TY - JOUR
T1 - Potentiometric studies of the rutile-water interface
T2 - Hydrogen-electrode concentration-cell versus glass-electrode titrations
AU - Ridley, Moira K.
AU - Machesky, Michael L.
AU - Palmer, Donald A.
AU - Wesolowski, David J.
N1 - Funding Information:
M.L. Machesky and M.K. Ridley acknowledge the support of the National Science Foundation (EAR-9627784), as well as the Illinois State Water Survey and the Illinois Department of Natural Resources. The efforts of D.J. Wesolowski and D.A. Palmer were supported by the office of Basic Energy Sciences, US Department of Energy, under contract DE-AC05-000R22725 with ORNL, managed and operated by UT-Battelle, LLC. The authors wish to thank Dr L.M. Anovitz for his help in characterizing the solid phase used in this study. The comments of an anonymous reviewer are also appreciated.
PY - 2002/5/23
Y1 - 2002/5/23
N2 - This paper represents a comparison of surface protonation studies of rutile in NaCl media obtained using a conventional glass-electrode autotitrator system from 10 to 50°C, and hydrogen-electrode concentration cells from 25 to 250°C [J. Colloid Interface Sci., 200 (1998) 298]. Experimental conditions were matched as closely as possible between the two techniques, permitting a direct comparison of the results. Values for the pH of zero net proton charge (pHznpc) of the rutile surface obtained at 10 and 35°C were consistent with the temperature trends observed previously using hydrogen-electrode concentration cells. The pHznpc of rutile decreases systematically from 5.7 to 4.2 as temperature increases from 10 to 250°C. Moreover, the experimentally determined pHznpc values agree with independent estimates of the pH at the pristine point of zero charge (pHznpc) calculated from an extension of the revised Multi-Site Complexation (MUSIC) Model of Hiemstra et al. [J. Colloid Interface Sci., 184 (1996) 680]. Surface protonation curves obtained from the glass-electrode titration results were rationalized using surface protonation constants derived from the MUSIC Model, in conjunction with a Basic Stern representation of the electrical double layer (EDL) structure. Best-fit parameters (Stern layer capacitance values, and electrolyte cation and anion binding constants) are consistent with those obtained from fits to titration curves obtained using hydrogen-electrode concentration cells at 25 and 50°C. Consequently, this comparison demonstrates that independent conventional glass-electrode and hydrogen-electrode concentration cell titrations provide completely compatible results despite the intrinsic differences in the two techniques (pH calibration, equilibration times, stirring rates, gas phase composition, etc).
AB - This paper represents a comparison of surface protonation studies of rutile in NaCl media obtained using a conventional glass-electrode autotitrator system from 10 to 50°C, and hydrogen-electrode concentration cells from 25 to 250°C [J. Colloid Interface Sci., 200 (1998) 298]. Experimental conditions were matched as closely as possible between the two techniques, permitting a direct comparison of the results. Values for the pH of zero net proton charge (pHznpc) of the rutile surface obtained at 10 and 35°C were consistent with the temperature trends observed previously using hydrogen-electrode concentration cells. The pHznpc of rutile decreases systematically from 5.7 to 4.2 as temperature increases from 10 to 250°C. Moreover, the experimentally determined pHznpc values agree with independent estimates of the pH at the pristine point of zero charge (pHznpc) calculated from an extension of the revised Multi-Site Complexation (MUSIC) Model of Hiemstra et al. [J. Colloid Interface Sci., 184 (1996) 680]. Surface protonation curves obtained from the glass-electrode titration results were rationalized using surface protonation constants derived from the MUSIC Model, in conjunction with a Basic Stern representation of the electrical double layer (EDL) structure. Best-fit parameters (Stern layer capacitance values, and electrolyte cation and anion binding constants) are consistent with those obtained from fits to titration curves obtained using hydrogen-electrode concentration cells at 25 and 50°C. Consequently, this comparison demonstrates that independent conventional glass-electrode and hydrogen-electrode concentration cell titrations provide completely compatible results despite the intrinsic differences in the two techniques (pH calibration, equilibration times, stirring rates, gas phase composition, etc).
KW - Glass-electrode
KW - Hydrogen-electrode concentration cell
KW - Point of zero charge
KW - Potentiometric titrations
KW - Rutile
KW - Surface protonation
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U2 - 10.1016/S0927-7757(02)00017-1
DO - 10.1016/S0927-7757(02)00017-1
M3 - Article
AN - SCOPUS:0037161644
SN - 0927-7757
VL - 204
SP - 295
EP - 308
JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects
JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects
IS - 1-3
ER -