Clay minerals play an important role in soil organic matter (SOM) accumulation. This study used a series of pot experiments to observe carbon (C) storage in rhizosphere of two plant species Festuca rubra and Lotus corniculatus growing in three soil forming substrates dominated by various clay minerals (kaolinite, illite, and montmorillonite). Plants were either grown in separate pots filled with different substrates or plants were grown in larger pots filled with sand where clay substrates were buried in mesh bags. We tested the hypothesis that mineral associated organic matter (MAOM) storage will increase with increasing surface area of clay minerals (kaolinite < illite < montmorillonite), while the volume of larger pores (Illite > kaolinite and montmorillonite) will promote the storage of particulate organic matter (POM). Overall, the largest C storage was in montmorillonite dominated substrates followed by illite and kaolinite. These trends were the same across both types of clay exposure and for both plant species used. Accumulation of MAOM followed a similar pattern. On the contrary, accumulation of free POM was not affected by clay mineral identity and accumulation of occluded POM was significantly higher in illite compared to the other two minerals. Our results suggest that total surface area of clay minerals is crucial for accumulation of MAOM while occluded POM is more affected by the availability of larger pores.

Municipal sewage sludge (MSS) pyrolysis is constrained by low carbon stability and high heavy metal (HM) content. This study examined whether co-pyrolysis with two underexplored lignocellulosic residues, oak bark (OB) and hemp hurd (HH), could enhance biochar properties relevant to carbon sequestration and environmental safety. MSS was blended with OB or HH at different ratios and pyrolyzed at 400 and 700 °C. The biochars were characterized for physicochemical and textural properties, carbon stability and sequestration, HM fractionation, stability, and ecological risk (MRI). Pyrolysis temperature determined biochar development, while co-substrate type influenced the balance between carbon stabilization and HM immobilization. HH, with higher cellulose and hemicellulose content and lower ash content, promoted devolatilization-driven restructuring of the carbon matrix, enhancing pore development and carbon stability. The highest specific surface area (182 m2/g) was achieved for MSS:HH (50:50) at 700 °C. In contrast, OB, with higher lignin content and greater ash and Ca-rich mineral contribution, favored solid-phase condensation, higher biochar yield, and stronger mineral-mediated stabilization of Cd, Cr, Ni, and Pb. Among the tested blends, MSS:HH (25:75) at 700 °C showed the best carbon sequestration, with the lowest H/Corg (0.20) and O/Corg (0.05), the highest thermostable fraction (88%), the highest long-term carbon storage (0.62 t C/t biochar), and the greatest CO2-equivalent storage (2.3 t CO2/t biochar). All biochars remained within the low-risk MRI category. At 700 °C, Zn decreased by 87% in MSS:HH (25:75) compared to MSS biochar. Strategic feedstock selection enables production of stabilized MSS-derived biochars for carbon sequestration and environmental safety.

Platinum nanoparticles were supported on polybenzimidazole nanofibrous mats prepared by electrospinning. We have shown that electrospinning from solution, colloid, or suspension leads to different morphologies of the support. Consequently, catalysts with various Pt dispersions were obtained after the impregnation of the support with platinum acetylacetonate. In the gas-phase oxidation of model volatile organic compounds (toluene, acetone, and ethanol), the catalytic activity sharply increased when the mean Pt particle size changed from 9 to 11 nm. During catalytic tests, sintering of Pt nanoparticles was observed, which contributed to an increased catalytic activity of the aged catalysts. The sintering was ascribed to the creation of hotspots at Pt active sites. The main advantage of using electrospun polybenzimidazole as a support material is its high porosity (up to 80 %). Thus, the effect of internal diffusion can be suppressed and the Pt active sites are easily accessible to the reactants. The obtained results highlight the critical role of nanofibrous catalyst morphology in tailoring metal dispersion and catalytic performance, offering a versatile support for the design of high-performance VOC oxidation catalysts.

