Chen Wang

Nano-titanium dioxide (TiO₂) is currently the most widely studied photocatalyst. However, its rapid recombination of photogenerated carriers and narrow range of light absorption have limited its development. Crystal form regulation and polymer modification are important means for improving the photocatalytic activity of single-phase materials. In this paper, TiO₂ materials of different crystal forms were prepared by changing the synthesis conditions, and they were compounded with trimesoyl chloride–melamine polymers (TMPs) by the hydrothermal synthesis method. Then, their photocatalytic performance was evaluated by degrading methylene blue (MB) under visible light. The mechanisms of influence of TiO₂ crystal form on the photocatalytic activity of TiO₂-TMP were explored by combining characterization and theoretical calculation. The results showed that the TiO₂ crystal form, through interface interaction, the built-in electric field intensity of the heterojunction, and active sites, affected the interface charge separation and transfer, thereby influencing the photocatalytic activity of TiO₂-TMP. In the 4T-TMP photocatalytic system, the degradation rate of MB was the highest. These studies provide theoretical support for understanding the structure–property relationship of the interfacial electronic coupling between TiO₂ crystal forms and TMP, as well as for developing more efficient catalysts for pollutant degradation.

We investigated the growth-promoting mechanism of salt-tolerant plant growth promoting rhizobacteria (ST-PGPR) in wheat under sodium chloride (NaCl) stress by measuring the growth and physiological and biochemical responses of wheat plants inoculated with ST-PGPR under 0–400 mM NaCl. The results showed that ST-PGPR plays a significant role in the growth of wheat under NaCl stress. Under 300 mM NaCl, wheat plants inoculated with the three ST-PGPR strains increased in plant height, root length, dry weight, and fresh weight by 71.21%, 89.19%, 140.94%, and 36.31%, respectively, compared to the control group. The proline and soluble sugar contents of wheat inoculated with Bacillus thuringiensis increased by 38.8% and 21.4%, respectively. The average content of antioxidant enzymes increased by 13.89%, and compared with the control, in wheat inoculated with the three species of ST-PGPR, the average content of ethylene decreased 2.16-fold. In addition, a mathematical model based on the “interaction equation” revealed that the best results of mixed inoculation were due to the complementary strengths of the strains. The analysis of experimental phenomena and data revealed the mechanisms by which Brevibacterium frigoritolerans, Bacillus thuringiensis, and Bacillus velezensis alleviate NaCl stress in wheat: (1) by lowering of osmotic stress, oxidative stress, and ethylene stress in wheat and (2) by using root secretions to provide substances needed for wheat. This study provides a new approach for the comprehensive understanding and evaluation of ST-PGPR as a biological inoculant for crops under salt stress.

Ru Wang, Chen Wang, Qing Feng, Rey-May Liou, and Ying-Feng Lin. J. Microbiol. Biotechnol. 2021;31:398-407. https://doi.org/10.4014/jmb.2009.09032

The discharge of industrial wastewater containing dyes is a matter of concern because dyes have harmful effects on the environment and human health. In this work, a novel magnetic separation agent of Fe₃O₄/poly (acrylamide-acryloyloxyethyl thimethylammonium chloride) [MCPAM] was designed for high-performance removal dyes by taking advantage of magnetic separation property of Fe₃O₄ nanoparticles. MCPAM was synthesized through inverse emulsion polymerization and the optimal reaction conditions were obtained by orthogonal experiments. The shape and size of MCPAM was detected by transmission electron microscopy (TEM). The chemical bonds and functional groups of MCPAM were measured by fourier transform infrared spectroscopy (FT-IR). The magnetic properties of MCPAM was surveyed by Superconducting Quantum Interference Device (SQUID MPMSXL). The magnetic separation performance of MCPAM was studied through detecting the removal efficiency of reactive red dye X-3B. The results showed that the MCPAM had core-shell structures and good magnetic properties. And the MCPAM has great potential in accelerating solid-liquid separation and improving removal efficiency of pollutants such as dye colloid in wastewater.

The ordinary flocculants rely on gravity settling for solid-liquid separation, it is difficult to meet the requirements of wastewater treatment in short flocculation settling time, few sludge production and low moisture content. A new type of flocculant is required to solve these difficulties. Magnetic materials are given more attention because of the magnetism in magnetic field. It is significant to prepare magnetic composite flocculant to realize solid-liquid separation with the combined effects of both gravity and external magnetic field. The gelatin-based magnetic flocculant consisted of poly (acrylamide-co-acryloyloxyethyl thimethylammonium chloride) grafted gelatin-coated Fe₃O₄ [magnetic poly (AM-co-DAC)-g-gelatin] was prepared in this article. A Box-Behnken design for determination of optimal plan with three-level and three-variable was designed. The best conditions of preparing magnetic poly (AM-co-DAC)-g-gelatin were determined. The structure of magnetic poly (AM-co-DAC)-g-gelatin was studied by infrared spectrum and its magnetic properties were characterized by magnetic hysteresis loop. The flocculation of magnetic poly (AM-co-DAC)-g-gelatin was compared with conventional flocculant. The flocculation experiment results showed that the magnetic poly (AM-co-DAC)-g-gelatin was effective for removal of turbidity and significantly reduced the settling time of flocs, compared to conventional flocculants.

Tris-(2,3-dibromopropyl) isocyanurate (TBC) is a brominated flame retardant, which has been found in several environmental and biological matrices in recent years. TBC has aroused high environmental concerns because of its bioaccumulation and biological toxicity. This work studied photodegradation of TBC for the first time. The optimal degradation conditions have been found that 95% of 10 μmol/LTBC was effectively decomposed after 120 min of UV radiation. UV lamp was found to be more effective than Xe lamp on the photodegradation. The degradation rate of TBC increased with increasing light intensity. Under UV illumination, the effect of pH on the photodegradation of TBC could be ignored and degradation reactions followed the pseudo-first-order kinetics. The addition of could not accelerate the degradation of TBC. The quenching experiments showed that TBC was directly photodegraded by UV illumination. These findings suggest that UV photodegradation is a potential method for the removal of TBC in aqueous solutions.