Concentration Of Sites Research Articles

Mn/CeO2 contains enriched surface lewis acid sites and pore structures accelerated catalytic oxidation of propane at low temperature

The development of highly efficient non-precious metal catalysts for the low-temperature catalytic oxidation of volatile organic compounds (VOCs) is a critical imperative in VOCs control. In this study, a series of highly active CeMnOx catalysts with Mn-doped CeO2 were investigated. The catalysts (WHSV=30,000 mL g−1 h−1) exhibited the highest catalytic propane oxidation activity (T90 = 230 °C) and excellent stability over 600 h, When the Mn:Ce ratio was 2.5. The introduction of Mn doping resulted in modifications to the pore structure of CeO2, leading to an increase in specific surface area and enhanced gas transfer kinetics. Additionally, it induced surface electronic defects and elevated the concentration of acidic sites, thereby facilitating the adsorption and activation of propane. Consequently, these improvements contributed to an enhanced catalytic performance of the catalyst. The in-situ DRIFTS infrared spectra revealed that Mn doping reduced the activation energy of the reaction and facilitated the conversion of acetone groups as well as decomposition of carboxylic acid groups.

Advancements in Methane Dry Reforming: Investigating Nickel–Zeolite Catalysts Enhanced by Promoter Integration

A promising method for converting greenhouse gases such as CO2 and CH4 into useful syngas is the dry reformation of methane (DRM). 5Ni-ZSM-5 and 2 wt.% Ce, Cs, Sr, Fe, and Cu-promoted 5Ni-ZSM-5 catalysts are investigated for the DRM at 700 °C under atmospheric pressure. The characterization, including XRD, TPR, TPD, TPO, N2 adsorption–desorption, TGA, TEM, and Raman spectroscopy, revealed that the catalyst’s active sites are distributed throughout the pore channels and on the surface, contributing to the stability of the catalyst. Specifically, the CO2-TPO followed by the O2-TPO experiment using spent catalysts confirmed the oxidizing capacity of CO2 during the DRM reaction. The Ce-promoted catalyst showed the greatest increase in catalytic activity among other catalysts. The 5Ni+2Ce-ZSM-5 catalyst exhibited twice the concentration of acid sites compared to the Cs-promoted counterpart, even though both catalysts achieved similar quantities of active and basic sites. Without compromising H2 and CO selectivity, this finding underscores the crucial role of acid sites in enhancing CH4 and CO2 conversion. With a GHSV of 42,000 mL/(h.gcat), the 5Ni+2Ce-ZSM-5 catalyst demonstrated impressive CH4 conversion rates of 42% at 700 °C and 70% at 800 °C. The reactants spend more time over catalysts during the subsequent reduction of GHSV to 21,000 mL/(h.gcat), resulting in the best catalytic performance with 80% CH4 and 83% CO2 conversions.

Trace metal interaction with thermophilic phototrophic anaerobic bacterium Chloroflexus aurantiacus

Towards improving the knowledge of possible paleo-microorganisms interaction with trace metals (micro-nutrients and toxicants), we studied adsorption of Mn, Zn, Sr, Cd, and Pb onto modern Chloroflexus aurantiacus, thermophilic anoxygenic phototrophic bacterium which could be highly abundant in the Precambiran aquatic environments. Acid-base surface titrations allowed quantifying the number of proton-active surface groups, whereas non-electrostatic linear programming method (LPM) was used to assess the surface site concentrations and adsorption reaction constants between divalent cations (Zn, Mb, Sr, Cd, Pb) and bacterial surface, based on results of pH-dependent adsorption edge and constant-pH ‘langmuirian’ adsorption experiments. The total proton/hydroxyl binding site number of Chl. aurantiacus surfaces was sizably lower than that of other phototrophic anaerobic bacteria studied previously using similar experimental and modeling approach. Divalent metals exhibited a decreasing order of adsorption affinity (Pb > Cd ≥ Zn ≥ Mn > Sr), which reflected the order of cation hydrolysis and was similar to adsorption order on other phototrophic bacteria. At the same time, adsorption of Zn increased with increasing of temperature, from 4 °C to 60 °C and was stronger under light compared to the darkness. This suggested some active metabolic control involved in this metal interaction with bacterial surfaces. Overall, Chl. aurantiacus exhibited trace metal adsorption parameters (site number and binding constants) which were lower compared to other anoxygenic phototrophic bacteria (Rhodopseudomonas palustris; Rhodobacter blasticus) and cyanobacteria. This may reflect different bioavailability of trace metals in the paleo-ocean, given that thermophilic Chl. aurantiacus are among the oldest phototrophs on the planet.

