Synergistic Effect of Sr-O Divacancy and Exposing Facets in SrTiO3 Micro/Nano Particle: Accelerating Exciton Formation and Splitting, Highly Efficient Co2+ Photooxidation.

As a typical perovskite-type crystal, polyhedral strontium titanate (SrTiO3 ) has shown anisotropic charge transport behavior in recent studies, however, the carrier transportation and transition of which has not been explained very clearly. This work present the existence of Sr and O divacancies in the novel rhombicuboctahedron SrTiO3 micro/nano particles (Sr1- x TiO3- x /TiO2- x ) with exposing (100), (110) and (111) facets and the diameter of 300-700 nm synthesized via hydrothermal synthesis, and also summarizes the dissociation mechanism of self-trapped excitons (STEs) caused by the divacancy and facet effect. In addition, most importantly, the metastable STEs with ultra-low binding energy (Eb  < 3 meV) under illumination are discovered. Combining the model of S-scheme heterojunction, a conversion mechanism of photoinduced carriers is proposed. The photocatalytic reaction of Co2+ is used as the probe reaction, and the unique Sr1- x TiO3- x /TiO2- x possesses a high photooxidation efficiency of Co2+ , by which 70.3% of Co2+ is oxidized to Co3+ (CoOOH) in 5 min. This finding may provide a guideline for an optimal design of the photocatalytic materials for the recovery and extraction of metal ions based on SrTiO3 .

Design and application of a dust suppression technology of the forcing air curtain in fully mechanized rock tunnelling faces.

To effectively reduce high dust concentrations and keep clean air in fully mechanized rock tunnelling faces in coal mine, this study carried out a research of dust suppression technology of the forcing air curtain. First, the mechanism of dust diffusion controlled by the forcing air curtain was introduced in this study. Then, numerical simulations of the formation of the forcing air curtain as well as the influence for dust diffusion under the different distance between forcing air duct outlet and heading end were carried out. Moreover, a dust suppression technology of the forcing air curtain was designed and tested in a fully mechanized rock tunnelling face of southern return air tunnel which was located in the Tangkou coal mine of China. It shows that the numerical simulation results were in good agreement with the in situ tests. The average removal rate of total and respirable dust could reach up to 95.1% and 96.1%, respectively, at manned working areas in the tunnel. Research results show that the dust suppression technology of the forcing air curtain is an effective method of dust control in fully mechanized rock tunnelling faces.

strong synergistic effect of the (110) and (100) facets of the SrTiO3 perovskite micro/nanocrystal: decreasing the binding energy of exciton and superb photooxidation capability for Co2.

Crystal facet regulation is an effective method for preparing SrTiO3 or other perovskite semiconductor materials with high photochemical catalysis performance. In general, the edge-truncated cube of SrTiO3 micro-nano particles has been widely reported because of the multiple crystal facets exposed at the same time. However, the effect of the (110) facet and the interaction between the (100) and (110) facets on the properties of photo-induced carriers is still not very clear. In this article, we have designed and prepared two edge-truncated cube SrTiO3-a small and large area proportion of the (110) facet, respectively. In addition to the morphological and structural characterization, high-resolution XPS and femtosecond multiphoton transient absorption (fs-TA) spectroscopy were used to detect the atomic vacancy and were applied to confirm the state of carrier transition. The results showed that the larger (110) facet led to two influences-more Sr vacancies and more self-trapping excitons (STEs) with an ultra-low binding energy (Eb = 2.13 meV), about 1.17 meV lower than that of the sample with the smaller (110) facet. In particular, the larger (110) facet also caused a much higher photooxidation performance for Co2+ to Co3+. This study not only enriches the arsenal of SrTiO3 materials but also sheds new insights into the understanding of the synergistic effect essence of the (100) and (110) facets, which could promote the development of new perovskite photocatalytic materials, particularly in the recovery of heavy metals.

Effects of press-in airflow rate and the distance between the pressure duct and the side wall on ventilation dust suppression performance in an excavating tunnel.

