Changes in levels of N-nitrosamine formed from amine-containing compounds during chloramination via photocatalytic pretreatment with immobilized TiO2: Effect of source water and pH

We investigated the effectiveness of photocatalytic pretreatment (PCP) of precursors in minimizing the formation potentials (FPs) of carcinogenic nitrosamines, including N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), and N-nitrosodiethanolamine (NDELA), during water chloramination. A steel mesh substrate with immobilized TiO2 was highly efficient at mitigating nitrosamine formation and removing targeted precursors such as ranitidine, nizatidine, trimebutine, triethanolamine, and metoclopramide. Compared to UVC/H2O2, PCP under UVA irradiation (intensity of 0.67 mW cm−2) was more effective for reducing nitrosamine-FPs during post-chloramination. However, the PCP efficacies varied with the water source, pretreatment pH, and irradiation time. For example, PCP of eutrophic water increased the NDMA-FPs, but produced notable reductions (up to 99%) for NDELA- and NDEA-FPs. Shorter irradiation times, up to 15 min, increased the NDELA-FP in triethanolamine, and the NDMA-FP in nizatidine and trimebutine. However, the nitrosamine-FP decreased by > 50% after PCP at a pH > 5.6, following irradiation for 120 min. Oxygen addition, N-de(m)ethylation, and N-dealkylation were responsible for decreasing nitrosamine-FPs via the destruction of key moieties; this has been elucidated by mass spectroscopy. This study suggests that PCP could be used as an alternative strategy for minimizing nitrosamine-FPs during water treatment.11Nsciescopu

Doped and immobilized titanium dioxide photocatalysts as a potential source of nitrosamine formation

© 2023 The AuthorsImmobilized and visible-light-active titanium dioxide (TiO2) is widely used for water treatment. However, the accelerated generation of degradation byproducts is a potential risk of TiO2-based photocatalysis. This study aimed to investigate the structural effect of engineered TiO2 samples on the formation of major nitrosamines during photocatalysis. The nitrogen-containing impurities and leached metal ions from doped-TiO2 samples could exacerbate nitrosamine formation potential (FP) in distilled water, secondary effluent, and chloraminated water. Doped-TiO2 with 2-ethylimidazole, trimethylamine, triethylamine, and N-carbon nanotubes could leach in the range of 47–64 ng L−1 nitrosamines (including N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitrosodimethylamine, and N-nitrosopyrrolidine) even under dark conditions. Furthermore, we investigated the role of metal dopants on nitrosamine-FP during the chloramination of precursors such as dimethylamine and microcystin-LR. Metal ions such as Cu that leached from the metal-doped catalysts may catalyze the nitrosamine-FP. Therefore, pre-purification (washing) and immobilization of doped-TiO2 samples on substrates are suggested to remove a considerable amount of nitrosamines. However, during the prolonged tryout, the selection of substrates was critical. Polymeric supports, such as polyimide and polyvinylpyrrolidone, can produce up to 85 ng L−1 nitrosamine, whereas TiO2 immobilized onto steel mesh can remove nitrosamine formation during photocatalytic oxidation followed by chloramination. This study systematically screened a diverse range of dopants, supports, and solvents in engineered TiO2 photocatalysts, in 61 samples, and provided novel insights into their effect on nitrosamine formation.11Nsciescopu

Highly Efficient Catalytic Cyclic Carbonate Formation by Pyridyl Salicylimines

Cyclic carbonates as industrial commodities offer a viable nonredox carbon dioxide fixation, and suitable heterogeneous catalysts are vital for their widespread implementation. Here, we report a highly efficient heterogeneous catalyst for CO₂ addition to epoxides based on a newly identified active catalytic pocket consisting of pyridine, imine, and phenol moieties. The polymeric, metal-free catalyst derived from this active site converts less-reactive styrene oxide under atmospheric pressure in quantitative yield and selectivity to the corresponding carbonate. The catalyst does not need additives, solvents, metals, or co-catalysts, can be reused at least 10 cycles without the loss of activity, and scaled up easily to a kilogram scale. Density functional theory calculations reveal that the nucleophilicity of pyridine base gets stronger due to the conjugated imines and H-bonding from phenol accelerates the reaction forward by stabilizing the intermediate