The increasing global volumes of waste, specifically electronic waste and sewage sludge, and their use as an alternative fuel are addressed. Only half of the collected empty printer and toner cartridges can be reused. These are “original toner cartridges” bearing the same trademark as the corresponding printer or copier, contrary to “compatible toner cartridges” with a different trademark. The other half is not reused and is either combusted or sent to landfills. This work investigates safe ways of disposing of a growing mass of waste toner powder. No present methods of disposing of the toner powder seem to be an environmentally friendly solution. Therefore, it appears that the most suitable use is as an alternative fuel in a mixture with another fuel/waste, e.g. sewage sludge. In this work, pellets of sewage sludge with waste toner powder were combusted in a fluidised bed of sand at a temperature of 800–900°C. After reaching a steady state, the flue gas was analysed for Hg, CO, CO2, NOx, SO2, NH3, HCl, heavy metals, PCDD, PCDF, PCB, and PAH at an oxygen flue gas concentration of 11%. The emissions are discussed in relation to the IED Annex VI Part 3 ELVs and the WI BAT-AELs.

Graphitic carbon nitride (GCN) is an attractive metal-free photocatalyst; however, its application in immobilized form is often limited by insufficient mechanical stability and poor adhesion of catalyst layers. Here, we report the fabrication and surface-science investigation of durable photocatalytic coatings composed of submicron GCN flakes consolidated by an oligomeric siloxane binder undergoing in-situ mineralization under UV irradiation. The photocatalytic activity of GCN induces oxidative transformation of the siloxane binder into an amorphous silica-like network, leading to pronounced changes in surface chemistry, wettability, and coating cohesion.The interfacial transformation of the binder and its impact on coating properties are elucidated using X-ray photoelectron spectroscopy, infrared spectroscopy, contact-angle measurements, and electron microscopy. Mechanochemical wet milling enables the preparation of submicron GCN flakes suitable for uniform coating formation while preserving their crystalline structure. A systematic optimization of the catalyst-to-binder ratio reveals a balance between coating porosity, mechanical durability, and photocatalytic performance.The optimized coatings exhibit stable and reproducible photocatalytic activity during repeated degradation of model organic pollutants and pharmaceutical contaminants. Their durability is further demonstrated under high hydrodynamic stress in a slit-type photomicroreactor. The results provide insight into interfacial mineralization processes in hybrid photocatalytic coatings and demonstrate a surface-engineered strategy for producing mechanically robust and functionally efficient GCN-based photocatalytic surfaces.

In this study, novel TiO2 doped photocatalysts based on carbon foam derived from Typha capensis, a sustainable and naturally abundant biomass source, were prepared and evaluated for removal of an organic dye. The carbon foam was produced through a unique two-step process involving baking and carbonization, followed by chemical activation using either NaOH or HCl to improve its surface area, porosity, and surface chemistry. TiO2 was then immobilised onto the activated carbon foam using a sol-gel method to enhance photocatalytic activity. The materials were extensively characterised, with BET surface area analysis showing a significant increase after chemical activation. The base-activated foam demonstrated the highest surface area. Microscopic analysis revealed a porous foam structure and confirmed the even distribution of TiO2 particles on the carbon surface. X-ray diffraction analysis verified the presence of the anatase phase of TiO2, which is known for its superior photocatalytic activity. Photocatalytic tests showed that the acid-activated carbon foam doped with TiO2 exhibited the best performance, achieving a Rhodamine B degradation efficiency of approximately 19% under UV light. The superior activity is believed to stem from the improved surface chemistry introduced by acid activation, which aids TiO2 dispersion and interaction with the pollutant molecules. This study highlights the potential of the novel carbon foam as a sustainable, low-cost, and potentially effective photocatalyst support for water treatment.

