Hypercrosslinking porous polymer layers on TiO2-graphene photocatalyst: Enhanced adsorption of water pollutants for efficient degradation

Porphyrin-Based Conjugated Microporous Polymer Loaded with Nanoscale Zerovalent Iron for the Degradation of Organic Pollutants under Visible Light

The degradation of organic dye from waterbodies is of great significance for clean production and environmental remediation. Herein, two porphyrin-based conjugated microporous polymers (CMPs) loaded with nanoscale zerovalent iron (named as Por-CMPs-1-2@nZVI) were successfully fabricated by Sonogashira-Hagihara coupling reactions and the liquid-phase method. The as-synthesized Por-CMPs-1-2@nZVI composites were characterized by various means of analysis, and it was confirmed that Por-CMPs-1-2 loaded with nZVI had good photocatalytic performance. Calculated by ultraviolet-visible spectrum, the band-gap energies of Por-CMPs-1@nZVI and Por-CMPs-2@nZVI were 1.45 and 1.32 eV, respectively, indicating that both can be activated by visible light. The photodegradation of organic dye experiments demonstrated that Por-CMPs-2@nZVI degraded 98.0% of 10 ppm Methylene Blue (MB) within 150 min, which is higher than that of Por-CMPs-1-2 and Por-CMPs-1@nZVI. The experiment of active substance capture and mechanism of ESR confirmed that superoxide anion and hydroxyl radical were the primary valid substances in the photodegradation process of MB. In addition, the preparation of membrane materials was shown to be a successful strategy to realize engineered scale-up production.

Carbonaceous Materials-Based Photothermal Process in Water Treatment: From Originals to Frontier Applications

The photothermal process has attracted considerable attention in water treatment due to its advantages of low energy consumption and high efficiency. In this respect, photothermal materials play a crucial role in the photothermal process. Particularly, carbonaceous materials have emerged as promising candidates for this process because of exceptional photothermal performance. While previous research on carbonaceous materials has primarily focused on photothermal evaporation and sterilization, there is now a growing interest in exploring the potential of photothermal effect-assisted advanced oxidation processes (AOPs). However, the underlying mechanism of the photothermal effect assisted by carbonaceous materials remains unclear. This review aims to provide a comprehensive review of the photothermal process of carbonaceous materials in water treatment. It begins by introducing the photothermal properties of carbonaceous materials, followed by a discussion on strategies for enhancing these properties. Then, the application of carbonaceous materials-based photothermal process for water treatment is summarized. This includes both direct photothermal processes such as photothermal evaporation and sterilization, as well as indirect photothermal processes that assisted AOPs. Meanwhile, various mechanisms assisted by the photothermal effect are summarized. Finally, the challenges and opportunities of using carbonaceous materials-based photothermal processes for water treatment are proposed.

Photocatalytic degradation of alkyl imidazole ionic liquids by TiO2 nanospheres under simulated solar irradiation: Transformation behavior, DFT calculations and promoting effects of alkali and alkaline earth metal ions

In this study, TiO2 nanospheres prepared by the sol-gel method were found to efficiently catalyze the photodegradation of 1-butyl-2,3-dimethylimidazolium bromide salt ([BMMIm]Br) under simulated solar irradiation through the main attack of hydroxyl radicals (•OH). The promoting effect of alkali metal (Li+→Cs+) and alkaline earth metal ions (Mg2+→Ba2+) was particularly emphasized. In-situ EPR tests showed that the introduction of alkali and alkaline earth metal ions could enhance the formation of •OH thus leading to a 7%-30.3% increase in the degradation efficiency of. [BMMIm]+. Moreover, the removal efficiency of [BMMIm]+ still reached > 96.19% in four real waters. A total of 23 products of [BMMIm]Br were detected, and hydroxyl substitution, bond breaking, direct oxidation and ring opening were considered as the main reactions during the photocatalytic degradation process. The results of toxicity evaluation showed that hydroxylation was a reaction process of increasing toxicity, while the bond breaking reaction had great detoxification capacity for [BMMIm]+. These findings may enhance our understanding on the effects of alkali or alkaline earth metal ions on the photocatalytic activity of TiO2, which could also provide reference for the efficient and green removal of alkylimidazolium ionic liquids in waters.

Coral-like, self-assembled, and spatially bounded Ag nano-particles on franzinite zeolite composite sensor toward accurate, synergetic, and ultra-trace sulfadiazine detection

A coral-like Ag@FRA zeolite nanocomposite sensor reveals high sensitivity toward sulfadiazine (SDZ) in a dual detection of fluorescence and electrochemistry. The sensor has been as-synthesized in the hydrothermal condition through a one-pot self-assembly process in which the high crystalline Ag nanoparticles (NPs) are closely arranged and stacked on the nanosized surface cage window of the FRA (Franzinite) zeolite. Strong ultrasound can drive the coral-like composite release Ag nanoparticles whose distribution range mainly from 10 to 12 nm lead to the purple fluorescence in an emission spectrum. In sea water, the fluorescence increases linearly in the SDZ concentration range of 5 × 10-18-5 × 10-10 M. Furthermore, the LOD (limit of detection) reaches 1.4 × 10-22 M by the spatial confinement effect of the coral-liked FRA cage structure in CV (cyclic voltammetry) method at the characteristic potential peak position of 0.1 V vs. SCE. The theoretical calculation also confirms that the FRA cage structure matches well with the SDZ molecules. Further studies indicate the generation of a novel stable composite sensor with high specificity, good recovery and repeatability, which depends on the induction of silver ions upon the artificial synthesis of FRA.

