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Degradation kinetics and mechanism of 3-Chlorobenzoic acid in anoxic water environment using graphene/TiO <sub/>2</sub> as photocatalyst
摘要： Degradation kinetics and mechanism of 3-Chlorobenzoic acid(3-CBA) in anoxic water environment using graphene/TiO2 (GR/TiO2) as photocatalyst had been investigated. The effects of various parameters such as catalyst dosage, pH, initial concentration, catalyst reuse and dissolved oxygen(DO) on 3-CBA photocatalytic degradation kinetics were studied. The qualitative and quantitative analysis for degradation intermediate products and parent compound were studied by using HPLC, HPLC/MS/MS and IC technologies. The results show that the residual concentration of 3-CBA has a good linear relationship and its correlation coefficient R2are all greater than 0.985 by Langmuir-Hinshelwood (L-H) dynamic model under different photocatalytic degradation conditions; Some oxidative degradation products such as 3-chlorophenol, resorcinol, hydroxyquinol are generated, and some reductive degradation products such as 3-chlorobenzaldehyde, 3-hydroxybenzaldehyde, 3-hydroxybenzyl alcohol, cyclohexanediol are produced, and part of 3-CBA are mineralized to generate CO2 when DO is in the range of 0.5~1.0 mg/L; When DO is less than 0.28 mg/L, photocatalytic reduction mainly occurs. The results provide a theoretical basis for photocatalytic in-situ remediation of pollutants in anoxic water environment.
关键词： Degradation kinetics,Degradation mechanism,3-Chlorobenzoic acid,GR/TiO2,Anoxic water environment
更新于2025-09-04 15:30:14
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Changes in cerebral oxygenation and cerebral blood flow during hemodialysis – A simultaneous near-infrared spectroscopy and positron emission tomography study
摘要： Near-infrared spectroscopy (NIRS) is used to monitor cerebral tissue oxygenation (rSO2) depending on cerebral blood flow (CBF), cerebral blood volume and blood oxygen content. We explored whether NIRS might be a more easy applicable proxy to [15O]H2O positron emission tomography (PET) for detecting CBF changes during hemodialysis. Furthermore, we compared potential determinants of rSO2 and CBF. In 12 patients aged (cid:2) 65 years, NIRS and PET were performed simultaneously: before (T1), early after start (T2), and at the end of hemodialysis (T3). Between T1 and T3, the relative change in frontal rSO2 (DrSO2) was (cid:3)8 (cid:4) 9% (P ? 0.001) and (cid:3)5 (cid:4) 11% (P ? 0.08), whereas the relative change in frontal gray matter CBF (DCBF) was (cid:3)11 (cid:4) 18% (P ? 0.009) and (cid:3)12 (cid:4) 16% (P ? 0.007) for the left and right hemisphere, respectively. DrSO2 and DCBF were weakly correlated for the left (r 0.31, P ? 0.4), and moderately correlated for the right (r 0.69, P ? 0.03) hemisphere. The Bland-Altman plot suggested underestimation of DCBF by NIRS. Divergent associations of pH, pCO2 and arterial oxygen content with rSO2 were found compared to corres- ponding associations with CBF. In conclusion, NIRS could be a proxy to PET to detect intradialytic CBF changes, although NIRS and PET capture different physiological parameters of the brain.
关键词： cerebral oximetry,hemodialysis,water-PET,Brain perfusion,NIRS
更新于2025-09-04 15:30:14
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Efficient synthesis of BiFeO3 by the microwave-assisted sol-gel method: “A” site influence on the photoelectrochemical activity of perovskites
摘要： BiFeO3 (BF) and LaFeO3 (LF) perovskites were synthesized using a microwave-assisted (MW) and sol-gel (SG) methods. XRD, XPS, TEM, UV-DRS techniques were applied to study physicochemical properties of perovskites. In addition, Incident Photon-to-Current Efficiency (IPCE) measurements, Linear Sweep Voltammetry (LSV) and impedance spectroscopy were used to characterize electrochemical properties of the material. The band gap energy increases in the following way: BF-MW (2.05 eV), LF-MW (2.18 eV), BF-SG (2.26 eV) and LF-SG (2.54 eV), demonstrating a remarkable influence of the synthesis method on the optical and electronic properties of the materials. Furthermore, XRD showed a significant impact of the synthesis methods on the crystal structure. Perovskites synthesized under WM irradiation showed a pure crystal structure compared to the perovskites prepared by SG method, which contained some admixtures. IPCE shows that LF-MW has a better charge separation ability compared to BF-MW. However, BF-SG showed the highest activity. Temperature programmed reduction tests (TPR) revealed a better ability of BiFeO3 to adsorb/desorb oxygen, compared to LaFeO3. XPS measurements pointed at the presence of Fe4+. Finally, the photocatalytic activity of the perovskites was tested in solar water-splitting as a function of the synthesis method and presence of Bi and La in “A” sites of the ABO3 perovskites. We postulate, that the Jahn-Teller distortion effect in LF-MW increases its catalytic activity by decreasing the binding energy compared to BF-MW.