Encapsulation of cobalt molybdate on modified hierarchical porous TS-1 zeolite catalyst for efficient oxidative desulfurization of fuel

Morphological modulation of heterogeneous catalysts has been shown to be a useful strategy for adjusting the concentration or intrinsic activity of active sites and their catalytic activity in catalysis. Herein, a hierarchical porous TS-1-supported cobalt molybdate catalyst (CoMoO4/TS-1-DR) was obtained through a facile dissolution-regrowth strategy. In an oxidative desulfurization reaction using O2 as the oxidant, the as-prepared catalyst demonstrated exceptional performance compared to the supported catalyst prepared via the impregnation method due to the bimodal pore architecture presented. Moreover, in situ CoMoO4 synthesis lowers active site leaching, thus showing better reaction stability. After 7 recycles, the removal rate of DBT still remained at 88.8%. This work offers a generic in situ encapsulation strategy for designing hierarchical porous zeolite catalysts and the synthesis of loaded metal oxides.

Enhancing hydrogen production via dry reforming of methane: Optimization of Co and Ni on scandia-ceria-zirconia supports for catalytic efficiency and economic feasibility

The Novel “Scandia-ceria incorporated zirconia” (10ScCeZr) is a well-recognized material in ceramic and solid oxide electrolytes due to stable phases (like cubic ZrO2) and oxide conducting phases (like hexagonal Sc4Zr3O12 phases). The objective of the current study is to introduce 10ScCeZr as support for bearing a proportional ratio of active sites (Ni and Co), investigating catalytic performance in DRM and studying the economic viability with respect to other catalysts. The 10ScCeZr support is used first time where the concentration of ceria is minimal to minimize the risk of oxidation of active sites but achieve the benefit of mobile lattice oxygen along with scandia and zirconia. Upon dispersion of different proportions of Ni and Co over 10ScCeZr, the reducibility pattern, stability of active sites, stability of oxide vacancy, and type of carbon deposit are modified markedly. Upon using 3: 1 Ni and Co over 10ScCeZr, the crystallinity of the catalyst is minimal, and the total concentration of active site and stable active sites doesn’t fluctuate more than 5Ni/10ScCeZr, and active sites are majorly derived by NiO. During the DRM, less inert carbon is deposited over the catalyst (than 5Ni/10ScCeZr). These physiochemical modifications over 3.75Ni1.25Co/10ScCeZr result in the highest 45 % H2 yield at 700 °C and 79 % H2 yield at 800 °C at the end of 300 min. The significant high operational savings due to the 0.44 % increased H2-yield validate the long-term financial benefits upon industrialization of the current catalyst. Now, this catalyst is open for further investigation on promotors’ effect and process optimization for developing a high-performance catalyst with excellent savings in H2-production through DRM.

A New Type of Acidic OH-Groups in the LTL Zeolite

Acidic properties of ion-exchanged LTL zeolites have been studied using FTIR spectroscopy, complemented by X-ray powder diffraction, SEM-EDX, XRF and N2 physisorption. Infrared spectra of the ion-exchanged zeolites show the presence of two intense bands of the bridging OH-groups: a narrow band at ~3640 cm−1 that is attributed to Si(OH)Al groups freely vibrating in 12 MR and a broad, intense band at ~3250 cm−1 that is assigned to bridging OH groups forming hydrogen bond with neighbouring oxygen atoms, e.g., in six-membered rings. The former can be selectively removed by caesium or rubidium cations with up to 3 Cs+ or Rb+ per unit cell readily ion-exchanged into the LTL zeolite, replacing an equivalent number of acidic OH-groups or K+ cations within the structure. The cation migration of the larger cation, evaluated by the Rietveld refinement method, occurs mostly via the main 12 MR channels. By contrast, less than 1 Li+ or Na+ cation per unit cell can be introduced under similar conditions. Accordingly, the concentration of Si(OH)Al groups in back-exchanged NH4-K-LTL with smaller cations (Li+, Na+) does not differ considerably from the concentration of Brønsted acid sites in the original NH4-K-LTL. Lower concentrations of acid sites have been detected in the samples back-exchanged with Cs+, Rb+ and K+. In addition, the acidic properties of NH4-LTL samples have been compared with a structurally related NH4-MAZ zeolite.

