Investigation Of Degradation Products Research Articles

One-step bleaching method for animal fiber by persulphate/hydrogen peroxide: Degradation mechanism of eumelanin

Dark animal fiber is bleached to satisfy the demand of color diversity for clothing. Comparing with frequently-used Fe2+ catalyzed H2O2 (Fe2+/H2O2) bleaching method, the ammonium persulfate (APS)/H2O2 bleaching method based on the persulfate (PDS)-based advanced oxidation process is considered to be an environmentally animal fiber bleaching method, which is advantageous in high efficiency, heavy metal-free and low damage. However, the degradation mechanism of eumelanin of APS/H2O2 bleaching method remains to be explored. Herein, standard eumelanin (SM) which has higher purity of eumelanin was used as reaction model, and SM was proved to degrade into five soluble oligomers by chemical structure analysis. Therefore, a new degradation pathway of eumelanin in APS/H2O2 solution was simulated and proposed by in vitro experiment. In addition, the yak wool fiber was low damage by testing the fiber structure before and after bleaching. The dyeing property of yak wool fabrics had no effect on APS/H2O2 bleaching. This investigation of degradation products provides new insights into the bleaching mechanism of APS/H2O2 environmentally dark animal fiber bleaching method.

Flower like Ni doped BiVO4 composite with efficient visible light photocatalytic performance for the removal of Naproxen: A detailed mechanism and DFT study

BiVO4 and Ni doped BiVO4 (Ni-BiVO4) photocatalysts were synthesised by the co-precipitation method. BiVO4 and Ni-BiVO4 photocatalysts were characterized by various analytical techniques. PXRD studies of the BiVO4 and Ni-BiVO4 catalysts shows monoclinic-scheelite structure. Density functional theory calculations were carried out to predict the density of states and band gaps. The flower bunch is arrayed in a rod-like pattern on the HRTEM images, and the particle size was estimated using d-spacing and found to be in the range of 98-415 nm. Furthermore, the charge separation mechanism of photogenerated charge carriers of BiVO4 and Ni-BiVO4 photocatalysts were studied by photoelectrochemical response and impendence spectroscopy. The result shows that the Ni-BiVO4 photocatalyst possess the higher photocatalytic performance, and this can be attributed to the enhanced absorption of visible light, and lower recombination of electron and holes. Further, enhanced photocatalytic activity of Ni-BiVO4 photocatalyst was observed by addition of hydrogen peroxide (H2O2). The order of photocatalytic activity for the degradation of Naproxen under visible light: Ni-BiVO4 +H2O2 > Ni-BiVO4 > BiVO4 > Ni-BiVO4 + IPA. The investigation of degradation products was carried out utilising liquid chromatography mass spectroscopy coupled UV-visible absorption spectrum technique. Radical quenching is studied to reveal the substantial contribution of hydroxyl free radicals in the Ni-BiVO4 with H2O2 system.

Evaluation of the influence of fluoroquinolone chemical structure on stability: forced degradation and in silico studies

Fluoroquinolones are a known antibacterial class commonly used around the world. These compounds present relative stability and they may show some adverse effects according their distinct chemical structures. The chemical hydrolysis of five fluoroquinolones was studied using alkaline and photolytic degradation aiming to observe the differences in molecular reactivity. DFT/B3LYP-6.31G* was used to assist with understanding the chemical structure degradation. Gemifloxacin underwent degradation in alkaline medium. Gemifloxacin and danofloxacin showed more degradation perceptual indices in comparison with ciprofloxacin, enrofloxacin and norfloxacin in photolytic conditions. Some structural features were observed which may influence degradation, such as the presence of five member rings attached to the quinolone ring and the electrostatic positive charges, showed in maps of potential electrostatic charges. These measurements may be used in the design of effective and more stable fluoroquinolones as well as the investigation of degradation products from stress stability assays.

Detoxification of azinophos methyl using gamma radiation mediated advance oxidation process and investigation of degradation products by HPLC and GC-MS

Abstract Gamma radiolytic degradation of azinophos-methyl was studied in water and methanol separately, using 60Co as a radiation source under varied experimental conditions. Solution of azinophos-methyl was prepared in pure methanol at concentration of 50 μg ml−1, irradiated at gamma dose of 1 to 7 kGy and high performance liquid chromatography (HPLC) coupled with diode array detector was used to monitor the extent of degradation along with numbers of degradation products. At dose of 7 kGy ≥ 99% of azinophos-methyl was degraded. The degradation occurred by interaction of CH3O. and H. radicals generated by the radiolysis of high purity methanol while in water by .OH radical. The degradation in water was increased by 30% than in methanol due the high oxidation potential of .OH while keeping the gamma ray dose constant at 3 kGy. The generated degradation products were identified using GC-MS and their possible transformation pathways are proposed. It is suggested that use of ionization radiations can be an effective and efficient tool for the removal of organophosphate pesticides in waste water.

Advanced oxidation of a commercially important nonionic surfactant: Investigation of degradation products and toxicity

The evolution of degradation products and changes in acute toxicity during advanced oxidation of the nonionic surfactant nonylphenol decaethoxylate (NP-10) with the H2O2/UV-C and photo-Fenton processes were investigated. H2O2/UV-C and photo-Fenton processes ensured complete removal of NP-10, which was accompanied by the generation of polyethylene glycols with 3–8 ethoxy units. Formation of aldehydes and low carbon carboxylic acids was evidenced. According to the acute toxicity tests carried out with Vibrio fischeri, degradation products being more inhibitory than the original NP-10 solution were formed after the H2O2/UV-C process, whereas the photo-Fenton process appeared to be toxicologically safer since acute toxicity did not increase relative to the original NP-10 solution after treatment. Temporal evolution of the acute toxicity was strongly correlated with the identified carboxylic acids being formed during the application of H2O2/UV-C and photo-Fenton processes.

Investigation of degradation products in a topical gel containing erythromycin and benzoyl peroxide by liquid chromatography–mass spectrometry

Benzamycin ®, combining benzoyl peroxide and erythromycin, is a topical gel used in the treatment of acne vulgaris. Because of the reactivity of benzoyl peroxide, preparations containing both erythromycin and benzoyl peroxide might be unstable and degradation products could be formed. To investigate and identify these latter products, a gradient-based liquid chromatographic method using volatile mobile phase constituents was developed. Mass spectrometry data were acquired on solutions containing erythromycin and benzoyl peroxide and on freshly prepared, 2-month-old and 18-month-old samples of Benzamycin ®. With the reference spectra as interpretative templates, it was concluded that erythromycin undergoes oxidation, followed by benzoylation.