Iranian Journal of Chemistry and Chemical Engineering
Year:2002 | Volume:21 | Issue:1|Papers Count:10

Bioactive materials including glass and glass-ceramics are nowadays used as medical implants for orthopedic applications. In this study several samples of glass-ceramics have been prepared using both heat treatment and sol-gel processes. The structure and bioactivity of these samples based on their interaction with simulated body fluid (SBF) have been determined, invitro, using the Raman spectroscopic technique. It is found that most samples exhibit bioactivity when they are soaked in SBF. It is also concluded that Raman spectroscopy is a powerful technique in such studies.

Deuterium substitution on two ortho-substituted –OCH2 fragments in Nitro-Benzo-9-Crown-3 induces low frequency shifts, positivemn DCj, in all13 C NMR resonances which are an indication of the increased shielding in this crown ether. The magnitude of these shifts vary from 15DC7=716 to 54DC3=15 ppb for C7 and C3 carbons directly attached to 2H, respectively. The influences of concentration and solvent, CDCl3, CD3COCD3, and C6D6, on mn DCj values were investigated. The mn DCj values depended more on the nature of the solvent than on the concentration. The order of induced isotope shifts is: 15D, 51D> 24D, 42D > 34 D>, 43D> 56D, 65D> 45D, 54 D. The isotope shifts observed are suggested to be a sum of contributions from low frequency shift due to inductive-type and negative hyper conjugation perturbations. The C-D bond, as a poorer electron acceptor than a C-H bond induces less positive charge on directly attached oxygen's O1 and O2. This, in turn, causes shielding of C1 and C2 in C1O1CD2 and C2O2CD2 fragments. The difference in 34DC1 and 43DC2 values is attributed to the conformational dependence of the negative hyper conjugation. The C1 and C2 are in fact, not equally affected by the two CD2 groups by negative hyperconjogation because of the existence of NO2 group attached to the benzene ring.

Electrochemically generated iron can remove most contaminants present in water and waste water, by precipitation, adsorption, electrostatic interaction, and complex formation (generally called electro coagulation- EC). In the present paper, pretreatment of brackish water having high total hardness (TH), alkalinity (A), SO2-4 and Cl- ions, is studied by application of a DC-electrical current to the iron electrodes. Operating parameters such as electrical current density, volume flow, surface area of electrodes, distance between the two electrodes, water temperature, aerating flow, retention time, contact time of produced sludge before and after the process, addition of coagulant aid (bentonite) and the colloidal additive(clay particles) were optimized. The results of this study for a brackish sample with 11.8TH, 5.6 HCO3- (A), 12.4 SO2-4, and 23.5 Cl- meq/lit indicate that the process is able to lower more than %94 the (TH), %92 (.4), %50 SO2-4 and %43 Cl-.

Six new complexes of the type trans-[LCo((DO)(DOH)pn)L '] where (DO)(DOH)pn = N2, N2'- propanediolbis (2,3-butanedione 2- imine 3- oxime), L=Cl- and L' =mono-anaion of phenylcyanamide (pcyd),2,5-dichlorophenylcyanamide(2,5-Cl2pcyd), 2,4-dimethyl phenylcyanamide (2.4-Me2 pcyd) and L=L' = pcyd, 2.5-Cl2pcyd, 2,4-Me2 pcyd, have been synthesized and characterized by elemental analysis, spectroscopy and cyclic voltammetry. The electronic absorption spectra of the Co(III) complexes show two low-energy ligand to metal charge transfer band that are associated with Co(III)-NCN chromophore. The cyclic voltammogram of these complexes exhibit two subsequent quasi-reversible reduction couple repated to Co (III)/Co(II) and Co(II)/ Co(I), respectively.

Iron is quantitatively retained on an adsorbent made by coprecipitation of 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) and tetradecyldimethylbenzylammonium chloride (TDBA) an microcrystalline naphthalene as a slurry or packed in a column, in the pH range 6.0- 9.0 from a large volumes of aqueous solutions (up to 200 ml on microcrystalline naphthalene and up to 500 ml of aqueous solutions in the case of column method) of various samples. After filtration, the solid mass consisting of iron complex and naphthalene is dissolved in 5 ml of dimethylformamide and the metal determinate by eight derivative spectrophotometry. Alternatively iron can be quantitatively adsorbed on Tiron-TDBA-naphthalene adsorbent packed in a column at a flow rate of 0.5 to 5.0 ml/min and determined similarly. About 0.05 µg iron can be concentrated in a column from 500 ml of aqueous sample, where its concentration is as low as 0.1ng/ml. Various parameters such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of iron have been studied in detail to optimize the conditions for its determination in standard alloys and biological samples.

In order to gain a better understanding of the chemistry of methanol-to-hydrocarhon conversion, it is necessary to determine the nature of the primary reaction products. Experiments carried out in this work on H-ZSM-11, using a continuous flow reactor linked to an on-line gas chromatograph demonstrated that ethylene and methane are the primary reaction products. The results obtained using solid state MAS NA1Rfor the same reaction further support the findings of this work. The results from H-ZSM-5 catalyst do not confirm that the CO of the reaction acts as a catalyst.

FT-Raman Spectra of human dental enamel, both Laser-irradiated and untreated, are reported. Spectra are compared with hydroxyapatite. It is evident that unlike the CO2 laser, the Nd/YAG laser does not induce any chemical change in dental enamel.

Corophium valuator (pallas) has been recommended by the Paris Commission as one of the standard speciesf or testing chemicals used in offshore oil and gas exploration production. In the present study, gut contents of Corophium volutator have been analysed by electron probe microanalysis (EPMA) for BaSO4 and other heavy metal impurities after expo Sure to spiked sediments following a standard ASTM sediment bioassay protocol. Results show that depuration of Corophium gut for 48 h in clean filtered seawater after exposure to sediments containing barytes, prior to whole body metal analysis, is required to reflect the true metal burdens.

Anionic DBS surfactant can be photo degraded in a Ti02 dispersion and H2O2 solution under an Hg-lamp (15W) UV illumination or solar exposure. Degradation process has been monitored through cleavage of aromatic moiety. Degradation of the detergent was small when the photolysis was carried out in the absence of TiO2 and H2O2 and it was negligible in the absence of light. Most of the curves representing the semi-log of pollutant concentration versus time were nearly linear, suggesting first order reactions. In the UV/TiO2 process, the extent of surfactant degradation was found to be influenced by the TiO2 loading, initial detergent concentration, agitation rate, temperature and initial pH The UV peroxided degradation of the anionic detergent (DBS) by the UV/H2O2 process is more effective than UV/I'i02 process making it apromissable method for destroying the aquatic pollutants. A combination of UV and Solar light is used, degradation of DBS it is more effective than UV/H2O2 process.

The search for new stationary phases has been one of the predominant concerns in high performance liquid chromatography (HPLC) in order to achieve better resolutions, longer column lives, and reduce the time of analysis. A chromatographic packing for separation of underivatized amino acids (AAs) were prepared by dynamically coating 2-amino tetraphenylporphyrin (atpp) on a C-18 reversed-phase packing and its properties were examined. The retention characteristics of 20 AAs forming the building blocks of proteins were investigated on the atpp coated C-18 column at pH 7. Results obtained seem to confirm a mixed mechanism of retention involving the hydrophobic interaction between the aromatic porphyrin macrocycle and some of the AAs, pi-pi interaction between the IT-electrons of the porphyrin macrocycle and the;pi-electrons of analyte, and the hydrogen bonding interactions between AAs and the porphyrin nitrogens.