Sulphur and cerium co-doped mesoporous titanium dioxide photocatalysts and their photocatalytic activity in the degradation of methylene orange

A series of sulphur and cerium co-doped mesoporous titanium dioxide photocatalysts have been prepared by a template method using thiourea, ammonium ceric nitrate and tetrabutyl titanate as precursors and Pluronic P123 as a template. The morphology, crystal structure, surface structure and optical absorption properties of the prepared samples are characterized by scanning electron microscopy, X-ray diffraction, N2 adsorption-desorption measurements and UV-vis absorption spectra. The microcrystal of the co-doped photocatalyst comprises the anatase­ phase. Compared with mesoporous titanium dioxide, the co-doped samples extends the photoabsorption edge into the visible light region. The photocatalytic activities of the obtained photocatalysts under UV and visible light have been estimated by measuring the degradation rate of methylene orange in aqueous solution. Results show that the co-doped mesoporous titanium dioxide exhibits higher photocatalytic activity than mesoporous titanium dioxide under light irradiation. The synergistic effect of sulphur and cerium co-doping plays an important role in improving the photocatalytic activity.

Melatonin Treatment Inhibits the Growth of Xanthomonas oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae (Xoo) causes rice bacterial blight (BB), one of the most widespread and destructive diseases in rice-growing regions worldwide. Melatonin enhances pathogen resistance by inducing plant innate immunity, but the direct effect of melatonin on plant pathogenic bacteria is poorly understood. In this study, we investigated the direct effects of melatonin on Xoo. Exogenous melatonin at 200 μg/mL significantly inhibited the proliferation of Xoo and reduced the mRNA expression of five genes involved in cell division. This concentration of melatonin also inhibited the motility and biofilm formation of Xoo. Notably, melatonin was observed to alter the length of Xoo cells. To provide deeper insights into the mechanisms underlying this antibacterial activity, we examined global gene expression changes in Xoo strain PXO99 in response to the application of 200 μg/mL melatonin using RNA sequencing (RNA-Seq). A wide range of differentially expressed genes (DEGs) related to catalytic activity and metal-binding activity were downregulated in Xoo cells in response to the melatonin treatment. In addition, DEGs responsible for carbohydrate and amino acid metabolism were also downregulated. These results suggest that the inhibitory mechanism of melatonin on Xoo proliferation may involve the regulation of cell division in combination with a reduction in the concentration or activity of enzymes involved in metabolism

Low-Carbon Binder for Cemented Paste Backfill: Flowability, Strength and Leaching Characteristics

Blast furnace slag was used as the main raw material to prepare the alkali activated slag (AAS), a low-carbon binder, for cemented paste backfill (CPB). The optimum parameters for preparing the AAS binders using an orthogonal experiment were obtained. Under the optimum conditions (NaOH content was 3 wt. %, Ordinary Portland cement (OPC) content was 7 wt. %, and gypsum dosage was 4 wt. %), the 28 days compressive strength of the binder was 29.55 MPa. The flow ability of the fresh CPB slurry decreased with solid content due to the increased yield stress, while the flow ability increased when rising the binder dosage. A predictive model for the compressive strength of CPB samples was reached through multivariate analysis and the R2 values were higher than 0.9. Sensitivity analysis showed that the solid content is the most important parameter which influences on the development of the CPB strength with a correlation coefficient of 0.826. From the Toxicity Characteristic Leaching Procedure (TCLP) tests, the leaching concentrations of Pb and Cd were below the threshold. As a result, the AAS has potential application as an alternative binder and cemented paste backfill

Factors Affecting Brittleness Behavior of Coal-Gangue Ceramsite Lightweight Aggregate Concrete

Coal gangue, which is the solid waste produced during the coal processing, causes serious environmental problems. Lightweight concrete by making use of the coal-gangue ceramsite as the aggregate has many advantages as the construction material. However, the high brittleness of lightweight aggregate concrete is one of the problems for its application in building infrastructure. In this paper, the variation regularity, influencing factors and reinforcing/toughening method were studied as the reference data for future practical applications of coal-gangue ceramsite lightweight aggregate concrete (CGCLWAC). The results show that the brittleness of CGCLWAC increases with age, but the rate of the increase of brittleness keeps decreasing, and the brittleness is basically stable when the age beyond 28 days. When the sand ratio is above 0.38, the brittleness of CGCLWAC increases with the sand ratio; when the water cement ratio is above 0.32, the brittleness increases with the decrease of the water-cement ratio. Experiments show that when the content of steel fibers is less than 1.5%, the brittleness decreases with the increase of steel fiber content; when the content of steel fibers exceeds a critical value, the toughening effect decreases. From the macro-destructive morphology of the specimens, it is concluded that the incorporation of steel fibers can significantly change the brittleness of CGCLWAC. This study can serve to provide reference data for making use of the solid waste of the coal gangue and optimizing the infrastructure application scheme of CGCLWAC

<span style="font-size:15.0pt;mso-bidi-font-size:10.0pt" lang="EN-US">Preparation, characterization and photocatalytic activity of B, La co-doped mesoporous TiO₂ for methylene blue degradation </span>

