Search Results (51)

Biochemical monomer upcycling of plastic waste and its conversion into value-added products is deemed necessary, as it provides a greener and more sustainable solution to plastic waste management. In the current study, the polystyrene (PS) biodegradation potential of the fungus Phanerochaete chrysosporium NA3 was evaluated using various analytical techniques, such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), gel permeation chromatography (GPC), and high-performance liquid chromatography (HPLC). The biodegradation capacity of the fungal strain was further evaluated using a carbon dioxide (CO₂) evolution test, which showed that the PS films treated with NA3 produced more CO₂, indicating the strain’s ability to successfully utilize PS as a carbon source. The FTIR analysis of the PS films treated with NA3 showed modifications in the polymer chemical structure, including the formation of carbonyl and hydroxyl groups, which suggests the enzymatic dissociation of the polymer and the associated biodegradation mechanism. Pretreatments were found to be effective in modifying the polymer’s properties, making it more susceptible to microbial degradation, thus further accelerating the biodegradation process. The current study strongly advocates that P. chrysosporium (NA3) can be effectively used for the biochemical monomer recovery of PS waste and could be further utilized in the upcycling of plastic waste for its conversion into value-added products under the concept of circular economy. Full article

The global reliance on fossil fuels, particularly natural gas, underscores the urgency of developing sustainable methods for methane (CH₄) and carbon dioxide (CO₂) conversion. Methane, which constitutes 95% of natural gas, is a critical feedstock and fuel source. However, its high bond dissociation energy and volatility pose challenges for large-scale utilization and transport. Current research emphasizes the catalytic and plasma-assisted conversion of CH₄ and CO₂ into value-added products such as methanol, higher hydrocarbons, and organic oxygenates. Advancements in these technologies aim to overcome obstacles such as high operating temperatures, coking, and low product selectivity while addressing methane’s environmental impact, as leakage during extraction and distribution significantly contributes to global warming. Plasma-assisted conversion has emerged as a promising approach, leveraging electron impact processes to generate reactive species that facilitate CH₄ and CO₂ transformation at near-room temperatures. The integration of catalysts within plasma environments enhances reaction pathways, product yields, and selectivity by modifying plasma properties and surface interactions. This review comprehensively discusses the various methods investigated for CH₄ conversion and energy efficiency. We attempt to highlight the recent progress in plasma-assisted catalytic processes for CH₄ and CO₂ valorization, with a focus on the mechanisms of product formation, catalyst modifications, and their impact on plasma discharge characteristics. The insights gained could pave the way for scalable, energy-efficient solutions to produce sustainable fuels and chemicals, thereby contributing to global efforts in carbon cycle fixation and climate change mitigation. Full article

Since it was proposed, the replacement process, in natural gas hydrate reservoirs, has been considered as one of the most promising options to obtain an alternative and potentially carbon-neutral energy source. However, such a process shows high complexity, and its maximum efficiency cannot exceed 75% if carried out with pure carbon dioxide. The addition of minor quantities of other guest species in mixture with carbon dioxide allows higher efficiencies to be reached. This study deepens the production of hydrates with a binary mixture containing carbon dioxide and propane, with corresponding concentrations equal to 85/15 vol%. Several experiments were carried out consecutively and with the same gas–water mixture in order to ensure the system retains memory of previous formations. The results were then discussed in terms of the quantity of hydrates produced and the evolution of the formation process as a function of time. The data collected during the dissociation of hydrates were finally used to define the phase boundary of the system. Full article

The electrocatalytic reduction of nitric oxide and nitrogen dioxide (NOx) remains a significant challenge due to the need for stable, efficient, and cost-effective materials. This study presents a novel support system for NOx reduction in alkaline media, composed of ZrO₂-WO₃-C (ZWC), synthesized via coprecipitation. Platinum nanoparticles (10 wt.%) were loaded onto ZWC and Vulcan carbon support, using similar methods for comparison. Comprehensive physicochemical and electrochemical analyses (N₂ physisorption, XRD, XPS, SEM, TEM, and cyclic and linear voltammetry) revealed that PtZWC outperformed PtC and commercial PtEtek in NOx electrocatalysis. Notably, PtZWC exhibited the highest total electric charge for NOx reduction. At the same time, the hydrogen evolution reaction (HER) was shifted to more negative cathodic potentials, indicating reduced hydrogen coverage and a modified dissociative Tafel mechanism on platinum. Additionally, the combination of WO₃ and ZrO₂ in ZWC enhanced electron transfer and suppressed HER by reducing NO and hydrogen atom adsorption competition. While the incorporation of WO₃ and ZrO₂ lowered the surface area to 96 m²/g, it significantly improved pore properties, facilitating better Pt nanoparticle dispersion (3.06 ± 0.85 nm, as confirmed by SEM and TEM). XRD analysis identified graphite and Pt phases, with monoclinic WO₃ broadening PtZWC peaks (20–25°). At the same time, XPS confirmed oxidation states of Pt, W, and Zr and tungsten-related oxygen vacancies, ensuring chemical stability and enhanced catalytic activity. Full article

