Ultrasmall Bismuth Nanoparticles Supported Over Nitrogen-Rich Porous Triazine-Piperazine Polymer for Efficient Catalytic Reduction

The development of inexpensive and reusable nanocatalysts to convert the hazardous pollutant 4-nitrophenol (4-NP) into a valuable platform chemical 4-aminophenol (4-AP) is quite demanding due to environmental and public health concerns. Herein, we report a facile strategy for the preparation of supported Bi nanoparticles (NPs) over the surfaces of nitrogen-rich porous covalent triazine-piperazine-3D nanoflowers (BiNPs@3D-NCTP). SEM and TEM image analysis suggested 3D-flower-like morphology of the composite consisting of the self-assembly of interweaving and the slight bending of the nanoflakes. The powder X-ray diffraction (PXRD) analysis also confirmed the loading of Bi NPs. N2 sorption analysis suggested BET surface areas of 663 and 364 m2 g-1 for the 3D-NCTP and BiNPs@3D-NCTP materials, respectively. The large surface area, bimodal pores and 3D nanoflower architecture enable uniform loading of Bi nanoparticles, while its nitrogen-rich functionality stabilizes and acts as a capping agent restricting further nanoparticle expansion. BiNPs@3D-NCTP showed a 99.85 % conversion for the 4-NP to 4-AP within four minutes. The normalized rate constant of 38.3 min-1 mg-1 of BiNPs@3D-NCTP catalyst for the reduction of 4-NP suggested its superior catalytic efficiency. Nitrogen-rich functionality activates the catalytic site to accelerate the reaction, while bimodal pores can promote the diffusion of reactant molecules. After five catalytic cycles, the nanocatalyst showed high chemical stability and negligible activity loss.

Abatement of hydrated silica, arsenic, and coexisting ions from groundwater by electrocoagulation using iron electrodes

The paper deals with the removal of arsenic (As), hydrated silica (HS), and coexisting ions from groundwater by electrocoagulation (EC) using a laboratory-scale up-flow reactor with sacrificial iron anodes (1018 steel, >99% wt. Fe). Natural groundwater, taken in the northern region of Mexico, contained 25.7 μg L^-1 As, 237.8 mg L^-1 HS, 1.43 mg L^-1 F^-, 45.0 mg L^-1 SO₄^2-, 0.61 mg L^-1 PO₄^3-, pH 8.62, and 577 μS cm^-1 conductivity. The effect of current densities (4≤j≤8 mA cm^-2) and mean linear flow velocities (1.1≤u≤4.6 cm s^-1) on the pollutant's removal was systematically addressed. The best EC trial that showed the lowest overall cost and complied with the WHO guideline (<10 μg L^-1 As) was obtained at j = 6 mA cm^-2 and u = 2.3 cm s^-1, reaching residual concentrations of As and HS of 4.6 μg L^-1 and 150.0 mg L^-1, respectively. A large amount of HS was found after electrolysis; therefore, a second EC was applied to reduce the HS concentration further. This time, residual concentrations of HS and As of 37.0 mg L^-1 and 1.2 μg L^-1 were obtained, with electrolytic energy consumption and overall cost of EC of 0.872 kWh m^-3 and 0.178 USD m^-3, respectively. XRF, EDS, XRD, and FTIR analyzes on flocs indicate that hydrated silica reacts with iron, forming iron silicates with divalent cations as flocs. Arsenic and PO₄^3- are abated by adsorption on flocs. The modest removal of F^- and SO₄^2- (44% and 12%, respectively) is due to its weak adsorption on flocs.

G, Prabhakaran K, Joseph K, Salih A. Selective catalytic reduction of NO over hierarchical Cu ZSM-5 coated on an alumina foam support

Hydrothermal coating of hierarchical Cu ZSM-5 catalyst on alumina foam.

Cytotoxicity of mesoporous silica modified by amino and carboxyl groups on vascular endothelial cells

Mesoporous silica is widely used because of its unique and excellent properties, especially it can be used as a drug carrier and gene carrier in the biomedical field. After the mesoporous silica is put into clinical use, it is more likely to be exposed in human body. Therefore, the effect of mesoporous silica on human body cannot be ignored. The injury of vascular endothelial cells is a prerequisite for the occurrence of many cardiovascular diseases. As a drug and gene carrier, mesoporous silica increases its contact with vascular endothelial cells, so its toxic effect on cardiovascular system cannot be ignored. In this study, amino (NH₂ ) and carboxyl (COOH) were modified on mesoporous silica SBA-15 by post-grafting. The results showed that it still maintained the one-dimensional hexagonal mesoporous structure of SBA-15 and had typical mesoporous structure. Then human umbilical vein endothelial cells (HUVECs) were infected with SBA-15, NH₂ -SBA-15, and COOH-SBA-15. The results showed that the functionalized mesoporous silica SBA-15 had cytotoxicity to HUVECs and damaged the cell membrane, but compared with the unmodified mesoporous silica SBA-15 the cytotoxicity of functionalized mesoporous silica SBA-15 was lower and the toxicity of carboxyl modified group was the lowest. By comparing the cell inhibition rate and the expression level of lactate dehydrogenate and reactive oxygen species induced by the three materials, oxidative damage and cell membrane damage may be two mechanisms of cytotoxicity. Mesoporous silica SBA-15 has an effect on cardiovascular system by inducing the high expression of nitric oxide, intercellular adhesive molecule-1 and vascular cell adhesive molecule-1 in HUVECs. In summary, our results show that mesoporous silica is toxic to vascular endothelial cells.

Synergistic effects of Cu species and acidity of Cu-ZSM-5 on catalytic performance for selective catalytic oxidation of n-butylamine

In this work, a series of Cu-ZSM-5 catalysts with different SiO₂/Al₂O₃ ratios (25, 50, 100 and 200) were synthesized and investigated in n-butylamine catalytic degradation. The n-butylamine can be completely catalytic degradation at 350°C over all Cu-ZSM-5 catalysts. Moreover, Cu-ZSM-5 (25) exhibited the highest selectivity to N₂, exceeding 90% at 350°C. These samples were investigated in detail by several characterizations to illuminate the dependence of the catalytic performance on redox properties, Cu species, and acidity. The characterization results proved that the redox properties and chemisorption oxygen primarily affect n-butylamine conversion. N₂ selectivity was impacted by the Brønsted acidity and the isolated Cu²⁺ species. Meanwhile, the surface acid sites over Cu-ZSM-5 catalysts could influence the formation of Cu species. Furthermore, in situ diffuse reflectance infrared Fourier transform spectra was adopted to explore the reaction mechanism. The Cu-ZSM-5 catalysts are the most prospective catalysts for nitrogen-containing volatile organic compounds removal, and the results in this study could provide new insights into catalysts design for VOC catalytic oxidation.