The high surface area MgO catalysts (300 m2g−1) were prepared by mechanochemical reaction of low-surface-area MgO sources (<35 m2g−1) with water or water/alcohol mixtures in a planetary mill or mortar and pestle mill, followed by drying, dechlorination and calcination in air. The content of residual chlorides in catalysts was determined by instrumental neutron activation analysis. The microstructural properties of the catalyst were determined by X-ray diffraction and nitrogen physisorption measurements. The addition of alcohols broadened mesopores of MgOs. The intensive milling in the planetary mill effected MgO mesopores with diameters of about 20–60 nm and increased activity in Guerbet coupling of absolute ethanol to 1-butanol. This MgO catalyst was also evaluated in Guerbet coupling at atmospheric pressure and 400 °C using azeotropic bioethanol/water mixture. About 40 wt.% conversion of ethanol was reached yielding about 13 wt.% of 1-butanol and about 12 wt.% of other alcohols. The modeling of rectification showed feasibility of the product separation. The lowest energy and mass losses were achieved using a 3-column set-up enriched for the C6 and C8 alcohol separation. At the same time, up to 55 wt.% of ethanol can be recycled.

The urgent demand for efficient carbon capture technologies has sparked the search for simple, scalable materials with tailored sorption properties. In this study, we demonstrate that unmodified cellulose acetate (CA) nanofiber membranes can serve as effective CO2 sorbents at room temperature, offering a low-cost and environmentally friendly alternative to chemically modified polymeric systems. The distinct wrinkled morphology of the CA nanofibers achieved through targeted electrospinning conditions (solvent selection and high humidity) enhances the surface area and contributes to a CO2 sorption capacity of up to 2.14 mmol/g, comparable to that of more complex porous materials. Beyond single-material systems, we emphasize the often-overlooked role of matrix–additive compatibility in composite membranes. Using a CA/β-zeolite system as a case study, we show that specific interactions between the polymer matrix and active phase–β- ammonium zeolite can entirely suppress CO2 sorption instead of the assumed synergy of sorption properties for both components. The cellulose-based support was chosen for its biodegradability and biocompatibility, further supporting its use in sustainable technologies. To address the stability of modifying agents, we introduce a sandwich-type nanofiber membrane architecture (CA/Zeolite/CA) in which active nanocrystals–β-zeolites are embedded and fixed within layered structures. However, the sandwich structure of the membrane in this case indicated a negative effect of the mutual interaction of the CA carrier and β-ammonium zeolites on the sorption capacity of the composite membrane. Overall, the combination of simplicity, performance, and green chemistry makes CA nanofiber membranes a promising candidate for scalable and sustainable CO2 capture.

The mixed oxides (MOs) serve as catalysts for many reactions such as transesterification, transformation of ethanol to butanol, catalytic cracking, or dehydrogenation reactions. MOs are usually synthesized from hydrotalcites, which are often prepared by the coprecipitation method. However, some chemicals can remain after coprecipitation and influence the properties of MOs, including subsequent applications. The novelty lies in investigating how the residual chemicals affect the properties of hydrotalcites, MOs, and the transesterification reaction (conducted in both one- and two-step processes). Mg-Al and Mg-Fe hydrotalcites were synthesized from chloride and nitrate salts via coprecipitation with NaOH, followed by washing with varying amounts of redistilled water, resulting in variations in the sodium ion content (more water, less sodium ions). All materials were characterized by many analytical methods such as X-ray diffraction, metal determination, scanning electron microscopy, textural properties, and basicity determination. MOs synthesized from chlorides contained stable NaCl, which is not catalytically active, and blocked the pores, leading to a reduced surface area and, consequently, a lower transesterification yield. In contrast, MOs prepared from nitrates contained unstable NaNO3, which decomposed during calcination and, upon exposure to water, formed basic species (NaOH) that promoted transesterification. Therefore, the effect of residual sodium varies depending on the material precursors. This understanding helps us to improve the synthesis of hydrotalcites and mixed oxides.