Rotor cooling water is a pivotal element for the safe operation of a synchronous condenser in an ultrahigh-voltage grid. To decrease the dissolved oxygen and carbon dioxide contents, tremendous efforts have been dedicated to regulating the solution pH and conductivity. The traditional chemical pH adjustment and resin regeneration methods for rotor cooling water alkalization have the disadvantages of high chemical consumption and high operation and maintenance costs. Here, we propose an electrochemical method for alkalizing the rotor cooling water of a synchronous condenser by taking advantage of the accelerating water dissociation feature in bipolar membranes. The experiments with carbon dioxide injected deionized water revealed that water dissociation in bipolar membrane is capable of increasing the solution pH from 4.6 to 5.6 and decreasing the conductivity from 9.5 μS/cm to less than 2.0 μS/cm. It is convenient to increase the solution pH from 6.5 to even 10.0 when real rotor cooling water is used. BP-A-BP is more competitive than BP-C-A-BP for alkalization purposes. The present study also provides a cost-effective and chemical-free technique to precisely control the water quality of the rotor cooling water in a synchronous condenser. Full article

The catalytic conversion of carbon dioxide (CO₂) into carbon monoxide (CO) via the reverse water–gas shift (RWGS) reaction offers a promising pathway toward a sustainable carbon cycle. However, the competing Sabatier reaction presents a significant challenge, underscoring the need for highly efficient catalysts. In this study, we developed a novel catalyst comprising cobalt-oxide-supported nickel-hydroxide nanoparticles (denoted as Co@Ni). This catalyst achieved a remarkable CO production yield of ~5144 μmol g⁻¹ at 573 K, with a CO selectivity of 77%. These values represent 30% and 70% improvements over carbon-supported Ni(OH)₂ (Ni-AC) and CoO (Co-AC) nanoparticles, respectively. Comprehensive physical characterizations and electrochemical analyses reveal that the exceptional CO yield of the Co@Ni catalyst stems from the synergistic electronic interactions between adjacent active sites. Specifically, cobalt-oxide domains act as electron donors to Ni sites, facilitating efficient H₂ splitting. Additionally, the oxygen vacancies in cobalt oxide enhance CO₂ adsorption and promote subsequent dissociation. These findings provide critical insights into the design of highly efficient and selective catalysts for the RWGS reaction, paving the way for advancements in sustainable carbon utilization technologies. Full article

Clathrate hydrate-based technologies are considered promising and sustainable alternatives for the effective management of the climate change risks related to emissions of carbon dioxide produced by human activities. This work presents a combined experimental and computational investigation of the effects of the operational procedures and characteristics of the experimental configuration, on the phase diagrams of CO₂-H₂O systems and CO₂ hydrates’ formation, growth and dissociation conditions. The operational modes involved (i) the incremental (step-wise) temperature cycling and (ii) the continuous temperature cycling processes, in the framework of an isochoric pressure search method. Also, two different high-pressure PVT configurations were used, of which one encompassed a stirred tank reactor and the other incorporated an autoclave of constant volume with magnetic agitation. The experimental results implied a dependence of the subcooling degree, (P, T) conditions for hydrate formation and dissociation, and thermal stability of the hydrate phase on the applied temperature cycling mode and the technical features of the utilized PVT configuration. The experimental findings were complemented by a thermodynamic simulation model and other calculation approaches, with the aim to resolve the phase diagrams including the CO₂ dissolution over the entire range of the applied (P, T) conditions. Full article

Calcium carbonate, renowned for its affordability and potent dephosphorization capabilities, finds widespread use as a dephosphorization agent in the direct reduction roasting of high-phosphorus oolitic hematite (HPOIO). However, its precise impact on iron recovery and the dephosphorization of iron minerals with phosphorus within HPOIO, particularly the mineral transformation rule and dephosphorization mechanism, remains inadequately understood. This study delves into the nuanced effects of calcium carbonate on iron recovery and dephosphorization through direct reduction roasting and magnetic separation. A direct reduction iron (DRI) boasting 95.57% iron content, 93.94% iron recovery, 0.08% phosphorus content, and an impressive 92.08% dephosphorization is achieved. This study underscores how the addition of calcium carbonate facilitates the generation of apatite from phosphorus in iron minerals and catalyzes the formation of gehlenite by reacting with silicon dioxide and alumina, inhibiting apatite reduction. Furthermore, it increases the liquid phase, enhancing the dissociation of metallic iron monomers during the grinding procedure, thus facilitating efficient dephosphorization. Full article

