Role Of Active Species Research Articles

Synthesis and Characterization of WO3/BiVO4/Graphene Ternary Nanocomposites for the Photodegradation of Methlyene Blue and Tetracycline

In this study, a hydrothermal method was employed to synthesize the ternary nanocomposites comprising WO3/BiVO4/Graphene, all driven by visible light. The characteristics of these nanocomposites were interpreted through techniques such as UV–Vis, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and photoluminescence spectroscopy (PL). The enhanced performance of the composite, attributed to its heightened capability for separating charge carriers, outperformed that of the individual semiconductor components. The PL results validated the composite's improved charge separation. The nanocomposites have weaker PL peaks, indicating slower e−/h+ recombination. The balanced concentrations of the mixed semiconductors in the composite affected both PL intensity and photodegradation efficiency. The photocatalytic degradation of methylene blue (MB) and tetracycline (TC) was observed by nanocomposites. The heterogeneous nanocomposite WOBV/G-5 with 0.03 mg graphene content has a better photocatalytic activity for both MB (63 %) and TC (80 %) than other concentrations. It has also been investigated using TOC and COD analysis. Moreover, zeta potential analysis and pH analysis have been done to check the conductivity of optimized photocatalyst. Additionally, to check the stability of WOBV/G-5 photocatalyst, recyclability test that shows 58 % degradation rate after five cycles and analysis of XRD after recyclability have also been performed. Role of active species (h+, O2−, and OH.) was observed by using different scavengers (EDTA, BQ, and IPA) in trapping experiment that plays a vital role in photocatalytic degradation process.

Efficient synthesis and characterization of novel BiVO4/ZnO/graphene composites to study enhanced photocatalytic activity for organic pollutant degradation

This study reports the efficient synthesis and thorough characterization of novel graphene doped BiVO4/ZnO nanocomposites. Among these doping percentages, 3% BVZO/G is optimized composite as it shows the highest photocatalytic performance i–e 98% and 95% among all the doping percentages. Under the visible light exposure λ⩾420nm , the decomposition of tetracycline (TC) and methylene blue has been studied to evaluate the photocatalytic activity of the prepared composites. The characterization techniques such as photoluminescence spectroscopy, UV visible (UV-Vis) spectroscopy, x-ray diffraction, scanning electron microscopy, and Fourier transform infrared have been used to investigate the optical, structural, morphological, and vibrational properties respectively. The findings of the research indicate that the doping of graphene resulted in enhanced absorption of visible light and efficient mitigation of charge carrier recombination. To check the stability of optimized photocatalyst, reusability test has been performed. Additionally, role of active species has been examined using different scavengers in trapping experiment. By understanding the composite material for the enhanced photocatalysis, the results of this research help to design a sustainable and efficient photocatalyst.

Enhanced photo-Fenton degradation of contaminants in a wide pH range via synergistic interaction between 1T and 2H MoS2 and copolymer tea polyphenols/polypyrrole

In this study, we present the successful development of a unique photo-Fenton catalyst, 1T-2H MoS2@TP/PPy (MTP), achieved through the coating of a copolymer of tea polyphenol (TP) and polypyrrole (PPy) onto the surface of heterophase molybdenum disulfide (1T-2H MoS2). This innovative approach involves the integration of hydrothermal synthesis with copolymerization techniques. Our strategy utilizes nanoflower-like 1T-2H MoS2 as the foundational framework, which is then enveloped in TP and PPy copolymer. This innovative approach involves the integration of hydrothermal synthesis with copolymerization techniques. Our strategy utilizes nanoflower-like 1T-2H MoS2 as the foundational framework, which is then enveloped in TP and PPy copolymer. This distinctive architecture demonstrates exceptional catalytic performance owing to the hetero-phase entanglement of 1T-2H MoS2, which provides a diverse array of active sites. The coupled structure of TP and iron (TP-Fe2+/Fe3+) effectively overcome the limitation associated with the iron source. The incorporation of PPy not only reduces the recombination of photogenerated electron-hole pairs but also enhances the stability of 1T-2H MoS2. Remarkably, our experiments on the degradation of methylene blue (MB) and tetracycline (TC) degradation demonstrate that TP-Fe2+/Fe3+ significantly expands the pH applicability range of the MTP composite catalyst. Additionally, we examine several factors, including different catalysts, H2O2 addition, variations in light intensity, solution pH, temperature fluctuations, and the role of active species, to comprehensively understand their impact on the photo-Fenton degradation process. In conclusion, MTP composite exhibits robust catalytic stability and demonstrates a broad pH utilization range in the photo-Fenton oxidation process, highlighting its promising potential for a wide range of applications.

