Conventional Wet Impregnation Research Articles

Ultrasonic-assisted synthesis of α-Fe2O3@TiO2 photocatalyst: Optimization of effective factors in the fabrication of photocatalyst and removal of non-biodegradable cefixime via response surface methodology-central composite design

Environmental pollution becomes a major worldwide issue that threatens the entire biosphere.On the other hand, visible-light photocatalysis technology is one of the most effective approaches to wastewater treatment due to its superb removal efficiency, facile process, and ecological friendliness.Herein, a highly efficient α-Fe2O3@TiO2 nanocomposite was synthesized using a rapid sonochemical technique and a conventional wet impregnation route for the elimination of cefixime. Towards achieve the optimal photocatalyst, the influences of operational parameters including calcination temperature (300–600 °C), and Fe2O3 loadings (1-5 wt%) were examined utilizing the Response Surface Methodology (RSM). Additionally, two important factors, irradiation time (3–8 min) and power (50–90 W) of ultrasonic waves, were investigated to optimize the efficiency, dimension, and structure of the photocatalyst. Then, the manufactured nanocomposites were characterized with the aid of techniques TEM, XRD, BET, FE-SEM, EDS-map, FTIR, and UV–Vis band gap analysis. The optimal photocatalyst (3.09 wt%, 439.34 °C, 70 W, and 8 min) was used to study the effect of four efficacious variables on cefixime removal by RSM. Maximum cefixime degradation (98.8%) occurred at optimum conditions (cefixime concentration = 20.5 mg/L, pH = 4.76, Irradiation time = 103 min and catalyst dose = 0.012 g/l). Based on the empirical data, statistical analysis proved the regression model's validity and adequacy. The COD elimination revealed that in comparison with other studies the α-Fe2O3@TiO2 photocatalyst could successfully mineralize cefixime (82.4%). Generally, the stability of α-Fe2O3@TiO2 in the photocatalytic degradation of cefixime was observed across five cycles with minimal iron leaching, making it a perfect catalyst for the removal of non-biodegradable pharmaceuticals.

Bimetallic Ru–Pd supported on CeO2 for the catalytic partial oxidation of methane into syngas

A series of monometallic Ru, Pd, and bimetallic Ru–Pd catalysts loaded on CeO2 support have been prepared via mechanochemical and conventional incipient wetness impregnation methods and used in the partial oxidation of methane (POM) to obtain synthesis gas (H2 and CO). The influence of the preparation method, the order of addition of the metals, the Ru:Pd metal ratio, and the milling energy and time for samples prepared by the mechanochemical method, have been evaluated between 300 and 600 °C. The results revealed that bimetallic Ru–Pd/CeO2 catalysts outperform monometallic Ru–CeO2 and Pd–CeO2 for POM, both in terms of catalytic activity and stability. Additionally, the bimetallic Ru–Pd/CeO2 catalysts prepared by ball milling produced syngas at a much lower temperature compared to the conventional catalysts prepared by incipient wetness impregnation. Raman spectroscopy, temperature programmed reduction (H2–TPR), X–ray photoelectron spectroscopy (XPS) and high–resolution transmission electron microscopy (HRTEM) have been used to characterize the catalysts before and after reaction.

Boosting the catalytic performance of Fe/Zr catalyst by tungsten addition for selective catalytic reduction of NOx with ammonia

To clarify the effect of WO3 doping over Fe/Zr catalyst, several Fe/Zr-xW catalysts were prepared via conventional wet impregnation method, and the selective catalytic reduction (SCR) performance was studied. The Fe/Zr-0.1 W catalyst showed the highest catalytic activity and achieved nearly 100 % in a wide operating temperature window of 300–500 °C, and the N2 selectivity exceeded 90 % over the entire temperature range under a high hour space velocity of 90, 000 h−1. In addition, Fe/Zr-0.1 W catalyst also exhibited superior resistance to SO2 compared to Fe/Zr catalyst without WO3 introduction. Further characterization results indicated that the Fe/Zr-0.1 W catalyst possessed larger BET specific surface area, better dispersion of active component, higher concentration of Fe3+ and more surface chemisorbed oxygen species, which might be the predominant factors for its superior catalytic performance. More importantly, WO3 doping improved the redox capacity and surface acidity, thus promoting the redox circle and enhancing the adsorption ability of NH3. According to the transient in-situ DRIFTS experiment results, the doping of WO3 increased the L-H reaction pathway on the surface of Fe/Zr catalyst during the NH3-SCR reaction. The present work could provide a new way for developing a high-performance non-vanadium SCR catalyst in practical application.