Vegetation plays an important role in absorbing carbon dioxide and accelerating the achievement of carbon neutrality. As the ecological barrier of North China, the Taihang Mountains are pivotal to the ecological construction project of China. Nevertheless, the dynamic development of the vegetation carbon sink in the region and the impact factors on the sink have not been systematically evaluated. This study employed a comprehensive approach, utilising remote sensing technology and meteorological and topographic data, in conjunction with the net ecosystem productivity (NEP) estimation model to reveal the characteristics of vegetation carbon sinks in the Taihang Mountain, and then revealed the dynamics evolution of the NEP and the inter-annual trend by using Theil–Sen Median slope estimation, the Mann–Kendall test, and the coefficient of dissociation and analysed the driving roles of the influencing factors by using the parameter optimal geographic detector. Our findings suggest that the NEP in the Taihang Mountain area has a clear growth trend in time, the average value of NEP in the Taihang Mountain area is 289 gC-m⁻²-a⁻¹ from 2000 to 2022, and the spatial distribution shows the characteristics of high in the northeast and low in the middle and west, with a gradual increase from the northeast to the southwest; the areas with high fluctuation of NEP are mainly distributed in the areas around some cities that are susceptible to the interference of natural or anthropogenic factors. The vegetation carbon sinks in the Taihang Mountains are influenced by a variety of natural factors, among which the explanatory power of each natural factor is as follows: DEM (0.174) > temperature (0.148) > precipitation (0.026) > slope (0.017) > slope direction (0.003). The natural factor DEM had the strongest explanatory power for NEP changes, and the two-by-two effects of the natural factors on vegetation carbon sinks were all significantly stronger than the effects of a single factor, in which the interaction between DEM and precipitation had the strongest explanatory power; distinguishing from climate change factors, the contribution of anthropogenic activities to NEP changes in more than 90% of the area of the Taihang Mountainous Region was more than 60%, and the driving force of anthropogenic factors on NEP changes in the Taihang Mountainous Region was significantly stronger than that of natural climate change. The contribution of anthropogenic factors to NEP changes in the Taihang Mountains was significantly stronger than that of natural climate change. The results of this study can not only provide a reference for carbon reduction and sink increase and ecological restoration projects in the Taihang Mountains but also benefit the research paradigm of vegetation carbon sequestration in other regions. Full article

The synthesis and dissociation of methane hydrate and carbon dioxide hydrate were studied. Nonflammable gas hydrates can be used to extinguish flames in confined spaces. To increase the extinguishing efficiency, it is necessary to increase the dissociation rate (gas release rate) by using surfactant. The work investigates gas hydrates synthesized using sodium dodecyl sulfate (SDS). Experimental studies were carried out in wide ranges of surfactant concentration, the number of the stirrer revolutions and the initial water volume. To achieve the maximum rate of synthesis and dissociation, optimization of the specified parameters was performed. The influence of the key parameters on the dissociation rate was investigated experimentally and theoretically. The novelty of the work lies in solving a complex of interrelated tasks on the synthesis and dissociation of gas hydrate. It is shown that in order to achieve the maximum dissociation rate of carbon dioxide hydrate, it is necessary to optimize the following parameters: the diameter of the particles and their porosity, the porosity of the layer and the external heat flux. Full article

By itself, propane is capable to form hydrates at extremely contained pressures, if compared with the values typical of “guests” such as methane and carbon dioxide. Therefore, its addition in mixtures with gases such as those previously mentioned is expected to reduce the pressure required for hydrate formation. When propane is mixed with carbon dioxide, the promoting effect cannot be observed since, due to their molecular size, these two molecules cannot fit in the same unit cell of hydrates. Therefore, each species produces hydrates independently from the other, and the beneficial effect is almost completely prevented. Conversely, if propane is mixed with methane, the marked difference in size, together with the capability of methane molecules to fit in the smaller cages of both sI and sII structures, will allow to form hydrates in thermodynamic conditions lower than those required for pure methane hydrates. This study aims to experimentally characterize such a synergistic and promoting effect, and to quantity it from a thermodynamic point of view. Hydrates were formed and dissociated within a silica porous sediment and the results were compared with the phase boundary equilibrium conditions for pure methane hydrates, defined according to experimental values available elsewhere in the literature. The obtained results were finally explained in terms of cage occupancy. Full article

The carbamate post-translational modification (PTM), formed by the nucleophilic attack of carbon dioxide by a dissociated lysine epsilon-amino group, is proposed as a widespread mechanism for sensing this biologically important bioactive gas. Here, we demonstrate the discovery and in vitro characterization of a carbamate PTM on K9 of Arabidopsis nucleoside diphosphate kinase (AtNDK1). We demonstrate that altered side chain reactivity at K9 is deleterious for AtNDK1 structure and catalytic function, but that CO₂ does not impact catalysis. We show that nucleotide substrate removes CO₂ from AtNDK1, and the carbamate PTM is functionless within the detection limits of our experiments. The AtNDK1 K9 PTM is the first demonstration of a functionless carbamate. In light of this finding, we speculate that non-functionality is a possible feature of the many newly identified carbamate PTMs. Full article

