Transforming CO2 into fuels by utilizing sunlight is promising to synchronously overcome global warming and energy-supply issues. It is crucial to design efficient photocatalysts with intriguing features such as robust light-harvesting ability, strong redox potential, high charge-separation, and excellent durability. Hitherto, a single-component photocatalyst is incapable to simultaneously meet all these criteria. Inspired by natural photosynthesis, constructing artificial Z-scheme photocatalysts provides a facile way to conquer these bottlenecks. In this review, we firstly introduce the fundamentals of photocatalytic CO2 reduction and Z-scheme systems. Thereafter we discuss state-of-the-art Z-scheme photocatalytic CO2 reduction, whereby special attention is placed on the predominant factors that affect photoactivity. Additionally, further modifications that are important for efficient photocatalysis are reviewed.
A novel microextraction method based on vortex- and CO2 -assisted liquid-liquid microextraction with salt addition for the isolation of furanic compounds (5-hydroxymethyl-2-furaldehyde, 5-methyl-2-furaldehyde, 2-furaldehyde, 3-furaldehyde, 2-furoic and 3-furoic acids) was developed. Purging the sample with CO2 was applied after vortexing to enhance the phase separation and mass transfer of the analytes. The optimum extraction conditions were: extraction solvent (volume), propyl acetate (125 μL); sample pH, 2.4; vortexing time, 45 s; salt concentration, 25% w/v and purging time, 5 min. The analytes were separated using an ODS Hypersil C18 column (250×4.6 mm i.d, 5 μm) under gradient flow. The proposed method showed good linearities (r(2) >0.999), low detection limits (0.08-1.9 μg/L) and good recoveries (80.7-122%). The validated method was successfully applied for the determination of the furanic compounds in concentrated juice (mango, date, orange, pomegranate, roselle, mangosteen and soursop) and dried fruit (prune, date and apricot paste) samples.
Difficult access to 40-m-tall emergent trees in tropical rainforests has resulted in a lack of data related to vertical variations in wood CO2 efflux, even though significant variations in wood CO2 efflux are an important source of errors when estimating whole-tree total wood CO2 efflux. This study aimed to clarify vertical variations in wood CO2 efflux for emergent trees and to document the impact of the variations on the whole-tree estimates of stem and branch CO2 efflux. First, we measured wood CO2 efflux and factors related to tree morphology and environment for seven live emergent trees of two dipterocarp species at four to seven heights of up to ∼ 40 m for each tree using ladders and a crane. No systematic tendencies in vertical variations were observed for all the trees. Wood CO2 efflux was not affected by stem and air temperature, stem diameter, stem height or stem growth. The ratios of wood CO2 efflux at the treetop to that at breast height were larger in emergent trees with relatively smaller diameters at breast height. Second, we compared whole-tree stem CO2 efflux estimates using vertical measurements with those based on solely breast height measurements. We found similar whole-tree stem CO2 efflux estimates regardless of the patterns of vertical variations in CO2 efflux because the surface area in the canopy, where wood CO2 efflux often differed from that at breast height, was very small compared with that at low stem heights, resulting in little effect of the vertical variations on the estimate. Additionally, whole-tree branch CO2 efflux estimates using measured wood CO2 efflux in the canopy were considerably different from those measured using only breast height measurements. Uncertainties in wood CO2 efflux in the canopy did not cause any bias in stem CO2 efflux scaling, but affected branch CO2 efflux.
Limited knowledge about vertical variation in wood CO2 efflux (Rwood) is still a cause of uncertainty in Rwood estimates at individual and ecosystem scales. Although previous studies found higher Rwood in the canopy, they examined several tree species of similar size. In contrast, in the present study, we measured vertical variation in Rwood for 18 trees including 13 species, using a canopy crane for a more precise determination of the vertical variation in Rwood, for various species and sizes of trees in order to examine the factors affecting vertical variation in Rwood and thus, to better understand the effect of taking into account the vertical and inter-individual variation on estimates of Rwood at the individual scale. We did not find any clear pattern of vertical variation; Rwood increased significantly with measurement height for only one tree, while it decreased for two more trees, and was not significantly related with measurement height in 15 other trees. Canopy to breast height Rwood ratio was not related to diameter at breast height or crown ratio, which supposedly are factors affecting vertical variation in Rwood. On average, Rwood estimates at individual scale, considering inter-individual variation but ignoring vertical variation, were only 6% higher than estimates considering both forms of variation. However, estimates considering vertical variation, while ignoring inter-individual variation, were 13% higher than estimates considering both forms of variation. These results suggest that individual measurements at breast height are more important for estimating Rwood at the individual scale, and that any error in Rwood estimation at this scale, due to the absence of any more measurements along tree height, is really quite negligible. This study measured various species and sizes of trees, which may be attributed to no clear vertical variation because factors causing vertical variation can differ among species and sizes.
