- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Evaluation of photocatalytic thin film pretreatment on anaerobic degradability of exopolymer extracted biosolids for biofuel generation
摘要： This study reports the result of sodium citrate induced exopolymer extraction on the photocatalytic thin film (TiO2) pretreatment efficiency of waste activated sludge (WAS). TiO2 is immobilized through DC spluttering method followed by annealing process. The exopolymer removal of 94.2 % by sodium citrate (0.05 g/g SS) promotes better disintegration. This TiO2 thin film efficiently extricate the intracellular components of exopolymer extracted sludge at 50 minutes increasing the solubilization to 19.33 %. As a result, the exopolymer extracted sludge shows high methane generation (0.24 gCOD/gCOD) than the other (pretreated sludge without exopolymer removal – 0.12 gCOD/gCOD and raw sludge without treatment – 0.075 gCOD/gCOD). The methane generated in sodium citrate induced TiO2 thin film pretreated sludge is 398.99 kWh. In cost analysis, it gives net cost of -57.46 USD/ ton of sludge. In addition, the proposed method also accounts 51.3 % of solid reduction.
关键词： Methane,Photocatalytic oxidation,Sodium citrate,Pretreatment,Cost analysis
更新于2025-09-19 17:15:36
-
Compact dual-gas sensor for simultaneous measurement of atmospheric methane, and water vapor using a 3.38?μm antimonide-distributed feedback laser diode
摘要： A simple, compact sensor involving a continuous-wave 3.38 mm distributed feedback laser in combination with a novel compact dense-pattern multipass cell was demonstrated for simultaneous measurement of atmospheric methane and water vapor. The calibration-free direct absorption spectroscopy approach was adopted for data generation and processing. Allan deviation analysis indicates that minimum detection limits (1s) of 11.0 ppb for CH4 and 100 ppm for H2O were achieved with a 1-s integration time at an optimum pressure of 50 Torr. Atmospheric environmental mixing ratios of these two gases were recorded and analyzed. This newly developed mid-infrared dual-gas sensor is very suitable for trace gas sensing in weight-limited unmanned aerial vehicle- or balloon-embedded field observations.
关键词： Multipass cell,Laser sensors,Water vapor,Distributed feedback laser,Laser absorption spectroscopy,Methane
更新于2025-09-19 17:13:59
-
Visible-light-driven selective oxidation of methane to methanol on amorphous FeOOH coupled m-WO3
摘要： Direct conversion of methane into value-added fuels or chemicals under ambient conditions remains a great challenge. Constructing solar-energy-driven catalytic systems is considered as a promising strategy, but the conversion e?ciency and products selectivity are still low, especially for producing alcohol derivatives. Herein, to promote the photocatalytic activity of methane partial oxidation to methanol, a series of FeOOH/m-WO3 consisting of ordered mesoporous WO3 (m-WO3) and highly dispersed amorphous FeOOH were synthesized by using KIT-6 silica as hard template. The prepared FeOOH/m-WO3 catalysts exhibit dramatically improved visible-light catalytic activities toward selective oxidation methane into methanol in the presence of H2O2. A methane conversion rate of 238.6 μmol·g?1·h?1 is achieved over the optimal 1.98% FeOOH/m-WO3, which is 3 times higher than that of pristine m-WO3 (79.2 μmol·g?1·h?1). Moreover, a methanol production rate of 211.2 μmol·g?1·h?1 with a selectivity of 91.0% is obtained on the optimum catalyst under 4 h visible-light irradiation. Signi?cantly, the greatly improved methane conversion and methanol production can be attributed to e?cient electron migration from the conduction band of m-WO3 to highly dispersed FeOOH, evidenced by in-situ XPS analysis, transient photocurrent response and photoluminescence spectra. Furthermore, based on radicals trapping experiments and electron spin resonance (ESR) results, methane is primarily activated by photoholes accumulated on the valence band of m-WO3 to generate methyl radicals (·CH3) and the produced hydroxyl radicals (·OH) via decomposing H2O2 by photoelectrons on FeOOH surface are predominant oxidant for methanol generation. Desired methanol is selectively produced via radicals reaction between ·CH3 and ·OH.
