6533b82efe1ef96bd1293d15

RESEARCH PRODUCT

Protonation constants and association of polycarboxylic ligands with the major components of seawater

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Apparent protonation constants, log βjH*, of 11 carboxylic acids were determined potentiometrically ([H+]-glass electrode) in artificial seawater containing six of the major components (Na+, K+, Mg2+, Ca2+, Cl-, and SO42-) at different salinities:  S (‰) = 5, 15, 25, 35, 45. Values of log βjH* were fitted by the simple polynomial equation log βjH* = log TβjH + a1S1/2 + a2S + a3S3/2 (log TβjH = protonation constants at infinite dilution; a1, a2, a3 = empirical parameters), for mono-, di-, and tricarboxylates. For carboxylic anions with charge < −3, a better fit was obtained using the equation log βjH* = log TβjH + b1I + b0z* log(1 + b2I) (b0, b1, b2 = empirical parameters, z* = square sum of reactants minus square sum of products). The potentiometric data were also interpreted in terms of complex formation between the cationic component of artificial seawater and the carboxylic anion (also partially protonated) using the single-salt approximation (the artificial seawater considered as a single salt with B1...