Experimental Study on Tailings Deposition Distribution Pattern and Sedimentation Characteristics.

Tailings pond accidents frequently occur during an extended period, resulting in loss of life and property, wastage of resources, and environmental pollution. Relying on tailings pond engineering, this paper carried out sample particle fragmentation experiments and settling column experiments to explore the deposition distribution pattern of tailings in both horizontal and vertical directions as well as the impact of particle size distribution on the sedimentation stratification effect. The results show that the median particle size on the dry beach surface in the horizontal direction slowly decreased with the increase in the distance from the subdam. The particle size of tailings showed great fluctuations in the vertical direction, which gradually became finer with the increase in the depth overall. At the same time, saturated sedimentation experiments suggested the inconsistent variation rule with the field test, namely, coarse on the bottom and fine at the top, and the change in particle size greatly affected the tailing sedimentation stratification effect. With the increase in fine particle content in tailings, the appearance time of the water-sand interface was shortened to within 30 min, but the sedimentation and consolidation completion times were delayed to about 1400 min. The settling column results indicate that the increase in fine particle content gradually weakened the sedimentation stratification effect, and the sedimentation pattern transformed from independent sedimentation to floc-type average sedimentation, which led to the enhanced water-retaining property of the settled layer. This may lead to an increase in the saturation line and a decrease in the length of the dry beach, seriously affecting the safe operation of the tailings pond. The research results provide some theoretical guidance and basic data for analyzing the consolidation efficiency of tailings and the stability of the tailings pond.

Photoelectrocatalytic Processes of TiO2 Film: The Dominating Factors for the Degradation of Methyl Orange and the Understanding of Mechanism.

Various thicknesses of TiO2 films were prepared by the sol-gel method and spin-coating process. These prepared TiO2 films exhibit thickness-dependent photoelectrochemical performance. The 1.09-µm-thickTiO2 film with 20 spin-coating layers (TiO2-20) exhibits the highest short circuit current of 0.21 mAcm-2 and open circuit voltage of 0.58 V among all samples and exhibits a low PEC reaction energy barrier and fast kinetic process. Photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TiO2 films was carried out under UV light. The roles of bias, film thickness, pH value, and ion properties were systematically studied because they are the four most important factors dominating the PEC performance of TiO2 films. The optimized values of bias, film thickness, and pH are 1.0 V, 1.09 µm, and 12, respectively, which were obtained according to the data of the PEC degradation of MO. The effect of ion properties on the PEC efficiency of TiO2-20 was also analyzed by using halide as targeted ions. The "activated" halide ions significantly promoted the PEC efficiency and the order was determined as Br > Cl > F. The PEC efficiency increased with increasing Cl content, up until the optimized value of 30 × 10-3 M. Finally, a complete degradation of MO by TiO2-20 was achieved in 1.5 h, with total optimization of the four factors: 1.0 V bias, 1.09-µm-thick, pH 12, and 30 × 10-3 M Cl ion content. The roles of reactive oxygen species and electric charge of photoelectrodes were also explored based on photoelectrochemical characterizations and membrane-separated reactors. Hydrogen peroxide, superoxide radical, and hydroxyl radical were found responsible for the decolorization of MO.

Substantial impact of surface charges on electrochemical reaction kinetics on S vacancies of MoS2 using grand-canonical iteration method.

The surface charges of catalysts have intricate influences on the thermodynamics and kinetics of electrochemical reactions. Herein, we develop a grand-canonical iteration method based on density functional theory calculations to explore the effect of surface charges on reaction kinetics beyond the traditional Butler-Volmer picture. Using the hydrogen evolution reaction on S vacancies of MoS2 as an example, we show how to track the change of surface charge in a reaction and to analyze its influence on the kinetics. Protons adsorb on S vacancies in a tough and charge-insensitive water splitting manner, which explains the observed large Tafel slope. Grand-canonical calculations report an unanticipated surface charge-induced change of the desorption pathway from the Heyrovsky route to a Volmer-Tafel route. During an electrochemical reaction, a net electron inflow into the catalyst may bring two effects, i.e., stabilization of the canonical energy and destabilization of the charge-dependent grand-canonical part. On the contrary, a net outflow of electrons from the catalyst can reverse the two effects. This surface charge effect has substantial impacts on the overpotential and the Tafel slope. We suggest that the surface charge effect is universal for all electrochemical reactions and significant for those involving interfacial proton transfers.