Sugar Transporter HmSWEET8 Cooperates with HmSTP1 to Enhance Powdery Mildew Susceptibility in Heracleum moellendorffii Hance.

The powdery mildew caused by Eeysiphe heraclei is a serious concern in Heracleum moellendorffii Hance. Therefore, exploring the mechanisms underlying sugar efflux from host cells to the fungus during the plant-fungus interaction showed great significance. The study successfully cloned HmSWEET8 and HmSTP1 genes based on RNA-seq technology. The complementation assays in yeast EBY.VW4000 found HmSWEET8 and HmSTP1 transporting hexose. Over-expressing or silencing HmSWEET8 in H. moellendorffii leaves increased or decreased powdery mildew susceptibility by changing glucose concentration in infective sites. Meanwhile, over-expressing HmSTP1 in H. moellendorffii leaves also increased powdery mildew susceptibility by elevating the glucose content of infective areas. Additionally, HmSTP1 expression was up-regulated obviously in HmSWEET8 over-expressed plants and inhibited significantly in HmSWEET8 silenced plants. Co-expressing HmSWEET8 and HmSTP1 genes significantly increased powdery mildew susceptibility compared with over-expressed HmSWEET8 or HmSTP1 plants alone. The results demonstrated that HmSTP1 may assist with HmSWEET8 to promote E. heraclei infection. Consequently, the infection caused by E. heraclei resulted in the activation of HmSWEET8, leading to an increased transfer of glucose to the apoplasmic spaces at the sites of infection, then, HmSTP1 facilitated the transport of glucose into host cells, promoting powdery mildew infection.

Value-added bioproducts by bioethanol dehydrogenation to acetaldehyde through Cu and Zn modified biochar catalysts

ABSTRACT In this study, the efficiency of a series of biochar-supported Cu catalysts, biochar-supported Zn catalysts, and biochar-supported Cu-Zn catalysts was determined through bioethanol dehydrogenation to the high-value chemical, acetaldehyde. Each metal, with weight percentages of 10, 20, and 30, and the combination of Cu-Zn, including 10 wt% of Cu and Zn, 15 wt% of Cu – 5 wt% of Zn, and 15 wt% of Cu and Zn, were fully loaded onto biochar using an incipient wetness impregnation technique. Subsequently, all biocatalysts were subjected to bioethanol dehydrogenation reactions in a temperature range of 200–400 °C. The optimum metal loading for the catalyst was found to be the combination of 15 wt% Cu and 15 wt% Zn. This catalyst resulted in a reasonable acetaldehyde yield of 56.2%, an initial bioethanol conversion of 57.3%, and a very high acetaldehyde selectivity of 98.1% at a mild reaction temperature of 300 °C and ambient pressure. These results were attributed to the optimal concentration of weak-medium acid and medium base sites. Active acid and base sites were identified through temperature-programmed desorption of ammonia (NH3-TPD) and temperature-programmed desorption of carbon dioxide (CO2-TPD), respectively. Furthermore, the reaction stability test of the best biocatalyst (15Cu-15Zn/BB) was proven by maintaining this reaction at the same temperature (300 °C) for 10 h. However, the catalytic performance slightly decreased due to the coke formation of Cu species.

Ni-Sr/TiZr for H2 from methane via POM: Sr loading & optimization.

Achieving remarkable H2 yield with significantly high H2/CO over Ni-based catalysts through partial oxidation of methane (POM) is a realistic approach to depleting the concentration of CH4 and using H2 and CO as synthetic feedstock. This study examined Ni catalysts on titania-zirconia for methane conversion via POM at 600 °C and atmospheric pressure. The addition of strontium to the catalyst was explored to improve its performance. Catalysts were characterized by X-ray diffraction, Raman-infrared-UV-vis spectroscopy, and Temperature-programmed reduction-desorption techniques (TPR, TPD). 2.5 wt% Sr addition induced the formation of the highest concentration of extreme basic sites. Interestingly, over the unpromoted catalyst, active sites are majorly generated by hardly reducible NiO species whereas upon 2.5 wt% promoted Sr promotional addition, most of active sites are derived by easily reducible NiO species. 45% CH4 conversion and 47% H2 yield with H2/CO = 3.5 were achieved over 2.5 wt% Sr promoted 5Ni/30TiO2 + ZrO2 catalyst. These results provide insight into the role of basic sites in enhancing activity through switching indirect pathways over direct pathways for POM. Further process optimization was carried out in the range of 10 000-22 000 SV, 0.35-0.75 O2/CH4, and 600-800 °C reaction temperature over 5Ni2.5Sr/30TiO2 + ZrO2 by using central composite design under response surface methodology. The optimum activity as high as ∼88% CH4 conversion, 86-87% yield of H2, and 2.92H2/CO were predicted and experimentally validated at 800 °C reaction temperature, 0.35O2/CH4 ratio, and 10 000 space velocity.

