Abstract: |
The surface chemistry of δMnO2 in major ion seawater is defined by determining the stoichiometry of the reactions which describe the association of the surface hydroxyl groups with Na, Mg, Ca, and K ions, the intrinsic equilibrium constants which define these reactions, and the speciation of the surface at pH 8.
The results indicate:
- that the surface forms monodentate compfexes with Na and K ions and bidentate complexes with Mg and Ca ions;
- that pK2INT = 4.2, p*KNaINT = 3.0 ± 0.3, p*KKINT = 2.0 ± 0.2, p*K>MgINT = 3.9 ± 0.1, and p*K>CaINT = 3.3, and
- ion exchange processes other than with H are important and as a result 84.8% of the surface sites of δMnO2 in major ion seawater at pH 8 are complexed by H, 8.4% by Mg, 4.6% by Ca, 1.6% by Na, and 0.6% by K. Chloride and sulphate do not adsorb on δMnO2 in the pH range of natural waters.
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