1332-1337Mesoporous titanium dioxide co-doped with boron and lanthanum has been prepared by template method using boric acid triethyl ester, lanthanum nitrate hexahydrate&nbsp; and tetrabutyl titanate as precursors and Pluronic P123 as template. The as-prepared photocatalyst is characterized by thermogravimetric differential thermal analysis, N2 adsorption-desorption measurements, X-ray diffraction, scanning electron microscopy and UV-vis adsorption spectroscopy. The microcrystalline structure of the co-doped photocatalyst comprises the anatase phase and is present in the form of almost spherical particles. Compared with pure mesoporous TiO2, the photoabsorption edge of the B,<span style="font-size: 12.0pt;mso-bidi-font-size:10.0pt" lang="EN-US"> La co-doped samples extends into the visible light region. The photocatalytic performance has been studied by photodegradation of methyl blue in water under UV and visible light irradiation. The results of MB photodecomposition show that co-doped mesoporous TiO2 exhibits higher photocatalytic activity than pure mesoporous TiO2 under UV light irradiation. The synergistic effect of boron and lanthanum co-doping plays an important role in improving the photocatalytic activity. </span

Shrinkage and Strength Properties of Coal Gangue Ceramsite Lightweight Aggregate Concrete

It is a promising and effective method for waste treatment by using coal gangue to make lightweight aggregate concrete. However, lightweight aggregate concrete with low-density coal gangue ceramsite is prone to cracking during volume shrinkage, which limits its application in the construction industry. In an attempt to resolve the problem of cracking in shrinkage, this study investigated the effect of prewetting time and shrinkage reducing agents on shrinkage volume and concrete strength through a series of concrete shrinkage and strength tests. The experimental results show that shrinkage volume reduced at a prewetting time of 12 hrs or with a 2% addition of D-230 polyether amine reductant. With the optimal conditions of 12 hrs prewetting time and 2% addition of the reductant, the concrete shrinkage volume significantly decreased with a negligible impact on its strength. Appropriate amount of shrinkage reducing agent and adjustment of prewetting time of coal gangue ceramsite are necessary to reduce the shrinkage rate and improve the stability of the specimen. This is of great significance to wide application of lightweight aggregate concrete with coal gangue ceramsite

Microstructural and Mechanical Properties of Alkali Activated Materials from Two Types of Blast Furnace Slags

This paper investigated the effect of blast furnace slags (BFS) characteristics on the properties achievement after being alkali activated. The physical and chemical characteristics of BFS were determined by X-ray fluorescence (XRF), X-ray Diffraction (XRD) and laser granulometry. Multi-technical characterizations using calorimetry, XRD, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG-DTG), scanning electron microscope (SEM), nitrogen sorption and uniaxial compressive strength (UCS) were applied to give an in-depth understanding of the relationship between the reaction products, microstructure and BFS characteristics. The test results show that the microstructure and mechanical properties of alkali activated blast furnace slags (BFS) highly depend on the characteristics of BFS. Although the higher content of basic oxide could accelerate the hydration process and result in higher mechanical properties, a poor thermal stabilization was observed. On the other hand, with a higher content of Fe, the hydration process in alkali activated BFS2 lasts for a longer time, contributing to a delayed compressive strength achievement

Fly Ash/Blast Furnace Slag-Based Geopolymer as a Potential Binder for Mine Backfilling: Effect of Binder Type and Activator Concentration

This article investigated the potential of fly ash (FA)/blast furnace slag- (BFS-) based geopolymer as a novel backfilling material. The effects of NaOH concentration and FA/BFS mass ratio were explored through XRD, FTIR, and TG-DTG analyses. The results indicated that the reaction products and strengths of geopolymer depended on the NaOH concentration and types of source materials. Slump, final setting time, and setting ratio increased as a function of FA content. However, the increase in FA content reduced the compressive strength and microstructure of the backfilling material (BM) due to the lower reactivity than BFS. Microstructure analysis reveals that the matrix tends to be denser with the BFS content and NaOH concentration increase

Preparation and characterization of visible light-driven praseodymium-doped mesoporous titania coated magnetite photocatalyst

1257-1262A visible light-driven magnetic composite photocatalyst, viz., (Pr/MTiO2/Fe3O4), has been prepared by coating photoactive praseodymium-doped mesoporous titania (Pr/MTiO2) onto magnetic Fe3O4 via hydrolysis of tetrabutyl titanate (Ti(OBu)4) with Pr(NO3)3•6H2O and Ti(OBu)4 as precursors in the presence of Fe3O4 particles. The photocatalytic activities of the obtained photocatalysts under visible light are estimated by measuring the degradation rate of methylene orange in aqueous solution. Results show that the prepared photocatalyst is activated by visible light and may be used as effective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst is also confirmed; ca. 88% of the photocatalytic activity of as-prepared Pr/MTiO2/Fe3O4 is retained after being used four times. Moreover, the photocatalyst can be easily recovered by application of external magnetic field and reused without any mass loss up to four cyclicity. The photocatalyst therefore may be potentially applied for the treatment of water contaminated by organic pollutants.<span style="mso-bidi-font-size: 9.0pt;font-family:" times="" new="" roman","serif";letter-spacing:-.1pt"="" lang="EN-GB"> </span