Revue des sciences chimiques

Metal organic frameworks based on Copper- and cobalt-1,2,4,5-tetrabenzenecarboxylates (Cu- and Co-MOFs) were synthesized, characterized and employed in metal adsorption studies. Characterization results were obtained from scanning electron microscopy, energy dispersive x-ray, thermogravimetric analysis and x-ray diffraction spectroscopy. The morphological features of Copper- and Cobalt-MOFs showed highly crystalline material as confirmed by the SEM micrographs. EDX spectra of both Metal organic frameworks also showed the presence of C, O and OH which may facilitate in creating charges and functionalities on the surface of the Metal organic frameworks for adsorption. Thermodynamic, equilibrium and isotherm batch adsorption experiments were carried out to determine concentration, time and temperature effects. The results obtained showed that Cu-MOFs were more effective adsorbent than Co- MOFs.

The adsorption behavior of a mixture of two polycyclic aromatic hydrocarbons (PAHs); naphthalene and pyrene and one cyclic aromatic hydrocarbon using clay and sandy soil as adsorbents was examined under ambient conditions in this study. The adsorption from the aqueous solution was observed to be time dependent and the time taken to attain adsorption equilibrium for benzene, naphthalene and pyrene in the mixture were 22, 16 h, 18 and 14 h, and 26 and 18 h in clay and sandy soil, respectively. Among the tested kinetics model in this study, the pseudo-second order equation successfully predicted the adsorption. The rate of adsorption using the pseudo-second order rate expression for benzene, naphthalene and pyrene were 0.00096, 0.00072, 0.00092 min-1 and 0.00091, 0.00080, 0.00090 min-1 for clay and sandy soils respectively. These results suggest that benzene was more selectively adsorbed than naphthalene and pyrene in both clay and sandy soil.

The application of titanium dioxide in the field of photocatalyst was limited. Since, it was activated only a small extend under UV irradiation. While the metal doped TiO2 had shown better photocatalytic activity. The work designed to prepare tin titanate (SnTiO3) by a simple co-precipitation peroxide method. The ratio of the starting compounds, Sn and Ti was taken as 1:1. The prepared powder was calcined at 850°C. The stoichiometric ratio of the synthesized titanate was measured by using AAS. The synthesized titanate had analyzed by X- ray diffraction (XRD). FTIR was taken for confirming the bonding characteristics of Sn-O and O-Ti-O. Thermo gravimetric analysis (TGA) was used to analyze the decomposition temperature. The optical and photocatalytic activity of the synthesized powder was evaluated by Lead carbonate test by using Hunter lab color difference meter. Color difference was determined using a white medium and strength had been determined using black medium. The prepared SnTiO3 powder had exhibited better photocatalytic activity.

The need to analyze multi pesticide residues continues to be imperative and applying a suitable experimental design remains the core to achieving a comprehensive chemical analysis. The pretreatment of a sample has been found to be the most important rate-determining step as it affects the instrumental process and data analysis. The use of the SPME technique coupled with GC-MS to determine multi-residue pesticides is found to be applicable in environmental, pharmaceutical, food, clinical, forensic samples in three modes (DI-SPME, HS-SPME and MD-SPME). This has gained much recognition due to its advantage over the classical or previous sample pretreatment methods such as SPE, LLE, LDME, HFME and DLME. Before applying SPME coupled to a GC-MS detector, several conditions need to be met in order to accomplish enhanced extraction rate, efficiency and sensitivity of experimental procedures. The large numbers of data sets obtained with the advent of various instrumental techniques can be analyzed speedily by applying chemometric methods to screen the various parameters affecting the calibration methods by statistical application so as to achieve the best optimization of the experiment. This review aims at looking at the different chemometric methods for multivariate parameter optimization in experimental design for the analysis of pesticide residues in water.

The conductivity of sea water and of 0.9% physiologic saline was examined as a function of temperature over a broad range. By inserting multimeter probes into samples prior to quick freezing, accurate resistance measurements were obtained even for the solid solutions at temperature below freezing. Data are also analyzed that suggest charge separation and charge density must be optimal for maximum conductivity of aqueous salt solutions. Ion mobility is not a requirement for conductivity. The data suggest a mechanism for electron transfer through salt solutions. The importance of saline and seawater differences is discussed.

This article discusses the possibility of coupling a polymerization reaction to an oscillatory kinetic model, complemented by diffusion which can lead to spatial structure. We used three well–known mathematical models of oscillators: a variant of the Rossler multivibrator, a model proposed by Edelstein, and the Oregon Oscillator. One or some of the terms in the equations of these models come from a polymerization reaction, while the other terms of these equations will come from collateral processes. So, almost any reaction could become oscillatory and/or with dissipative structure, adding the adequate collateral processes. The propagation stages are considered as invariants and initiation reactions of order α = 0, 1, or 2, and termination reactions of order β = 1 or 2 are assumed. Except in the case α = 1, β = 2, all six remaining reactions combinations (α, β) can be coupled to least one, and often to several of the models. The effects of destabilization a stable homogeneous steady state by the presence of diffusion is also discussed, which is always be possible.