Electronegativity principle for hydrogen evolution activity using first-principles calculations.

The catalytic activity of a heterogeneous catalyst is routinely described by the Sabatier principle using molecule/proton adsorption energy ΔGH as the thermodynamic descriptor. This descriptor, however, fails in quantitatively tracking the reaction rate due to the lack of charge transfer information during a reaction. Herein, we use density functional theory (DFT) calculations combining both canonical and grand-canonical ensembles to report a positive correlation between reaction kinetics and interfacial charge transfer for the hydrogen evolution reaction (HER). The Sabatier relationship for the HER catalysts exhibits a large dispersion in the canonical calculation but an improved linearity under the grand-canonical ensemble, indicating that surface charges are indeed important. This charge effect can be well captured by the Mulliken electronegativity χ of a catalyst because the reaction barrier shows a linear dependence on χ for a wide range of catalysts. Specifically, a catalyst with lower electronegativity exhibits a lower barrier and thus a faster reaction rate. This electronegativity principle is reaction route and pH independent and is founded on the thermoneutral requirement on ΔGH.

Vacancy and strain engineering of Co3O4 for efficient water oxidation.

Co3O4 has been widely explored in electrocatalysis but seriously limited by its poor intrinsic ability. Defect engineering is an effective method to improve the electrocatalytic ability of catalysts by regulating electronic structure and optimizing the binding energy with surface adsorbates. Herein, in this work we have successfully integrated metal vacancies and tensile strain into Co3O4. With the formation of metal vacancies, the electronic structure of Co3O4 has been regulated. Moreover, the d-band center of Co3O4 has been modulated with the presence of tensile strain. The electrochemical oxygen evolution reaction (OER) ability of the obtained electrocatalyst was improved dramatically. The overpotential to reach 10 mA cm-2 was only 327 mV. Reaction kinetics was rapidly facilitated as indicated by smaller Tafel slope and charge transfer resistance. Density Functional Theory (DFT) calculations revealed that the relocated atoms induced the formation of tensile strain and made d-band center of electrocatalyst near to Fermi level leading to enhanced the adsorption to reaction intermediates. What's more, the free energy barrier of rate-determining step (RDS) has been decreased with the integration of metal vacancies and tensile strain. This work provides an efficient strategy to develop defective and effective electrocatalysts.

Molten salt-induced vertical CoP/Co nanosheets array coupled with carbon for efficient water splitting.

The exploration of high-efficiency non-noble metal catalysts for improving the intrinsic activity and active sites for overall water splitting persists as a bottleneck issue. Herein, a facile heterogeneous molten salt strategy has been proposed to fabricate CoP/Co nanosheets array that is vertically attached to a carbon matrix. Such a hierarchical structure endows the hybrid with abundant active sites and favorable reaction kinetics. Experimental results reveal that the molten salt determines the final shape of metallic Co, which is not sensitive to the organic sources. After optimization of the molten salt mass, the CoP/Co/C-6 shows the best bifunctional performance, requiring an overpotential of 132 mV and 320 mV at 10 mA cm-2 for hydrogen evolution reaction and oxygen evolution reaction, respectively. Theoretical simulation results manifest the CoP/Co heterostructure alters the electronic structure of Co and CoP, and reduces the adsorption free energy of intermediates, thus further boosting the electrocatalysis activity. This work proposes a molten salt-assisted method for the rational design of novel two-dimensional nano-hybrids for energy conversion applications.