An in-depth insight into the simultaneous oxidation of sulfamethoxazole and reduction of Cr (VI) by one system of water film DBD plasma: The interaction effect, role of active species, and their dominant to pathways

This study aims to deeply investigate the simultaneous elimination of sulfamethoxazole (SMZ) and Cr (VI) through one system of water film dielectric barrier discharge (WFDBD) plasma. The interaction effect of SMZ degradation and Cr (VI) reduction and dominant effect of active species were highlighted. Results showed that the oxidation of SMZ and the reduction of Cr (VI) directly promote each other. When the concentration of Cr (VI) raised from 0 to 2 mg L−1, the degradation rate of SMZ enhanced from 75.6% to 88.6%, respectively. Similarly, when the concentration of SMZ improved from 0 to 15 mg L−1, the removal efficiency of Cr (VI) improved from 70.8% to 84.3%, respectively. ·OH, 1O2 and ·O2− play crical roles for SMZ degradation, and e−, ·O2−, ·H and H2O2 dominated to the Cr (VI) reduction. The variations of pH, conductivity and TOC during the removal process were also explored. The removal process was studied by UV–vis spectroscopy and a three-dimensional excitation-emission matrix. Based on DFT calculation and LC-MS analysis, free radicals dominated SMZ degradation pathways in the WFDBD plasma system were clarified. Besides, the influence of Cr (VI) on SMZ degradation pathway was clarified. The ecotoxicity of SMZ and the toxicity of Cr (VI) into Cr (III) were greatly reduced. This study provides a significant reference value for the application and mechanism of plasma simultaneous removal of organic pollutants and heavy metals in wastewater.

Enhancing photodecomposition of cationic organic dyes of rhodamine and methylene blue employing the Ta2O5–CdS composite driven by visible light irradiation

The Ta2O5–CdS composites with the various ratios of Ta2O5/CdS were synthesized to study their employment in the photodecomposition of RhB (rhodamine B)/MB (methylene blue). The samples characterized by XRD, FESEM, EDS, and TEM proved the formation of the Ta2O5–CdS with cauliflower morphology. According to DRS analysis, Ta2O5–CdS exhibited redshifts, and their band-gaps (2.00 eV and 2.10 eV for Ta2O5/CdS = 1 and 3) decreased in contrast to pure CdS (2.18 eV). The BET-specific surface areas (9.221 m2/g) of the Ta2O5–CdS composite (Ta2O5/CdS = 1) measured by N2 adsorption-desorption isotherms were enhanced in contrast to pure CdS (1.817 m2/g). Moreover, MB photodecomposition by Ta2O5–CdS with the weight ratios of Ta2O5/CdS = 3 and 1 improved to 90% and 99%, respectively, in contrast to pure CdS (80%). Besides, the Ta2O5–CdS composite (Ta2O5/CdS = 1) exhibited the highest RhB decomposition (97%). Hence, for the first time, this study has surveyed the photodecomposition of the cationic dyes by the Ta2O5–CdS with excellent photocatalytic performance. The role of active species was detected through species quenching tests. A reliable mechanism was suggested to reveal how the RhB/MB decomposition was promoted compared to CdS. The photodecomposition results corresponded to the pseudo first order kinetic model.

