Iranian Journal of Chemistry and Chemical Engineering
Volume:10 Issue: 2, Nov-Dec 1991

Some of the N-substituted urea and acetamide complexes of Ti(III), of general formula [TiL6]3+ were synthesized using N-substituted urea liqands and TiCl3 (aqueous, anhydrous, non – aqueous). The resultant complexes, generally isolated as iodide and chloride salts, [TiL6]3, [TiL6]3 Cl3, are blue, crystalline, and somewhat air-stable, (though very senitive to moisture). They were studied by visible, infrared, and Raman spectroscopies.

Zeolite – Lanthanum catalysts were prepared by ion exchange method using synthetic zeolites like X, A, P, HS; as well as Iranian Natural Zeolite (Natrolite). The said catalysts were examined by X-Ray fluorescence experiments, Their catalytic cracking activities and selectivites were tested for n-hexane feed in the temperature range 350-550ºC using a pulse microreactor system. The results show a high conversion of feed in the case of La-X catalyst as compared with La-A, La-P, La-Hs and La-Natrolite zeolite catalysts. This is attributed to the differences in properties as surface acidity, pore size dimensions and / or concentration of the active metal present on the surface of catalyst systems.

In search of an easy, practical and cost effective method for removal of heavy metal ions from industrial and mining waste waters using agricultural residues, aqueous solutions containing Cu2+ and/or Pb2+ (1.25 and 3.4 g/L respectively) were passed through a column of sawdust. It was found that the concentration of the said ions (as measured via atomic absorption spectroscopy) could be deduced to below 1 ppm. The absorption capacity of sawdust for Cu2+ an Pb2+ was @75 mg/g and @160 mg/g of dry sawdust, respectively, making it’s usage quite feasible I waste water treatments. The absorption of the said ions on sawdust seems to be independent of one another, but sensitive to pH with no absorption below pH 2.0. Removal of calcium and magnesium ions by sawdust proved to be unsuccessful.

The maximum distribution ratio (D) and recovery factor of xanthates of Co(II), Pb(II), Ni(II), Cu(II), Ag(I), Fe(II), Cd(II), in aqueous and 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, molar nitric acid media with chloroform and carbon tetrachloride were investigated by using flame atomic absorption spectrometer. The effect of successive extractions with chloroform and carbon tetrachloride, at maximum distribution ratio, were determined. The distribution ratio in the case of chloroform was higher than that of carbon tetrachloride. The extraction of above elements, except for Fe(III), trom aqueous media were more efficient than from acidic media. A decrease in distribution ratio was observed as the concentration of nitric acid increased. This method may be used for enrichment of very dilute solutions that can not be used for direct measurement in flame atomic absorption spectroscopy.

In the first part of this work the mechanisms of hydrolysis of [Co(NH3)5Cl]2+ in binary aqueous-organic solvent mixtures are reported. The organic components were acetonitrile, dioxane, ethanol, dimethylacetamide (DMA), dimethylformamide (DMF), and dimethylsulphoxide (DMSO). The linear relationship between the pseudo-first order reaction rate constant, kobsd, and H2O concentration in the binary mixtures is suggestive of a limiting second-order reaction. An associative mechanism is thus postulated. The effect of [H+] and the ionic strength upon the hydrolysis in acetonitrile-water mixture was also studied. It was found that the rate, at a fixed ionic strength, is dependent upon the [H+] at pH’s below 5. In the second part, the kinetics and mechanisms of the substitution reactions of [Co(NH3)5X]n+ with various nucleophiles (Y) in dimethylsulphodixe (DMSO) solvent are reported, where X and Y are Cl¯, Br¯, NO¯2, N¯3, H2O and DMSO. The kinetics of the process was followed spectrophotometrically and interpreted I terms of a rapid ionic – pair equilibration followed by an interchange of Y for X in the coordinations sphere (Id mechanism).

The activity of b-galactosidase (Lactase, EC. 3. 2. 1. 23) in cheese whey hydrolysis was determined using free and immobilized enzyme, entrapped in polyvinyl pyrrolidone gel. Inadverdently the gel structure impedes the reaction by creating some diffusive resistance, so an optimal thickness is necessary for the enzymatic hydrolysis of lactose. By studying the enzymatic hydrolysis of whey and product inhibition effect, a kinetic model based on Michaelis – Menten type mechanism incorporating a competitive product inhibition is proposed. Studies on the storage stability of free and immobilized lactase in gel at 50°C, shows a significant improvement in the latter case.

Kinetics of the interaction between histone (H1) and sodium n-dodecyl-sulphate (SDS) at various concentrations was studied in 2.5 mM U.V. spectroscopy. The interaction of 0.5 mM SDS was also studied at various ionic strengths of the phosphate buffer at pH 6.4.

The complexes [WS4(CuNCS)x]-2 where x = 2, 3, 4 and [WOS3CuNCS)2]-2 have been prepared by the reaction of CuSCN with [P(C6H5)4]2[WS4] or [P(C6H5)4]2[WOS3] in dry degassed acetone or DMF solution and recrystallized from CH2Cl2. The attempted preparation of [P(C6H5)4]2[WOS3(CuNCS)3] was failed. The raman, IR, UV/VIS and 13C-nmr spectra of the complexes are discussed.

To prevent hygroscopic absorption of water by ammonium perchlorate crystals they were coated with organosilicon compounds such as trichlorovinyl silane (TCVS) and polymethyl hydrogen siloxane (PMHS). By this method, the hygroscopic ity of crystals was reduced up to 60% by weight. This process eliminates the caking problem of particles during storage and improves the mechanical properties of products obtained.

Two new labdanes, 7b, 9a - dihydroxy – 15 – 16 – epoxy labda – 13 (16), 14- Dien –6 – one (1) and 7b - hydroxy - 9a, 13, 15, 16 – bis – epoxy labd – 14 – en – 6 – one (2) were isolated from the aerial parts of Ballota aucheri The structures were elucidated by spectroscopic methods, mainly by high field NMR.

An electrochemical biosensor is developed that is suitable for use in an easy to make and portable alarm system. The enzyme, butyylcholinestrase is deposited on the internal pore surfaces of a soft polyurethane foam with the aid of a starch – aluminum hydroxide gel. A piece of the foam is placed between two parallel perforated platinum electrodes that are connected to a D. C source. The changes in enzyne activity due to presence of organophosphorous agents can be determined by passing a substrate solution and contaminated water through the electrodes and the foam, and monitoring the changes in voltage constant m A current. To gai the information required for making a portable alarm system, a number of key parameters affecting the performance of biosensor were studied in batch type experiments. The biosensor was tested against an agricultural organophosphorous compounds (Dursban®). Data found are in agreement with those reported in the literature and reliable enough for designing a continuous monitoring system.