Preparation, acid modification and catalytic activity of kaolinite nanotubes in α-pinene oxide isomerization.

In this work kaolinite nanotubes (KNT) were obtained from commercial kaolin AKF-78 (Uzbekistan) by starting material sequential intercalation by DMSO and methanol, followed by treatment with a cetyltrimethylammonium chloride solution. Acid functionalization of KNT for catalytic applications was successfully performed for the first time using a two-step treatment with piranha solution (H2SO4-H2O2), which resulted in the removal of organic impurities as synthetic artifacts and an increase in specific surface area by 3.9 times (up to 159 m2 g-1), pore volume by 1.5 times (0.23 cm3 g-1) and acidity by 4.1 times (49 μmol g-1). The values of the porous structure parameters and concentration of acid sites in processed kaolinite nanotubes practically corresponded to those for natural halloysite nanotubes (HNT) modified in the same way. Both types of materials demonstrated catalytic activity in the model reaction of α-pinene oxide isomerization in various solvents, including green ones, with selectivity to trans-carveol up to 55-57% and campholenic aldehyde of 50-51%, depending on the medium used. A satisfactory correlation between solvent polarity and selectivity was also observed. To the best of our knowledge, this is the first example of using modified kaolinite nanotubes per se as a catalyst. Overall, treatment of KNT with piranha solution provides not only catalytic activity but also the opportunity for further functionalization and application of these nanomaterials.

Electrodeposition of CoSx-graphene nanoplatelets on Ni(OH)2 nanosheets for improving the pseudocapacitance performance

In the present work, binder-free CoSx–graphene nanoplatelets porous structures were coated on Ni(OH)2 nanosheets using a one-step electrodeposition process. The graphene was produced from the electroreduction of CO2∗ intermediates during the electrodeposition of CoSx. The surface morphology and interfacial bonding states of CoSx–graphene@Ni(OH)2 were sensitive to the deposition time and Co–to–thiourea molar ratio (Mr). The interface reconstruction between CoSx–graphene NCs and Ni(OH)2 nanosheets improved the pseudocapacitance performance, which was investigated at different Mr and varying deposition times. Raman spectra verified the presence of graphene and CoSx mixed phases in all heterostructure electrodes, where CoS2 was dominant at Mr = 0.2. An XPS analysis indicated the evolution of various interfacial bonding states (CO, CO, CoONi, and SO) between Ni(OH)2 nanosheets and CoSx-graphene nanoplatelets, revealing the improvement in the interfacial synergy and concentration of electroactive sites. The hybrid CoSx-graphene@Ni(OH)2 NCs at Mr = 0.2 exhibited the highest capacitance of 2116 F∙g−1 at 2 mV∙s−1 and 1618 F∙g−1 at 1 A∙g−1 compared with bare Ni(OH)2, which achieved 1212 F∙g−1 at 2 mV∙s−1 and 882.88 F∙g−1 at 1 A∙g−1, and other NCs. Bare Ni(OH)2 nanosheets retained only capacitance retention of 25 % after 2000 cycles, which improved to 70 % in all CoSx-graphene@Ni(OH)2 nanoplatelets.