In situ synthesis of g-C3N4/TiO2 heterojunction by a concentrated absorption process for efficient photocatalytic degradation of tetracycline hydrochloride.

The construction of heterojunctions between semiconductors is a preferred route to improve overall photocatalytic activity. In this work, a facile and feasible method was innovatively developed to one-step prepare g-C3N4/TiO2 heterojunctions via an absorption-calcination process using nitrogen and titanium precursors directly. This method can effectively avoid interfacial defects and establish a tight interfacial connection between g-C3N4 and TiO2. The resultant g-C3N4/TiO2 composites exhibited prominent photodegradation efficiency for tetracycline hydrochloride (TC-HCl) under visible light and simulated-sunlight irradiation. The optimal g-C3N4/TiO2 composite (urea content of 4g) showed the highest photocatalytic efficiency, which can degrade 90.1% TC-HCl under simulated-sunlight irradiation within 30min, achieving 3.9 and 2 times increases compared to pure g-C3N4 and TiO2, respectively. Besides, photodegradation pathways based on the role of active species ·O2- and ·OH were identified, indicating that a direct Z-scheme heterojunction was formed over the g-C3N4/TiO2 photocatalyst. The enhanced photocatalytic performance can be attributed to the close-knit interface contact and the formation of Z-scheme heterojunction between g-C3N4 and TiO2, which can accelerate the photo-induced charge carrier separation, broaden the spectra absorption range, and retain a higher redox potential. This one-step synthesis method may provide a new strategy for the construction of Z-scheme heterojunction photocatalysts consisting of g-C3N4 and TiO2 for environmental remediation and solar energy utilization.

Photocatalytic degradation and pollutant-oriented structure-activity analysis of carbamazepine, ibuprofen and acetaminophen over faceted TiO2

Photocatalytic degradation of carbamazepine, ibuprofen, acetaminophen and phenol was studied in the presence of anatase photocatalyst, exposing three different crystal facets in the majority of {0 0 1}, {1 0 0} or {1 0 1}. It was found that octahedral anatase particles exposing {1 0 1} facets allow to achieve the best degradation and mineralization of all persistent organic pollutants. This confirms that the previous findings, showing high {1 0 1} activity, are not limited to phenol and could be generalized for other water pollutants. Based on the obtained results, a correlation model including exposed TiO2 crystal facet and chemical hardness of the pollutant was developed to predict the degradation rate of pollutants with a possibly diverse electronic structure. The structure-activity analyses, based on the reactivity predictors obtained from the DFT calculations for all tested compounds, have shown that pollutants with higher chemical hardness react faster with the photocatalyst. Alternatively, a similar effect was observed for the higher HOMO-LUMO energy gap of the compound. This relation indicates that for compounds with a low energy position of LUMO orbital, e.g., carbamazepine, process efficiency is not strictly dependent on the stability of h+ generated organic radical, which is often pointed out as an initial reactive form. Based on these results, a correlation model was developed for the first time to quantitatively describe the effect of the facet-pollutant interactions based on their independent electronic properties. Finally, this was followed by the detailed degradation study of the pharmaceuticals mixture, showing the impact of the total concentration and role of active species on the degradation efficiency over facet-engineered TiO2 photocatalysts.

Visible light and iodate/iodide mediated degradation of bisphenol A by self-assembly 3D hierarchical BiOIO3/Bi5O7I Z-scheme heterojunction: Intermediates identification, radical mechanism and DFT calculation