Sulphide catalysts containing Co, Ni, Mo and/or W catalyse hydrogenolysis of carbon sulphur/nitrogen/oxygen bonds and they are widely used in the hydrodesulphurization (HDS) of petroleum fractions. The HDS process produces H2S, which is subsequently partially oxidized to water and elemental sulphur in the Claus process. Nevertheless, this process can be overflowed with H2S. Sulphide catalysts are therefore investigated for the direct thermo-catalytic decomposition of H2S to form H2 and elemental sulphur. This work tailors on a novel and straightforward preparation method of the unsupported form of Co/MoS2, Ni/MoS2, Ni/WS2 and Ni/MoWS2 catalysts. The aqueous slurry of CoCO3.Co(OH)2 or 2NiCO3.3Ni(OH)2 & sdot;4H2O reacts with MoS2, WS2 or MoS2+WS2 during milling in a planetary mill. After drying and re-sulphidation, the catalyst is characterised by its specific surface area (SBET), free sulphur vacancies (O2 up-take), crystalline size of molybdenite and/or tungstenite (DXRD), activity in thiophene (Th) and 4,6-dimethyldibenzothiophene (4,6DMDBT) HDS, and activity in thermocatalytic decomposition of H2S. We concluded that the prepared catalysts are active in Th and 4,6DMDBT hydrodesulphurization, and thermo-catalytic decomposition of H2S. The Ni/WS2 is the most active in all reactions and also the most selective to direct desulphurization (DDS) during the 4,6DMDBT HDS. WS2 best suits the studied preparation method.

Consensus holds that clay minerals play an important role in accumulation of soil organic matter, especially mineral associated organic matter (MAOM). However, little is known about how clay minerals interact with litter and soil fauna. This study used a series of year long microcosms experiments to observe the carbon (C) storage trajectories of three soil forming substrates dominated by the individual clay minerals of kaolinite, illite, and montmorillonite, supplied by litter from two tree species with contrasting carbon (C) to nitrogen (N) ratios (alder and oak), in the presence or absence of earthworms. We tested the hypothesis that MAOM would become a major source of soil organic matter. We expected storage to increase with increasing surface area of clay minerals (kaolinite < illite < montmorillonite), litter decomposability (oak < alder), and earthworm processing. Experiment showed that illite provided the greatest C storage in mineral layer (in average 0.53 g microcosms(-1)) followed by montmorillonite (0.25 g) and kaolinite (0.10 g), despite highest surface area of montmorillonite. C storage also appeared higher in soils supplied by alder litter relative to those supplied by oak litter. Soils with earthworms showed higher C storage relative to those evolving in the absence of earthworms. Most of the C stored in soils resided in the particulate organic matter fraction (POM), most pores of montmorillonite were nm size, too small to accommodate POM, while illite showed the highest proportion of micrometer size pores. Statistics detected a positive correlation between C storage, microbial biomass, respiration, and hot water extractable carbon. Results also showed that incorporation of POM from litter into mineral soil is a crucial transfer. This process becomes more pronounced in the presence of earthworms and easily decomposable litter.

Copper silicide based electrocatalytical system produces distinguishable main products depending on electrolyte's pH value with both high selectivity and faradaic efficiency. No material deterioration is observed even after 700 hours of operation.

Download This Paper Open PDF in Browser Add Paper to My Library Share: Permalink Using these links will ensure access to this page indefinitely Copy URL Copy DOI

In recent years, porous materials have been extensively studied by the scientific community owing to their excellent properties and potential use in many different areas, such as gas separation and adsorption. Hyper-crosslinked porous polymers (HCLPs) have gained attention because of their high surface area and porosity, low density, high chemical and thermal stability, and excellent adsorption capabilities in comparison to other porous materials. Herein, we report the synthesis, characterization, and gas (particularly CO2) adsorption performance of a series of novel styrene-based HCLPs. The materials were prepared in two steps. The first step involved radical copolymerization of divinylbenzene (DVB) and 4-vinylbenzyl chloride (VBC), a non-porous gel-type polymer, which was then modified by hyper-crosslinking, generating micropores with a high surface area of more than 700 m(2) g(-1). In the following step, the polymer was impregnated with various polyamines that reacted with residual alkyl chloride groups on the pore walls. This impregnation substantially improved the CO2/N-2 and CO2/CH4 adsorption selectivity.