We report a case of a 59 year old man who developed venous air embolism (VAE) during an elective craniotomy for parasagittal meningioma resection. The surgery was done in the supine position with slightly elevated head position. VAE was provisionally diagnosed by sudden decreased in the end tidal carbon dioxide pressure from 34 to 18 mmHg, followed by marked hypotension and atrial fibrillation. Prompt central venous blood aspiration, aggressive resuscitation and inotropic support managed to stabilize the patient. Post operatively, he was admitted in neuro intensive care unit and made a good recovery without serious complications.
In an effort to seek a new technical platform for disposal of drinking water treatment sludge (DWTS: alum sludge), pyrolysis of DWTS was mainly investigated in this study. To establish a more sustainable thermolytic platform for DWTS, this study particularly employed CO2 as reactive gas medium. Thus, this study laid great emphasis on elucidating the mechanistic roles of CO2 during the thermolysis of DWTS. A series of the TGA tests of DWTS in CO2 in reference to N2 revealed no occurrence of the heterogeneous reaction between CO2 and the sample surface of DWTS. As such, at the temperature regime before initiating the Boudouard reaction (i.e., ≥700 °C), the mass decay patterns of DWTS in N2 and CO2 were nearly identical. However, the gaseous effluents from lab-scale pyrolysis of DWTS in CO2 in reference to N2 were different. In sum, the homogeneous reactions between CO2 and volatile matters (VMs) evolved from the thermolysis of DWTS led to the enhanced generation of CO. Also, CO2 suppressed dehydrogenation of VMs. Such the genuine mechanistic roles of CO2 in the thermolysis of DWTS subsequently led to the compositional modifications of the chemical species in pyrolytic oil. Furthermore, the biochar composite was obtained as byproduct of pyrolysis of DWTS. Considering that the high content of Al2O3 and Fe-species in the biochar composite imparts a strong affinity for As(V), the practical use of the biochar composite as a sorptive material for arsenic (V) was evaluated at the fundamental levels. This work reported that adsorption of As(V) onto the biochar composite followed the pseudo-second order model and the Freundlich isotherm model.
The CO2 capture capacity and cyclic stability of calcium oxide (CaO) prepared from cockle shells (CS) were enhanced by incorporating rice husk (RH) and binder through wet-mixing method. The cyclic reaction of calcination and carbonation was demonstrated using thermal gravimetric analyzer (TGA) which the calcination was performed in a pure N2 environment at 850 °C for 20 min and carbonation at 650 °C for 30 min in 20 vol% of CO2 in N2. The analysis using x-ray fluorescence (XRF) identified silica (Si) as the major elements in the sorbents. The RH-added sorbents also contained several types of metal elements such as which was a key factor to minimize the sintering of the sorbent during the cyclic reaction and contributed to higher CO2 capture capacity. The presence of various morphologies also associated with the improvement of the synthesized sorbents performance. The highest initial CO2 capture capacity was exhibited by CS+10%RH sorbent, which was 12% higher than the RH-free sorbent (CS). However, sorbents with the higher RH loading amount such as 40 and 50 wt% were preferred to maintain high capture capacity when the sorbents were regenerated and extended to the cyclic reaction. The sorbents also demonstrated the lowest average sorption decay, which suggested the most stable sorbent for cyclic-reaction. Once regenerated, the capture capacity of the RH-added sorbent was further increased by 12% when clay was added into the sorbent. Overall, the metal elements in RH and clay were possibly the key factor that enhances the performance of CaO prepared from CS, particularly for cyclic CO2 capture. Graphical abstract Cyclic calcination and carbonation reaction.