A case of opioid-induced rigidity requiring naloxone administration at the time of anesthesia emergence

BackgroundOpioid-induced rigidity is typically observed during rapid administration of fentanyl. Herein, we present a case in which rigidity occurred after reversal of rocuronium during emergence from anesthesia.Case presentationA 73-year-old man underwent video-assisted partial lung resection. General anesthesia was induced with propofol, remimazolam, remifentanil, and rocuronium. Fentanyl was administered early during anesthesia. The surgery was completed without complications, and sugammadex sodium was administered for rocuronium reversal. The patient became agitated, but spontaneous breathing was maintained; therefore, the intratracheal tube was removed after the administration of flumazenil. The patient developed stiffness in the neck and jaw muscles along with remarkable skeletal muscle contractions. Dramatic improvement was observed immediately after administration of naloxone.ConclusionsEven as the simulated effect site concentration of fentanyl decreases during anesthesia emergence, opioid-induced rigidity may still occur. Rapid reversal of remimazolam by flumazenil might have contributed to the rigidity in this case.

Enhancing Water Tolerance and N2 Selectivity in NH3-SCR Catalysts by Protecting Mn Oxide Nanoparticles in a Silicalite-1 Layer.

Mn-based catalysts are promising candidates for eliminating harmful nitrogen oxides (NOx) via selective catalytic reduction with ammonia (NH3-SCR) due to their inherent strong redox abilities. However, poor water tolerance and low N2 selectivity are still the main limitations for practical applications. Herein, we succeeded in preparing an active catalyst for NH3-SCR with improved water tolerance and N2 selectivity based on protecting MnOx with a secondary growth of a hydrophobic silicalite-1. This protection suppressed catalyst deactivation by water adsorption. Interestingly, impregnating MnOx on MesoTS-1 followed by silicalite-1 protection allowed for a higher dispersion of MnOx species, thus increasing the concentration of acid sites. Consequently, the level of N2O formation is decreased. These improvements resulted in a broader operating temperature of NOx conversion and a modification of the NH3-SCR mechanism. Diffuse reflectance infrared Fourier transform spectroscopy analysis revealed that unprotected Mn/MesoTS-1 mainly followed the Eley-Rideal mechanism, while Mn/MesoTS-1@S1 followed both Langmuir-Hinshelwood and Eley-Rideal mechanisms.

Tumor-targeted delivery of hyaluronic acid/polydopamine-coated Fe2+-doped nano-scaled metal–organic frameworks with doxorubicin payload for glutathione depletion-amplified chemodynamic-chemo cancer therapy

Chemodynamic therapy (CDT), an emerging cancer treatment modality, uses multivalent metal elements to convert endogenous hydrogen peroxide (H2O2) to toxic hydroxyl radicals (•OH) via a Fenton or Fenton-like reaction, thus eliciting oxidative damage of cancer cells. However, the antitumor potency of CDT is largely limited by the high glutathione (GSH) concentration and low catalytic efficiency in the tumor sites. The combination of CDT with chemotherapy provides a promising strategy to overcome these limitations. In this work, to enhance antitumor potency by tumor-targeted and GSH depletion-amplified chemodynamic-chemo therapy, the hyaluronic acid (HA)/polydopamine (PDA)-decorated Fe2+-doped ZIF-8 nano-scaled metal–organic frameworks (FZ NMs) were fabricated and utilized to load doxorubicin (DOX), a chemotherapy drug, via hydrophobic, π-π stacking and charge interactions. The attained HA/PDA-covered DOX-carrying FZ NMs (HPDFZ NMs) promoted DOX and Fe2+ release in weakly acidic and GSH-rich milieu and exhibited acidity-activated •OH generation. Through efficient CD44-mediated endocytosis, the HPDFZ NMs internalized by CT26 cells not only prominently enhanced •OH accumulation by consuming GSH via PDA-mediated Michael addition combined with Fe2+/Fe3+ redox couple to cause mitochondria damage and lipid peroxidation, but also achieved intracellular DOX release, thus eliciting apoptosis and ferroptosis. Importantly, the HPDFZ NMs potently inhibited CT26 tumor growth in vivo at a low DOX dose and had good biosafety, thereby showing promising potential in tumor-specific treatment.

