Studies on complexation and solvent extraction of lanthanides in the presence of diaza-18-crown-6-di-isopropionic acid.
Stability constants of some lanthanides with K22DAP (diaza-18-crown-6-diisopropionic acid) were determined by potentiometric titration method. The logarithmic values of these constants for La(III), Nd(III), Sm(III), Gd(III), Tb(III), Dy(III), Er(III), and Lu(III) are 11.14, 11.43, 11.78, 11.74, 11.95, 12.09, 11.49, and 10.88, respectively. Solvent extraction studies were carried out on the K22DAP complexes of La(III), Nd(III) and Lu(III) using TTA (thenoyltrifluoroacetone) as an extractant in different diluents. It appears that nitrobenzene, a diluent with high dielectric constant, favors the extraction of the complexes. Extraction rates of the K22DAP complexes of lanthanides were investigated at pH 5.5 and 8.0 with TTA in chloroform. The rates of extraction are found to be dependent upon the nature of the extracted species. Competitive extractions were carried out to see if selective extractions could be achieved.
Sorption studies of yttrium (III) ions on nano maghemite
Abstract Sorption capacity of the yttrium (III) on nano maghemite gave maximum Y (III) uptake as 13.5 mg/g under optimum conditions (pH: 6.9, sorbent dosage: 5.0 mg/20.0 mL, initial metal ion concentration: 3.6 mg/L, equilibrium time: 50 min, temperature: 298 K). The sorption data followed well for Langmuir and Dubinin–Radushkevich (D-R) isotherms. Sorption increased with increase in temperature and no significant desorption occurred in the studied temperature range. Sorption was endothermic and the value of ΔH ° , ΔG ° and ΔS ° were also evaluated. Pseudo second order equation fitted the kinetics of sorption. Further Weber-Morris, Reichenberg equations were employed to explain the diffusion process. The effect of co-ions presence on sorption was also investigated. XRD, HR-TEM data supported that the size of the sorbent as 30.22 nm.
Electrochemical detection of copper(II) at a gold electrode modified with a self-assembled monolayer of penicillamine
A penicillamine (PCA) self-assembled monolayer (SAM) was prepared on a gold electrode. It has been found that the modified electrode exhibited a selective response to copper ions. As demonstrated by cyclic voltammetric experiments, the SAM-based electrode showed an attractive ability to preconcentrate efficiently traces of copper(II) from solutions. Under optimum conditions, the anodic peak current was proportional to the concentration of Cu(II) in the range from 8.0 × 10−7 to 1.0 × 10−4 M with a detection limit of 4.0 × 10−7 M. Moreover, this modified gold electrode is also characterized by excellent repeatability, showing a relative standard deviation of 3.2% for nine successive measurements of 1.0 × 10−5 M Cu(II). The PCA/Au SAM gold electrode was used for the determination of Cu(II) in a tap water sample and the results showed a good agreement with the data obtained by atomic emission spectrometry.