Converting raw biomass into valuable products protects the environment, improves economics, and helps tackle climate change by cutting resource demand and waste production. Thermochemical treatment is a common method for producing biochars, hydrochars and torreficates from biomass and organic wastes, which can also generate dioxins and furans and consequently limit the use of thermochemically converted chars. Here we review the presence of dioxins and furans in chars produced by hydrothermal carbonization, torrefaction, and pyrolysis processes under the influence of temperature, residence time, heating rate, pressure, and feedstock type. Dioxins and furans were mostly below 20 ng total toxic equivalence per kilogram (TEQ kg −1 ), with the highest level of 113 ng TEQ kg −1 found in over 100 samples of different char types. The most toxic products were hydrochars produced from sewage sludge. Processing temperature and feedstock type were key factors resulting in high dioxin levels in chars, and care should be taken when producing chars at temperatures up to 300 °C or using feedstocks previously contaminated with dioxins or preservatives.

The treatment and disposal of sewage sludge is one of the most important and critical problems of wastewater treatment plants. 8.7 million tonnes of dry matter of sewage sludge were produced annually in the European Union in the year 2020. Due to the fact that sewage sludge contains a large number of substances that are not beneficial for human health, the conditions for sludge management will be significantly tightened in the EU countries. One option for sludge liquidation is the production of biofuel in a form of granules or pellets from sewage sludge enriched by waste celluloses. The achieved results show that the resulting quality of such alternative biofuel is fully comparable to conventional fossil fuels. The economic analysis is based on the simulation of cash flows associated with the implementation of the project over the lifetime and the calculation of levelised cost (LCOE). Results shows (under the current economic situation) that solar dryer technology ensures the lowest LCOE at the level of 26 EUR/GJ in fuel. If the LCOE of the alternative biofuel includes the price of the saved emission allowance and the future costs of sewage sludge disposal, the resulting price is directly competitive with lignite. The results thus clearly show that there is an ecological and economically competitive substitute for solid fossil fuels, which may be an important step for the future use of local combustion sources such as district heating plants.

This study focused on mullite-based and forsterite-based ceramic bricks fired at 1000 °C from mixtures of fly ash (40 mass%) and kaolins or vermiculites (60 mass%). The structural, physical, and mechanical properties were characterized by X-ray powder diffraction, nitrogen physisorption, mercury porosimetry, thermogravimetry, and compressive strength. In the development of green-material-derived photocatalysts, we evaluated fly ash ceramic bricks based on kaolins and vermiculites, which deserve deeper research. Alkali potassium in the mixtures positively influenced the reduction of the firing temperature, shrinkage, small porosity, and high compressive strength of ceramic bricks. The crystallization of mullite in fly ash was observed on exotherm maxima from 813 to 1025 °C. Muscovite/illite admixture in kaolins precursor of mullite-based ceramics reduced the crystallization temperature of mullite by up to 70 °C. Vermiculite–hydrobiotite–phlogopite in mixed layers of a raw vermiculite precursor of forsterite-based ceramics controlled the formation of enstatite and forsterite in the temperature range from 736 ± 6 °C to 827 ± 6 °C. Mullite- and forsterite-based ceramic bricks were also investigated for photocatalytic hydrogen production. The photocatalytic generation of hydrogen in the presence of mullite-based ceramic bricks was positively correlated with the percentages of Fe2O3 in the lattice of mullites and in the presence of forsterite-based ceramics with the presence of diopside. Mullite-based ceramic produced the highest yield of hydrogen (320 µmol/gcat after 4 h of irradiation) in the presence of mullite with the highest 10.4% substitution of Fe2O3 in the lattice. The forsterite-based ceramic produced the highest hydrogen yields (354 µmol/gcat after 4 h of irradiation) over more active diopside than forsterite.