The role of cell surface sulfhydryl and amine binding sites in the removal of Cr(VI) from solution by Bacillus subtilis bacterial cells

A range of bacterial species are known to be capable of reducing soluble Cr(VI) to Cr(III), causing the precipitation of Cr(III) phases from solution, but the mechanism responsible for the initial interaction between anionic aqueous Cr(VI) and the negatively charged cell surface has not been identified. Our study examines Cr(VI) removal from solution by the Gram-positive soil bacterial species Bacillus subtilis. We measured the kinetics of Cr(VI) removal as a function of pH in B. subtilis suspensions with different Cr(VI):cell ratios, and we measured the effect of pH on the extent of Cr(VI) removal at a fixed time in experiments with B. subtilis biomass (cells plus exudates) and in experiments involving B. subtilis exudates alone. The roles of sulfhydryl and amine binding sites in Cr(VI) removal were constrained using site–specific blocking molecules, and the impact of the site blocking on Cr(VI) removal was studied as a function of pH. Our results indicate that Cr(VI) removal by B. subtilis cells under the experimental conditions is at least partially non-reversible and is dependent on binding site concentration, pH, and metal loading. Our results are consistent with a two step removal process: Cr(VI) first adsorbs reversibly onto a cell wall binding site, followed by Cr(VI) reduction to Cr(III) likely via electron transfer from cell wall electron transport chain molecules. B. subtilis exudates are capable of removing a relatively small fraction of Cr(VI) from solution, and hence our results indicate that the dominant mechanism of Cr(VI) removal requires interaction with bacterial biomass. The presence of either the sulfhydryl-specific blocking molecule or the amine-specific blocking molecule or both in the experimental systems dramatically reduces the extent of Cr(VI) reduction, especially under circumneutral pH conditions, strongly suggesting that both sulfhydryl and amine binding site types participate in the initial attachment of Cr(VI) onto the cell surface. The experiments with either sulfhydryl or amine sites blocked both exhibited a similar reduction in Cr(VI) removal to the experiments with both types of sites blocked, strongly suggesting that both types of sites are involved simultaneously in binding Cr(VI) species to the cell surface. For example, these sites could both be involved in forming a bidentate bond with Cr(VI) species, or the positive charge of an amine site in close proximity to a sulfhydryl site could be necessary in order to enable the Cr(VI) species to approach the cell wall and to bind to a sulfhydryl site. The results of this study are the first to propose a viable mechanism that can explain the binding of anionic Cr(VI) onto an overall negatively charged cell surface as a first step in the reduction to Cr(III) and subsequent removal of Cr from solution.

Impact of Sn Lewis Acid Sites on the Dehydration of Cyclohexanol.

The impact of Sn on the concentration and strength of acid sites in Al containing zeolites with MFI topology and their catalytic activity for the dehydration of cyclohexanol in the aqueous phase has been investigated. The materials maintain constant Al concentrations and consequently Bro̷nsted acid site (BAS) concentrations, while exhibiting an increasing concentration of Sn Lewis acid sites (LAS). The presence of water alters LAS(Sn), leading to weak BAS(Sn) that increases the concentration of water in the zeolite micropore, while leaving the rate of dehydration of cyclohexanol unchanged. The TOF increases with the concentration of BAS(Al) in close contact with framework LAS(Sn), referred to as BAS(Pair). The increase in the Arrhenius pre-exponential factor, without affecting the activation barrier (E a), leads to the hypothesis that the proximity of both sites allows for a later transition state induced by the polarization of the C-O bond, leading in turn to a higher transition entropy.

Adsorption of cadmium (II) on organic xerogel microspheres: effect of adding sepiolite or vermiculite and operating conditions on the adsorption capacity.

The organic xerogel (OX) was synthesized through sol-gel polymerization of formaldehyde and resorcinol in inverse emulsion using Na2CO3 as a catalyst. Meanwhile, OX containing sepiolite (OX-Sep) and vermiculite (OX-Ver) were prepared similarly to OX but adding clays during synthesis. All materials were mesoporous and presented spherical morphology, and the surface of these materials exhibited an acidic character because the concentration of acidic sites was higher than those of basic sites. Cd(II) adsorption from aqueous solutions onto OX, OX-Sep, and OX-Ver was examined, and the OX-Sep showed the highest adsorption capacity towards Cd(II) of 189.7mg/g, being 1.5, 2, and 36 times higher than that of OX-Ver, OX, and Sep. The OX-Sep capacity for adsorbing Cd(II) was significantly lessened by decreasing the pH from 7 to 4 and raising the ionic strength from 0.01 N to 0.1 N. This trend was ascribed to electrostatic attraction between the Cd+2 in water and the negatively charged surface of OX-Sep. Besides, desorption studies at pH 4 showed that the average desorption percentage of Cd(II) adsorbed on OX-Sep was 80%. The characterization results and the effect of the operating conditions on the adsorption capacity proved that electrostatic attraction and cation exchange play a crucial role in the adsorption mechanism.

