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N-doped carbon (N-C) materials are increasingly popular in different electrochemical and catalytic applications. Due to the structural and stoichiometric diversity of these materials, however, the role of different functional moieties is still controversial. We have synthesized a set of N-C catalysts, with identical morphologies (∼27 nm pore size). By systematically changing the precursors, we have varied the amount and chemical nature of N-functions on the catalyst surface. The CO

Abstract In the present study, NiO modified ZnAl2O4 and ZnO modified NiAl2O4 spinel along with pure Al2O3, ZnAl2O4 and NiAl2O4 for comparison in the CO2 hydrogenation reaction have been investigated. It was found that NiAl2O4, NiO/ZnAl2O4 and ZnO/NiAl2O4 catalysts exhibited outstanding activity and selectivity towards methane even at high temperature compared to similar spinel structures reported in the literature. NiO/ZnAl2O4 catalyst showed CO2 consumption rate of ~ 19 μmol/g·s at 600 °C and ~ 85% as well as ~ 50% of methane selectivity at 450 °C and 600 °C, respectively. The high activity and selectivity of methane can be attributed to the presence of metallic Ni and Ni/NiO/ZnAl2O4 interface under the reaction conditions as evidenced by the XRD results. Graphic Abstract High performance Ni–Zn–Al-based oxide/spinel nanostructures is synthesized and NiO/ZnAl2O4 catalyst exhibited higher catalytic activity in the CO2 hydrogenation reaction due to the presence of metal support interaction between Ni and ZnAl2O4 support.

In this study, a series of free-standing as well as controlled size Pt nanoparticles-loaded mesoporous metal oxides (NiO, Co3O4, CeO2 and MnO2) with high surface area and designed pore structure were prepared by hard template method and used as catalysts for CO2 hydrogenation together with dry reforming of CO2 with methane. The physicochemical properties of catalysts were analysed by N2 adsorption-desorption isotherm, XRD, TEM, and H2-TPR. Pt-free and Pt-loaded mesoporous NiO and Co3O4 performed with high catalytic activity and selectivity for both CO2 activation reactions. Pt-free NiO exhibited the highest catalytic activity and also showing 100% CH4 selectivity between 473–673 K and ˜1:1 H2/CO2 ratio between 673–973 K in CO2 hydrogenation and dry reforming with methane, respectively. The enhanced catalytic properties can be due to the existence of metallic Ni as well as the optimal dynamics of Ni/NiOx structure under reaction conditions.

Water is currently becoming a strategically important material, and the importance of water and wastewater treatment technologies is therefore increasing. Wastewater from the food industry has many special features originating from its high organic matter content. Meat industry wastewater additionally has a high fat content. We investigated the effects of ultrafiltration and ozonation, individually and in combination, for the treatment of meat industrial wastewater. Ozone gas was generated from oxygen with an Ozomatic Modular 4 ozone generator (Wedeco Ltd., Germany), and filtration was carried out with a micellar-enhanced ultrafiltration (MEUF) apparatus, through a flat membrane with a surface area of 40 cm2. The experimental data revealed that pre-ozonation of the wastewater affected ultrafiltration. The flux was higher and persisted longer than in the case of non-ozonated samples. The chemical oxygen demand was decreased by ozonation treatment. The duration of ozonation and the subsequent ultrafiltration exhibited a very interesting relationship. The most important effect of ozonation was observed on membrane fouling. The fouling mechanism was modelled, and the rate constants of flux decline (k1) and deposit removal from the membrane (k2) were calculated. The effect of the Reynolds number was also shown. The aim of our work was to study the industrial effects of combined cleaning techniques, i.e. ozonation on meat processing wastewater. The optimum ozonation time was 2 to 10 min before ultrafiltration with a PES membrane with a cut-off of 5 kDa.

A series of 5 wt% NiO-xP-Al2O3 with different phosphorus loading contents (x = 0, 5, 15 and 20 wt%) were prepared by a modified sol-gel method. A significant promotional effect of phosphorus on NiO-Al2O3 in CO2 hydrogenation is observed. All the catalysts reach the highest conversion at 600 °C with 61.54 %, 62.89 %, 63.88 % and 66.13 % respectively for 5 wt% NiO-Al2O3, 5 wt% NiO-5P-Al2O3, 5 wt% NiO-15P-Al2O3 and 5 wt% NiO-20P-Al2O3 catalysts. Ni/NiO/Ni2P/Ni5P12/AlPO4 interfacial species were detected on the surface as active species on the used catalysts by X-ray photoelectron spectroscopy. The formation ratio of the metal-phosphide is relatively low ∼3−5 %, and this atomic concentration is decreasing with the rising of the phosphate content. However, the nickel enrichment in the surface layer presumable in Ni2P/Ni5P12 form is very likely according to the P 2p spectra and the authors assume that could be responsible for the enhanced catalytic activity.

The ultrafiltration of whey solutions is a common feature of dairy processes. However, the frequent fouling of ultrafiltration membranes and the subsequent cleaning cycle significantly affects the economics of the process. In this work, we investigated the effect of ultrasonically assisted ultrafiltration. The ultrafiltration of whey solution was investigated in order to determine the main parameters affecting the flux, retention and membrane fouling. The experiments were carried out with an ultrasonic combined laboratory ultrafiltration device, using regenerated cellulose ultrafiltration membranes. The results showed that increasing resistance during filtration is predominantly caused by the concentration polarization, while the participation of membrane fouling in the total resistance is negligible. The ultrasonically assisted ultrafiltration actively reduces the concentration polarization layer resistance. The retention changed slightly with ultrasound power. Practical Applications Combination of ultrasound and ultrafiltration processes in dairy industry may enhance the efficiency of whey separation processes during ultrafiltration of why solutions. The given model for describing the filtration mechanism and modified Reynolds number for ultrasonically assisted batch reactor allow the scale up of coupled ultrafiltration process for dairy industry.

The importance of biofuels is growing for both environmental and economic point of view. The usage of wastes in bio-ethanol production is investigated in our paper. Cellulose contained wastes i.e. byproduct of tobacco is used for experiments. The paper is focused mainly on the investigation of the enzyme recovery that followed the saccharification process. The membrane filtration combined with sonication was used for enzyme recovery. Our results show that recovered enzyme did not lose its activity. The patterns were originated from fermented solutions made from tobacco byproducts. Based on our results, the ultrasound accompanied by a membrane separation would be a possible and effective operation of bio-ethanol production technology.

The development of second-generation biofuels from cellulosic/lignocellulosic biomass has advantages from energy and environmental aspects, but the overall cost of the process is mainly dependent on the cost of the enzymes. Enzyme recovery and recycling is one of the most important and effective means of increasing the efficiency of enzymatic hydrolysis processes by lowering the enzyme costs. The primary objective of this study was to investigate the possibilities of enzyme recovery by membrane separation. Ultrafiltration (UF) membranes with various cut-off values and materials were used to recycle cellulase and cellobiase in model solutions and cellulosic hydrolysates. The membrane separation process was followed by determination of the flux, and its efficiency of it was measured via sugar and protein retention, and the resistances were also calculated. A polyether–sulfone membrane with a cut-off value of 5 kDa, (PES5) operated at 26.8 L m−2 h−1 with 87.3% protein rejection while a thin-film mem...