Metabonomics analysis of flavonoids in seeds and sprouts of two Chinese soybean cultivars.

A popular food in China, soybean seeds and sprouts contained many biologically active substances which are beneficial to the human body, such as flavonoids. Northeast of China is the main producing area of soybean. The experimental materials came from the main soybean producing areas in Northeast China, this study compared flavonoids of two China cultivars of soybeans, Heinong52(HN52) and Heinong71(HN71). Here, we also considered the effects of germination on the chemical profile of flavonoids. Using a LC-ESI-MS/MS system, 114 differential flavonoid metabolites were identified. A total of 18 metabolites were significantly different between the two soybean varieties before germination, of which 14 were up-regulated and 4 were down-regulated. After germination, 33 significantly different metabolites were found in the two soybean sprouts, of which 19 were up-regulated and 14 were down-regulated. These experimental results revealed significant up-regulation of metabolites in soybean sprouts compared with soybean seeds, thus suggesting that soybean germination may increase content of flavonoid metabolites. There are six main pathways for the synthesis of flavonoids: isoflavonoid biosynthesis, flavonoid biosynthesis, flavone and flavonol biosynthesis, biosynthesis of secondary metabolites, and biosynthesis of phenylpropanoids. Soybean seeds lack flavone and flavanol biosynthesis and develop the capacity for this biosynthetic pathway after germination as sprouts. Isoflavonoid biosynthesis is the most abundantly utilized pathway.

On the Sensitivity to Density-Functional Approximations for CO Binding Energies of Single-Atom Catalysts in Nitrogen-Doped Graphene.

Density functional theory (DFT) methods are the working horse in screening new catalytic materials. They are widely used to predict trends in binding energies, which are then used to compare the activity of different materials. The binding strength of CO is an important descriptor to the CO2 reduction catalytic activity of the single transition metal atoms embedded on nitrogen-doped graphene (TM/NG). In this work, however, we show that CO binding strengths in different TM/NG has very different sensitivity to DFT methods. Specifically, Fe/NG CO binding energy changes dramatically with the percentage of exact exchange in the functional; Co/NG does less so, while Ni/NG nearly has no change. Such varying behaviors is a direct result of different local spin configurations, similar to the performance of DFT methods for metal porphyrin complexes. Therefore, caution should be exercised when using DFT binding energies for quantitative predictions in TM/NG single atom catalysis.

Defective Bimetallic Selenides for Selective CO2 Electroreduction to CO.

CO2 electroreduction (CO2 RR) to CO is promising for the carbon cycle but still remains challenging. Au is regarded as the most selective catalyst for CO2 RR, but its high cost significantly hinders its industrial application. Herein, the bimetallic CuInSe2 is found to exhibit an Au-like catalytic feature: i) the interaction of Cu and In orbitals induces a moderate adsorption strength of CO2 RR intermediates and favors the reaction pathway; and ii) the hydrogen evolution is energetically unfavorable on CuInSe2 , as a surface reconstruction along with high energy change will occur after hydrogen adsorption. Furthermore, the Se vacancy is found to induce an electron redistribution, slightly tune the band structure, and optimize the CO2 RR route of bimetallic selenide. Consequently, the Se-defective CuInSe2 (V-CuInSe2 ) achieves a highly selective CO production ability that is comparable to noble metals in aqueous electrolyte, and the V-CuInSe2 cathode shows a satisfactory performance in an aqueous Zn-CO2 cell. This work demonstrates that designing cost-effective catalysts with noble-metal-like properties is an ideal strategy for developing efficient electrocatalysts. Moreover, the class of transition bimetallic selenides has shown promising prospects as active and cost-effective electrocatalysts owing to their unique structural, electronic, and catalytic properties.

Seepage field characteristic and stability analysis of tailings dam under action of chemical solution.