Green technologies using renewable and alternative sources, including supercritical carbon dioxide (sc-CO₂), are becoming a priority for researchers in a variety of fields, including the control of enzyme activity which, among other applications, is extremely important in the food industry. Namely, extending shelf life of e.g., flour could be reached by tuning the present enzymes activity. In this study, the effect of different sc-CO₂ conditions such as temperature (35–50 °C), pressure (200 bar and 300 bar), and exposure time (1–6 h) on the inactivation and structural changes of α-amylase, lipase, and horseradish peroxidase (POD) from white wheat flour and native enzymes was investigated. The total protein (TPC) content and residual activities of the enzymes were determined by standard spectrophotometric methods, while the changes in the secondary structures of the enzymes were determined by circular dichroism spectrometry (CD). The present work is therefore concerned for the first time with the study of the stability and structural changes of the enzyme molecules dominant in white wheat flour under sc-CO₂ conditions at different pressures and temperatures. In addition, the changes in aggregation or dissociation of the enzyme molecules were investigated based on the changes in particle size distribution and ζ-potential. The results of the activity assays showed a decrease in the activity of native POD and lipase under optimal exposure conditions (6 h and 50 °C; and 1 h and 50 °C) by 22% and 16%, respectively. In contrast, no significant changes were observed in α-amylase activity. Consequently, analysis of the CD spectra of POD and lipase confirmed a significant effect on secondary structure damage (changes in α-helix, β-sheet, and β-turn content), whereas the secondary structure of α-amylase retained its original configuration. Moreover, the changes in particle size distribution and ζ-potential showed a significant effect of sc-CO₂ treatment on the aggregation and dissociation of the selected enzymes. The results of this study confirm that sc-CO₂ technology can be effectively used as an environmentally friendly technology to control the activity of major flour enzymes by altering their structures. Full article

The conversion of carbon dioxide to fuels and chemicals is a promising long-term approach for mitigating CO₂ emissions. Despite extensive experimental efforts, a fundamental understanding of the bimetallic catalytic structures that selectively produce the desired products is still lacking. Here, we report on a computational surface science approach into the effect of the Fe doping of Co(111) surfaces in relation to CO₂ hydrogenation to C₁ products. Our results indicate that Fe doping increases the binding strength of surface species but slightly decreases the overall catalytic activity due to an increase in the rate-limiting step of CO dissociation. FeCo(111) surfaces hinder hydrogenation reactions due to lower H coverages and higher activation energies. These effects are linked to the Lewis basic character of the Fe atoms in FeCo(111), leading to an increased charge on the adsorbates. The main effect of Fe doping is identified as the inhibition of oxygen removal from cobalt surfaces, which can be expected to lead to the formation of oxidic phases on bimetallic FeCo catalysts. Overall, our study provides comprehensive mechanistic insights related to the effect of Fe doping on the catalytic behavior and structural evolution of FeCo bimetallic catalysts, which can contribute to the rational design of bimetallic catalysts. Full article

The CO₂ electrochemical reduction reaction (CO₂RR) is one of the most promising methods to reduce carbon dioxide emissions and store energy. At the same time, the pathways of CO₂ reduction reaction are diverse and the products are abundant. Converting carbon dioxide to C₂₊ products, a critical feedstock, requires a C–C coupling step with the transfer of more than 10 electrons per molecule and, hence, is kinetically sluggish. The production of some key adsorptions is conducive to the formation of C₂₊ products. In this work, we used in situ techniques to figure out the reason why hexagonal-close-packed (hcp) Co nanosheets (NSs) have high activity in CO₂RR to ethanal. According to the in situ Raman spectra, the high local pH environment on the catalyst surface is favorable for CO₂RR. The high pH at low potentials not only suppresses the competing hydrogen evolution reaction but also stimulates the production of COCO* intermediate. The isotopic labeling experiment in differential electrochemical mass spectrometry (DEMS) provides a possible sequence of the products. The ¹³CO is generated when we replace ¹²CO₂ with ¹³CO₂, which identifies the origin of the products. Besides, in situ electrochemical impedance spectroscopy (EIS) shows that the hcp Co at −0.4 V vs. RHE boosts the H₂O dissociation and proton transfer, feeding sufficient H* for CO₂ to *COOH. In the end, by analyzing the transmission electronic microscopy (TEM), we find that the Co (002) plane may be beneficial to the conversion of CO₂ and the adsorption of intermediates. Full article