Thermodynamic Parameters of the Uncatalyzed Complxation Reaction between Ni (II) Ion and Bioactive Isatin-Bishydrazone

The stoichiometries and stability constants of Nickel (II) ions with 2-pyridyl-3-Isatin bishydrazone have been determined spectrophotometrically at different temperatures 200C, 250C, 300C, 350C and 400C by using Job’s continuous variation method.  In all cases, the Job’s curves displayed a maximum at a mole fraction Xligand =0.5 indicating the formation of complex with 1:1 metal to ligand ratio. It was observed that metal-ligand stability constant decreases with increasing temperature indicating exothermic nature of the reaction. The thermodynamic parameters i.e., ?G0, ?H0 and ?S0 have also been calculated. Keywords:Isatin-bishydrazone ligands, Ni(II) complexes, thermodynamic parameters, Stability constant, spectrophotometrically

Electrochemical determination of Cu2+ complexation in the extract of E. crassipes by anodic stripping voltammetry

Chemical speciation of copper and its total dissolved concentration in the aqueous extract of Eichhornia crassipes (E. crassipes) were investigated by DPASV titration with Cu. Values of speciation parameters, logKCuLi′ and [Li], were calculated using Scatchard linearization and nonlinear fitting with the assumption of two complexing ligands. The total dissolved copper [Cu]T in the acid digested extract was found to be 0.48 μM ± 0.032. Results obtained from the linear and nonlinear transformations revealed that there were two classes of very strong copper complexation with average logKCuL1′∼14.34(±0.01), logKCuL2′∼13.54(±0.04), [L1] ∼ 1.41 μM (±0.29) and [L2] ∼ 2.08 μM (±0.1), calculated from the two methods. This reflects the great affinity of E. crassipes toward eliminating Cu2+ from its aqueous environment, and converting Cu2+ into less toxic by chelation with natural ligands released from the plant tissues

Evaluation of copper speciation in the extract of Eichhornia crassipes using reverse and forward/CLE voltammetric titrations

AbstractReverse and forward titrations coupled with the competitive ligand equilibration (CLE) technique were, for the first time, used to investigate the chemical organic speciation of copper ions in an aqueous extract of Eichhornia crassipes (E.C) plant growing in Egypt. Salicylaldoxime (SA) was used as the competitive ligand. Two samples were collected from huge submerged masses in the Nile water at Sohag and Mansura cities. In this study the concentration of the natural complexing ligands (CLn) and their conditional stability constants with copper (KCuLn′) in the aqueous extract were determined by linear and nonlinear modeling. Reverse titration resulted in two classes of copper complexation (CuL1 and CuL2) in both samples. The strongest class, CuL1, is predominant in Sohag-sample with average logKCuL1′ and CL1 of 15.66 and 435.5nM, respectively, and also dominated in the Mansura-sample with average 16.77 and 162nM, respectively. The second class (CuL2) is minor in both samples. For comparison, forward titration was performed for the Sohag-sample. The results indicated that reverse titration showed a breakthrough ability to detect, for the first time, different types of metal complexation present in equilibrium in the aqueous extracts of biological samples. Moreover, the presence of E.C in Nile water is so useful in transforming free Cu ions to less toxic forms by organic complexation

Qualitative and quantitative analysis of intercalated and exfoliated silicate layers in asymmetric polyethersulfone/cloisite15A® mixed matrix membrane for CO2/CH4 separation

In this study, flat sheet asymmetric MMMs were prepared from polyethersulfone (PES) containing 1 (PES/C15A1) and 5wt% (PES/C15A5) loading of Cloisite15A® via phase inversion to investigate the effect of dispersion of silicate layers on the properties and performance of the MMMs for CO2/CH4 separation. The MMMs were characterized by means of WAXD, TEM, tensile test and pure gas permeation measurement. Partial intercalated and exfoliated silicate layers for MMM with 1wt% loading contributed to the enhancement of the membrane morphological and mechanical properties. The increase tortuosity in PES/C15A1 reduced the CH4 permeance with a significant enhancement for the CO2/CH4 selectivity from 22.57 to 46.89. In addition, high degree of intercalation and exfoliation of silicate layers was also corroborated by particle size measurement (PSM), particle density measurement (PDM) and free-path spacing measurement (FPSM) with the increase in aspect ratio, dispersed single silicate layers, density and formation of several tactoid classes for PES/C15A1. The properties and performance of the MMMs, determined by qualitative and quantitative measurements for PES/C15A1 was higher compared to PES/C15A5; therefore, the extent of the silicate layers dispersion has a significant role in the fabrication of asymmetric MMMs