Stability Constants of Fe(III) and Cr(III) Complexes with dl-2-(2-Carboxymethyl)nitrilotriacetic Acid (GLDA) and 3-Hydroxy-2,2′-iminodisuccinic acid (HIDS) in Aqueous Solution

Abstract

The complex formation equilibria of Cr3+ and Fe3+ ions in aqueous solution with two biodegradable aminopolycarboxylate chelants (dl-2-(2-carboxymethyl)­nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2′-iminodisuccinic acid (HIDS)) were investigated. The potentiometric data obtained at the constant ionic strengths (I) of (0.1 and 1.0) mol·dm–3 KCl and at (25 ± 0.1) °C was processed with the aid of the computer program HYPERQUAD 2008. The formation constants of the proton–chelant and metal–chelant (log K ML) species (M = Fe3+ or Cr3+; L = GLDA or HIDS) were determined, and the concentration distributions of complex species in solution were evaluated for both metal ions. In various pH conditions, the interaction between the chelants (L = GLDA or HIDS) and the metal ions (M = Fe3+ or Cr3+) leads to the formation of different complexes formulated as MH2L+, MHL, ML–, M­(OH)­L2–, and M­(OH)2L3–. The log K ML values at I = 0.1 mol·dm–3 KCl (T = (25 ± 0.1) °C) were 15.27 (log K Fe–GLDA), 14.96 (log K Fe–HIDS), 13.77 (log K Cr–GLDA), 12.67 (log K Cr–HIDS), and at I = 1.0 mol·dm–3 KCl (T = (25 ± 0.1) °C) were 14.79 (log K Fe–GLDA), 14.34 (log K Fe–HIDS), 12.90 (log K Cr–GLDA), 12.09 (log K Cr–HIDS). The conditional stability constants (log K′ML) of the ML complexes were calculated in terms of pH in the range of 2 to 12 and compared with the same for EDTA and other biodegradable chelants (NTA and EDDS).

Complexation behavior of SrII and geochemically-related elements (MgII, CaII, BaII, and YIII) with biodegradable aminopolycarboxylate chelators (GLDA and HIDS)

“…The log10KML for Y III -L complexes were much higher than that observed for divalent Mg II , Ca II , Sr II , or Ba II . The log10KY-GLDA (14.75) was greater than the log10KY-HIDS (12.75), and the trend (log10KM-GLDA > log10KM-HIDS) was similar to that reported for Fe III -L or Cr III -L complexes (L Journal of Molecular Liquids, 242: 1123-1130, 2017 The original publication is available at: https://doi.org/10.1016/j.molliq.2017.07.126 10 = GLDA or HIDS) [35]. The comparison of log10KML values ( Figure 6) confirmed a similar order (log10KCr-L < log10KFe-L < log10KY-L) with both chelators, which followed the pattern of corresponding atomic radius (calculated in picometers) [43,44] of the elements: Cr III (140) < Fe III (156) < Y III (212).…”

Laboratory culture experiments to study the effect of lignite humic acid fractions on iron solubility and iron uptake rates in phytoplankton

“…The Fe sol concentration was significantly higher for the EDTA-spiked solution compared to all of the other chelators. Although the Fe dis concentration decreasing trend was observed in the other cases within the first 2 h, it was less prominent (0.75 µM) and was sustained to a significantly higher value of 0.68 µM even after 24 h. The sustenance of the higher Fe sol in the presence of EDTA in the solution can be attributed to the higher formation constant of the EDTA-Fe complexes in solution than many of the known aminopolycarboxylate chelators (Begum et al 2013;Begum et al 2012), which also facilitates better bioavailability (Brand 1991;Brand et al 1983). The HAs with hydroxyl-, phenoxyl-, and carboxyl-reactive groups have a complexing ability with metals (Robertson and Leckie 1999;Pandey et al 2000), and their facilitatory effect on the solubility of Fe has been presumed.…”

Complex formation constant of ferric ion with Gly, Pro-Hyp and Gly-Pro-Hyp

“…This was because Gly-Pro-Hyp had more amino acid residues and more groups, which were able to form chelate complexes. 27 The same trend was followed by the iron complex with Gly-Gly-Gly 24 as well as the iron complexes with L-norleucine and gallic acid. 26 Thermodynamic properties and the possible structure of the complex Thermodynamic properties such as Gibbs free energy (DG), enthalpy (DH) and entropy (DS) provide signicant information related to the complex.…”