Hollow cathode plasma sputtering is an advantageous method of preparing catalysts in the form of thin oxide films on supports. Such catalysts are particularly suitable for processes such as catalytic total oxidation of volatile organic compounds (VOCs), representing an economically feasible and environmentally friendly method of VOC abatement. Catalysts with Ni:Co molar ratios of 1:4, 1:1, and 4:1 were prepared on stainless-steel meshes and compared with single-component Ni and Co oxide catalysts. The properties of the catalysts were characterized by EDX, SEM, powder XRD, temperature-programmed reduction (H2-TPR), Raman spectroscopy, and XPS. Powder XRD revealed the formation of various crystalline phases that were dependent on molar the Ni:Co ratio. NiO and Co3O4 were identified in the single-component Ni and Co oxide catalysts, whereas Ni-Co mixed oxides with a spinel structure, together with NiO, were found in the catalysts containing both Ni and Co. Raman spectra of the catalysts prepared at high working pressures showed a slightly lower intensity of bands, indicating the presence of smaller oxide particles. The TPR profiles confirmed the improved reducibility of the Ni-Co oxide catalysts compared to the single-component Ni and Co catalysts. Catalytic activity was investigated in the deep oxidation of ethanol and toluene, which were used as model volatile organic compounds. In ethanol oxidation, the activity of sputtered catalysts was up to 16 times higher than that of the commercial Cu-Mn oxide catalyst EnviCat® VOC-1544. The main benefits of the sputtered catalysts are the much lower content of Ni and Co oxides and a negligible effect of internal diffusion. Moreover, the process of plasma jet sputtering can be easily implemented on a large scale.

Structured catalytic membranes with high porosity and a low pressure drop are particularly suitable for industrial processes carried out at high space velocities. One of these processes is the catalytic total oxidation of volatile organic compounds, which is an economically feasible and environmentally friendly way of emission abatement. Noble metal catalysts are typically preferred due to high activity and stability. In this paper, the preparation of a thermally stable polybenzimidazole electrospun membrane, which can be used as a support for a platinum catalyst applicable in the total oxidation of volatile organic compounds, is reported for the first time. In contrast to commercial pelletized catalysts, high porosity of the membrane allowed for easy accessibility of the platinum active sites to the reactants and the catalytic bed exhibited a low pressure drop. We have shown that the preparation conditions can be tuned in order to obtain catalysts with a desired platinum particle size. In the gas-phase oxidation of ethanol, acetone, and toluene, the catalysts with Pt particle sizes 2.1 nm and 26 nm exhibited a lower catalytic activity than that with a Pt particle size of 12 nm. Catalysts with a Pt particle size of 2.1 nm and 12 nm were prepared by equilibrium adsorption, and the higher catalytic activity of the latter catalyst was ascribed to more reactive adsorbed oxygen species on larger Pt nanoparticles. On the other hand, the catalyst with a Pt particle size of 26 nm was prepared by a solvent evaporation method and contained less active polycrystalline platinum. Last but not least, the catalyst containing only 0.08 wt.% of platinum achieved high conversion (90%) of all the model volatile organic compounds at moderate temperatures (lower than 335 °C), which is important for reducing the costs of the abatement technology.

NiMo sulfide catalysts were prepared by the impregnation of high surface area supports with an aqueous solution made of NiCO3·2Ni(OH)2, MoO3 and citric acid, followed by freeze drying and sulfidation in H2S/H2 mixture. N2 physisorption and X-ray diffraction were selected to investigate the amphoteric oxides Al2O3 and TiO2, acidic SiO2-Al2O3 and activated carbon supports, fresh prepared sulfide NiMo catalysts and spent catalysts after model parallel reaction of octanoic acid deoxygenation and 1-benzothiophene hydrodesulfurization. The studied mesoporous amphoteric oxides Al2O3 and TiO2 did not lead to highly active NiMo catalysts due to the low hydrothermal stability of these supports during the preparation of the active sulfide phase and deoxygenation reaction. The most active catalyst based on oxidic support was the NiMo sulfide supported on acidic mesoporous SiO2-Al2O3, which was explained by the increased stability of this support to the water and CO/CO2 mixture during the activation of the sulfidic phase and deoxygenation reaction. The extraordinarily high stability of the activated carbon support led to outstanding activities of the sulfidic NiMo/C catalyst.