A series of bimetallic catalysts containing nickel supported over MgO-ZrO2 were tested for activity in the dry reforming of carbon dioxide. A nickel-cobalt bimetallic catalyst gave the best performance in terms of conversion and coke resistance from a range of Ni-X bimetallic catalysts, X=Ca, K, Ba, La, and Ce. The nitrogen-adsorption and hydrogen-chemisorption studies showed the Ni-Co bimetallic supported catalyst to have good surface area with high metal dispersion. This contributed to the high catalytic activity, in terms of conversion activity and stability of the catalyst, at an equimolar methane/carbon dioxide feed ratio. The kinetics of methane dry reforming are studied in a fixed-bed reactor over an Ni-Co bimetallic catalyst in the temperature range 700-800 °C by varying the partial pressures of CH4 and CO2. The experimental data were analyzed based on the proposed reaction mechanism using the Langmuir-Hinshelwood kinetic model. The activation energies for methane and carbon dioxide consumption were estimated at 52.9 and 48.1 kJ mol(-1), respectively. The lower value of CO2 activation energy compared to the activation energy of CH4 indicated a higher reaction rate of CO2, which owes to the strong basicity of nanocrystalline support, MgO-ZrO2.
Iron and steel industries are among the contributors of CO2 emission in large volume into the atmosphere, causing detrimental effects to the environment and the ecosystem at large scale. These industries also generate solid wastes in the form of electric arc furnace (EAF) slag during operations which result in about 10-15% slag wastes per ton of steel produced. In this study, the EAF slags from an iron and steel-making factory in Klang, Malaysia was utilized for CO2 sequestration through direct aqueous mineral carbonation. According to the surface area analysis, the fresh EAF slag has a mesoporous structure, its elemental composition shows the presence of 20.91 wt.% of CaO that was used for the sequestration of CO2 through carbonation. The sequestration capacity was found to be 58.36 g CO2/kg of slag at ambient temperature in 3 h, with the liquid/solid (L/S) ratio of 5:1 and using <63μm particle size. Moreover, the shrinking core model (SCM) was used to analyze the solid-fluid reaction in a heterogeneous phase and the CO2 sequestration shows to be controlled by the product layer phase. The EAF slag is demonstrated to have the potential of CO2 sequestration at ambient temperature.
An innovative approach was developed by incorporating high-pressure CO2 into the separate hydrolysis-fermentation of aspen leftover branches, aiming to enhance the bioethanol production efficiency. The high-pressure CO2 significantly increased the 72-h enzymatic hydrolysis yield of converting aspen into glucose from 53.8% to 82.9%. The hydrolysis process was performed with low enzyme loading (10 FPU g-1 glucan) with the aim of reducing the cost of fuel bioethanol production. The ethanol yield from fermentation of the hydrolyzed glucose using yeast (Saccharomyces cerevisiae) was 8.7 g L-1, showing increment of 10% compared with the glucose control. Techno-economic analysis indicated that the energy consumption of fuel bioethanol production from aspen branch chips was reduced by 35% and the production cost was cut 44% to 0.615 USD L-1, when 68 atm CO2 was introduced into the process. These results furtherly emphasized the low carbon footprint of this sustainable energy production approach.
The developing world is facing pivotal challenges in recent times. Among these, global warming has ominous repercussions on every segment of society, thus tracing its underlying causes is imperative. This research attempts to investigate the impact of urbanization and energy consumption on carbon dioxide emissions (CO2) for a panel of 8 Asian countries (Bangladesh, China, India, Indonesia, Malaysia, Nepal, Pakistan, and Sri Lanka) over the period 1982 to 2017. The analyses are executed using panel co-integration and Granger causality techniques. The main findings of panel co-integration reveal a long-run relationship between urbanization, energy consumption, and CO2 emissions. Furthermore, the results indicate a positive and significant impact of urbanization and energy consumption on CO2 emissions, indicating that urban development and high energy consumptions are barriers to improve environmental quality in the long run. The results also highlight bi-directional causality between energy consumption and urbanization, while unidirectional causality exists between energy consumption and CO2 emissions. Based on the obtained results, this study offers useful policy implications for plummeting carbon emissions.
The main aim of this article is to examine empirically the impact of urbanization on carbon dioxide emissions in Singapore from 1970 to 2015. The autoregressive distributed lags (ARDL) approach is applied within the analysis. The main finding reveals a negative and significant impact of urbanization on carbon emissions in Singapore, which means that urban development in Singapore is not a barrier to the improvement of environmental quality. Thus, urbanization enhances environmental quality by reducing carbon emissions in the sample country. The result also highlighted that economic growth has a positive and significant impact on carbon emissions, which suggests that economic growth reduces environmental quality through its direct effect of increasing carbon emissions in the country. Despite the high level of urbanization in Singapore, which shows that 100 % of the populace is living in the urban center, it does not lead to more environmental degradation. Hence, urbanization will not be considered an obstacle when initiating policies that will be used to reduce environmental degradation in the country. Policy makers should consider the country's level of economic growth instead of urbanization when formulating policies to reduce environmental degradation, due to its direct impact on increasing carbon dioxide emissions.
