면은 pH 4 이상에서 음전하를 띄며 pH가 높아질수록 양성자 표면 전하 밀도는 낮아진다. 산성 및 중성 영역에선 Si 사리(≡$SiO^{-}$ )가, 염기성 영역에선 Al 자리(≡$AlO^{-}$)가 양이온을 흡착하는데 중요한 역할을 할 것으로 예상된다. 모델링 결과 캐올리나이트의 경우 $pK_{a2(si)}$ /$^{int}$, p $K_{al(Al) }$ /$^{int}$ /, $pK_{a2}$ $(Al)^{int}$ /는 각각 4.436. 4.564, 및 8.461이며, 할로이사이트의 경우는 각각 7.852, 3.885, 7.084이다. 캐올리나이트의 총 Si 표면자리 농도와 총 Al 표면자리 농도는 0.215와 0.148 mM이며, 할로이사이트의 경우는 0.357과 0.246 mM이다 두 광물 모두 Si 표면자리 밀도 : Al 표면자리 밀도가 1 : 0.69로 비슷하다. 캐올리나이트의 총 표면자리 밀도는 3.774 sites/$nm^2$로 할로이사이트의 2.292 sites/n $m^2$ 값보다 약 1.6배정도 높다.다.

Keywords

References

  1. 조현구, 김은영, 정기영 (2001) 영동 일라이트 광석의 표면 화학 특성: 영 전하점과 표면 전하 밀도. 한국광물학회지, 14, 12-20.
  2. Brady, P.V., Cygan, R.T., and Nagy, K.L. (1996) Molecular controls on kaolinite surface charge. J. Colloid Interface Sci., 183, 356-364.
  3. Churchman, G.J., Whitton, J.S., Charidge, G.G.C., and Theng, B.K.G. (1984) Intercalation method using formamide for differentiating halloysite from kaolinite. Clays Clay Minerals, 32, 241-248.
  4. Davis, J.A. and Kent, D.B. (1990) Surface complexation modeling in aqueous geochemistry, In: Hochella, M.f. Jr. and White, A.F. (eds.), Mineral-Water Interface Geochemistry, Reviews in Mineralogy, Vol. 23. Mineralogical Society of America, Book-Craftcrs, Inc., Michigan. 177-260.
  5. Davis, .J.A. and Leckie, J.O. (1978) Surface ionization and complexation at the oxide/water interface, II. Surface properties of amorphous iron oxyhydroxide and adsorption of metal ions. J. Colloid Interface Sci., 67, 90-107.
  6. Du, Q., Sun, Z., Forsling, W., and Tang, H. (1997) Acid-base properties of aqueous illite surfaces. J. Colloid Interface Scl., 187, 221-231.
  7. Goldberg, S. and Glaubig, R.A. (1986) Boron adsorption and silicon release by the clay minerals kaolinite, montmorillonite, and illite. Soil Sci. Soc. Am. J., 50, 1442-1448.
  8. Goldberg, S., Forster, H.S., and Godfrey, C.L. (1996) Molybdenum adsorption on oxides, clay minerals, and soils. Soil Sci. Soc. Am. J., 60, 425-432.
  9. Gran, G. (1952) Determination of the equivalence point in potentiometric titration, Part II. Analyst, 77,661-671.
  10. Grim, R.E. (1968) Clay Mineralogy, 2nd ed. MeGraw-Hill Book Company. 596p.
  11. He, L.M., Zelazny, L.W., Baligar, V.C., Ritchey, K.D., and Martens, D.C. (1997) Ionic strength effects on sulfate and phosphate adsorption on $\gamma$-alumina and kaolinite: triple-layer model. Soil Sci. Soc. Am. J., 61,784-793.
  12. Herbeline, A.L. and Westall, J.C. (1996) FITEQL - A computer program for determination of chemical equilibrium constants from experimental data. Report 96-01, Department of chemistry, Oregon State University, Corvallis, OR 97311.
  13. Hinckley, D.N. (1963) Variability in 'crystallinity' values among the kaolin deposits of the coastal plain of Georgia and South Carolina. Clays Clay Minerals, 11, 229-235.
  14. Huang, C.P. and Stumm, W. (1973) Specific adsorption of cations on hydrous a $\alpha$-$Al_2O_3$. J. Colloid Interlace Sci, 22, 231-259.
  15. Ioannou, A. and Dimirkou, A (1997) Phosphate adsorption on hematite, kaolinite, and kaolinitehematite (k-h) systems as described by a constant capacitance model. J. Colloid Interface Sci., 192, 119-128.
  16. Manning, B.A. and Goldberg, S. (1997) Adsorption and stability of arsenic (III) at the clay mineralwater interface. Environ. Sci. Technol., 31, 2005-2011.
  17. Manuela Motta, M. and Miranda, C.F. (1989) Molybdate adsorption on kaolinite, montmorillonite, and illite: constant capacitance modeling. Soil Sci Soc. Am. J., 53, 380-385.
  18. Riese, A.C. (1982) Adsorption of Radium and Thorium onto Quartz and Kaolinite, a Comparison of Solution/Surface Equilibria Models. Ph.D. Thesis, Colorado School of Mines, Golden, Colorado, USA.
  19. Schindler, P.W. and Stumm, W. (1987) The surface chemistry of oxides, hydroxides, and oxide minerals. In: Stumm, W. (ed.), Aquatic Surface Chemistry, John Wiley, New York, 83-110.
  20. Singh, S.P.N. and Mattigod, S.V. (1992) Modeling boron adsorption on kaolinite. Clays Clay Minerals, 40, 192-205.
  21. Spark, K.M., Johnson, B.B., and Wells, J.D. (1995) Characterizing heavy-metal adsorption on oxides and oxyhydroxides. European J. Soil Sci., 46, 621-631.
  22. Sposito, G. (1984) The Surface Chemistry of Soils, Oxford Univ. Press, New York.
  23. Stumm, W. and Morgan, J.J. (1996) Aquatic Chemistry, Chemical Equilibria and Rates in Natural Waters. 3rd ed., A Wiley-lnterscience Publication, New York, 1022p.
  24. Wieland, E. and Stumm, W. (1992) Dissolution kinetics of kaolinite in acidic aqueous solutions at $25^{\circ}C$. Geochim. Cosmochim. Acta, 56, 3339-3355.
  25. Xie, Z. and Walther, J.V. (1992) Incongruent dissolution and surface area of kaolinite. Geochim. Cosmochim. Acta, 56, 3357-3363.
  26. Zachara, J.M., Cowan, C.E. , Schmidt, R.L., and Ainsworth, C.C. (1988) Chromate adsorption by kaolinite. Clays Clay Minerals, 36, 317-326.