Chelating Behavior between Metal Ions and EDTA in Sol−Gel Matrix

Abstract

Ethylenediamine tetraacetic acid (EDTA) was encapsulated in a sol-gel-derived optically transparent glass. The complexation of metal cations, Cu(II), Ni(II), Fe(III), Cr(III), Co(II), Mn(II), Pd(II), and Ir(IV), with EDTA in solutions and in gels was evidenced by the formation of individual colors. A comparison of the absorption spectra of M n+ /EDTA in solution, M n+ /EDTA in gel, and M n+ /EDTA complex in gel was performed. The results show that (i) all six chelating sites in EDTA remain active in a sol-gel matrix as they bind readily with Cu 2+ , Ni 2+ , Fe 3+ , Pd 2+ , and Ir 4+ , (ii) EDTA is rigidly oriented in a sol-gel matrix that inhibits its heat-or catalyst-assisted complexation with Cr 3+ , Co 2+ , and Mn 2+ , (iii) no absorption spectral shift for the d-d metal transitions was observed compared to those in solution, yet a 10-30 nm shift for the MLCT transitions of Cu 2+ , Ni 2+ , Fe 3+ , Pd 2+ , Ir 4+ was detected, and (iv) the level of sensitivity in detecting metal cations using EDTA in gel is at least an order of magnitude higher than that in solution. The response time of M n+ /EDTA complexation in gel is quite short, ranging from 1/30 to 15 min. This response time and the mode of sensing device guarantee that no leaching of EDTA from the sol-gel matrix is possible.

Comparative Study of Binding Behaviour of Cu(II) with Humic Acid and Simple Organic Compounds by Ultrasound Spectrometry

“…Contrary of the citric acid the "constant region" begins at = 0.25. EDTA forms the complexes with metal ions usually in molar ratio 1:1, independently on its valence [28], but formation of the binuclear Cu-EDTA complexes in ratio 2:1 was also published [29]. Our results indicates that the change of slope in the concentrations dependence of U corresponds with the ratio one copper(II) ion and four functional groups (which is ratio Cu:EDTA = 1:1).…”

A robust approach for the determination of dimethylsulfoxide in sea ice

“…The significantly lower yields of DMSP hydrolysis observed for both treatments A and B compared with the levels measured in treatment C suggested that one of the reagents present in the DMSOr cocktail (DMSOr itself, ethylenediaminetetraacetic acid [EDTA] or flavine mononucleotide [FMN]) might have hampered the reaction of DMSP hydrolysis by OH -. Because DMSP is a zwitterion (i.e., an electrically neutral molecule bearing formal unit electrical charges of opposite sign on different atoms), interaction with EDTA, which is a well-known chelating agent (Zaitoun and Lin 1997) was plausible. EDTA could make DMSP partially unavailable for hydrolysis by OH -by interacting with DMSP at the level of the sulfur atom bearing a positive charge.…”

Hydrogen production by steam reforming of liquefied natural gas (LNG) over mesoporous Ni/Al2O3 catalyst prepared by an EDTA-assisted impregnation method

“…According to the theoretical background [42], it is known that formation constant (K f ) of chelated Ni(EDTA) 2− complex anion from free Ni 2+ ion and EDTA 4− ion is 10 18.4 (Eqs. (3) and (4)).…”