Total and Specific Solubility and Activity Coefficients of Neutral Species of (CH2)2i−2Ni(CH2COOH)i+2Complexons in Aqueous NaCl Solutions at Different Ionic Strengths, (0 ≤I≤ 5) mol·L−1, and 298.15 K

Abstract

The total solubility ST of (CH2)2i−2Ni(CH2COOH)i+2 complexons (i = 1, nitrilotriacetic acid (NTA); i = 3, diethylenetriaminepentaacetic acid (DTPA); i = 4, triethylene tetraaminehexaacetic acid (TTHA)) in aqueous NaCl solutions at different ionic strengths, (0 ≤ I ≤ 5) mol·L−1, and at 298.15 K are determined and are reported in both molar (mol·L−1) and molal (mol·kg−1) concentration scales, together with the protonation constants. The total solubility in pure water S0T is (8.1, 8.9, and 4.5) mmol·L−1 for NTA, DTPA, and TTHA, respectively. Increasing the ionic strength from (0.1 to 5) mol·L−1 (NaCl), the total solubility decreases for NTA, while the opposite trend is observed for DTPA and TTHA. From total solubility and protonation constant data, the solubility of the neutral species S0 and the solubility products KS0 are calculated. The dependence on ionic strength is analyzed, and the Setschenow (km) coefficients are obtained, together with the solubility of the neutral species in pure water S00 [S00 = (...