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Towards CNTs; Functionalization and Their Sensing Applications
Published in Mahmood Aliofkhazraei, Advances in Nanostructured Composites, 2019
Nada F. Atta, Hagar K. Hassan, Ahmed Galal
Liang et al. used phytate to non-covalently functionalize CNT to be used as a promising Cu2 + sensor (Liang et al. 2014). Phytic acid and its salts are present in seeds, all eukaryotic cells and in the grains (Maga 1982, Raboy et al. 2003). Phytate (IP6) is usually used as an oral cleansing agent, food additive and in water treatment (Yang et al. 2004). IP6 can capture many metal ions and form stable complexes with them (Pang et al. 2006, Crea et al. 2008). The stability constant of the formed complexes depends on the type of metal ions. As reported by Tamim and Angel (Tamim and Angel 2003), the stability of metal–phytate complexes are in the order of Cu(II) > Zn(II) > Co(II) > Mn(II) > Fe(II) > Ca(II). Therefore, phytate can be used as a promising sensor for Cu(II) ions with no or little interference from other metal ions. The functionalization process occurred via sonication of the acid treated MWCNTs with IP6 for five hours. The composite was kept for adsorption on indium tin oxide surface (ITO) for another three hours to form IP6-MWCNTs-ITO electrode. IP6-MWCNTs-ITO exhibited very good sensitivity and selectivity toward Cu(II) ions with no interference from Ni(II), Mg(II), Ca(II), Pb(II), Cd(II), Mn(II), Zn(II) and Fe(II, III) as well as some anionic and organic species. The detection limit obtained was 2.5 × 10−9 M in the linear range between 0.01 to 0.8 μM. A negative shift in the oxidation potential from 0.4 and 0.72 V (two oxidation peaks were are observed) on bare ITO to 0.29 V (only one oxidation peak was obtained) on IP6-MWCNTs-ITO was obtained.
Cyanide Control in Petroleum Refineries
Published in Bell John W., Proceedings of the 44th Industrial Waste Conference May 9, 10, 11, 1989, 1990
Joseph M. Wong, Patrick M. Maroney
Table I shows the stability constants for several complex metal cyanides.2 A greater stability constant indicates increased metal-ligand stability. Other than the extremely stable hexacyanoco-baltate complex, the most stable among these listed are the iron cyanide complexes, ferric cyanide [Fe(CN)6]−3 and ferrocyanide [Fe(CN)6]−4, whose iron component can originate either in the feed or from the carbon-processing equipment.
A Novel Type of Tetradentate Dipyridyl-Derived Bis(pyrazole) Ligands for Highly Efficient and Selective Extraction of Am3+ Over Eu3+ From HNO3 Solution
Published in Solvent Extraction and Ion Exchange, 2023
Lianjun Song, Xueyu Wang, Long Li, Zhuang Wang, Lanlan He, Qiuju Li, Qingjiang Pan, Songdong Ding
The extraction power of a ligand depends on its affinity for metal ion that can be described by a complex stability constant. Utilizing the analysis of UV–vis spectrophotometric titration spectra, the complex stability constant of the ligand with metal ion can be obtained. Moreover, due to the fact that the complexation equilibrium strongly depends on the temperature, the thermodynamic parameters for the complexation can also be acquired from the temperature dependence of the complex stability constant.[59,60] To elucidate the thermodynamics underlying the formation of the complexes, the stability constants (log β) at temperatures ranging from 15 °C to 35 °C were determined via UV–vis spectrophotometric titration. Based on the linear relationship between log β and 1/T, the apparent thermodynamic parameters for the complexion: standard state enthalpy change (ΔHo), entropy change (ΔSo), and Gibbs free energy change (ΔGo) can be obtained from Eq. (4) and Eq. (5).
Discrepancies in Solvent Extraction Slope Analysis Caused by Aqueous Buffer Complexation
Published in Solvent Extraction and Ion Exchange, 2020
Aaron J. Unger, Mark P. Jensen
The definition of D0 assumes all of the aqueous metal exists as aqua cations uncomplexed by other ligands. However, buffer molecules such as the aromatic carboxylic acids are known to form complexes with the lanthanides.[4,31] As the concentration of deprotonated ligands increases, the concentration of free metal ions available for Eq. (2) decreases; consequentially, the distribution ratio will be reduced proportionally. Stability constants represent the equilibrium complex formation strength of a metal and its coordinating ligand and can be used to determine the fraction of free metal available in a complex system. The metal-ligand equilibrium in the aqueous phase follows the form:
Influence of substituent effects on the coordination ability of salicylaldehyde Schiff bases
Published in Journal of Coordination Chemistry, 2018
In coordination chemistry, stability constant is an important index of the coordination ability of ligands with metals. Some studies indicated that the activity order of complexes was almost in accord with the stability constants order of metal complexes [30, 31]. Thus, metal complexes with high stability constants had higher biological activity [32] and separability of metal ions depended on the stability constants of the complexes formed [33]. Thus, stability constants provide important information on the selectivity of ligands for a specific metal and the evaluation of the biological activity of complexes.