The efficiency of mine excavation has been significantly enhanced by continuing improvements in tunneling capabilities; however, this has also resulted in serious environmental pollution and greater safety risks for workers. To ensure safe production, the focus of this study is on the effect of varying the air pressure and the distance between the air pressure cylinder and the side wall settings on dust dispersion behavior and dust control in excavated tunnels. We also investigated temporal-spatial dust diffusion rules in tunnels by combining numerical simulation data with field measurement results. Through further analysis, when the pressure air volume and the exhaust air volume are both equal to 250 m3/min, the dust diffusion distance could be fitted as: [Formula: see text]. When the exhaust air volume is equal to 250 m3/min, dust control effects were improved as the pressure air volume decreased, becoming optimal when the pressure air volume dropped to 150 m3/min. Under these conditions, areas of high dust pollution were contained within 16 m of the cutting face, and the dust diffusion distance satisfied the formula: [Formula: see text]. When the pressure air volume is fixed, the change of the distance between the pressure air cylinder and the side wall has little effect on the dust diffusion. When the distance is 1.5 m, the dust control effect is the best, and the high dust pollution area is controlled within 14 m of the cutting surface. This alleviated dust pollution to a certain degree, thereby enhancing the air quality and ensuring safer production. This study provides a new understanding of the environmentally sustainable development of tunnels and is of great significance for clean production.

The control effect of 3D spiral wind-curtain generator on respirable dust pollution during tunnelling process.

The respirable dust pollution produced in the cutting process of tunnelling machine during tunnelling process is a serious threat to the health of workers. The key to solve this problem is to build an effective ventilation system in the tunnel. In this paper, experiments were designed and implemented to obtain the temporal-spatial evolution of respirable dust pollution before and after the 3D spiral wind-curtain generator was used for tunnel auxiliary ventilation, and the CFD method was used to supplement and visualize the experimental results. Before the 3D spiral wind-curtain generator was used, the respirable dust gradually diffused from the cutting face to other spaces of the tunnel, and finally presented a stable state with time. After using the 3D spiral wind-curtain generator for auxiliary ventilation, the dust diffusion speed in the tunnel was slower than before, and the dust concentration was lower than before. When adjusting the position of the generator and installing it 20m away from the cutting face, an effective dust control wind-curtain formed within the range of 3.5 ~ 6.5m away from the cutting face. With the increase of time, the dust is stably controlled within the space of 4.5m away from the cutting face, and then pumped away by the exhaust fan, so as to purify the tunnel environment and ensure the tunnel's cleanliness and safety and efficient excavation.

Effect of spraying on coal dust diffusion in a coal mine based on a numerical simulation.

Aimed at effectively controlling coal dust pollution in the mining face of a coal mine, this study first conducted a theoretical analysis and then combined a spraying experiment and a numerical simulation to perform an in-depth examination of the atomizing characteristics and dust suppression performance of a coal cutter external spraying device. Based on the experimental spraying results, the optimal nozzle was determined to be a pressure round-mouth nozzle with an X-shaped core. The characteristics of the spray fields from nozzles of different calibers (1.6, 2.0 and 2.4 mm) at different spraying pressures (2, 4, 6 and 8 MPa) were then analyzed. It was found that the droplet concentration in the spray field increased with increasing spraying pressure and nozzle caliber. The droplet diameter was mainly dependent on the spraying pressure and varied more slowly with increased spraying pressure. At a spraying pressure of 8 MPa, the spray field formed could achieve effective dust suppression; specifically, the droplet concentration in the spray field was mostly more than 15 g/m3, and the droplet size was mainly distributed in the range of 30-100 µm. When using a 2.4 mm caliber nozzle, the dust concentration measured around the coal cutter operator was reduced to 87.21 mg/m3 under a spraying pressure of 8 MPa, suggesting adequate dust suppression.

Near-UV photooxidation of As(III) by iron species in the presence of fulvic acid.

Photooxidation of As(III) in ternary As(III) - Fe(III) - Fulvic acid system at pH 4 was investigated by optical spectroscopy, steady-state photolysis (365 nm) and atomic-emission spectrometry with inductively coupled plasma techniques. It was found that at all values of [FA]/[Fe] ratio the main photoactive species is OH radical formed by photolysis of Fe(III) hydroxocomplexes. Addition of fulvic acid leads to mainly negative effect on As(III) photooxidation due to the following reasons: (i) slow dark reduction of photoactive Fe(III) species with formation of scattering particles and photoinert Fe(II) species; (ii) formation of photoreductive Fe(III)-FA complexes incapable to oxidize As(III), (iii) competition of both FA and Fe(III)-FA complexes for UVA quanta with FeOH2+ complex and for OH radicals with As(III). Aging of ternary system is also very important parameter leading to one order decrease of quantum yields of both Fe(II) formation and As(III) photooxidation.