Highly Characteristic Adsorption Based on Single Crystal {001}-TiO2 Surface Molecular Recognition Promotes Enhanced Oxidation

Enhanced Mass Transfer of Ozone and Emerging Pollutants through a Gas-Solid-Liquid Reaction Interface for Efficient Water Decontamination

Ozone (O3), as an environmentally friendly oxidant, is widely used to remove emerging pollutants and ensure the safety of the water supply, whereas the restricted accessibility of O3 and limited collision frequency between pollutants and O3 will inevitably reduce the ozonation efficiency. To promote the chemical reactions between O3 and target pollutants, here we developed a novel gas-solid-liquid reaction interface dominated triphase ozonation system using a functional hydrophobic membrane with an adsorption layer as the O3 distributor and place where chemical reactions occurred. In the triphase system, the functional hydrophobic membrane simultaneously improved the interface adsorption performance of emerging pollutants and the access pathway of O3, leading to a marked enhancement of interfacial pollutant concentration and O3 levels. These synergistic qualities result in high ciprofloxacin (CIP) removal efficiency (94.39%) and fast apparent reaction rate constant (kapp, 2.75 × 10-2 min-1) versus a traditional O3 process (41.82% and 0.48 × 10-2 min-1, respectively). In addition, this triphase system was an advanced oxidation process involving radical participation and showed excellent degradation performance of multiple emerging pollutants. Our findings highlight the importance of gas-solid-liquid triphase reaction interface design and provide new insight into the efficient removal of emerging pollutants by the ozonation process.

Recent advances in the removal of emerging contaminants from water by novel molecularly imprinted materials in advanced oxidation processes-A review

Recently, there has been a global focus on effectively treating emerging contaminants (ECs) in water bodies. Advanced oxidation processes (AOPs) are the primary technology used for ECs removal. However, the low concentrations of ECs make it difficult to overcome the interference of background substances in complex water quality, which limits the practical application of AOPs. To address this limitation, many researchers are developing new catalysts with preferential adsorption. Molecular imprinting technology (MIT) combined with conventional catalysts has been found to effectively enhance the selectivity of catalysts for the targeted catalytic degradation of pollutants. This review presents a comprehensive summary of the progress made in research on molecularly imprinted polymers (MIPs) in the selective oxidation of ECs in water. The preparation methods, principles, and control points of novel MIP catalysts are discussed. Furthermore, the performance and mechanism of the catalysts in photocatalytic oxidation, electrocatalytic oxidation, and persulfate activation are analyzed with examples. The possible ecotoxicological risks of MIP catalysts are also discussed. Finally, the challenges and prospects of applying MIP catalysts in AOP are presented along with proposed solutions. This review provides a better understanding of using MIP catalysts in AOPs to target the degradation of ECs.

Co3O4 with upshifted d-band center and enlarged specific surface area by single-atom Zr doping for enhanced PMS activation

In this work, single-atom Zr doping is demonstrated to be an effective strategy to enhance the catalytic performance of Co₃O₄ toward peroxymonosulfate (PMS) by modulating electronic structure and enlarging specific surface simultaneously. The d-band center of Co sites upshifts owing to different electronegativity of Co and Zr in the bonds of Co-O-Zr confirmed by density functional theory calculations, leading to enhanced adsorption energy of PMS and strengthened electron transfer from Co^(II) to PMS. The specific surface area of Zr-doped Co₃O₄ increases by 6 times due to the decrease of crystalline size. Consequently, the kinetic constant of phenol degradation with Zr-Co₃O₄ is 10 times higher than that with Co₃O₄ (0.31 vs. 0.029 min^-1). The relative surface specific kinetic constant of Zr-Co₃O₄ for phenol degradation is still 2.29 times higher than that of Co₃O₄ (0.00660 vs. 0.00286 g m^-2 min^-1). In addition, the potential practical applicability of 8Zr-Co₃O₄ was also confirmed by practical wastewater treatment. This study provides deep insights into modifying electronic structure and enlarging specific surface area to enhance the catalytic performance.

Fabrication and Photocatalytic Activity of Single Crystalline TiO2 Hierarchically Structured Microspheres

Single crystalline anatase TiO2 microspheres with co-exposed {001}/{101} facets were prepared by a facile one-pot hydrothermal method using NaF as a morphology controlling agent. The influences of the NaF amount on the morphology and also on the photocatalytic activity were investigated systematically. The obtained microspheres possessed better morphology when the concentration of NaF was chosen at 0.1 mol/L, and the experimental results indicated that the crystal structure and morphology played important roles on the photocatalytic activity, based on the experimental results it was found that the photocatalytic degradation efficiency of TiO2 microspheres on Tetracycline hydrochloride could reach 76.4% in 2 h. Finally, a growth mechanism was proposed by investigating the growth process, i.e., a synergistic effect of F ions modified Ostwald ripening and oriented attachment.

