Search

Some seriously weathered jades of Fubin culture were unearthed at the Moyishan site in Lingnan, South China. These long-buried jades have many secondary changes such as discoloration, microstructural change and chemical composition variation. To explore the formation mechanism of secondary changes, the microstructure, mineral components, and chemical content of the jade samples and their buried soil are analyzed separately. The jade with red-brown shell is preserved well and shows better structural stability, further research indicates that it's the result of surface complexation reactions. During the long-term burial in acidic soil environment, the jade wrapped in the negatively charged kaolinite which absorbed Fe3+ to complexed on the jade surface. Iron(ⅲ) precipitates causes the dense shell to appear red-brown. [ABSTRACT FROM AUTHOR]

The co-combustion of various ultra-low volatile coal-based solid fuels (UVCFs) under oxy-fuel condition could consume semi-coke and residual carbon cleanly and efficiently. However, the fuel-nitrogen (fuel-N) migration behaviors of various UVCFs blends in O 2 /CO 2 atmosphere are still unclear. In addition, the heterogeneous reactions on surfaces of char could also affect the synergistic effects between various UVCFs blend. Here, the fuel-N migration features of various UVCFs in O 2 /CO 2 atmosphere were investigated by Chemkin simulation and the oxy-fuel co-combustion mechanism of various coal-based solid fuels (OCF mechanism) included heterogeneous reactions was developed. Moreover, the methods of sensitivity and rate of production analyses were both employed to clarify the synergistic effects on nitrogen conversion pathways of various blends. The heterogeneous reaction between char and NO (R15) is the key reaction for NO reduction in primary zone. The free radicals OH and H provided by UVCFs could react with main NO precursors NCO, HNCO, HOCN, NH and NH 2 to generate NO. The conversion pathways of HCN to NO are more complex than those of NH 3 to NO. The rises of residual carbons proportions and temperature in primary zone (T 1) could both reduce the NO formation amount due to the promoted R15. The sensitivity coefficients (S) on NO formation of 50% SS/50% CR blend in the burnout zone are lower than those of 50% SS/50% FR blend. The transformations of HNCO, HNO and NO 2 to NO and the heterogeneous reactions of NO could both be enhanced with the O 2 concentration in burnout zone. The increasing burnout air position (P b) results in the rise of NO generation owing to that the NO reducing reactions R15 and R16 are greatly inhibited with the P b raised. The present study could be beneficial for the clean and effective utilization of UVCFs, together with the reduce of NO x emission and realization of carbon neutral in China. [Display omitted] [ABSTRACT FROM AUTHOR]

Increasing severe and persistent ozone pollution in China has resulted in serious harm to human health in recent years, yet the precise pollution sources are poorly known because there is few knowledge on large-scale extreme ozone episodes. Here, we studied the formation of the historical orange-alert regional ozone episode in eastern China on 6 June, 2021, by combining process analysis, integrated source apportionment modelling, and chemical and meteorological data. Results show that during the pollution episode, 94% of cities in eastern China suffered ozone pollution, and 39% had daily maximum 8-h average ozone concentrations higher than 100 ppb. This is explained by favorable local ozone formation and transports provided by the prevailing northwestern winds in the upper air, and by sinking atmospheric motions favoring the persistence of high surface ozone concentrations. During daytime, local photochemical production induced an ozone increase of 0.3–28.4 ppb h−1 and vertical transport induced an ozone increase of 0.4–56.1 ppb h−1. As a consequence, vertical downward transport of ozone generated in the upper air by photochemical reactions aggravated surface ozone pollution. Surface ozone concentrations include 25.8–53.9% of ozone from local provincial emissions, 0–42.6% of ozone from inter-regional transports from neighboring regions, 4.6–23.1% of ozone from outer-regional transport, and 13.6–52.9% of ozone from boundary conditions in the selected cities. Overall, our findings show that favorable meteorological conditions promoted the chemical productions of ozone on the surface and at high altitudes, thus resulting in this heavy ozone pollution. In addition, regional and vertical downward transports of aloft ozone further aggravated the surface ozone pollution, leading to the large-scale extreme ozone pollution episode. [ABSTRACT FROM AUTHOR]