Broadening the light absorption and inhibiting carrier's recombination are vital to the improvement of photocatalytic performance. Herein, self-assembly 3D hierarchical microsphere BiOIO3/Bi5O7I Z-scheme heterojunction with carrier transfer channel was firstly fabricated by in-situ solvothermal method. The degradation efficiency for bisphenol A (BPA) reached 98.9 % within 60 min visible light irradiation. The enhanced photocatalytic activity was benefited from the Z-scheme system assisted by iodate/iodide (IO3-/I-) as carrier transfer channel that not only accelerated the interfacial charge separation, but also provided massive reactive centers for obtaining high redox capacity. The vulnerable sites and the degradation pathways of BPA were identified by density functional theory calculations and liquid chromatography-mass spectrometry analyses. The toxicity of BPA and its intermediates were predicted by ECOlogical Structure Activity Relationship (ECOSAR) and the results demonstrated that BPA was eventually mineralized to harmless products. The Z-scheme charge transfer mechanism was deeply elucidated based on the role of active species (·O2-, ·OH and h+), band structure and carrier separation efficiency. This study provides a promising strategy for the photoactivity enhancement of bismuth based heterojunction in environment purification.

The effect of internal stress on the photocatalytic performance of the Zn doped BiOBr photocatalyst for tetracycline degradation

BackgroundThe serious environmental pollution caused by the massive deposition of antibiotics in the environment has aroused widespread concern. MethodsIn this work, stress engineering is used to modulate the visible-light-driven photodegradation of tetracycline (TC) by Zn-doped BiOBr flower microspheres, which were successfully prepared by a solvothermal method. Significant findingsCompared with pure BiOBr, zinc-doped BiOBr significantly improved the visible light catalytic degradation efficiency of TC. When increasing the content of Zn, a local n-type zone gradually formed in the p-type BiOBr matrix to form pseudo-heterojunction with lateral heterojunction properties, and the best photocatalytic performance is 12%Zn-BiOBr. In addition, the role of active species in TC photodegradation was evaluated by adding different trapping agents. The association with internal stress and photodegradation performance was established, and the mechanism to enhance the photodegradation performance under visible light irradiation of Zn-doped BiOBr photocatalysts was proposed.

Electrochemical degradation of PFOA and its common alternatives: Assessment of key parameters, roles of active species, and transformation pathway

This study investigates an electrochemical approach for the treatment of water polluted with per- and poly-fluoroalkyl substances (PFAS), looking at the impact of different variables, contributions from generated radicals, and degradability of different structures of PFAS. Results obtained from a central composite design (CCD) showed the importance of mass transfer, related to the stirring speed, and the amount of charge passed through the electrodes, related to the current density on decomposition rate of PFOA. The CCD informed optimized operating conditions which we then used to study the impact of solution conditions. Acidic condition, high temperature, and low initial concentration of PFOA accelerated the degradation kinetic, while DO had a negligible effect. The impact of electrolyte concentration depended on the initial concentration of PFOA. At low initial PFOA dosage (0.2 mg L−1), the rate constant increased considerably from 0.079 ± 0.001 to 0.259 ± 0.019 min−1 when sulfate increased from 0.1% to 10%, likely due to the production of SO4•–. However, at higher initial PFOA dosage (20 mg L−1), the rate constant decreased slightly from 0.019 ± 0.001 to 0.015 ± 0.000 min−1, possibly due to the occupation of active anode sites by excess amount of sulfate. SO4•– and •OH played important roles in decomposition and defluorination of PFOA, respectively. PFOA oxidation was initiated by one electron transfer to the anode or SO4•–, undergoing Kolbe decarboxylation where yielded perfluoroalkyl radical followed three reaction pathways with •OH, O2 and/or H2O. PFAS electrooxidation depended on the chemical structures where the decomposition rate constants (min−1) were in the order of 6:2 FTCA (0.031) > PFOA (0.019) > GenX (0.013) > PFBA (0.008). PFBA with a shorter chain length and GenX with –CF3 branching had slower decomposition than PFOA. While presence of C–H bonds makes 6:2 FTCA susceptible to the attack of •OH accelerating its decomposition kinetic. Conducting experiments in mixed solution of all studied PFAS and in natural water showed that the co-presence of PFAS and other water constituents (organic and inorganic matters) had adverse effects on PFAS decomposition efficiency.