Carbon capture technologies are becoming increasingly crucial in addressing global climate change issues by lowering CO2 emissions from industrial and power generation activities. Post-combustion carbon capture, which uses membranes instead of adsorbents, has emerged as one of promising and environmentally friendly approaches among these technologies. The operation of membrane technology is based on the premise of selectively separating CO2 from flue gas emissions. This provides a number of different benefits, including improved energy efficiency and decreased costs of operation. Because of its adaptability to changing conditions and its low impact on the surrounding ecosystem, it is an appealing choice for a diverse array of uses. However, there are still issues to be resolved, such as those pertaining to establishing a high selectivity, membrane degradation, and the costs of the necessary materials. In this article, we evaluate and explore the prospective applications and roles of membrane technologies to control climate change by post-combustion carbon capturing. The primary proposition suggests that the utilization of membrane-based carbon capture has the potential to make a substantial impact in mitigating CO2 emissions originating from industrial and power production activities. This is due to its heightened ability to selectively absorb carbon, better efficiency in energy consumption, and its flexibility to various applications. The forthcoming challenges and potential associated with the application of membranes in post-carbon capture are also discussed.
This paper investigates the non-linear impacts of the agricultural, industrial, financial, and service sectors on environmental pollution in Malaysia during the 1980-2018 period. It employs the extended STIRPAT model and two indicators of environmental pollution (carbon dioxide emissions and ecological footprints). It uses the autoregressive distributed lag (ARDL) technique to estimate the parameters. Evidence from the study indicate that the agricultural, industrial, and service sectors have inverted U-shaped non-linear impacts on carbon dioxide emissions and ecological footprints, while the financial sector has a U-shaped non-linear relationship with carbon dioxide emissions and ecological footprint. These empirical outcomes are robust to diagnostic tests, structural breaks, and alternative estimation technique and proxies. The economic implication of this paper is that, at the early stage of sectoral growth, the pollution intensity of sectoral output increases, but after a certain turning point, a further increase in sectoral output will reduce environmental pollution. Precisely, environmental pollution will reduce if the agricultural, industrial, and service sectors exceed threshold levels of 11%, 44%, and 49% of GDP, respectively, while environmental pollution will be aggravated if financial sector exceeds a threshold level of 94%. Therefore, efforts to mitigate environmental pollution in Malaysia should integrate sectoral growth to attain sustainable development.
There are many advantages of geothermal energy, as an environmental friend resource. This heat radiation emanating from beneath the earth's surface presents man with good opportunities to harness it and makes a good level of agricultural food production and its processing in the EU region. The primary objective of this research is to examine the impact of geothermal energy on agri-food supply among the 27 European countries (EU27), within the time frame 1990 to 2021. The study adopted the autoregressive distributed lag (ARDL), and the findings from this study revealed that agri-food supply can increase significantly among the 13 European countries (EU13 emerging economies), leveraging on geothermal energy and economic growth variables than in the EU14 emerged economies. Furthermore, the outcome of this study showed that there could be a significant decrease in the food products coming from agricultural practices among the 13 European countries (EU13 emerging economies), due to an ineffective population density than in EU14 emerged economies. Furthermore, fossil fuel and institutional quality contribute more positively to the agri-food supply in the EU14 emerged economies than in the EU13 emerging economies. This results in an outcome that means that the agri-food supply among the EU13 emerging economies could be greatly boosted by replacing fossil fuel consumption with geothermal energy, and this facilitates the attainment of the European energy goals by the year 2030. Substituting fossil fuels with geothermal will also assist in minimizing the risks of environmental pollution and climate change. All projected calculations were seen as valid in this study, and this was confirmed by the three estimators adopted which are the pooled mean group, the mean group, and the dynamic fixed effect. This study, therefore, recommends that the 27 European countries should lay more emphasis on geothermal energy production as this will help in ensuring food security in the region. Policymakers and other government authorities as well as local and foreign investors should make more investments in geothermal energy resources as this study has proven that this will lead to agri-food security and sustainability. Not only this, it will as well curb the incidence of climate change and environmental pollution.