• REGR system can assists to achieve "double carbon" target promised by China. • 1-D reforming model coupled with detailed mechanism and verified by experimental data. • Study on performance of reformer from a view of surface reaction kinetics analysis. • COM and SRM dominate in exhaust gas-methane reforming system accompanied by some DRM. • Optimal zone of high reforming characteristics and η RF for reformer operation is acquired. In the present study, for an insight into the catalytic reforming process of the exhaust reformer and its optimization strategy, a one-dimensional inhomogeneous reforming model and a thermodynamic model were implemented in a Ni/Al 2 O 3 catalytic packed-bed description of single reforming tube inside the reformer. The models were evaluated by comparison of numerical simulations with data derived from reforming experiments in a flow reactor over a columnar nickel-based catalyst. Meanwhile, the effects on reforming characteristics and energetics of the process of exhaust gas-methane reforming inside the reformer was investigated from a view of surface reaction kinetics under the variation of temperature and O 2 concentration of the exhaust gas from the engines, as well as the supply of CH 4 and H 2 O into reformer. The results showed that the hydrogen production characteristics of exhaust gas-methane reforming is mainly controlled by the exhaust temperature and various inlet feedstock of the reformer. There is a critical exhaust temperature of 610 K to activate the process of exhaust gas-methane reforming. For the efficient operation of the exhaust reformer, it is necessary to increase the O 2 concentration of the exhaust gas via adjusting the excess air coefficient of the engine, because in this case the dehydrogenation process of CH i (s) is enhanced and more hydrogen production on the catalyst surface with an atmosphere of more H(s) through the desorption way. Compared with the thermodynamic values, the used catalyst still has some space for improvement in the catalytic properties to approach the thermodynamic hydrogen production characteristics of the reforming system at different initial exhaust temperatures and M/O values. Summarily, the optimal operation conditions for the exhaust reformer were determined: M/O = 0.8–1.5 and S/M = 0.5–1.5, which can achieve efficient hydrogen production (about 13–23 %) and maintain high reforming energy efficiency (≥60 %). [ABSTRACT FROM AUTHOR]

[Display omitted] • An MG binary composite (green rust deposited MoS2) was prepared to remove EDTA-Cu(II). • The removal of EDTA-Cu(II) can be enhanced by the synergistic effect of MoS2 and GR. • MG (pH = 3–7) replacing EDTA-Cu(II) is wider than common Fe3+ (pH = 2.7–5.2). • MG could effectively remove EDTA-Cu(II) under different dissolved oxygen conditions. EDTA-Cu(II) is usually observed in electroplating wastewater, and its removal is very challenging due to its easy dissolution, stability and difficult biodegradation characteristics. In this work, an excellent binary composite (MG) was prepared via the combination of green rust (GR) and MoS 2 to remove EDTA-Cu(II) from an aqueous solution. Batch test results showed that the maximum capacity of EDTA-Cu(II) uptake by MG was 89.85 mg/g. Thus, up to 98.5% of EDTA-Cu (20 mg/L) was removed. The residual Cu content was lower than the discharge standard of China (0.5 mg/L); additionally, the leaching of Fe ions was lower than 22 mg/L under ambient conditions. MG could satisfactorily remove EDTA-Cu(II) from complex environments in one step and was only minimally affected by various experimental conditions (the presence of different salt ions, different ratios of EDTA organic groups, and different dissolved oxygen concentrations). The highly active MG composite has a wider pH range (pH = 3–7) for the efficient replacement reaction with EDTA-Cu(II) than for the replacement of common Fe(III) ions (pH = 2.7–5.2). GR deposited on MoS 2 could not only effectively increase the surface reaction sites of MG composites but also enhance EDTA-Cu(II) removal performance through the mutual synergy between GR and MoS 2. These experimental results suggest that MG holds promise for use in removing EDTA-Cu(II) from contaminated wastewater. [ABSTRACT FROM AUTHOR]

In this study, collocated samples of particulate matter with aerodynamic diameter less than 2.5 μm (PM 2.5) were collected every sixth day on quartz filters (Q f) at a suburban site in northern Nanjing, China for one year. A backup quartz filter (Q b) was installed behind Q f to estimate positive artifacts. The analysis of gravimetric mass, water-soluble inorganic ions (WSIIs), total organic (OC) and elemental carbon (EC), water-soluble OC (WSOC), total nitrogen (WSTN) and organic nitrogen (WSON) were performed on both Q f and Q b. Due to the high mass loadings on Q f (17.9 ± 7.82 mg filter−1, 4.71–38.5 mg filter−1), the collocated precision of gravimetric mass and dominant species (NH 4 +, NO 3 −, SO 4 2−, OC, and EC) is better than that from previous work. Except K+, EC, and WSON, all other target components were detected on Q b with average Q b /Q f ratios ranging from 3.02 ± 3.48–21.7 ± 22.4%. The final concentrations and uncertainties of PM 2.5 components were determined based on duplicate Q f –Q b data. The results suggest that using an error fraction of 10% will underestimate the uncertainty of less concentrated species (e.g., Ca2+ and Mg2+) in PM 2.5. Due to the evaporation loss of semi-volatile materials from the Q f , the Q f –Q b calculation would lead to an estimate of the lower limit for particulate NH 4 +, NO 3 −, and OC. Synchronized hourly data of PM 2.5 mass and components were obtained at downtown Nanjing. The comparisons of gravimetric versus reconstructed PM 2.5 and filter-based versus continuous measurements of PM 2.5 components indicate that a substantial fraction of the unexplained gravimetric PM 2.5 can be attributed to aerosol water. Image 1 • Collocated precision of PM 2.5 components depends largely on filter loadings. • Besides OC adsorption, quartz filter sampling is also subject to surface reactions. • Assuming a constant error fraction of 10% is appropriate for PM 2.5 major components. • Water content contributes a substantial fraction of the unexplained gravimetric PM 2.5. [ABSTRACT FROM AUTHOR]