Synthesis of Cu–TiO2/CuS p-n heterojunction via in situ sulfidation for highly efficient photocatalytic NO removal

Cu doped TiO2/CuS (Cu–TiO2/CuS) p-n heterojunction was synthesized via in situ sulfidation method for efficient photocatalytic removal of NO at ppb-level. The results show that optimized Cu–TiO2/CuS heterojunction possessed a maximum efficiency of 85% for the removal of NO under visible light irradiation, which was approximately 8.5, 4.3 and 1.2 times that of CuS, TiO2 and Cu–TiO2, respectively. The improved photocatalytic performance is attributed to the enhancement of visible light absorption and charge carrier separation induced by the construction of p-n heterojunction. Meanwhile, the p-n heterojunction charge transfer mechanism of Cu–TiO2/CuS was verified by systematic investigations. The appropriate band structures of the two components and the internal electric field formed at the interface of the heterojunction were two factors for this charge transfer mechanism. Furthermore, the role of active species in NO removal was explored, and the corresponding mechanism for NO removal of the heterojunction was proposed. This work provides a promising approach for the synthesis of heterojunction photocatalysts and facilitates the application of photocatalysts in sustainable and efficient pollutant removal.

Sodium Percarbonate Activation by Plasma-Generated Ozone for Catalytic Degradation of Dye Wastewater: Role of Active Species and Degradation Process

In this paper, sodium percarbonate (SPC) was activated by ozone (O3) from plasma for catalytic treatment of dye wastewater. Methyl blue (MB), a typical industrial dye, was selected as the target dye contaminant. Results showed that enhancing O3 dosage and reducing MB concentration were beneficial to MB degradation. Compared to acid condition, a higher removal efficiency of MB was obtained in alkaline condition. With an increase of SPC dosage, the removal efficiency of MB first was raised, and then it declined. Under the optimal dosage of 50 mg/L, the removal efficiency of MB reached 85.7% with 30 min treatment time. The energy efficiency was improved from 5.21 g/kWh to 5.71 g/kWh. A synergetic effect can be established between O3 and SPC. Radical capture experiments verified that ·OH, ·O2−, 1O2, and ·CO3− played important parts in MB degradation. With increasing reaction time, the amount of total organic carbon (TOC) declined and the amount of ammonia nitrogen (NH3-N) increased. The addition of SPC enhanced the solution’s pH value and conductivity. The degradation pathway was proposed based on density functional theory (DFT) analysis and relevant literatures. The toxicity of MB was alleviated after O3/SPC treatment. The O3/SPC process was also suitable for the treatment of other dyes and actual wastewater.

Electrochemical Degradation of Pfoa: Assessment of Key Parameters, Roles of Active Species, and Transformation Pathway

Electrochemical Degradation of Pfoa: Assessment of Key Parameters, Roles of Active Species, and Transformation Pathway

3D interconnected porous g-C3N4 hybridized with Fe2O3 quantum dots for enhanced photo-Fenton performance

Currently, the photo-Fenton oxidation has been increasingly studied in the domain of contaminant elimination. However, the lack of active sites and the slow charge migration in the catalytic process, still limit its practical application. 3D/0D hybrids offer a better opportunity for improving photo-Fenton activity due to their high charge mobility and increased number of catalytic sites, which is highly desirable but remains a large challenge. Herein, 3D interconnected porous g-C3N4 hybridized with Fe2O3 QDs (FCN) was developed and exhibited a porous structure and large specific areas. A large number of active sites and rapid charge separation/migration were achieved by the loading of ultrasmall Fe2O3 QDs on the surface of g-C3N4. Moreover, the high charge mobility of this material promoted the fast conversion of Fe3+ to Fe2+, resulting in the optimum synergistic effect between the photocatalytic and Fenton oxidation processes. Thus, the FCN catalysts exhibited excellent photo-Fenton oxidation activity towards the decomposition of organic contaminants (such as phenol, 2,4-dibromophenol, 2,4,6-trichlorophenol, rhodamine B and methyl orange). In addition, the roles of active species in the photo-Fenton oxidation reaction were also studied, and the results imply that the hydroxyl radicals played the most important role in the degradation of organic contaminants.

