The surface element distribution, valence and relative density of marine sedimentary phosphate ores from Guizhou province were analyzed by X-ray photoelectron spectrometric(XPS). The effect and mechanism of flotation reagents on collophane flotation was discussed. The raise of C content indicates that the collector can be adsorbed on collophane surface. After treatment with Ca2+, the new compound formed on collophane surface is similar to that before the treatment. No Fe and Mg have been observed after treatment with Fe3+ and Mg2+. The reason might be Ferric and magnesium hydroxide and hydroxo complex absorption occurs on the surface. Then, Fe and Mg2+ could consume collector because of the formation of precipitate resulting from chemical reaction. In other words, Fe3+ and Mg2+ are covered with collectors, thus, they can’t be observed by XPS.
The 76-element Geochemical Mapping (76 GEM) Project was undertaken in southwestern China in 2000 and in southeastern China in 2008. In this project, 5244 composite samples of stream sediment at a density of one composite sample for each 1:50,000-scale map sheet were prepared from sample archives of the China Regional Geochemistry-National Reconnaissance (RGNR) Project, which have been available since 1978. The 76 elements were analyzed by using inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence (XRF), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). In the present study, a new quality-control method known as the visualized standard map method was applied to the results of the 76 GEM project. Mean value and background value, which indicate the average concentration of the 76 elements in southern China, were derived from statistical data. Moreover, geochemical maps were compiled to demonstrate the distribution of the 76 elements in southern China.
Abstract Surface self‐reconstruction via incorporating an amorphous structure on the surface of a catalyst can induce abundant defects and unsaturated sites for enhanced hydrogen evolution reaction (HER) activity. Herein, an electrochemical activation method is proposed to reconstruct the surface of a Cu‐Fe 3 O 4 catalyst. Following a “dissolution–redeposition” path, the defective FeOOH is formed under potential stimulation on the surface of the Cu‐Fe 3 O 4 precursor during the electrochemical activation process. This Cu‐FeOOH/Fe 3 O 4 catalyst exhibits excellent stability as well as extremely low overpotential toward the alkaline HER (e.g., 129 and 285 mV at the large current densities of − 100 and 500 mA cm −2 , respectively), much superior to the Pt/C catalyst. The experimental and density functional theory calculation results demonstrate that the Cu‐FeOOH/Fe 3 O 4 catalyst has abundant oxygen vacancies, featuring optimized surface chemical composition and electronic structure for improving the active sites and intrinsic activity. Introducing defective FeOOH on the surface of a Cu‐Fe 3 O 4 catalyst by means of an electrochemical activation method decreases the energy barrier of both H 2 O dissociation and H 2 generation. Such a surface self‐reconstruction strategy provides a new avenue toward the production of efficient non‐noble metal catalysts for the HER.
Temperature and pore pressure have a significant impact on the mechanical behavior of methane hydrate-bearing soil (MHBS). To characterize the mechanical responses of MHBS under different temperatures and pore pressures, an elastoplastic constitutive model is developed within the framework of the critical-state theory. In the proposed model, an additional variable, called the phase state parameter, is introduced to characterize the temperature and pore pressure condition. Meanwhile, the elastic parameter, plastic modulus, and tensile bonding stress are related to the phase state parameter through several empirical formulas. As a consequence, the influences of temperature and pore pressure on the stiffness, strength, and dilatancy of MHBS are addressed by the proposed constitutive model. Through comparing the predicted results and experimental data, the proposed model is demonstrated to have the ability to capture the influences of hydrate saturation, temperature, and pore pressure on the mechanical behavior of MHBS. In addition, the proposed model is used to analyze the response of MHBS to an increase in temperature or a decrease in pore pressure within the hydrate stability boundary. The result shows that the proposed model can reasonably reflect the mechanical behavior of MHBS induced by heating or depressurization procedures within the hydrate stability boundary.
Ecological sluices were constructed along the Tarim River to supplement the ecosystem’s water supply. However, the impact of water regulation by these sluices on the surface water area (SWA) and its relationship with the vegetation response remain unclear. To increase the efficiency of ecological water use, it is crucial to study the response of SWA to water control by the ecological gates and its relationship with vegetation restoration. We utilized the Google Earth Engine (GEE) cloud platform, which integrates Landsat-5/7/8 satellite imagery and employs methods such as automated waterbody extraction via mixed index rule sets, field investigation data, Sen + MK trend analysis, mutation analysis, and correlation analysis. Through these techniques, the spatiotemporal variations in SWA in the middle reaches of the Tarim River (MROTR) from 1990–2022 were analyzed, along with the relationships between these variations and vegetation restoration. From 1990–2022, the SWA in the MROTR showed an increasing trend, with an average annual growth rate of 12.47 km2 per year. After the implementation of ecological gates water regulations, the SWA significantly increased, with an average annual growth rate of 28.8 km2 per year, while the ineffective overflow within 8 km of the riverbank notably decreased. The NDVI in the MROTR exhibited an upward trend, with a significant increase in vegetation on the northern bank after ecological sluice water regulation. This intervention also mitigated the downward trend of the medium and high vegetation coverage types. The SWA showed a highly significant negative correlation with low-coverage vegetation within a 5-km range of the river channel in the same year and a significant positive correlation with high-coverage vegetation within a 15-km range. The lag effect of SWA influenced the growth of medium- and high-coverage vegetation. These findings demonstrated that the large increase in SWA induced by ecological gate water regulation positively impacted vegetation restoration. This study provides a scientific basis for water resource regulation and vegetation restoration in arid regions globally.
Abstract The universal preparation of noble metal single‐atom catalysts (NMSACs) is critical for efficient sustainable energy conversion. In this study, a versatile sowing strategy is proposed to prepare the NMSACs with hyper‐low loading. A metal‐organic framework derived Ni(OH) x with Ni 2+ vacancies serves as fertile soil with plentiful trapping holes, where the Pt atom seeds can be inserted. The Pt atoms tend to form tetradentate Pt‐O 4 as the roots, confining the loading concentration to a hyper‐low range (≈0.17 wt%). This Pt‐Ni(OH) x catalyst exhibits an overpotential of 58 mV at a current density of 10 mA cm −2 in 1 m KOH for hydrogen evolution reaction and needs only 1.47 V to achieve η 10 for water splitting. This approach is extended to the formation of other NMSACs such as Ir and Ru. The versatile sowing strategy thus provides guidance to prepare different NMSACs with excellent catalytic performance.
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