As one of the important influencing factors of tailings dam stability, seepage field distribution within the dam is often affected by the tailings mineral characteristics. While the alkalinity or acidity of reservoir water and long term immersion will partially change the physical and mechanical properties of tailings. This study carried out permeability tests of tailings under the action of chemical solution. On this basis, a three dimensional (3D) model was constructed to analyze the velocity field and effective saturation within the tailings dam. Moreover, the dam section along the valley bottom was selected as the basic section in calculation, so as to analyze the changes in infiltration point and buried depth of the phreatic line under different permeability coefficient ratios. The results suggest that, under the action of acid-alkaline solution, the permeability coefficients of tailings reduced, and the stronger solution acidity-alkalinity resulted in the longer action time and more obvious change; under the action of chemical solution, the fluid flow velocity in the dam gradually decreased, and the drat beach length in the reservoir gradually shortened. Besides, when the upper layer permeability coefficients of tailings was lower than that of the lower layer, the dam phreatic line had a shallow buried depth and a high infiltration point.

Inversely Tuning the CO2 Electroreduction and Hydrogen Evolution Activity on Metal Oxide via Heteroatom Doping.

Tuning the electronic states near the Fermi level can effectively facilitate the reaction kinetics. However, elucidating the role of a specific electronic state of metal oxide in simultaneously regulating the CO2 electroreduction reaction (CO2 RR) and competing hydrogen evolution reaction (HER) is still rare, making it difficult to accurately predict the practical CO2 RR performance. Herein, replacing the Zn site by heteroatoms with different outer electrons (Mo and Cu) is found to tune both occupied and unoccupied orbitals near the Fermi level of ZnO. Moreover, the different electronic states significantly modulate both CO2 RR and HER activity with a totally inverse trend, thus dramatically tuning the practical CO2 RR performance. In parallel, the correlation between electronic states, reaction free energies and practical activity is demonstrated. This work provides a possibility for engineering efficient CO2 RR eletrocatalysts through tunable composition and electronic structures.

Author Correction: Molecular Simulations of Adsorption and Energy Storage of R1234yf, R1234ze(z), R134a, R32, and their Mixtures in M-MOF-74 (M = Mg, Ni) Nanoparticles.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Molecular Simulations of Adsorption and Energy Storage of R1234yf, R1234ze(z), R134a, R32, and their Mixtures in M-MOF-74 (M = Mg, Ni) Nanoparticles.

The refrigerant circulation heat can be enhanced through the mutual transformation between thermal energy and surface energy during the adsorption and separation process of fluid molecules in porous materials. In this paper, the adsorption and energy storage of R1234ze(z), R1234yf, R32 and R134a, as well as their mixed refrigerants in Mg-MOF-74 and Ni-MOF-74 nanoparticles were investigated by means of molecular dynamics simulations and grand canonical Monte Carlo simulations. The results suggested that, in the case of pure refrigerant adsorption, the adsorption quantities of R32 and R134a in MOFs were higher than those of R1234yf and R1234ze(z). However, in the case of saturation adsorption, the desorption heat of R32 was lower than that of R1234yf and R1234ze(z). The addition of MOF-74 nanoparticles (NPs) could enhance the energy storage capacity of the pure refrigerant; besides, R1234yf and R1234ze(z) nanofluids had superior enhancement effect to that of R32 nanofluid. In mixed refrigerant adsorption, the adsorption quantities of R1234ze(z) and R1234yf were lower than those of R32 and R134a; with the increase in temperature, the adsorption of R1234ze(z) and R1234yf showed a gradually increasing trend, while that of R32 was gradually decreased.

In vitro digestion and human gut microbiota fermentation of longan pulp polysaccharides as affected by Lactobacillus fermentum fermentation.