Visible light driven reduced graphene oxide supported ZnMgAl LTH/ZnO/g-C3N4 nanohybrid photocatalyst with notable two-dimension formation for enhanced photocatalytic activity towards organic dye degradation

In this study, 2D/2D/2D heterostructured r-GO/LTH/ZnO/g-C3N4 nanohybrid were synthesized through hydrothermal method. The strong electrostatic interaction between the negatively charged g-C3N4 and r-GO nanosheets with positively charged layered triple hydroxide (LTH) nanosheets are effectively influences the successful formation of heterojunction. The LTH nanosheets are well spread on the g-C3N4 nanosheets combined with r-GO. In particular, the as prepared heterojunction shows a better photocatalytic degradation activity compared to pristine samples and the significant enhancement in the photocatalytic performance is mainly accredited to the large interfacial charge transition of photogenerated charge carriers under the visible light irradiation. Although the 2D/2D/2D heterojunction effectively hinders the charge carrier recombination resulting high photocatalytic activity with good stability. In addition, the r-GO supported LTH/ZnO/g-C3N4 heterojunction shows high photo-stability after sequential experimental runs with no obvious change in the dye degradation process. Consequently, the role of active species was investigated over the r-GO/LTH/ZnO/g-C3N4 heterojunction with the help of different scavengers.

Novel rare earth ions doped Bi2WO6/rGO hybrids assisted by ionic liquid with enhanced photocatalytic activity under natural sunlight

Rare earth ions doped Bi2WO6/rGO hybrids (Re-BWG) were synthesized by a two-step process, and the introduction of rGO was achieved with the assistance of imidazole based ionic liquids (IL). IL could enhance the dispersion uniformity of rGO, which was beneficial to the combination of Bi2WO6 (BWO) and rGO. Rare earth ions and rGO increased the separation of electron–hole pairs of BWO and enhanced the adsorption for pollutants. Physical-chemical properties of BWO and Re-BWG were investigated by XRD, SEM/TEM, XPS, UV-Vis DRS, PL, EIS, and N2 adsorption analysis. The photocatalytic activity of Re-BWG was envaulted by rhodamine (RhB) degradation under natural sunlight irradiation. Re-BWG possessed excellent photocatalytic activity compared to pure BWO. The proposed mechanism of photocatalytic degradation was deduced, in which the photogenerated O2•- and h+ (on the surface of Re-BWG) played the role of active species during reaction. The photocatalytic performance of Er-BWG was better than the other three Re (La, Ce, and Pr)-BWG hybrids, and the RhB removal efficiency was up to 99.12% within 60 min.

Photocatalytic degradation of diclofenac using TiO2-CdS heterojunction catalysts under visible light irradiation.

The present study reports the photocatalytic degradation of analgesic drug diclofenac using the hydrothermally prepared TiO2-CdS heterojunction catalyst. The results suggest that the prepared catalysts exhibited excellent photocatalytic activity under visible light irradiation. The photodegradation kinetics were well fitted to the pseudo-first-order reaction. The apparent reaction rate constant for TC5 catalyst in the diclofenac degradation was 0.02316min-1. Mineralisation of diclofenac using TC5 photocatalyst was around 86% within 4h of irradiation time. The operating parameters such as optimal catalyst dosage, apparent solution pH and the effect of initial diclofenac concentration were also studied using the TC5 catalyst. The role of active species in the degradation mechanism was elucidated and it was found that the hydroxyl radical is the main active species in the diclofenac degradation mechanism. The charge transfer between heterojunction catalysts is facilitated by direct Z-scheme heterojunction structure. The coupled photocatalysts also showed good photochemical stability and reusability over five successive reaction cycles. The tentative degradation pathway has been devised based on LC-MS peaks, and it is found that only m/z 224, m/z 178 and m/z 124 were persisted at the end of the reaction.