Regulation of coordination and doping environment via target molecular transformation for boosting selective photocatalytic ability

Here, a novel transformed CdO with low coordination and N doping environment was simply synthesized through the involvement of the target molecule tetracycline (TC). The results showed that the shedding of surface hydroxyl groups led to a low coordination environment, and N doping formed a new doping energy level, which increased the charge density and promoted the migration and separation of photo-generated carriers. Its photocatalytic performance was 4.32 times higher than that of hydroxy-rich CdO and the selectivity coefficient was 4.8. Combined with theoretical calculation and in situ Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) analysis, the significant improvement of selectivity was due to the interaction of the doped N atom with the methyl carbon in TC. This work provided a new idea for the simultaneous construction of low coordination environment and N-doped materials for efficient selective photocatalysis.

Complete mineralization of phenolic compounds in visible-light-driven photocatalytic ozonation with single-crystal WO3 nanosheets: Performance and mechanism investigation

Complete mineralization of phenolic compounds into CO₂ and H₂O is desirable for removing them in wastewater, but it is challenging due to the generated recalcitrant intermediates, which requires highly effective advanced oxidation process with proper catalysts. Herein, we found that single-crystal WO₃ nanosheets (NSs)-based photocatalytic ozonation (PCO) can realize complete mineralization of phenols (phenol and 2-chlorophenol) under visible light irradiation. Almost 100% mineralization ratio of phenols was achieved through WO₃ NSs-based PCO system within short time. By comparing their performances with those of polycrystalline WO₃ nanoparticles, detecting and analyzing the intermediates, identifying the dominant radicals and conducting some electrochemical characterizations, the origin of superior catalytic activity of WO₃ NSs was uncovered, the mineralization pathways and the overall mechanism were proposed. The excellent PCO performance of WO₃ NSs was contributed to their nanosheet morphology with single-crystal microstructure and good dispersion, which can provide continuous interior channels for the photogenerated charge transport from the bulk to surface of WO₃ NSs and enough active sites for the surface reactions triggered by these charges. This work puts forwards new ideas to design highly active photocatalysts for PCO and helps deepen understanding of the catalytic mechanism of PCO.

Accurate Removal of Toxic Organic Pollutants from Complex Water Matrices

Characteristic emerging pollutants at low concentration have raised much attention for causing a bottleneck in water remediation, especially in complex water matrices where high concentration of interferents coexist. In the future, tailored treatment methods are therefore of increasing significance for accurate removal of target pollutants in different water matrices. This critical review focuses on the overall strategies for accurately removing highly toxic emerging pollutants in the presence of typical interferents. The main difficulties hindering the improvement of selectivity in complex matrices are analyzed, implying that it is difficult to adopt a universal approach for multiple targets and water substrates. Selective methods based on assorted principles are proposed aiming to improve the anti-interference ability. Thus, typical approaches and fundamentals to achieve selectivity are subsequently summarized including their mechanism, superiority and inferior position, application scope, improvement method and the bottlenecks. The results show that different methods may be applicable to certain conditions and target pollutants. To better understand the mechanism of each selective method and further select the appropriate method, advanced methods for qualitative and quantitative characterization of selectivity are presented. The processes of adsorption, interaction, electron transfer, and bond breaking are discussed. Some comparable selective quantitative methods are helpful for promoting the development of related fields. The research framework of selectivity removal and its fundamentals are established. Presently, although continuous advances and remarkable achievements have been attained in the selective removal of characteristic organic pollutants, there are still various substantial challenges and opportunities. It is hopeful to inspire the researches on the new generation of water and wastewater treatment technology, which can selectively and preferentially treat characteristic pollutants, and establish a reliable research framework to lead the direction of environmental science.

