வேதியியல் அறிவியல் இதழ்

Impurity, Pharmacopoeias

Detailed investigation of HCOOH electro-oxidation started about five decades ago, with the advent of modern potentiodynamic techniques, driven initially by the purpose of elucidating some of the most interesting and challenging electrode kinetic problems. Many pioneering works that withstood the test of time and the continuous sophistication of surface electrochemistry techniques were published in the 1960s. Stimulated results were obtained, such as: (i) phenomenological interpretation of anodic polarization curves (e.g., Determination of Tafel parameters), HCOOH oxidation on Pd and Pt catalysts; (ii) discovery of the catalytic effect with respect to Pt and Pd for HCCOH oxidation; (iii) investigation of the potential dependent adsorption of HCOOH on Pt and Pd catalysts which are accompanied by a dual pathway mechanism and (iv) formic acid concentration, temperature effects and crossover of nafion membrane.

Polymer layered silicate nano-composites were prepared in melt by reactive extrusion (25:1 21 mm Rondol twinscrew compounding line) using poly(ethylene-co-propylene- co-ethylidenenorbornene) terpolymer (EPDM) as a matrx polymer, PP-g-MA and poly[(maleic anhydride-alt-1-octadecene)-g-PEO (poly(MA-alt-OD)-g-PEO) as functionalized polymer compatibilizer-internal plasticizer, octadecyl amine-montmorillonite (ODA-MMT) and dimethyldidodecyl ammonium -MMT (DMDA-MMT) as reactive and non-reactive nano-fillers, respectively. The formation of nano structural fragments, polymer blend composition-properties (thermal behavior and morphology) was studied using FTIR, XRD, TGA-DTG and DSC analysis methods. It was found that intercalation/exfoliation degree of EPDM macromolecules significantly depends on the origin and content of organoclays. Better results were obtained for nanocomposites prepared in the presence of reactive organo-filler (ODA-MMT) and PEO grafted alternating copolymer. The results of FTIR (chemical structure) and XRD (physical structure and exfoliation degree) analyses indicate that amidization of anhydride copolymer with alkyl amine groups of organo-filler and esterification of alternating copolymer with α -hydroxy- ω -methoxy- PEO occur in melt compounding in situ processing in the chosen extrusion conditions (barrel temperature: 120, 130, 140 and 145°C, twin-screw speed around 30-40 mrp). The glass-transition (Tg), melting (Tm) and recrystallization (Tc) temperatures strongly depend on the origin and content of organoclay and PEO-grafted copolymer-compatibilizer, respectively. Thermal behavior, crystallinity and thermostability of nanocomposites were significantly improved as compared with pristine EPDM terpolymer.

Green chemistry is an approach to the synthesis, processing and use of chemicals that reduces risks to humans and the environment. A synthesis of benzopinacol from benzophenone is carried out using ethanol as a solvent. This is a free radical reaction and reduction of benzophenone occurred by sunlight via UV radiation. Benzopinacol is a catalyst of the formation of unsaturated polyesters. It is also used as an organic synthesis intermediate and as an initiator of polymerization by free radicals. Characterization of Benzopinacol was done by using spectroscopic technique like IR, NMR etc. Results positively show that solvent ethyl alcohol can be used as an alternative for photoreduction of benzphenone in case of non-availability of isopropyl alcohol.

Gallstones disease is well known over the world. It causes death for about 5% of Al-Maghreb people. Whereas Missan city showed a lot of cases for new born babies which they born with gallstones in their gallbladders. These unusual cases lead this research to study the reason of this disease and its right treatment. Results of this research based on atomic absorption technique that indicated that gallstones of different samples contain: 0.386, 0.75, 1.17 and 1.283% of aluminum ions. While references indicated that there is no aluminum in gallstones in the world. These stones are mainly developed from cholesterol, bile salts, phospholipids (lecithin), bilirubin, calcium, and estrogen (for women). Gallstones disease is another disease that mainly caused by civilization and its treatment according to this research is by eating different food with so little cholesterol content comparing with very high other lipids such as triacylglycerol or different fatty acids in relatively limiting time etc. Although gallstones disease was well studied by many scientists during the last hundred years, it reason is not clear because it needs chemists touch.

In this study, the Co:La:TiO2 nanocomposite was prepared by the wet chemical method. Synthesized TiO2 and Co:La:TiO2 were characterized by X-Ray Diffractometer, SEM, TEM, UV- vis, FT-IR, Band gap energy and BET. The TiO2 and Co:La:TiO2 were used as photocatalyst for the degradation of Methyl Blue. The XRD pattern confirmed the presence of anatase and rutile phase in the catalyst. The particle size was estimated by the Scherrer’s and found 68 and 32 nm for TiO2 and Co:La:TiO2 respectively. The particle morphology of the photocatalysts was found in nanodiamension. The surface area of the photocatalysts was found 37.52 and 106.68 m2/g for TiO2 and Co:La:TiO2 respectively. The band gap energy of TiO2 and Co:La:TiO2 were 3.2 and 3.0 eV. The photodegradation of Methyl Orange has been found 18% and 88% at 5 pH for TiO2 and Co:La:TiO2 respectively. The photodegradation of Methyl Orange has been found 19% and 98.9% at 25 ppm concentration of dye. The photodegradation of Methyl Orange has been found 25% and 96% at 800 mg/L amount of photocatalyst and 180 min illumination of visible light. The photodegradation was following the first order kinetics.

Crystal structure of metal-organic frameworks (MOF’s) compound [Hdma]∙(Fe2+Fe3+F6(Hamtaz)2) was hydrothermally synthesized, eventually assisted via classical heating (Acid Digestion Autoclave). Crystalline structure determination is formed from single crystal X-ray diffraction data. The unit cell is orthorhombic space group Imma, with cell parameters a=15.9520(14) Å, b=9.4548(7) Å, c=9.7056(8) Å, V=1463.8(2) Å3 and Z=4. The structure [Hdma]∙(Fe2+Fe3+F6(Hamtaz)2) exhibits a three-dimensional inorganic network resulting from the association of FeIIFeIIIF6N4 planes with Hamtaz molecules in the [010] direction, as well as uncoordinated dimethylammonium cations [Hdma] which are formed by the hydrolysis of DMF solvent. The thermal analysis (TG) of the title compound shows that the decomposition undergoes two steps between 200°C and 600°C and the total experimental mass loss 63.03% assuming that the hematite Fe2O3, is the final product of the decomposition.

Acid mine drainage (AMD) from decant in Krugersdorp (South Africa) was dosed with acid-free polyferric chloride (af- PFCl) of CaOH2 or MgOH2 (PFCl-Ca(OH)2 or-Mg(OH)2). A 200 mL sample was poured into five 500 mL glass beakers and the flocculent was added in a jar test respectively using different methods of mixing and dosing. The mechanism tests were performed employing two methods of dispersing reagents throughout the colloidal suspension, i.e., rapid mixing and shaking in order to find the removal mechanism of mineral salts and relationship between the removal and characteristics of flocculent/pollutants. The results showed that the turbidity removal efficiency exhibited by FeCl3, PFCl-Ca(OH) 2 or Mg(OH)2, and hydroxides of Ca or Mg is identical, all above 90%. It also revealed that the effective AMD treatment is not necessarily dependent upon the pH, but the ability of the coagulant to destabilize the double layer (high electronegativity) of an aqua-colloid and optimal hydrolysis. The residual turbidity of the AMD samples at 15, 25 and 35°C does not exhibit significant deviations. The turbidity removal of the samples with low temperature shows that dynamic viscosity of the colloidal suspension has an influence in the destabilization-hydrolysis reaction.