Low-temperature partial oxidation of methane over Pd–Ni bimetallic catalysts supported on CeO2

Monometallic Pd and Ni and bimetallic Pd–Ni catalysts supported on CeO2 are prepared via mechanochemical and conventional incipient wetness impregnation methods and tested for the production of syngas by the partial oxidation of methane. Compared with monometallic Ni/CeO2 and Pd/CeO2, bimetallic Pd–Ni/CeO2 catalysts show considerable higher methane conversion and syngas yield. Additionally, the bimetallic catalysts prepared by ball milling produce syngas at lower temperature. Different preparation parameters, such as metal loading, Pd/Ni ratio, milling energy, milling time and order of incorporation of the metals are examined. The best performance is obtained with a bimetallic catalyst prepared at 50 Hz for 20 min with only 0.12 wt% Pd and 1.38 wt% Ni. Stability tests demonstrate superior stability for bimetallic Pd–Ni/CeO2 catalysts prepared by a mechanochemical approach. From the characterization results, this is explained in terms of an impressive dispersion of metal species with a strong interaction with the surface of CeO2.

Size effects on the formation of LaAlO3 phase in La-doped γ-Al2O3 after hydrothermal treatment

A series of La-doped alumina ceramics were prepared by a strong electrostatic adsorption technique in comparison with a conventional incipient wetness impregnation method. The commercial La-doped alumina support was used as a reference sample. The samples were calcined in a temperature range of 800–1200 °C. The characterization of the ceramics was performed using low-temperature nitrogen adsorption, transmission electron microscopy, X-ray diffraction analysis, and photoluminescence. A strong electrostatic interaction between alumina and lanthanum was found to affect the stabilization of alumina and the resistance of La2O3 towards agglomeration during the wet procedures. The size effects related to the formation of LaAlO3 of ∼10 nm in size from the amorphous oxide phase take place on the surface of alumina doped with lanthanum. In cases of the commercial La-modified alumina sample and the sample prepared by wetness impregnation with lanthanum nitrate, the hydrothermal treatment under mild conditions has two effects. Firstly, the La2O3 particles weakly bonded with the support grow in size. Secondly, the high-temperature calcination of the samples leads to the formation of the LaAlO3 phase. Oppositely, the samples prepared by the adsorption of La(EDTA)- complexes showed no formation of the LaAlO3 phase neither before nor after the hydrothermal treatment procedure. The key factor accelerating the dissolution of the La2O3 particles was found to be the regime of the suspension stirring.

Synthesis and Mathematical Modelling of the Preparation Process of Nickel-Alumina Catalysts with Egg-Shell Structures for Syngas Production via Reforming of Clean Model Biogas

For the work presented herein nickel catalysts supported on γ-alumina extrudates (Ni/Al) with an egg-shell structure were prepared, using a modified Equilibrium Deposition Filtration (EDF) technique. Their performance was compared, for the biogas dry reforming reaction, with corresponding Ni/Al catalysts with a uniform structure, synthesized via the conventional wet impregnation method. The bulk and surface physicochemical characteristics of all final catalysts were determined using ICP-AES, N2 adsorption-desorption isotherms, XRD, SEM, and TEM. A theoretical model describing the impregnation process for the EDF extrudates, based on the Lee and Aris model, was also developed. It was concluded that following specific impregnation conditions, the egg-shell macro-distributions can be successfully predicted, in agreement with the experimental results. It was shown that the Ni/Al catalysts with an egg-shell structure had a higher H2 yield in comparison with the ones with a uniform structure. The difference in catalytic performance was attributed to the improved surface and structural properties of the egg-shell catalysts, resulting from the modified EDF technique used for their preparation.