One-step synthesis of oxygen doped g-C3N4 for enhanced visible-light photodegradation of Rhodamine B

O-doped g-C3N4 (denoted as x-OCN, where x is the volume of 30% H2O2 for a given amount of urea) materials were prepared by calcining dried the mixtures of urea impregnated with H2O2 at 550 °C. The characterization shows that the x-OCN materials are formed by replacing N in g-C3N4 by O atoms, which is further supported by density functional theory calculations. The rhodamine B photodegradation performance on the x-OCN materials is higher than the pure g-C3N4. Among the x-OCN samples, 40-OCN shows the strongest photocatalytic activity, which could be attributed to the largest content of doped-O in the matrix of g-C3N4, leading to a reduced bandgap energy and a lower recombination rate of photogenerated electrons and holes, therefore enhancing the photocatalytic performance. The mechanism for the photocatalytic degradation of RhB was proposed based on the investigation on the role of active species and the pathway of RhB degradation.

Non-thermal plasma combined with zeolites to remove ammonia nitrogen from wastewater

In this work, non-thermal plasma combined with zeolites was used to remove inorganic pollutant ammonia nitrogen from wastewater. Ammonia nitrogen elimination performances at various operating parameters were investigated. Roles of active species in the removal of ammonia nitrogen were also discussed. The experimental results showed that 69.97% ammonia nitrogen can be removed from the plasma/zeolites synergistic system after 30 min treatment. The removal efficiency was 16.23% and 61.55% higher than that in sole zeolites adsorption system and that in sole discharge plasma system, respectively. Higher applied voltage, lower initial ammonia nitrogen concentration and weak acidic conditions were favorable for ammonia nitrogen removal. After the addition of zeolites, part of O3 and H2O2 generated in the plasma/zeolites system were decomposed into other oxygen species (•OH and 1O2), which improved the oxidation degree of ammonia nitrogen. In addition, the reaction mechanism of ammonia nitrogen in water by plasma/zeolites process was discussed. After repeated use three times, the effect of the zeolites in the plasma/zeolites system remained stable. Characterization of the zeolites after reaction was analyzed through BET, SEM, XRD and FT-IR. The experiments have confirmed the applicability of the plasma/zeolites system for the further treatment of low-concentration ammonia nitrogen wastewater.

Influence of Nanoscale Surface Arrangements on the Oxygen Transfer Ability of Ceria–Zirconia Mixed Oxide

Ceria-based materials, and particularly CeO2–ZrO2 (CZ) solid solutions are key ingredient in catalyst formulations for several applications due to the ability of ceria to easily cycling its oxidation state between Ce4+ and Ce3+. Ceria-based catalysts have a great soot oxidation potential and the mechanism deeply relies on the degree of contact between CeO2 and carbon. In this study, carbon soot has been used as solid reductant to better understand the oxygen transfer ability of ceria–zirconia at low temperatures; the effect of different atmosphere and contact conditions has been investigated. The difference in the contact morphology between carbon soot and CZ particles is shown to strongly affect the oxygen transfer ability of ceria; in particular, increasing the carbon–ceria interfacial area, the reactivity of CZ lattice oxygen is significantly improved. In addition, with a higher degree of contact, the soot oxidation is less affected by the presence of NOx. The NO oxidation over CZ in the presence of soot has also been analyzed. The existence of a core/shell structure strongly enhances reactivity of interfacial oxygen species while affecting negatively NO oxidation characteristics. These findings are significant in the understanding of the redox chemistry of substituted ceria and help determining the role of active species in soot oxidation reaction as a function of the degree of contact between ceria and carbon.