This study reports a thorough investigation of nanosized CuO/CeO2 materials as an efficient catalyst for decomposition of N2O, which is a strong greenhouse gas largely produced by chemical industry. ...Effect of terminating CeO2 crystalline planes ({100}, {110}, and {111}) on the behavior of CuO dispersed over CeO2 nanocubes, nanorods and polyhedral crystallites was examined in detail by using a variety of catalyst characterization techniques. The 4 wt % Cu was found as the most advantageous metal loading, whereas higher Cu content resulted in lower dispersion and formation of significantly less active, segregated bulk CuO phase. It was discovered that CuO/CeO2 solids should enable both excessive oxygen mobility on the catalyst surface as well as formation of highly reducible Cu defect sites, in order to ensure high intrinsic activity. Detailed studies further revealed that CeO2 morphology needs to be tailored to expose {100} and {110} high-energy surface planes, as present in CeO2 nanorods. Oxygen mobility and regeneration of active Cu phase on these surface planes is easier, which in turn facilitates higher catalytic activity through the recombination of surface oxygen atoms and desorption as molecular oxygen that replenishes active sites for subsequent catalytic cycles. As a consequence, CuO supported on CeO2 nanorods demonstrated lower activation energy (87 kJ/mol) in N2O decomposition reaction compared to catalysts based on CeO2 nanocubes (102 kJ/mol) or polyhedral CeO2 (92 kJ/mol).
Production of bisphenol A (BPA) analogues such as bisphenol F (BPF) and bisphenol AF (BPAF) has recently increased, due to clear evidence of adverse effects of BPA on humans and wildlife. Bisphenols ...(BPs) have already been released into aquatic environment without previous available information about potential adverse effects of BPs and their potential risk to aquatic ecosystems. In this study, lethal and sublethal effects of BPF and BPAF to bacteria, algae, crustacea and fish embryos were investigated and the results were compared to the adverse effects obtained for BPA. We found that BPAF was the most toxic compound to Daphnia magna, Danio rerio and Desmodesmus subspicatus; the lowest 72 h EC50 (median effective concentration) and 21 d NOEC (no observed effect concentration) values were determined at 2.2 mg/L regarding zebrafish hatching success and 0.23 mg/L of BPAF obtained for growth and reproduction of water fleas, respectively. In most cases, BPA was more toxic to D. magna, D. rerio and D. subspicatus in comparison to BPF, but pigmentation of zebrafish embryos after 48 h of exposure and reproduction of water fleas after 21-day D. magna reproductive test exposure to BPF were much more impaired. Risk quotients (measured environmental concentration/21 d NOEC) showed that BPA, BPF and BPAF are recently not chronically hazardous to the survival, reproduction and growth of water fleas in surface waters. On the other hand, we importantly show that currently present BPAF concentrations in surface waters could cause a potential ecological risk to aquatic organisms. In the near future, higher concentrations of BPF and BPAF in surface waters are anticipated and for this reason further testing using test systems with various aquatic species and endpoints are needed to provide additional information about toxic impacts of BPF and BPAF on aquatic biota.
•Higher toxicity of BPAF in comparison to BPF and BPA.•BPA was more toxic to the majority of tested organisms in comparison to BPF.•BPAF could cause ecological risk to aquatic organisms.•Industrial replacement of BPA with BPAF is questionable.
We reveal that BPAF was found to be more toxic to tested organisms than BPA and BPF and it could cause ecological risk to aquatic organisms.