Synthesis and Easy Functionalization of Highly Porous Networks through Exchangeable Fluorines for Target Specific Applications

Synthesis and Easy Functionalization of Highly Porous Networks through Exchangeable Fluorines for Target Specific Application

Nanoporous networks as caging supports for uniform, surfactant-free Co3O4 nanocrystals and their applications in energy storage and conversion

We report a new, surfactant-free method to produce Co3O4 nanocrystals with controlled sizes and high dispersity by caging templation of nanoporous networks. The morphologies of Co3O4 nanoparticles differ from wires to particulates by simply varying solvents. The composites of nanoparticles within network polymers are highly porous and are promising for many applications where accessible surface and aggregation prevention are important. The electrochemical performance of the composites demonstrates superior capacity and cyclic stability at a high current density (similar to 980 mA h g(-1) at the 60th cycle at a current density of 1000 mA g(-1)). In a catalytic oxidation reaction of carbon monoxide, the composites exhibit a remarkable stability (in excess of 35 hours) and catalytic performance (T-100 = 100 degrees C).

Highly stable nanoporous sulfur-bridged covalent organic polymers for carbon dioxide removal

Carbon dioxide capture and separation requires robust solids that can stand harsh environments where a hot mixture of gases is often found. Herein, the first and comprehensive syntheses of porous sulfur-bridged covalent organic polymers (COPs) and their application for carbon dioxide capture in warm conditions and a wide range of pressures (0–200 bar) are reported. These COPs can store up to 3294 mg g−1 of carbon dioxide at 318 K and 200 bar while being highly stable against heating up to 400 °C. The carbon dioxide capacity of the COPs is also not hindered upon boiling in water for at least one week. Physisorptive binding is prevalent with isosteric heat of adsorptions around 24 kJ mol−1. M06–2X and RIMP2 calculations yield the same relative trend of binding energies, where, interestingly, the dimer of triazine and benzene play a cooperative role for a stronger binding of CO2 (19.2 kJ mol−1) as compared to a separate binding with triazine (13.3 kJ mol−1) or benzene (11.8 kJ mol−1).Scopu

Quantitative evaluation of the antibacterial factors of ZnO nanorod arrays under dark conditions: Physical and chemical effects on Escherichia coil inactivation

Although zinc oxide nanorod (ZnO NR) arrays are a nanomaterial that offers effluent bactericidal activity, they have not been systematically evaluated to quantitatively investigate their disinfection mechanism under dark conditions. In this study, ZnO NR arrays of different lengths (0.5-4 mu m) were uniformly grown via hydrothermal synthesis. The longer arrays exhibited higher Escherichta coil (E. colt) inactivation efficiency up to 94.2% even under darkness for 30 min. When the NR arrays were coated via Al2O3 atomic layer deposition, the inactivation efficiency was decreased to 56.4% because the generation of reactive oxygen species (ROS) and the leaching of Zn2+ ions were both hindered by the surficial coverage of defect sites. The morphological effect, i.e., the mechanical rupture of E. cotton the surface, contributed 56.4%. of the bactericidal efficiency; chemical effects, i.e., ROS formation and zinc ion release, contributed the remaining 37.8% under dark conditions. The bactericidal effect of fabricated ZnO NR arrays was further validated in bottled and pond water spiked with E. colt, exhibiting 87.5% and 80.4% inactivation efficiencies, respectively, within 30 min. Understanding these antibacterial mechanisms is not only of significance for research in this and related fields but also beneficial for potential application in various fields, e.g., biomedical and antifouling areas