Kinetics of ethanol steam reforming over Ni/Olivine catalyst

Olivine, a natural mineral consisting of different metal oxides (mainly Mg, Si and Fe oxides) was used as a support for nickel catalyst used in steam reforming of ethanol. Catalyst containing different wt% of Ni on olivine were prepared by conventional wet-impregnation method and characterized by BET, XRD, SEM (coupled with EDS) and H2-TPR. The reaction was carried out in a tubular fixed bed reactor. Among all the catalysts, 5% Ni on olivine catalyst gave highest hydrogen yield as well as ethanol conversion through ethanol steam reforming reaction. The catalyst activity was analyzed by varying three important process parameters (temperature, ethanol to water molar ratio and space-time). The reaction was performed in the temperature range of 450 °C to 550 °C with 1:6 to 1:12 M feed ratio of ethanol to water at a space-time range 7.21–15.87 kg cat h/kmol ethanol. A maximum yield of 4.62 mol of hydrogen per mole of ethanol reacted was obtained at 550 °C with ethanol to steam molar ratio of 1:10 and space-time of 7.94 kg cat h/kmol ethanol with the ethanol conversion level of 97%. CHNS analysis of the spent catalyst was performed to find the coke deposited over the catalyst surface during the reaction. The power law and LHHW type kinetic models were developed. The power law model predicts the activation energy as 29.07 kJ/mol, whereas the LHHW type model gives the activation energy as 27.4 kJ/mol.

Encapsulation of ultra-small Cu–Fe into ZSM-5 zeolites for NH3-SCR with broad reaction-temperature ranges

A direct hydrothermal synthesis strategy is developed to prepare the Cu–Fe-ZSM-5 zeolites by using the ethylenediaminetetraacetic acid disodium dihydrate (EDTA-2Na·2H2O) chelated Cu2+ and Fe3+ precursors as metal sources. During the crystallization, the metal chelates were spontaneously embedded into the ZSM-5 crystals and subsequently transformed to the zeolites encapsulated copper and iron species after removing the chelating agent via the high-temperature calcination. Rigorous characterizations indicate that the resulted Cu2+/Cu+ and Fe3+/Fe2+ species are formed ultra-small nano-composites with an average diameter of ∼2.2 nm and highly dispersed in the ZSM-5 zeolite crystals. The acidity of the ZSM-5 zeolites is subtly modulated by the encapsulated Cu–Fe nano-composite. As expected, the as-prepared Cu–Fe-ZSM-5 exhibits outstanding catalytic performance for the selective catalytic reduction of NOx with ammonia (NH3-SCR) in the broad reaction temperature ranges of 220–480 °C, which is much better than the Cu–Fe/ZSM-5 prepared with the conventional wetness impregnation method. Furthermore, the resultant zeolites show high stability and good tolerance to H2O and SO2, and it is very competitive for practical application to eliminate NOx. The developed one-pot hydrothermal synthesis route by using EDTA-2Na·2H2O as chelating agent is very convenient and easily reproducible, providing a general guideline to design and fabricate the superior transition metal modified zeolite catalysts for NH3-SCR and the related reactions.

Facile synthesis of palladium incorporated NiCo2O4 spinel for low temperature methane combustion: Activate lattice oxygen to promote activity

While palladium-based catalysts are effective in low-temperature methane combustion, their high cost and scarcity render them unsuitable to fulfil the growing demand. The design of improved catalysts which can more efficiently utilize this precious metal is required. Here, by using a facile one-pot thermal decomposition method Pd-NiCo2O4 spinel catalysts with a unique structure are obtained, in which the majority of Pd incorporated into the bulk spinel structure of NiCo2O4 with limited highly dispersed PdOx species on the surface at an atomic scale. The robust 1 %Pd-NiCo2O4 spinel catalyst exhibits comparable activity in methane oxidation to that of the conventional incipient wetness impregnation 2 %Pd/NiCo2O4. Theoretical calculations and catalyst characterizations (SEM, HRTEM, XRD, XPS, XAS, ICP-OES, etc.) revealed that the enhanced activity is mainly originated from having the O p-band center closer to the Fermi level, with Pd ions incorporated into the bulk NiCo2O4via substituting for the octahedral coordinated Ni3+/Co3+.