Experimental and theoretical modeling on low-temperature dry methane reforming over Ni-containing CeO2 rods was studied. The catalyst was characterized by means of N2 physisorption, in-situ XRD, TPR ...and H2 chemisorption techniques. The characterization studies revealed the distortion of CeO2 flourite structure due to the Ni incorporation. Lattice expansion (due to reduction) and contraction (due to oxidation) suggest the reversible redox nature of CeO2. Ni–O–Ce solid solution formation was evidenced by both XRD and TPR studies. H2 chemisorption study revealed that the catalyst reduction temperature plays a significant role in Ni dispersion. The catalyst showed similar activity trends in two model geometries: a between-two-plates microchannel fixed-bed reactor and a conventional fixed-bed reactor. The activity tests were conducted in the kinetic regime, where conversions of CH4 were not influenced with the gas flow rate. A lattice Boltzmann model for mixed gas flow was developed along with a boundary condition for catalytic sites. The lattice Boltzmann model was used in a multiscale simulation of the studied reaction systems and produced data that qualitatively matched the experiments.
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•Ni was incorporated into CeO2 fluorite lattice to form Ni–O–Ce solid solution.•Reversible redox nature of rod-shaped CeO2 was observed in in-situ XRD examination.•A lattice Boltzmann (LB) model for gas mixtures is coupled with a macroscopic model.•Dry reforming of methane is simulated through a modified LB bounce-back boundary.•The multiscale model qualitatively reproduces the experimental results.
In this work we investigated the influence of CuO loading and catalyst pretreatment procedure to derive an optimal CuO-CeO2 catalyst for water-gas shift (WGS) reaction, and to study in detail ...structure-activity relationships. Nanostructured catalyst samples prepared by co-precipitation and a 10, 15 and 20 mol% CuO content were examined by XRD, BET and TPR/TPD analyses and subjected to pulse WGS activity tests in the temperature range of 180-400 deg C. As evaluated by TPR/TPD and N2O chemisorption analyses, with increasing CuO loading the portion of finely dispersed CuO nanoparticles decreases on behalf of larger CuO aggregates. Strong surface structure-activity dependence in WGS reaction was observed for all catalyst samples. It was established that increasing CuO content results in higher extent of CeO2 reduction, which has a positive effect on H2 production during the WGS reaction. Increasing calcination temperature on the other hand reduces BET surface area, induced by CuO sintering and agglomeration of CeO2 particles resulting in a negative effect on H2 production. Distinctive WGS activity dependence on surface acidity of examined solids was observed for all CuO loadings.
Catalytic liquid-phase hydrogenation of aqueous nitrate solutions is presented as a potential, advanced treatment technology for the removal of excessive quantities of nitrate ions from polluted ...drinking water streams. Catalysts are briefly reviewed first, followed by mechanistic speculations and kinetics that have been proposed for the liquid-phase nitrate reduction. Subsequently, a novel process scheme consisting of integrated ion-exchange and catalytic denitrification steps is discussed.
This paper reviews also the developments in the field of catalytic wet-air oxidation (CWAO). Particular attention was given to the heterogeneously catalyzed wet-air oxidation of real industrial wastewaters (such as Kraft bleach plant effluents) in batch and continuous-flow oxidation reactors. Finally, considerable potential of the CWAO process to ultimately destroy organic pollutants in industrial effluents and detoxify them by using novel titania-supported Ru catalysts is reported.
Solution combustion synthesis was used to produce a junction between different TiO2 supports (anatase TiO2 nanorods (TNR) and nanoparticles (TNP) and TiO2 with anatase core and amorphous shell ...(a-TNR)) and narrow bandgap (BG) semiconductor β-Bi2O3. β-Bi2O3 acted as a visible-light photosensitizer and enabled us to carry out photocatalytic oxidation of water dissolved bisphenol A (BPA) with TiO2 based catalysts under visible-light illumination. Heterojunction between TiO2 and β-Bi2O3 in TNR + Bi and TNP + Bi composites enables the transfer of visible-light generated holes from the β-Bi2O3 valence band (VB) to the upper lying TiO2 VB. A p–n junction, established upon close chemical contact between TiO2 and β-Bi2O3, enables the transfer of visible-light generated electrons in the β-Bi2O3 conduction band (CB) to the TiO2 CB. In TNR + Bi and a-TNR + Bi composites, the supplied heat energy during the synthesis of samples was not sufficient to completely transform (BiO)2CO3 into β-Bi2O3. A p–n junction between (BiO)2CO3 and β-Bi2O3 enables the transfer of electrons generated by β-Bi2O3 to (BiO)2CO3. Hindered charge carrier recombination originating from the crystallinity of TiO2 is a more important factor in the overall kinetics of BPA degradation than high specific surface area of the amorphous TiO2 and reduction/oxidation of surface adsorbed substrates.