The role of ceria in promoting Ni catalysts supported on phosphate‐modified zirconia for the partial oxidation of methane

AbstractThe catalytic partial oxidation of methane (POM) is aimed at the mitigation of CH4 (a highly potent greenhouse gas) from the environment and the synthesis of syngas with a high H2/CO ratio. Herein, to enhance the POM reaction, Ni‐supported phosphate‐modified‐zirconia were synthesized with promotor “Ce” to achieve high H2/CO ratio (2.4–3.2). The catalysts were characterized by surface area and porosity, X‐ray diffraction, RAMAN, temperature‐programmed experiments (TPR, CO2‐TPD, and TPO), and TEM. Increasing the ceria addition over 10Ni/PO4 + ZrO2 resulted in lower crystallinity, higher dispersion of active sites, and enhanced the surface area of catalyst. The unique and prominent reducibility and basicity of NiO‐species and surface oxide ions, respectively, are particularly notable at 4 wt.% ceria loading. At a reaction temperature of 600°C, the highest concentration of active sites and a unique concentration of moderate strength basic sites can be achieved with 4 wt.% ceria loading over 10Ni/PO4 + ZrO2. This leads to 44% conversion of CH4, 36% yield of H2, 35% yield of CO2, and H2/CO ratio of 3.16 for the POM reaction. The cyclic H2TPR‐O2TPO‐H2TPR experiment confirms the reorganization of the active site towards high temperature under oxidizing gas O2 and reducing gas H2 gas stream during the POM reaction.

“Gravettians in the Altmühl Valley”? Comprehensive Reassessment and New Data from the Sequence from the Abri I im Dorf (Neuessing, Bavaria, Germany)

Due to the high density of cave and rock shelter sites, the Altmühl Valley is one of the most essential regions of southern German Palaeolithic research. The site presented in this paper, the Abri I im Dorf, lies within the main concentration of Palaeolithic sites found in this valley, extending along its lowest stretch between Riedenburg and its confluence into the Danube in Kelheim. We present the results achieved in reassessing the archaeo-stratigraphic sequence uncovered during the excavation campaign of 1959, including the first radiocarbon dating and comprehensive analysis of the lithic, faunal and bone industry evidence. Radiocarbon evidence points to occupations dated to ca. 27 ka cal BP. At the same time, the features of the lithic assemblage (blade industry with a predominance of burins and an important presence of backed tools) fit those of Late/Final Gravettian technocomplexes in the Danube region. However, the characteristic evidence traditionally associated with these industries (Kostënki knives and shouldered points) is scarce and highly questionable. The same applies to the “shovel-like” ivory object, typically related to the Pavlovian but with a doubtful determination as a shovel and no clear parallels in this and other industries of Gravettian tradition. The faunal remains revealed that hunting activities, which occurred between late summer and the beginning of winter, concentrated on reindeer. Nonetheless, new excavations and analyses are required to confirm all these preliminary results. In this sense, future work at the Abri I im Dorf can significantly contribute to our understanding of pre-LGM human settlement dynamics in the Upper Danube.

Influence of anodic treatment of nickel in deep eutectic solvents on electrocatalytic activity in oxygen evolution and urea oxidation reactions

The influence of anodic potentiostatic treatment of nickel surface in deep eutectic solvents, ethaline and reline (eutectic mixtures of choline chloride with ethylene glycol and urea, respectively), on the electrocatalytic activity in the electrochemical reactions of oxygen evolution and urea oxidation in an aqueous alkaline medium (1 M NaOH) was investigated for the first time. It was shown that, depending on the chosen treatment potential and the nature of the eutectic solvent used, a significant increase in the rate of the studied processes was observed. Specifically, after anodic treatment of nickel under certain conditions, the polarization of the oxygen evolution reaction at a current density of 0.1 A/cm2 could be reduced by approximately 150–200 mV, and the maximum current density of urea oxidation could be increased by an order of magnitude (from 0.012 A/cm2 to 0.131 A/cm2 at a urea concentration of 0.33 mol/dm3 in alkaline solution). The observed increase in electrocatalytic activity after anodic treatment of nickel in deep eutectic solvents is likely related to changes in surface morphology patterns and the nature and concentration of relevant electroactive sites on the electrode surface. The results obtained in this work can be used for the development of highly efficient electrode materials for green hydrogen energy.