关键词： WO3,Methane,Methanol,Visible-light-driven,Amorphous FeOOH
更新于2025-09-19 17:13:59
-
Fabrication of ZnSe/InP Heterojunctions on Flat and Shaped Surfaces of InP Laser Crystals
摘要： We have studied the growth of zinc selenide layers on flat and shaped indium phosphide surfaces. The growth rate of zinc selenide has been shown to depend on substrate orientation. It has been shown that the present results can be useful in designing mesa stripe structures for quantum electronic instruments. We have fabricated mesa stripe laser diodes operating on the absorption band of methane and suitable for producing fiber-optic signal transmission systems.
关键词： methane,semiconductor heterostructures,zinc selenide,laser diodes
更新于2025-09-19 17:13:59
-
Interaction of Methane Concentration and Deposition Temperature in Atmospheric Laser Based CVD Diamond Deposition on Hard Metal
摘要： For laser-based plasma chemical vapour deposition (CVD) of diamond on hard metal at atmospheric pressure, without a vacuum chamber, the interaction between the deposition temperature and the methane concentration has to be understood to adjust the coating thickness, deposition duration, and medium diamond crystal size. The hypothesis of this study is that a wider range of methane concentrations could be used to deposit microcrystalline diamond coatings due to the increasing etching and deposition rates with rising deposition temperatures. The deposition of the CVD diamond coatings was carried out on K10 hard metal substrates. The process temperature and the methane concentration were varied from 650 to 1100°C and from 0.15% to 5.0%, respectively. The coatings were analysed by scanning electron and 3D laser-scanning confocal microscopy, energy dispersive X-ray and micro-Raman spectroscopy, as well as cryofracture-based microscopy analysis. The results showed that microcrystalline diamond coatings could be deposited in a wider range of methane concentrations when increasing the process temperature. The coating thickness saturates depending on the process temperature even though the methane concentration constantly increases. The coating thickness increases with an increasing deposition temperature until the cobalt diffusion hinders the deposition at the process temperature of 1100°C.
关键词： diamond film,chemical vapour deposition,hard metal,methane ratio,deposition temperature
更新于2025-09-19 17:13:59
-
A portable miniaturized laser heterodyne radiometer (mini-LHR) for remote measurements of column CH4 and CO2
摘要： We present the design of a portable version of our miniaturized laser heterodyne radiometer (mini-LHR) that simultaneously measures methane (CH4) and carbon dioxide (CO2) in the atmospheric column. The mini-LHR fits on a backpack frame, operates autonomously, and requires no infrastructure because it is powered by batteries charged by a folding 30 W solar panel. Similar to our earlier instruments, the mini-LHR is a passive laser heterodyne radiometer that operates by collecting sunlight that has undergone absorption by CH4 and CO2. Within the mini-LHR, sunlight is mixed with light from a distributive feedback (DFB) laser centered at approximately 1.64 μm where both gases have absorption features. The laser scans across these absorption features roughly every minute and the resulting beat signal is collected in the radio frequency (RF). Scans are averaged into half hour and hour data products and analyzed using the Planetary Spectrum Generator (PSG) retrieval to extract column mole fractions. Instrument performance is demonstrated through two deployments at significantly different sites in interior Alaska and Hawaii. The resolving power (λ/?λ) is greater than 500,000 at 1.64 μm with precisions of better than 20 ppb and 1 ppm for CH4 and CO2, respectively. Because mini-LHR instruments are portable and can be co-located, they can be used to characterize bias between larger, stationary, column observing instruments. In addition, mini-LHRs can be deployed quickly to respond to transient events such as methane leaks or can be used for field studies targeting geographical regions.