Well-Dispersed MgAl2O4 Supported Ni Catalyst with Enhanced Catalytic Performance and the Reason of Its Deactivation for Long-Term Dry Methanation Reaction

Dry methanation of syngas is a promising route for synthetic natural gas production because of its water and cost saving characteristics, as we reported previously. Here, we report a simple soaking process for the preparation of well-dispersed Ni/MgAl2O4-E catalyst with an average Ni size of 6.4 nm. The catalytic test results showed that the Ni/MgAl2O4-E catalyst exhibited considerably higher activity and better stability than Ni/MgAl2O4-W catalyst prepared by conventional incipient wetness impregnation method in dry methanation reaction. The long-term stability test result of 335 h has demonstrated that the deactivation of the Ni/MgAl2O4-E catalyst is inevitable. With multiple characterization techniques including ICP, EDS, XRD, STEM, TEM, SEM and TG, we reveal that the graphitic carbon encapsulating Ni nanoparticles are the major reasons responsible for catalyst deactivation, and the rate of carbon deposition decreases with reaction time.

Ultrasound-assisted decoration of CuOx nanoclusters on TiO2 nanoparticles for additives free photocatalytic hydrogen production and biomass valorization by selective oxidation

• Ultrasound-assisted ultra-wet (US-UWet) impregnation synthetic method is presented. • Mixed cupric and cuprous oxides nanoclusters (< 4 nm) were decorated on TiO 2 P25. • The nanocomposite showed H 2 formation capability under low power UV irradiation. • The additive free oxidation of biomass derived model platform chemicals was studied. • Nanocomposite revealed higher selectivity comparing to P25 for HMF and BnOH oxidation. The herein presented ultrasound-assisted ultra-wet (US-UWet) impregnation synthetic approach was followed in order to avoid the drawbacks of the conventional wet impregnation synthesis. The goal was to homogeneously decorate the surface of the TiO 2 nanoparticles with nanometric sized (< 4 nm) clusters of mixed cupric and cuprous oxides. The physicochemical features of the nanocomposite (TiO 2 CuO x ) were determined by high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and Diffuse reflectance (DR) spectroscopy. TiO 2 CuO x showed an enhanced and continuous capability to generate molecular hydrogen upon low power ultraviolet irradiation. The benchmark commercial TiO 2 P25 did not reveal any H 2 formation under these conditions. TiO 2 CuO x presented also a high efficiency for the additives-free selective partial oxidation of two well established biomass derived model platform chemicals/building blocks, 5-hydroxymethylfurfural (HMF) and benzyl alcohol (BnOH) to the value-added chemicals 2,5-diformylfuran (DFF) and benzyl aldehyde (PhCHO), respectively. The nanocomposite showed higher DFF and PhCHO yield compared to P25.

Sublimable xanthate-mediated solid-state synthesis of highly interspersed g-C3N4/Ag2S nanocomposites exhibiting efficient bactericidal effects both under dark and light conditions

The synthesis of exotic nanocomposites (NCs) comprising of highly dispersed metal sulfides is challenging owing to the formation of crystalline sulfides in the conventional wet-impregnation method and sublimation characteristics of the sulfide precursors in the thermal decomposition method. Here, we employ silver amyl xanthate (Ag-Xn) precursor to demonstrate a scalable solid-state synthesis of highly interspersed metal sulfide/g-C3N4 NCs. Two strategies, namely, (i) a one-step thermal decomposition of a mixture containing intimately mixed melamine and Ag-Xn, and (ii) a two-step method in which Ag-Xn is intimately mixed with a pre-synthesized g-C3N4 followed by thermolysis, have been explored. The characterization studies revealed a high degree of amorphization of Ag2S due to its high interspersion in the g-C3N4 matrix. Among the two strategies, the two-step method has yielded higher metal loading than the one-step method and correspondingly higher efficacy in the photodegradation of methylene blue. The incorporation of Ag2S in g-C3N4 has effectively modified the density of states and minimized the electron-hole pair recombination in the optimal composition, and thereby enhanced the photocatalytic activity. The studies over Staphylococcus aureus and Escherichia coli have revealed that the two-step method NCs exhibit good bactericidal efficacy under dark and remarkable activity under visible light irradiation conditions.