关键词： Microwave-assisted synthesis,Jahn-Teller distortion,Photocatalysts,Photoelectrochemical water splitting,Perovskites
更新于2025-09-04 15:30:14
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Soft X-ray Absorption Spectroscopy of Aqueous Solutions Using a Table-Top Femtosecond Soft X-ray Source
摘要： We demonstrate the feasibility of soft X-ray absorption spectroscopy in the water window using a table-top laser-based approach with organic molecules and inorganic salts in aqueous solution. A high-order harmonic source delivers femtosecond pulses of short wavelength radiation in the photon energy range from 220 eV to 450 eV. We report static soft X-ray absorption measurements in transmission on the solvated compounds CO(NH2)2, CaCl2, and NaNO3, using flatjet technology. We monitor the absorption of the molecular samples between the carbon (≈280 eV) and nitrogen (≈400 eV) K-edges and compare our results with previous measurements performed at the BESSYII facility. We discuss the roles of pulse stability and photon flux in the outcome of our experiments. Our work paves the way towards table-top femtosecond, solution phase soft X-ray absorption spectroscopy in the water window.
关键词： aqueous solution,high-order harmonic source,flatjet technology,soft X-ray absorption spectroscopy,table-top laser-based approach,femtosecond pulses,water window
更新于2025-09-04 15:30:14
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Novel Design for Thermal Management of PV Cells in Harsh Environmental Conditions
摘要： The abundance of solar energy is a blessing in the Arabian Peninsula, where more than 2000 kWh/m2 density has been recorded annually. This has resulted in sincere consideration of PV harvesting in the energy matrix and smart grid. However, artefacts such as degradation of PV efficiency due to the high temperature effect have to be addressed. This paper presents a novel design of a PV cooling system using water to mitigate the effect of high temperature. Several experiments have been conducted, and the results have been analyzed. It has been found that the collected water from the panel after 40 min of cooling gained a temperature of 10 ?C approximately, during December 2016. Eventually, the efficiency was improved by 10.35% (without using MPPT) using water at ambient temperature (24 ?C) compared to the non-cooled panel. Moreover, the temperature of the panel during solar peak hours dropped from 64.3 ?C to 32 ?C and from 59 ?C to 27 ?C in 3 min for the back and front surface, respectively. These results, which are the ?rst of their kind in Qatar, constitute good incentives and pave the way for further investigation to enhance PV ef?ciency in harsh environments. This would be of paramount signi?cance, especially for scaling up PV deployment, as is planned in Qatar and GCC countries in their 2030 vision.
关键词： overheating,ef?ciency,photovoltaic,water cooling,heat transfer,renewable energy
更新于2025-09-04 15:30:14
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Efficient bifunctional vanadium doped Ni3S2 nanorod array for overall water splitting
摘要： Electrochemical water splitting, allowing energy conversion from renewable resources into non-polluting chemical fuels, is vital in the future sustainable energy system, and great efforts have been paid on developing efficient and cheap bifunctional electrocatalysts. Herein we report a bifunctional vanadium doped Ni3S2 nanorod array electrode for overall water splitting in alkaline media. To afford a catalytic current of 10 mA cm-2, the designed V-Ni3S2 electrode only requires the overpotentials of 133 mV for hydrogen evolution and 148 mV for oxygen generation, meanwhile showing high long-term stability. The excellent catalytic properties are assigned to the V dopants and geometric advantages of nanorod array. The V-Ni3S2 electrodes are simultaneously utilized as cathode and anode in one two-electrode cell to function overall water splitting, exhibiting a cell voltage of 1.421 V at 10 mA cm-2. The water splitting in this cell can also be feasibly driven by a single-cell AA battery (1.5 V). Our report shows substantial advancement in the exploration of efficient bifunctional electrocatalysts for water splitting.
关键词： bifunctional electrocatalysts,water splitting,nanorod array,alkaline media,vanadium doped Ni3S2
更新于2025-09-04 15:30:14