关键词： atmospheric column,carbon dioxide,methane,portable,miniaturized laser heterodyne radiometer
更新于2025-09-19 17:13:59
-
Applicability of a gas analyzer with dual quantum cascade lasers for simultaneous measurements of N2O, CH4 and CO2 fluxes from cropland using the eddy covariance technique
摘要： We evaluated the applicability of a closed-path gas analyzer with two mid-infrared quantum cascade lasers (QCLs) for simultaneous measurement of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes from a cropland using the eddy covariance (EC) technique. The measurements were carried out in a typical vegetable field in the subtropical China during the wintertime, when the gas fluxes are at their lowest level in the year. A new approach was proposed to optimize the determination of lag times between the wind and gas concentration data, which was proven efficient to increase the reliability of the measured fluxes when the gas exchanges are weak. The dual-QCL analyzer showed a median precision (1σ) of 0.14 nmol mol?1 for N2O, 3.3 nmol mol?1 for CH4 and 0.36 μmol mol–1 for CO2 at sampling frequency of 10 Hz under the field conditions. Such precisions are better than, or comparable with, those of other commonly used closed-path or open-path gas analyzers, which are capable of measuring only one or two of the three gases. The detection limit of the EC system for measuring half-hourly fluxes were 0.05 nmol m?2 s?1 for N2O, 1.12 nmol m?2 s?1 for CH4 and 0.14 μmol m–2 s–1 for CO2. The results showed that 100% of the N2O, 87% of the CH4 and 96% of the CO2 fluxes were larger than the above detection limits. This study suggests that the EC technique using a closed-path gas analyzer with two quantum cascade lasers is qualified for reliable and simultaneous measurements of N2O, CH4 and CO2 fluxes from a subtropical cropland throughout the year. Moreover, EC method based on this type of gas analyzer provides an additional option for long-term and simultaneous flux measurements of the three greenhouse gases in a wide range of agricultural and natural ecosystems.
关键词： Nitrous oxide,eddy covariance,cropland,methane,flux,quantum cascade laser,carbon dioxide
更新于2025-09-19 17:13:59
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Broadband Dual-Comb Spectroscopy of Methane with a Free-Running Erbium Chip Laser
摘要： Dual-comb interferometry enables the identification of a gas through the measure of its unique spectral signature with high resolution and fast acquisition. It has been used here to study the spectroscopic properties of an important greenhouse gas: methane. The environmental influence of methane, as well as its economic impact, have proven the need to study its spectroscopic signature with a high level of accuracy. We report a free-running dual-comb spectrometer which has the potential to fulfil the need for high accuracy portable methane monitoring. The C-band spectrometer reported is now broadened from 1400 nm to 1700nm using fiber amplifiers and highly nonlinear fiber (HNLF). The dual-comb laser originates from two passively mode-locked waveguide lasers integrated into a single Er-doped ZBLAN chip. Free-running combs with high mutual coherence are produced with a repetition rate of 968 MHz and a repetition rate difference of 27 kHz. No phase locks, optical references or self-referencing are required. Through the use of a SESAM mode-locking configuration, the lasers self-start and occupy a volume less than 1.2 L, making it an efficient and compact design.
关键词： methane,free-running laser,dual-comb spectroscopy,spectrometer,erbium chip laser
更新于2025-09-16 10:30:52
-
Analysis of spectroscopic information for detecting methane emissions on local paths using CO and He – Ne lasers
摘要： Measuring the concentration of methane in the atmosphere is demonstrated to be very important, since an increase in methane content enhances the greenhouse effect. It is shown that the error in assessing the concentration of CH4 depends on many factors, including the reliability of the parameters of the spectral absorption lines of gases, the accuracy of determining the concentration, the measurement error, etc. The spectroscopic information necessary to detect sources of high methane concentration in the atmosphere using CO and He – Ne lasers is analysed.
关键词： concentration,absorption spectrum,methane,differential absorption method,laser
更新于2025-09-16 10:30:52
-
Ultrahigh brightness attosecond electron beams from intense X-ray laser driven plasma photocathode
摘要： The emerging intense attosecond X-ray lasers can extend the Laser Wakefield Acceleration mechanism to higher plasma densities in which the acceleration gradients are greatly enhanced. Here we present simulation results of high quality electron acceleration driven by intense attosecond X-ray laser pulses in liquid methane. Ultrahigh brightness electron beams can be generated with 5-dimensional beam brightness over 1020 A · m?2 · rad?2. The pulse duration of the electron bunch can be shorter than 20 as. Such unique electron sources can benefit research areas requiring crucial spatial and temporal resolutions.
关键词： attosecond X-ray lasers,ultrahigh brightness electron beams,liquid methane,Laser Wakefield Acceleration,5-dimensional beam brightness
更新于2025-09-16 10:30:52