Solid-phase impregnation promotes Ce doping in TiO2 for boosted denitration of CeO2/TiO2 catalysts

CeO2/TiO2 (denoted as CeTi) catalysts obtained by solid-phase impregnation behaved better in low-temperature selective catalytic reduction of NOx with NH3 (NH3-SCR) than that by conventional wet impregnation. To explore the main factors for activity distinction, the texture property, CeO2 dispersion and structure changes of TiO2 were comprehensively analyzed. It was found that surface changes of TiO2 had a significant impact on the improved activity. From results of inductively coupled plasma atomic emission spectrometer (ICP-AES), diffuse reflectance UV–vis spectroscopy (UV–vis-DRS) and Raman, it was inferred that Ce ions were partially incorporated into TiO2 lattice, accompanied with the formation of defects and vacancies during solid-phase impregnation. Accordingly, CeTi catalysts from solid-phase impregnation exhibited superiority in adsorption and activation of reactants. Further result from monitoring the preparation process indicated that the evolved NO played an important role in promoting Ce doping through depriving oxygen atoms on TiO2 surface. The interaction between Ce and Ti was enhanced. The catalyst performed better in NH3-SCR, especially at low temperature, which testified the solid-phase impregnation could be an effective method to modulate interface structure for designing efficient catalyst.

Pt/TS-1 catalysts: Effect of the platinum loading method on the dehydrogenation of n-butane

A series of catalysts in which platinum was supported on the crystalline pure titanium silicalite (TS-1) were prepared using two different loading methods, namely, an ethylene glycol (EG) reduction method and the conventional incipient wetness impregnation (IM) technique. Various characterization techniques were used to study the effect of the loading method on the physicochemical and morphological properties of the prepared catalysts. Also the effect of the platinum-loading method on the dehydrogenation of n-butane was investigated in a fixed-bed reactor. The results show that the EG method favors the formation of a more-concentrated Pt dispersion, which results in much better catalytic activities for the selective formation of butenes and butadiene (> 97 %). This phenomenon is interpreted by carrying out density functional theory (DFT) calculations with focus on the relationship between the coverage of n-butane on Pt surface and the activation barrier for the first CH bond cleavage.

Improved third-order optical nonlinearities in Ag/MoS2 Schottky-type nano/hetero-junctions

Molybdenum disulfide (MoS2) nanostructures have been prepared by a hydrothermal treatment and were decorated with metallic silver (Ag) using the conventional wet incipient impregnation process to form Ag/MoS2 nano/hetero-junctions. The physiochemical functionalities were characterized using X-ray diffraction, Fourier transfer infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. UV–Vis (ultraviolet–visible) spectroscopy shows an improved light absorption in visible region for Ag/MoS2 nano/hetero-junctions due to the surface plasmon resonance absorption. Photoluminescence (PL) studies suggest efficient photoexcited charge separation to occur in Ag/MoS2 nano/hetero-junctions due to an internal electric field formed across Schottky interface. The nonlinear responses of as-prepared samples to intense laser fields were examined using standard single-beam Z-scan technique under a 532 nm CW second-harmonic Nd:YAG laser irradiation wherein demonstrated reverse saturable absorption behaviors and self-defocusing responses due to negative lens effects were observed. The third-order nonlinear refractive index and absorption coefficient for Ag/MoS2 nano/hetero-junctions were found to be 6.5 × 10-7 cm2/W and 3.5 × 10-4 cm/W, respectively, showing 1.44 and 1.5 times enhancement than in MoS2 nanostructures.

