화학공학소재연구정보센터
Applied Surface Science, Vol.196, No.1-4, 343-355, 2002
Specific adsorption of Zn(II) and Cd(II) ions at the alpha-Fe2O3/electrolyte interface structure of electrical double layer
A study of adsorption of Zn(II) and Cd(II) ions at the alpha-Fe2O3/electrolyte solution interface is presented. For cations, the concentration range was from 1 X 10(-6) to 1 X 10(-3) mol/dm(3). Adsorption measurements were combined with determination of the surface charge density and C potential. The ionization and complexation constants of the surface hydroxyl groups of alpha-Fe2O3, determined from the potentiometric titration data, were pK(a1) = 5.99; pK(a2) = 10.45; pK(ClO4), = 7.26; pK(Na) = 9.25. The pH(pze) of alpha-Fe2O3 in NaClO4 solution was 8. Analysis of the cation adsorption data as a function of pH allowed us to determine characteristic parameters of the adsorption edge as pH(50%+) and DeltapH(10-90%). The parameters for Cd(II) ions (for all initial Cd(II) concentrations) at alpha-Fe2O3/NaCIO4 solution interface were: PH50% = 6.5 and DeltapH(10-90%) = 0.8. For Zn(II), a shift of pH(50%) adsorption was observed from 6 to 7. The value of DeltapH(10-90%) was 0.8 and it did not change with concentration increase. (C) 2002 Elsevier Science B.V. All rights reserved.