- Coupled heterogeneous photocatalysis using a P-TiO2-αFe2O3 catalyst and K2S2O8 for the efficient degradation of a sulfonamide mixture
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Phosphorous-doped Ti-Fe mixed oxide (P-TiO2-αFe2O3) catalysts were prepared by the microwave-assisted sol-gel route and characterized using XRD, SEM, N2 physisorption, UV–vis diffuse reflectance, FTIR, and XPS. P-TiO2-αFe2O3 was evaluated during the degradation of a sulfonamide mixture (5 mg/L, each) under visible light. The photocatalytic process was optimized with a face-centered central composite design. Under optimal conditions (0.5 wt% of αFe2O3, pH 10, and 0.75 g/L of catalyst loading), the sulfate radical advanced oxidation process was carried out using 5 mM K2S2O8 (PS). P doping shifted the light absorption of P-TiO2-αFe2O3 in the visible light range owing to substitutional doping, while the coupling of P-TiO2 with α-Fe2O3 enhanced the absorption in the visible range, which resulted in an increase in the lifetime of the charge carriers and in a superior photoactivity of the P-TiO2-αFe2O3 catalyst in comparison to that of TiO2. The mineralization yield of the sulfonamides (SNs) mixture was enhanced in the presence of an electron acceptor (SO4 ? [rad]), allowing nearly 69 % within 300 min with the P-TiO2-αFe2O3/PS system, while P-TiO2-αFe2O3 and K2S2O8 oxidation achieved only 27 % and 21 %, respectively. The biodegradability index was 0.48 using the P-TiO2-αFe2O3/PS system, indicating a less toxic effluent than the original compounds. Recycling tests demonstrated that P-TiO2-αFe2O3 exhibits good stability in activating PS for SNs degradation during three cycles. Two main intermediates (pyrimidine and hydroquinone) and their hydroxylated re-arrangements were detected during the degradation of the SNs by the coupled process. Oxalic, oxamic, sulfonic, and acetic acids were also identified as by-products from the degradation of the SNs.
- Guzmán-Mar, Jorge L.,Hernández-Ramírez, Aracely,Hinojosa-Reyes, Laura,Mendiola-Alvarez, Sandra Y.,Palomino-Cabello, Carlos,Turnes-Palomino, Gemma
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- Insight into sulfamethoxazole degradation, mechanism, and pathways by AgBr-BaMoO4 composite photocatalyst
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A composite photocatalyst, AgBr-BaMoO4 was fabricated by two step method; microwave hydrothermal and precipitation-deposition. The as prepared photocatalyst samples were characterized by various techniques. The facet coupling was seen between the (204) plane of BaMoO4 and (200)/(222) planes of AgBr on the basis of XRD/HRTEM analysis. The pharmaceutical pollutant, sulfamethoxazole was adopted to investigate the photocatalytic performances of samples under UV–vis irradiation. The AgBr-BaMoO4 composite degraded the aqueous sulfamethoxazole drug in UV–vis light about 64% within 75 min, which was attributed to efficient separation of photogenerated electron–hole pairs across the interface between Ag/AgBr and BaMoO4. The multi-electron induced oxygen reduced reaction (ORR) was observed. The radical trapping experiment indicates that OH? has major role for sulfamethoxazole degradation. The four successive photodegradation of sulfamethoxazole in UV–vis light indicates the stability of composite photocatalyst. Furthermore, the three different degradation pathways were designed on the basis of retention time and molecular masses of 18 degraded organic fragments that was confirmed by high-performance liquid chromatography photodiode array (HPLC-PDA) and high resolution-quadruple time of flight electrospray ionization mass spectroscopy (HR-QTOF ESI/MS) techniques. The total organic carbon (TOC) analysis suggested the mineralization of SMZ by composite photocatalyst. This study not only demonstrates the enhancement of photocatalytic performance of wide band gap semiconductor by making composite with narrow band gap semiconductor but also detail degradation pathways and mechanisms of sulfamethoxazole.
- Ray, Schindra Kumar,Dhakal, Dipesh,Lee, Soo Wohn
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p. 686 - 695
(2018/07/14)
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- 3-PHOSPHOGLYCERATE DEHYDROGENASE INHIBITORS AND USES THEREOF
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The present invention provides compounds, compositions thereof, and methods of using the same.
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Paragraph 00276
(2017/10/06)
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