Addressing global environmental concerns requires the widespread adoption of renewable energy sources. More research is needed to examine the relationships between renewable energy (RE) and globalization, economic growth, and environmental quality in Indonesia. Therefore, we examined how renewable energy usage in Indonesia has changed due to the dynamic effects of globalization, financial development, and environmental quality. Time-series data were analyzed using an autoregressive distributed lag (ARDL) model to test for cointegration and long-run/short-run dynamics between 1990 and 2020. In addition to ARDL bounds testing, we used the Johansen and Engle-Granger cointegration methods for confirmation. Globalization, financial progress, human capital, greenhouse gas emissions, and economic expansion have favorable long- and short-term effects on renewable energy sources. Globalization has enabled Indonesia to expand trade, FDI, and financial investment. It has also increased energy-efficient technology use due to environmental policies. The computed results are robust enough to substitute estimators, such as dynamic ordinary least squares (DOLS), fully modified least squares (FMOLS), and canonical cointegrating regression (CCR). We recommend the implementation of policies that support financial and environmental development by utilizing renewable resources and increasing investments in renewable energy ventures.
Four porous coordination networks have been synthesized from 1,4-benzenedicarboxylate with Cl, Br, I, and NO2 substituents whose different spatial differences are sufficient to influence the coordination mode of adjacent carboxyl moieties to unlock an inter-penetrating framework to give isostructural structures. Their size and polarity differences account for the diverging CO2 adsorption performances.
OECD countries have encountered the challenges of improving the environmental sustainability while maintaining economic growth by not impairing employment. This study attempts to reexamine the environmental Kuznets curve (EKC) hypothesis by using ecological footprint as an indicator of environmental degradation. Besides, our study aims to test the validity of environmental Phillips curve (EPC) and role of clean energy on ecological footprint. Our data cover a panel of 36 OECD countries from 1995 to 2015. We adopt the second-generation panel unit root and cointegration test to account for the presence of cross-section dependence (CSD). Moreover, the long-run relationship is estimated using Common Correlated Effect Mean Group (CCEMG) and Augmented Mean Group (AMG) that are robust to CSD. Our findings reveal that the EKC hypothesis is not valid while EPC is confirmed in OECD countries. Though there is a trade-off between unemployment and environmental degradation in OECD countries, the development of new technologies, especially in the clean energy sector, could be a key factor contributing to sustainable growth and better environmental quality. Thus, it is recommended that OECD countries should focus on the development of innovative green technologies and strengthen the initiatives that promote renewable energy consumption.
Dry reforming of methane (DRM) is one of the more promising methods for syngas (synthetic gas) production and co-utilization of methane and carbon dioxide, which are the main greenhouse gases. Magnesium is commonly applied in a Ni-based catalyst in DRM to improve catalyst performance and inhibit carbon deposition. The aim of this review is to gain better insight into recent developments on the use of Mg as a support or promoter for DRM catalysts. Its high basicity and high thermal stability make Mg suitable for introduction into the highly endothermic reaction of DRM. The introduction of Mg as a support or promoter for Ni-based catalysts allows for good metal dispersion on the catalyst surface, which consequently facilitates high catalytic activity and low catalyst deactivation. The mechanism of DRM and carbon formation and reduction are reviewed. This work further explores how different constraints, such as the synthesis method, metal loading, pretreatment, and operating conditions, influence the dry reforming reactions and product yields. In this review, different strategies for enhancing catalytic activity and the effect of metal dispersion on Mg-containing oxide catalysts are highlighted.
Recent research has shown a huge impact of non-renewable energy (NRE) production on environmental health. In this context, this work analyzes the effects of GDP growth and long- and short-term consumption of renewable and non-renewable energy (RE and NRE, respectively) on carbon emission in BRICS and OECD economies. The quantile autoregressive distributed lag (QARDL) model was employed on the panel data from 1980 to 2016. Findings suggest a negative GDP-carbon emission correlation and a positive NRE-carbon emission correlation in the considered economies. Furthermore, carbon emission decreases with increase in gross capital formation, whereas trade openness does not have any significant effect on carbon emission. It has been determined that the application of the error correction method (ECM) has less effect on energy consumption as compared to the past levels and changes in energy consumption. In the long-term, a positive correlation of carbon emission and energy consumption is observed, whereas limited short-term effects of energy consumption on carbon emission are observed. Therefore, an RE-based energy production approach is recommended in the selected region for the future projects.