Pd/CeO2 Catalysts Prepared by Solvent-free Mechanochemical Route for Methane Abatement in Natural Gas Fueled Vehicles

The increasing diffusion of alternative mobility solutions, ranging from electric technologies to natural gas fueled vehicles (NGVs), has led to a progressive life-cycle analysis approach of their environmental impact in terms of greenhouse gases (GHGs) emissions. This new approach prompted a careful design of the NGVs catalytic aftertreatment system in order to minimize the catalytic converter carbon footprint as well as the unburned methane emissions at tailpipe. Here, a series of Pd/CeO₂ methane oxidation catalysts were prepared by an environmentally friendly solvent-free method and compared to the commercial wet-synthesized state-of-the-art catalysts. Their application in NGVs aftertreatment systems was evaluated by testing powder catalysts and coated monolith cores for CH₄ oxidation and steam reforming, which are the main methane abatement reactions occurring in a three-way catalyst (TWC) under lean and rich conditions, respectively. Pd/CeO₂ catalysts prepared by mechanochemical synthesis initially displayed superior activity compared to their counterpart obtained by conventional wet impregnation, especially under lean oxidation conditions, but appeared less resistant to the industrial aging process after core washcoating. Lambda sweep experiments carried out under full gas composition proved that, despite needing further optimization in the washcoating and aging processes, the developed mild milling synthesis procedure is a viable way for the production of Pd/CeO₂ based catalysts for natural gas TWCs.

Nickel Supported Modified Zirconia Catalysts for CO&lt;sub&gt;2&lt;/sub&gt; Methanation in DBD Plasma Catalytic Hybrid Process

The methanation reaction has recently received considerable attention as a perspective CO2 utilization technology leading to the formation of renewable natural gas methane. This reaction is favorable at low temperature, but it is hindered of slow kinetic rates, whereas below a temperature of 270°C, the CO2 conversion is practically 0, and at higher temperatures, 350-400°C, the co-existence of secondary reactions favors the formation of CO. This is the reason why new catalysts and process conditions are continuously being investigated to maximize the methane selectivity, preferably at low reaction temperatures and at atmospheric pressure. Thus, this work is focused on the use of a heterogeneous catalyst Ni/ Zirconia supports modified by rare earth metals such as Lanthanum, tungsten and Yttrium combined to a Dielectric Barrier Discharge plasma. Three catalysts were prepared by a conventional wet impregnation method, using 15 wt% of Ni loading over zirconia supports modified with different promoters. To better define the physical, textural and chemical properties, the catalysts were characterized by the means of BET, XRD, H2-TPR, CO2-TPD. The influence of basicity, Ni crystallite size and the Ni-support interaction on the catalytic activity was clearly evidenced.

Strong metal–support interaction between palladium and gallium oxide within monodisperse nanoparticles: self-supported catalysts for propyne semi-hydrogenation

The strong metal–support interaction (SMSI) between metals and reducible supports (e.g., CeO2, TiO2, and SnO2), which has been widely investigated, plays a very important role in heterogeneous catalysis. We report the first example of SMSI between palladium (Pd) and gallium oxide (Ga2O3) within a PdGa nanoparticle (denoted as PdxGay NP, where x:y is the atomic ratio of Pd and Ga). The typical features of classic SMSI, such as electron transfer between Ga2O3 and Pd and suppression of H2 and CO adsorption, are successfully observed on PdxGay NPs. Detailed characterizations and control experiments demonstrate that the coexistence of PdGa alloy and Ga2O3 in PdxGay NPs plays a vital role in the formation of SMSI. To systematically study the effects of SMSI on catalytic performance, PdxGay NPs were used as “self-supported catalysts” for propyne semi-hydrogenation (PSH), a critical process for removing trace propyne from propylene in industry. It is shown that optimized Pd0.34Ga1 NPs give a propylene selectivity of 98.2% at a propyne conversion of 96.6% at 30 °C and atmospheric pressure, which is much higher than that of pure Pd NPs and Pd/Ga2O3 catalysts prepared by a conventional wet-impregnation method. The reaction paths of PSH on PdxGay NPs have been further revealed by density functional theory (DFT) calculations. This work may not only deepen the basic understanding of SMSI, but also promote the design and application of heterogeneous catalysts.

