Cr(II) 和 Cr(III) 与 EDTA、PDTA、柠檬酸、乙二胺、乙酸络合物的稳定常数与电势文献

… of the complexing agent, Na 2 EDTA, was much higher than that of the metallic ion, Cr(III), to … IV for the slopes of the log (k 1 /k 1,0 ) versus [organic solvent] 0 and log (k 2 /k 2,0 ) versus […

EDTA and soluble Cr(III) are usually both present in wastewaters coming from treatment plants handling tannery effluents. A well-established method to determine EDTA is based on the conversion of free and complexed EDTA into its Fe(III) complex. This procedure gives inconsistent data when Cr(III)-EDTA is present. This fact was here demonstrated by studying the kinetics of the exchange reaction between Fe(III) and Cr(III)-EDTA at 90 °C and various pH values, from acidic to neutral. The reaction is very slow (several weeks); the slow kinetics of conversion of Cr(III)-EDTA to Fe(III)-EDTA is even more accentuated at room temperature and the low concentrations of reactants in wastewaters. The presence of EDTA complexes of Fe(III) and Cr(III) was demonstrated in industrial effluents and wastewaters by developing a selective method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS), which was able to detect free and complexed EDTA at concentration levels <1 μM. A systematic underestimation of the EDTA expressed as Fe(III) complex was demonstrated in samples containing Cr(III)-EDTA. Cr(III)-EDTA was identified for the first time as a component of wastewater samples at a concentration level of about 2 μM and turned out to be an inert species that significantly contributes to the final soluble Cr amount. This study gives new insights into the inertness of Cr(III) toward metal exchange equilibria of EDTA complexes, resolves a bias in the analysis of total EDTA in samples containing Cr(III)-EDTA, allowing the direct determination of free and complexed EDTA by LC-MS.

… ) + Ni(II), respectively. Times required to reach exchange equilibrium … EDTA were less than 360 min. The influence of competition from Ni(II) and Cu(II) on the availability of complexed Cr(…

… (B-matrix), two sites were included per adsorbed EDTA to get … III)EDTA, with a log K in solution similar to Fe(III)EDTA shows … like (Co(III)EDTA, Cr(III)EDTA, and Fe(III)EDTA) show a weak …

… transfer in the [Cr III EDTA(OH)] 2− complex, leading to formation of a Cr(II) centre and the EDTA radical. Under defined conditions (pH ≥ 7, O 2 in excess over the Cr(II) concentration) …

… that Cr(VI) accounted for all of the dissolved Cr observed … of EDTA complexed with each metal ion in (a) M89 and (b) S89… Zn adsorption are as follows: log K values for reactions 4a and …

… O, containing an unsymmetrical edta-type ligand, … [Cr(edta-type)] − complexes of known configurations. The stoichiometry and stability of the complexes formed between the chromium(III…

The removal of Cr(III)-organic complexes, encompassing both decomplexation and ligand degradation, presents significant challenges in industrial wastewater treatment. As one of the most common anions in wastewater, Cl- significantly improves the efficiency of electrochemically removing Cr(III)-organic complexes through generated reactive chlorine species (RCS). In the electrochemical chlorine (EC/Cl2) process, extensive experimentation revealed that ClO• plays a dominant role in the degradation of Cr(III)-EDTA, surpassing the effects of free chlorine, direct electrooxidation, HO•, and other RCS. Density functional theory calculations indicated that RCS, primarily Cl• and ClO•, preferentially oxidize the ligand in Cr(III)-EDTA via H-abstraction, whereas HO• trends to attack the Cr atom through electron transfer. The influential factors on the degradation efficiency of Cr(III)-EDTA, Cr(VI) yield, and total organic carbon removal in EC/Cl2 were also assessed, including Cl- concentration, current density, and pH. Real industrial wastewater was employed as a reaction matrix to evaluate the application of the EC/Cl2 process for treating Cr(III)-EDTA, accompanied by energy efficiency calculations. Additionally, a two-chamber reactor was established to simultaneously oxidize Cr(III)-EDTA at the anode and reduce Cr(VI) at the cathode. This study provided insight into developing RCS-dominated AOPs to effectively decomplex and decompose organic Cr(III)-complexes in Cl--containing industrial wastewater.

The highly reducing CrII-(1,3-propylenediaminetetraacetate) (CrPDTA) complex (-1.1 V vs SHE) has been isolated from aqueous solution and the solid-state structure is described. The reduced CrIIPDTA complex is characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, UV-vis spectroscopy, magnetic moment, and density functional theory calculations. The concentration profile, state of charge, and pH of CrPDTA electrolyte were monitored in a flow battery system in situ by absorption spectroscopy and a pH probe. The stability of CrIIPDTA in aqueous environments is demonstrated by the ability to isolate CaCrPDTA, despite the common misconception that water spontaneously evolves hydrogen at such potentials. The reduced CrIIPDTA prevents water from coordinating to the metal center by maintaining the same coordinatively saturated pseudo-octahedral structure as the oxidized CrIIIPDTA, despite experiencing an increased geometric strain from a Jahn-Teller distortion of the high-spin CrII ion. The important difference between solvent reactivity and solvent thermodynamic window is examined by comparing the electrochemical behavior of the reduced species of CrPDTA in various organic solvents to its behavior in aqueous solution. When examined in tetrahydrofuran (THF), the reduction potential of CrPDTA is observed to be -1.19 V vs cobaltocene (-2.52 V vs ferrocene). Reduced CrPDTA in aqueous solution is also exposed to atmospheric O2 without exhibiting any decomposition of the Cr(III) or Cr(II) species. The techniques detailed provide a higher standard method of characterization for flow battery electrolyte species.

… Therefore, one can suggest close correlation between the logarithmic stability constants of Cu(II) and Cr(II) complexes. This can be seen from Fig. 1 and the following regression …

… pdta coordinated to substitution-inert Cr(III) and Co(III). Deuteron NMR spectroscopy demonstrates that the Cr(III) complexes of cdta and pdta … for the Cr(III) complexes of cdta and pdta at …

… of the 2H NMR spectrum of the Cr(III) complex of 1,2-pdta, a ligand closely related to 1,2-pdda. The partial assignment of the 2H NMR spectrum of [Cr( 1,2-pdta)]- has been reported.1 …

… would be somewhat anomalous if the parent complexes of the Cr-edta and Cr-pdta … rate constant of this reaction (eq 1) to be 3.3 M'1 s'1 with an equilibrium constant of 0.62 at pH 4.8.18 …

… The spectra of the air-sensitive species Cr(EDTA)2", Cr(CyDTA)2", Fe(EDTA)2", and Fe(CyDTA)2… exchange rate constant for reactions 3 (kn) and 2 (&22) and the equilibrium constant for …

… The equilibrium constants logK of partial reactions were calculated from the stability … ; for this reason, the confidence intervals for the logK values are omitted from Table 2. Protons in the …

… , we are suggesting that the dimer complexes formed for both the Cr 3+ ‐citric acid system and the Fe 3+ ‐citrate system in aqueous solutions will have similar structures. We are …

… complexes of chromium(III/II), vanadium(III/II), iron(III/II), and ruthenium(III/II), in order to understand trends that prevailamong the thermodynamic parameters of these redox couples. …

… Crystal structures of (−)589-trans(O5)-Na[Cr(ed3ap)]·3H2O and Na[Cr(u-eddadp)]·3H2O and CD spectra correlation: structural parameters of [Cr(edta-type)]− complexes and their …