N,P-codoped carbon quantum dots-decorated TiO2 nanowires as nanosized heterojunction photocatalyst with improved photocatalytic performance for methyl blue degradation

N,P-doped carbon quantum dots (N,P-CQDs) are deemed as a promising candidate to environmentally friendly materials owing to the inexpensive, biocompatible nature. TiO₂ nanowire is a prospective photocatalyst because of its efficient migration of photoexcited carriers in wastewater treatment. However, the N,P-CQDs-decorated TiO₂ nanowire (N,P-CQDs/NW-TiO₂) photocatalysts have been rarely reported. In this study, we build N,P-CQDs on the surface of TiO₂ nanowires via a simple deposition process. Our investigations demonstrate that N,P-CQDs/NW-TiO₂ has a great photocatalytic degradation for methyl blue (MB) under irradiation. The degradation rate of can reach 93.6% within 120 min under proper conditions. The excellent degradation performance of N,P-CQDs/NW-TiO₂ is ascribed to the mesoporous structure and high separation rate of photoexcited carriers. In addition, the N,P-CQDs/NW-TiO₂ have outstanding recycled photocatalytic capability. After being recycled four times, the N,P-CQDs/NW-TiO₂ still maintain 59.9% photocatalytic activity. The fabricated nanosized photocatalyst can be widely utilized in the field of photocatalysis for wastewater treatment.

Surface Enriching Promotes Decomposition of Benzene from Air

The low generation rate and short lifetime of reactive oxidation radicals typical like ·OH strictly limit the photocatalytic degradation of benzene in the air. Here, we adopt copper dopant to...

Construction and photocatalytic performance of fluorinated ZnO-TiO2 heterostructure composites

Titanium dioxide, as a promising photocatalytic material, has attracted extensive attention in the field of photocatalytic degradation of organic pollutants in sewage. However, the photocatalytic performance needs to be further improved. In this work, fluorinated ZnO–TiO₂ composites (F-ZTO) were prepared by a simple coprecipitation method. The photocatalytic performance of the samples was studied in detail with methyl orange as the target degradation product. The results indicated that under the same conditions, the degradation rates of 6% F-ZTO, F-TiO₂ and TiO₂ for methyl orange reached 93.75%, 76.56% and 62.89% respectively. This showed that the method used in this work could effectively improve the photocatalytic degradation performance of titanium dioxide. 6% F-ZTO showed an excellent photocatalytic activity, which was attributed to the small grain size, the large specific surface area and the effective inhibition of photoelectron–hole recombination due to fluorination and zinc oxide coupling. In three consecutive cycles, the photocatalytic activity was almost maintained, indicating that 6% F-ZTO had a good recycling performance.

Fluorinated ZnO-TiO₂ composites (F-ZTO) were prepared by a simple coprecipitation method, the method used could effectively improve the photocatalytic property of titanium dioxide, and 6% F-ZTO showed an excellent activity and recycling performance.

Mechanism of Photodegradation of Organic Pollutants in Seawater by TiO2-Based Photocatalysts and Improvement in Their Performance

The mechanism of photodegradation of organic pollutants in seawater by TiO₂-based catalysts irradiated by visible light was first explored by adding holes and free radical traps. The results showed that the photogenerated holes formed by the catalyst played a key role in the degradation of organic pollutants, regardless of whether the photodegradation occurred in seawater or pure water. Considering that the Yb-TiO₂-rGO catalyst has a strong adsorption for organics, the salt ion almost did not interfere with the adsorption of pollutants by Yb-TiO₂-rGO. Therefore, the degradation performance of Yb-TiO₂-rGO did not remarkably change in the two water systems. For P25-ZN with a weak adsorption capacity for organics, several salt ions in the seawater hindered the contact of pollutants with the catalyst surface. Thus, the degradation rate of P25-ZN for phenol was significantly reduced. After the solvothermal reduction treatment for catalysts using ethylene glycol (EG) as the solvent, the increase in the Ti³⁺ content in the catalyst improved the visible-light response and activity of the catalyst. In addition, a small amount of EG grafted on the catalyst surface promoted the photocatalytic reaction process on the catalyst surface, thereby effectively resisting the interference of salt ions.

Efficient self-photo-degradation of cationic textile dyes involved triethylamine and degradation pathway

Cationic textile dyes such as astrazon brilliant red (ABR), are frequently used in the textile industry and contaminait the water ecology. Photodegradation of such dyes in wastewater is considered as a promising method, while the existing approaches are usually involved complicated and costly materials as photocatalysts. Facial, effective and low-cost approaches for their decontamination are needed. What's more, the detailed decomposition path of ABR is not revealed. The present study shows that ABR could suffer effective self-photo-degradation under triethylamine treatment without a photocatalyst. Almost 100% of the dye degraded within 1 h under visible light irradiation. UV-vis, FTIR and UPLC-MS analysis conformed the degradation of ABR. Factors involved in the degradation system were investigated clearly. What's more, the accurate and detailed analysis of UV-vis, FTIR and UPLC-MS data combined with computational analysis revealed the decomposition process of ABR. Reactive oxygen species (ROS) was investigated from ROS trapping experiments and EPR measurements, which revealed that O₂^- was the critical ROS in the degradation process, while ¹O₂ and OH had slightly influence on the degradation progression.