This review paper briefly introduces the radiation chemistry of cellulose, the different grafting techniques used, and the methods of characterization of the grafted material. It shows the ...application of the grafted polymer for the removal of water pollutants and also the regeneration of the adsorbent.
The response of the antimicrobial compounds sulfamethoxazole (SMX) and trimethoprim (TMP) - individually and in mixtures - to ionizing radiation was investigated using laboratory prepared mixtures ...and a commercial pharmaceutical formulation. The residual antibacterial activity of the solutions was monitored using Staphylococcus aureus and Escherichia coli test strains. Based on antibacterial activity, SMX was more susceptible to ionizing radiation as compared to TMP. The antibacterial activity of SMX and TMP was completely eliminated at 0.2 kGy and 0.8 kGy, respectively. However, when SMX and TMP were in a mixture, the dose required to eliminate the antibacterial activity was 10 kGy, implying a synergistic antibacterial activity when these are present in mixtures. Only when the antibiotic concentration was below the Minimum Inhibitory Concentration of TMP (i.e., 2 µmol dm
-3
) did the antibacterial activity of the SMX and TMP mixture disappear. These results imply that the synergistic antimicrobial activity of antimicrobial compounds in pharmaceutical waste streams is a strong possibility. Therefore, antimicrobial activity assays should be included when evaluating the use of ionizing radiation technology for the remediation of pharmaceutical or municipal waste streams.
Polyphenols, like gallic acid (GA) released in the environment in larger amount, by inducing some unwanted oxidations, may constitute environmental hazard: their concentration in wastewater should be ...controlled. Radiolytic degradation of GA was investigated by pulse radiolysis and final product techniques in dilute aqueous solution. Subsidiary measurements were made with 3,4,5-trimethoxybenzoic acid (TMBA) and 3,4,5-trihydroxy methylbenzoate (MGA). The hydroxyl radical and hydrogen atom intermediates of water radiolysis react with the solute molecules yielding cyclohexadienyl radicals. The radicals formed in GA and MGA solutions in acid/base catalyzed water elimination decay to phenoxyl radicals. This reaction is not observed in TMBA solution. The hydrated electron intermediate of water decomposition adds to the carbonyl oxygen, the anion thus formed protonates on the ring forming cyclohexadienyl radical or on the carbonyl group forming carbonyl centred radical. The GA intermediates formed during reaction with primary water radicals in presence of oxygen transform to non-aromatic molecules, e.g., to aliphatic carboxylic acids.
Synopsis Series of inner-shell dielectronic resonances were measured in the 7-20-keV x-ray spectra of highly charged tungsten and iridium ions produced in ion traps by highly dense electron beams. A ...detailed analysis of the spectra with a non-Maxwellian collisional-radiative model allowed us to reliably assign the experimentally observed features.
The mechanism of high-energy radiation induced degradation of H-acid (4-amino-5-hydroxynaphthalene-2,7-disulphonic acid, (
I)) and its derivative, 4-hydroxynaphthalene-2,7-disulphonic acid (
II) ...(central parts of a large number of azo dyes), was investigated in aqueous solutions. These compounds can be efficiently destroyed by the
OH and hydrated electron intermediates produced during water radiolysis. As the first step of degradation mainly cyclohexadienyl-type radicals form, however, with
I H-atom elimination from the NH
2 group is also observed yielding anilino-type radicals. Both the cyclohexadienyl and the anilino-type radicals decay on the millisecond timescale. In the
OH reactions as stable products hydroxylated molecules and quinone-type compounds form. These molecules by further decomposition of the ring structure transform to open chain molecules. In the case of hydrated electron, the primarily formed products have absorption spectra shifted to the low-wavelength region indicating the destruction of at least one of the aromatic rings.
Cotton-cellulose samples with modified surface properties were prepared by simultaneous and pre-irradiation grafting methods, respectively, using
N-vinylpyrrolidone monomer. In the mutual grafting ...experiments Mohr salt was used to avoid homopolymer formation. Under optimal conditions a few percent grafting was obtained by pre-irradiation grafting while in the case of mutual grafting the yields were one order of magnitude higher. By using the mutual method at higher doses the samples were covered by a thick layer while in the case of the pre-irradiation method the samples disintegrated. NVP grafting increased the water uptake ability of cellulose by a factor of 2–3.
Modification of cotton-cellulose by preirradiation grafting Takács, E.; Wojnárovits, L.; Borsa, J. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
July 2005, 2005-07-00, Letnik:
236, Številka:
1-4
Journal Article
Recenzirano
Acrylamide (AAm), acylic acid (Aac), 2-hydroxypropil acrylate (HPA), 2-hydroxypropil methacrylate (HPMA) and N,N′-methylene bisacrylamide (BAAm) were grafted to cotton-cellulose by the preirradiation ...method. The samples were characterized by ESR, degree of polymerization (DP) and tensile strength measurements, by FTIR, gravimetry, X-ray diffraction and iodine sorption. The grafting yield was strongly monomer dependent: the highest yield was found for HPMA, for HPA a medium yield, whereas for the others relatively low values were measured. Grafting improved the swelling of the samples. The highest increase in swelling was observed on samples grafted with Aac and BAAm showing saturation at about 270% at natural pH. For AAm, HPA and HPMA at low grafting yield an increase in swelling was found and then the swelling decreased with increasing grafting yield. No direct connection was found between the grafting yield and the swelling properties.
Adsorptive filter media were developed based on UHMWPE (ultra high molecular weight polyethylene), perlite mineral and sol-gel synthesized silica gel as support and various cyclodextrin oligomers and ...polymers as active adsorbents. Adsorptive capacity was characterized by dye adsorption before and after Soxhlet extraction in water to check the hydrolytic stability of the structures obtained. Morphological and in some cases spectroscopic studies were made to understand the differences in behaviour. At the present stage the development of such structures hardly exceeds the trial and error approach, nevertheless some promising formulations were found.
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