Photocatalytic Synthesis of Ultrafine Pt Electrocatalysts with High Stability Using TiO2 -Decorated N-Doped Carbon as Composite Support

Commercial Pt/C (Com. Pt/C) electrocatalysts are considered optimal for oxygen reduction and hydrogen evolution reactions (ORR and HER). However, their high Pt content and poor stability restrict their large-scale application. In this study, photocatalytic synthesis was used to reduce ultrafine Pt nanoparticles in-situ on a composite support of TiO2 -decorated nitrogen-doped carbon (TiO2 -NC). The nitrogen-doped carbon had a large surface area and electronic effects that ensured the uniform dispersion of TiO2 nanoparticles to form a highly photoactive and stable support. TiO2 -NC served as a composite support that enhanced the dispersibility and stability of ultrafine Pt electrocatalyst, owing to the presence of N sites and the strong metal-support interaction. Relative to Com. Pt/C, the as-obtained Pt/TiO2 -NC had positive shifts of 44 and 10 mV in the ORR half-wave potential and HER overpotential at -10 mA cm-2 , respectively. After an accelerated durability test, Pt/TiO2 -NC had lower losses in electrochemical specific area (0.7 %) and electrocatalytic activity (0 mV shift) than Com. Pt/C (25.6 %, 22 mV shift). These results indicate that the developed strategy enabled the facile synthesis and stabilization of ultrafine Pt nanoparticles, which improved the utilization efficiency and long-term stability of Pt-based electrocatalysts.

Surface Modification of TiO2 by Hyper-Cross-Linked Polymers for Efficient Visible-Light-Driven Photocatalytic NO Oxidation

Solar-driven photocatalysis offers an environmentally friendly and sustainable approach for the removal of air pollutants such as nitric oxides without chemical addition. However, the low specific surface area and adsorption capacity of common photocatalysts restrict the surface reactions with NO at the ppb-level. In this study, imidazolium-based hyper-cross-linked polymer (IHP) was introduced to modify the surface of TiO₂ to construct a porous TiO₂/IHP composite photocatalyst. The as-prepared composite with hierarchical porous structure achieves a larger specific surface area as 309 m²/g than that of TiO₂ (119 m²/g). Meanwhile, the wide light absorption range of the polymer has brought about the strong visible-light absorption of the TiO₂/IHP composite. In consequence, the composite photocatalyst exhibits excellent performance toward NO oxidation at a low concentration of 600 ppb under visible-light irradiation, reaching a removal efficiency of 51.7%, while the generation of the toxic NO₂ intermediate was suppressed to less than 1 ppb. The enhanced NO adsorption and the suppressed NO₂ generation on the TiO₂/IHP surface were confirmed by in situ monitoring technology. This work demonstrates that the construction of a porous structure is an effective approach for efficient NO adsorption and photocatalytic oxidation.

g-C3N4/polyvinyl alcohol-sodium alginate aerogel for removal of typical heterocyclic drugs from water

Heterocyclic drugs (HCDs) detected at high frequencies in wastewater have raised great concerns and their advanced removal has been the hotspot for safe water reuse in recent years. Two-dimensional graphitic carbon nitride (g-C₃N₄) and its photocatalytic systems are increasingly emerging, however, there are inevitable drawbacks of stacking and difficulty in recycling, resulting in decreased pollutant removal and limited application. Herein, for the first time, this paper reported a three-dimensional g-C₃N₄/polyvinyl alcohol-sodium alginate aerogel (g-C₃N₄/PVA-SA aerogel) photocatalyst synthesized by ultrasonic exfoliation and in-situ polymerization for typical HCDs (sulfadiazine (SDZ), sulfamethoxazole (SMX), and carbamazepine (CBZ)) removal in water. The reduced stacking of g-C₃N₄ dispersed in PVA-SA aerogel was achieved as revealed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD) analysis, and g-C₃N₄/PVA-SA aerogel was observed to possess encouraging degradation efficiencies and rates for SDZ (100%, 0.0249 min^-1), SMX (100%, 0.1762 min^-1) and CBZ (69.8%, 0.0056 min^-1), which were improved by 50%-60% and 133%-216% compared to those of g-C₃N₄, respectively. Meanwhile, environmental impact factors such as pH and coexisting ions had less impact on the degradation of SDZ and SMX by g-C₃N₄/PVA-SA aerogel. The novel aerogel also had a good recyclability, with less than 5% reduction in degradation efficiency after five cycles observed. The photodegradation of SDZ, SMX and CBZ was confirmed to be driven by ⋅O₂^- and h⁺ through scavenger-quenching experiments. The new low carbon and recyclable g-C₃N₄/PVA-SA aerogel reported in this study indicated a good potential for efficient removal of HCDs from water, which provides an alternative strategy for advanced purification and safe reuse of wastewater.