In order to investigate the dissolution-releasing characteristics of the pollutants in coal gangue, this article carries out soaking experiment of coal gangue in different wind erosion degree of XINQIU strip mine under different conditions. The results show that the main dissolution releasing pollutants of the coal gangue are total hardness (CaCO 3 ), sulfate (SO 4 2- ), natrium (Na + ), total dissolved solid (TDS), fluoride (F - ), COD Mn , and total iron (Fe). Chloride (Cl - ), manganese (Mn) and zinc (Zn) occur in small quantities and heavy metals and arsenic (As) in trace concentration. The pH scale is nearly neutral. The higher the wind erosion degree is, the larger the quantity of the inorganic pollutants released by the gangue is. The quantity of the inorganic pollutants released by mixed coal gangue in high wind erosion degree inside the mountaintop is larger. Fluoride (F - ), oxygen consumed (OC), and total Fe are released by fresh mixed coal gangue in higher concentration. Soaking time, solid-to-liquid ratio, acidity, granularity and stirring have a significant impact on the dissolution-releasing of the pollutants. The longer the soaking time, the smaller the solid-to-liquid ratio, the stronger the acidity, the smaller the granularity and the faster the stirring intensity is, the quicker the rate of the pollutants dissolution-releasing is and the larger the total quantity of the pollutants is. Which can accelerate the dissolution-releasing of the pollutants which is controlled by diffusion.
Gas-phase synthesized binary nanoparticles (NPs) possess ultraclean surfaces, which benefit versatile uses in sensors and catalysts. However, precise control of their configuration and properties is still a big challenge because the growth mechanism and phase evolution dynamics in these NPs are very hard to unveil. Here, we report a strategy to investigate the phase evolution dynamics in binary NPs by using e-beam assisted ultrafast local heating and cooling inside a transmission electron microscope. With this strategy, the phase segregation and corresponding shape evolution of PbBi NPs are in situ revealed. It is found that the as-prepared PbBi alloy NPs will transform into heterostructures under e-beam stimulated structural relaxation, leading to the formation of featured Janus configurations with faceted Bi polyhedron parts and intermetallic hemisphere parts. During phase segregation, Pb1Bi1 and Pb7Bi3 phases are captured and identified, and a model of phase and shape evolution of PbBi nanoalloys is developed and contrasted with that of their bulk counterparts. These findings benefit the understanding of the phase dynamics of binary NPs and can provide in-depth information for engineering their structures for practical applications.
We report a quantitative analysis of the symmetry reduction phenomenon involved in the seed-mediated growth of Pd nanocrystals under dropwise addition of a precursor solution. In addition to the elimination of self-nucleation, the dropwise approach allows for the formation of a steady state for the number of precursor ions in the growth solution, which only fluctuates in a narrow range defined by experimental parameters such as the initial concentration of precursor solution and the injection rate. We can deterministically control the growth mode (symmetric vs asymmetric) of a seed by tuning these parameters to quantitatively manipulate the reaction kinetics and thus the lower and upper limits that define the steady state. We demonstrate that there exists a correlation between the growth mode and the lower limit of precursor ions in the steady state of a seed-mediated growth process. For the first few drops of precursor solution, the resultant atoms will only be deposited on a limited number of available sites on the seed if the lower limit of the steady state is below a critical value. Afterward, the deposition of atoms will be largely confined to these initially activated sites to induce symmetry reduction if atom deposition is kept at a faster rate than surface diffusion by controlling the lower limit of precursor ions in the steady state. Otherwise, the migration of atoms to other regions through surface diffusion can access other sites on the surface of a seed and thus lead to the switch of growth mode from asymmetric to symmetric. Our study suggests that symmetry reduction can only be initiated and retained by keeping the atom deposition at a rate slow enough to limit the number of initial nucleation sites on a seed but fast enough to beat the surface diffusion process.
Abstract Rechargeable metal–air batteries and water splitting are highly competitive options for a sustainable energy future, but their commercialization is hindered by the absence of cost-effective, highly efficient and stable catalysts for the oxygen evolution reaction. Here we report the rational design and synthesis of a double perovskite PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+ δ nanofiber as a highly efficient and robust catalyst for the oxygen evolution reaction. Co-doping of strontium and iron into PrBaCo 2 O 5+ δ is found to be very effective in enhancing intrinsic activity (normalized by the geometrical surface area, ∼4.7 times), as validated by electrochemical measurements and first-principles calculations. Further, the nanofiber morphology enhances its mass activity remarkably (by ∼20 times) as the diameter is reduced to ∼20 nm, attributed to the increased surface area and an unexpected intrinsic activity enhancement due possibly to a favourable e g electron filling associated with partial surface reduction, as unravelled from chemical titration and electron energy-loss spectroscopy.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