This study investigated the effect of Lactobacillus fermentum fermentation treatment on the gastrointestinal digestion and fermentation in vitro of polysaccharides from longan pulp. Polysaccharide isolated from unfermented and fermented longan pulp named LP and LP-F, respectively. The molecular weight of LP-F declined from 109.62 ± 10.66 kDa to 51.46 ± 6.26 kDa while that of LP declined from 221.63 ± 2.41 kDa to 69.68 ± 2.36 kDa with gastrointestinal digestion. At same time, the reducing sugars content of LP and LP-F were both increased significantly. In addition, after 48 h gut microbiota fermentation, there were more total short chain fatty acids and acetic acid, as well as more Enterococcus, Bifidobacterium, and Clostridium in LP-F fermentation culture than those in LP fermentation culture. Moreover, LP-F fermentation culture showed lower pH value and less residual carbohydrate percentage than that of LP. These results indicated that LP-F is easier than LP to be fermented by human gut microbiota.

Optimal Geometrical Configuration of Cobalt Cations in Spinel Oxides to Promote Oxygen Evolution Reaction.

MgCo2 O4 , CoCr2 O4 , and Co2 TiO4 were selected, where only Co3+ in the center of octahedron (Oh), Co2+ in the center of tetrahedron (Td), and Co2+ in the center of Oh, can be active sites for the oxygen evolution reaction (OER). Co3+ (Oh) sites are the best geometrical configuration for OER. Co2+ (Oh) sites exhibit better activity than Co2+ (Td). Calculations demonstrate the conversion of O* into OOH* is the rate-determining step for Co3+ (Oh) and Co2+ (Td). For Co2+ (Oh), it is thermodynamically favorable for the formation of OOH* but difficult for the desorption of O2 . Co3+ (Oh) needs to increase the lowest Gibbs free energy over Co2+ (Oh) and Co2+ (Td), which contributes to the best activity. The coexistence of Co3+ (Oh) and Co2+ (Td) in Co3 O4 can promote the formation of OOH* and decrease the free-energy barrier. This work screens out the optimal geometrical configuration of cobalt cations for OER and gives a valuable principle to design efficient electrocatalysts.

Genome-wide identification and expression analysis of the 14-3-3 gene family in soybean (Glycine max).

In eukaryotes, proteins encoded by the 14-3-3 genes are ubiquitously involved in the plant growth and development. The 14-3-3 gene family has been identified in several plants. In the present study, we identified 22 GmGF14 genes in the soybean genomic data. On the basis of the evolutionary analysis, they were clustered into ε and non-ε groups. The GmGF14s of two groups were highly conserved in motifs and gene structures. RNA-seq analysis suggested that GmGF14 genes were the major regulator of soybean morphogenesis. Moreover, the expression level of most GmGF14s changed obviously in multiple stress responses (drought, salt and cold), suggesting that they have the abilities of responding to multiple stresses. Taken together, this study shows that soybean 14-3-3s participate in plant growth and can response to various environmental stresses. These results provide important information for further understanding of the functions of 14-3-3 genes in soybean.

Genome-wide identification and expression analysis of the VQ gene family in soybean (Glycine max).

BACKGROUND: VQ proteins, the plant-specific transcription factors, are involved in plant development and multiple stresses; however, only few articles systematic reported the VQ genes in soybean. METHODS: In total, we identified 75 GmVQ genes, which were classified into 7 groups (I-VII). Conserved domain analysis indicated that VQ gene family members all contain the VQ domains. VQ genes from the same evolutionary branches of soybean shared similar motifs and structures. Promoter analysis revealed that cis-elements related to stress responses, phytohormone responses and controlling physical as well as reproductive growth. Based on the RNA-seq and qRT-PCR analysis, GmVQ genes were showed expressing in nine tissues, suggesting their putative function in many aspects of plant growth and development as well as response to stress in Glycine max. RESULTS: This study aims to understand the roles of VQ genes in various development processes and their expression patterns in responses to stimuli. Our results provide basic information in identification and classification of GmVQ genes. Further experimental analysis will allows us to know the functions of GmVQs participation in plant growth and stress responses.