Template-free synthesis of inorganic hollow spheres at water/"water-brother" interfaces as Fenton-like reagents for water treatment

Carbon-Based Nanocomposites as Fenton-Like Catalysts in Wastewater Treatment Applications: A Review

Advanced oxidation (e.g., fenton-like reagent oxidation and ozone oxidation) is a highly important technology that uses strong oxidizing free radicals to degrade organic pollutants and mineralize them. The fenton-like reactions have the characteristics of low cost, simple operation, thorough reaction and no secondary pollution. Fenton-like reagents refer to a strong oxidation system composed of transition metal ions (e.g., Fe3+, Mn2+ and Ag+) and oxidants (hydrogen peroxide, potassium persulfate, sodium persulfate, etc). Graphene and carbon nanotube possess a distinctive mechanical strength, flexibility, electrical and thermal conductivity and a very large specific surface area, which can work as an excellent carrier to disperse the catalyst and prevent its agglomeration. Fullerene can synergize with iron-based materials to promote the reaction of hydroxyl groups with organic pollutants and enhance the catalytic effect. Fenton-like catalysts influence the catalytic behavior by inducing electron transfer under strong interactions with the support. Due to the short lifespan of free radicals, the treatment effect is usually enhanced with the assistance of external conditions (ultraviolet and electric fields) to expand the application of fenton-like catalysts in water treatment. There are mainly light-fenton, electro-fenton and photoelectric-fenton methods. Fenton-like catalysts can be prepared by hydrothermal method, impregnation and coordination-precipitation approaches. The structures and properties of the catalysts are characterized by a variety of techniques, such as high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption near-edge structure spectroscopy. In this paper, we review the mechanisms, preparation methods, characterizations and applications status of fenton-like reagents in industrial wastewater treatment, and summarize the recycling of these catalysts and describe prospects for their future research directions.

Melt Electrospinning Writing of Magnetic Microrobots

The magnetic microrobots actuated by an external magnetic field can access distant, enclosed, and small spaces under fuel-free conditions, which is apromising technology for manipulation and delivery under microenvironment; however, the complicated fabrication method limits their applications. Herein, three techniques including melt electrospinning writing (MEW), micromolding, and skiving process are combined to successfully mass-produce tadpole-like magnetic polycaprolactone/Fe3O4 (PCL/Fe3O4) microrobot. Importantly, the tadpole-like microrobots under an external magnetic field can achieve two locomotions: rolling mode and propulsion mode. The rolling motion can approach the working destination quickly with a speed of ≈2 mm s-1. The propulsion motion (0-340 µm s-1) can handle a microcargo. Such a simple and cost-effective production method shows a great potential for scale-up fabrication of advanced shape-design, mass-production, and multifunctionality microrobot.

Hollow TiO2 spheres with improved visible light photocatalytic activity synergistically enhanced by multi-stimulative: Morphology advantage, carbonate-doping and the induced Ti3

Great efforts have been devoted to improve the photocatalytic activity of TiO₂ in the visible light region. Rational design of the external structure and adjustment of intrinsic electronic status by impurity doping are two main effective ways to achieve this purpose. A facile one-pot synthetic approach was developed to prepare C-doped hollow TiO₂ spheres, which simultaneously realized these advantages. The synthesized TiO₂ exhibits a mesoporous hollow spherical structure composed of fine nanocrystals, leading to high specific surface area (~180m²/g) and versatile porous texture. Carbonate-doping was achieved by a post-thermal treatment at a relatively low temperature (200°C), which makes the absorption edge red-shifted to the visible region of the solar spectrum. Concomitantly, Ti³⁺ induced by C-doping also functions in improving the visible-light photocatalytic activity by reducing the band gap. There exists a synergistic effect from multiple stimulatives to enhance the photocatalytic effect of the prepared TiO₂ catalyst. It is not out of expectation that the as-prepared C-doped hollow TiO₂ spheres exhibits an improved photocatalytic activity under visible light irradiation in organic pollutant degradation.