Palladium metal oxide/hydroxide clustered cobalt oxide co-loading on acid treated TiO2 nanorods for degradation of organic pollutants and Salmonella typhimurium inactivation under simulated solar light

Here, metal oxides/hydroxide (MO = (PdO)n·[Pd(OH)2]m, Co(OH)2, and (PdO)n·[Pd(OH)2]m/CoO, n > m) clusters were successfully co-loaded on the surface of acid-treated molten salt fluxed TiO2 nanorods (ATO-NRs) via conventional wet impregnation. The synergistic effect of palladium oxide/palladium hydroxide and cobalt oxide [((PdO)n·[Pd(OH)2]m/CoO)] co-loading on ATO-NR demonstrated by the photocatalytic degradation of Orange II dye, bisphenol A and S. typhimurium inactivation under mimicked and unfiltered solar light (Xe arc lamp) radiation. Optimum [((PdO)n·[Pd(OH)2]m/CoO)] co-loaded ATO-NRs exhibited significantly higher degradation efficiency (Orange II (91%) and BPA (97%) within 30 min of treatment) over (PdO)n·[Pd(OH)2]m (n > m) and CoO/ATO-NRs under Xe arc lamp light radiation. Also, optimal sample showed higher inactivation efficiency for S. typhimurium than (PdO)n·[Pd(OH)2]m (n > m)/ATO and CoO/ATO-NRs under UVA light radiation, however, the photocatalytic mechanisms for S. typhimurium inactivation was different than the BPA. Photoelectrochemical analyses demonstrated that the significantly accelerated charge-transfer process in metal oxides/hydroxide cluster [(PdO)n·[Pd(OH)2]m/CoO] co-loaded ATO-NRs leading to higher degradation efficiency than other studied samples. Radical trapping supports h+ and O2− as major reactive species, with OH playing a secondary role in Orange II and BPA degradation. Cell membrane interruption by reactive oxygen species (ROS) and reactions of photocatalyst with the –NH and –COOH group of protein and metalloproteins, nucleic acid in bacterial cells could be the main cause in S. typhimurium disinfection. Plausible charge transport pathways were proposed for photocatalytic degradation of organic pollutants and bacterial inactivation over the (PdO)n·[Pd(OH)2]m/CoO/ATO-NR’s.

The role of catalyst support on activity of copper oxide nanoparticles for reduction of 4-nitrophenol

Developing a facile and efficient method is an important approach for promising commercial catalytic applications. Toxic organic pollutants in waste waters are becoming a worldwide problem that threatens life on earth and prevents essential elements to sustain living organisms. Herein, the effect of catalyst support on the activity of copper oxide (CuO) nanoparticles for catalytic reduction of 4-nitrophenol (4-NP) in presence of sodium borohydride (NaBH4)-aqueous medium was discussed. A simple and conventional wet impregnation method was used for the deposition of CuO nanoparticles on several metal oxides (Al2O3, SiO2, MgO, CaO, ZnO, ZrO2). The prepared catalysts were characterized via using techniques such as X-ray diffraction (XRD), nitrogen sorption, inductively coupled plasma-optical emission spectrometry (ICP-OES), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The effect of support material on the catalytic performance of CuO nanoparticles for the reduction of 4-NP was evaluated and the performance order of support was ZrO2 > Al2O3 > SiO2 > CaO > MgO > ZnO. CuO/ZrO2 catalyst exhibited excellent catalytic activity and the pseudo-first-order rate constant was determined as 15.97 · 10−3 s−1. Considering the simple preparation process and the efficient catalytic reduction of 4-NP of CuO/ZrO2, this study opens up a marvelous chance to this material for practical application of waste water treatment.