Rhombic TiO2 grown on g-C3N4 nanosheets towards fast charge transfer and enhanced Cr(VI) and NO removal

Composite nanoarchitectonics with TiO2 nanocrystals and superior thin Ti3C2Tx nanosheets towards efficient NO removal

Accordion-like Ti₃C₂T_x MXene supplied a possibility to construct two-dimensional composites with novel performance. In this paper, few-layered Ti₃C₂T_x MXene was created via a chemical etching strategy. The oxidation in-situ using a powerful alkaline solution resulted successfully in TiO₂ nanocrystals grown on Ti₃C₂T_x nanosheets. The alkaline treatment adjusted terminations of the Ti₃C₂T_x MXene and controlled the oxidation degree by changing temperature. The ratio of Ti₃C₂T_x and TiO₂ was finally optimized. Because of Ti₃C₂T_x nanosheets with well conductivity and excellent light absorption as well as TiO₂ nanocrystal arrays on Ti₃C₂T_x nanosheets with a high specific surface area and more active sites, TiO₂/Ti₃C₂T_x composites revealed excellent photocatalystic activity, especially for NO removal. The improvement of separation and transfer efficiency of phootogenerated carriers is ascribed to the microstructure of TiO₂/Ti₃C₂T_x composites. The composite sample synthesized at 75 °C revealed the best NO removal efficiency, in which 70% of NO was removed at a concentration of 600 ppb. This study offers a new thought for preparing high performance MXene-based photocatalysts.

Removal of Chromium Species by Adsorption: Fundamental Principles, Newly Developed Adsorbents and Future Perspectives

Emerging chromium (Cr) species have attracted increasing concern. A majority of Cr species, especially hexavalent chromium (Cr(VI)), could lead to lethal effects on human beings, animals, and aquatic lives even at low concentrations. One of the conventional water-treatment methodologies, adsorption, could remove these toxic Cr species efficiently. Additionally, adsorption possesses many advantages, such as being cost-saving, easy to implement, highly efficient and facile to design. Previous research has shown that the application of different adsorbents, such as carbon nanotubes (carbon nanotubes (CNTs) and graphene oxide (GO) and its derivatives), activated carbons (ACs), biochars (BCs), metal-based composites, polymers and others, is being used for Cr species removal from contaminated water and wastewater. The research progress and application of adsorption for Cr removal in recent years are reviewed, the mechanisms of adsorption are also discussed and the development trend of Cr treatment by adsorption is proposed.

Role of a novel cationic gemini surfactant (CGS) on a one-step sol-gel process and photocatalytic properties of TiO2 powders

TiO₂ nanoparticles were prepared using a sol-gel process in combination with a novel cationic gemini surfactant (CGS) with amide functional groups at low temperatures. Titanium (IV) isopropoxide (TIP) and CGS were used as the starting materials and as effective agents, respectively, to orient the nanoparticles during the sol-gel synthesis. To reveal both the structural and morphological properties of the nanopowders prepared in this work, they were characterized using X-ray diffraction (XRD) analysis, scanning electron microscope (SEM), and Brunauer-Emmett-Teller (BET) surface area apparatus. The pore volume and pore size were calculated using the Barrett-Joyner-Halenda (BJH) model on the desorption branch. The experimental results show that the surface area and average crystallite size of the obtained TiO₂ nanopowders vary between 160-203 m²/g and 27-49 nm, respectively. It was observed that the N₂ adsorption-desorption isotherms for almost all samples of TiO₂-X% CGS (X: mass of CGS) show the typical Type I with a hysteresis loop of H4. The photocatalytic activities of the CGS-modified nanocomposites are evaluated not only by the photocatalytic degradation of methyl orange (MO) but also by the reduction of Cr(VI) as model pollutants in the presence of visible light.

A p–n heterostructural g-C3N4/PANI composite for the remediation of heavy metals and organic pollutants in water

A novel g-C3N4/PANI composite was fabricated via surface charge-induced electrostatic self-assembly method, which showed excellent a photocatalytic performance for Cr(vi) reduction and MO degradation under visible-light.