We performed in‐situ XAS study of N2O decomposition over CuO/CeO2 catalysts. The Cu K‐edge and Ce L3‐edge XANES and EXAFS analyses revealed the dynamic and crucial role of Cu2+/Cu+ and Ce4+/Ce3+ ...ionic pairs during the catalytic reaction. We observed the initial formation of reduced Cu+ and Ce3+ species during activation in helium atmosphere at 400 °C, while concentration of these species decreased significantly during steady‐state nitrous oxide degradation reaction (2500 ppm N2O in He at 400 °C). In‐situ EXAFS analysis further revealed a crucial role of copper−ceria interface in this catalytic reaction. We observed dynamic changes in average number of Cu−Ce scatters under reaction conditions, indicating an enlarging of the interface between both copper and ceria phases, where electron and oxygen transfer occurs.
Mechanistic study: In‐situ XAS study of N2O decomposition over CuO/CeO2 catalysts revealed the crucial role of copper−ceria interface and participating of Cu2+/Cu+ and Ce4+/Ce3+ ionic pairs in the catalytic cycle.
Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most important industrially applicable advanced oxidation processes (AOPs) for the decomposition of organic pollutants in water. It is ...demonstrated that manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton‐type nanocatalyst in WHPCO as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room temperature. By using X‐ray absorption spectroscopic techniques it is also shown that the superior activity of the nanocatalyst can be attributed uniquely to framework manganese, which decomposes H2O2 to reactive hydroxyls and, unlike manganese in Mn3O4 or Mn2O3 nanoparticles, does not promote the simultaneous decomposition of hydrogen peroxide. The presented material thus introduces a new family of Fenton nanocatalysts, which are environmentally friendly, cost‐effective, and possess superior efficiency for the decomposition of H2O2 to reactive hydroxyls (AOP), which in turn readily decompose organic pollutants dissolved in water.
Manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton‐type nanocatalyst in WHPCO (wet hydrogen peroxide catalytic oxidation) as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room temperature. By combined use of catalytic tests and X‐ray absorption spectroscopic techniques (XANES, EXAFS) direct evidence is given that the superior activity of the nanocatalyst is uniquely attributed to framework manganese.
The Special Issue “Engineering Materials for Catalysis” was inspired by the preceding 2020 Summer School of the European Federation of Catalysis Societies (EFCATS, https://skd2020 ...
ZnFe2O4/rGO/g-C3N4 ternary nanocomposite photocatalysts with different ZnFe2O4/g-C3N4 weight ratio (0.5, 0.75, 1) were prepared by a stepwise solvothermal method using ethylene glycol as the solvent. ...Physicochemical methods such as X-ray diffraction, UV-Vis diffuse reflectance spectroscopy and photoluminescence spectroscopy were applied in order to characterize the composites. The formation of a meso-/macroporous structure with specific surface area between 67 and 77 m2 g?1 was confirmed by N2 adsorption/desorption. The bandgap of the composites was found to be lower (2.30 eV) than that of g-C3N4 (2.7 eV). In contrast to pure g-C3N4, the composites showed no fluorescence, i.e. no recombination of e?/h+ took place. All samples, including pure g-C3N4 and ZnFe2O4, were tested for adsorption and photocatalytic degradation of aqueous malachite green model solutions (10?5 M) under visible light irradiation (? >400 nm). The results show that the prepared nanocomposites have higher absorption and photocatalytic activity than the pristine g-C3N4 and ZnFe2O4 and can be successfully used for water purification from organic azo-dyes.
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