In this study, several simple equations are suggested to investigate the effects of size and density on the number, surface area, stiffening efficiency, and specific surface area of nanoparticles in ...polymer nanocomposites. In addition, the roles of nanoparticle size and interphase thickness in the interfacial/interphase properties and tensile strength of nanocomposites are explained by various equations. The aggregates/agglomerates of nanoparticles are also assumed as large particles in nanocomposites, and their influences on the nanoparticle characteristics, interface/interphase properties, and tensile strength are discussed. The small size advantageously affects the number, surface area, stiffening efficiency, and specific surface area of nanoparticles. Only 2 g of isolated and well-dispersed nanoparticles with radius of 10 nm (
R
= 10 nm) and density of 2 g/cm
3
produce the significant interfacial area of 250 m
2
with polymer matrix. Moreover, only a thick interphase cannot produce high interfacial/interphase parameters and significant mechanical properties in nanocomposites because the filler size and aggregates/agglomerates also control these terms. It is found that a thick interphase (
t
= 25 nm) surrounding the big nanoparticles (
R
= 50 nm) only improves the
B
interphase parameter to about 4, while
B
= 13 is obtained by the smallest nanoparticles and the thickest interphase.
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•There is a global need to use plants to restore the ecological environment.•Here we conduct a systematic review of phytoremediation mechanisms and it’s the parameters.•Plants mainly ...use their own metabolism including the interaction with microorganisms.•This is affected by light intensity, stomatal conductance, temperature and microbial species.•Further research is needed to study the effects of catalysts in phytoremediation.
There is a global need to use plants to restore the ecological environment. There is no systematic review of phytoremediation mechanisms and the parameters for environmental pollution. Here, we review this situation and describe the purification rate of different plants for different pollutants, as well as methods to improve the purification rate of plants. This is needed to promote the use of plants to restore the ecosystems and the environment. We found that plants mainly use their own metabolism including the interaction with microorganisms to repair their ecological environment. In the process of remediation, the purification factors of plants are affected by many conditions such as light intensity, stomatal conductance, temperature and microbial species. In addition the efficiency of phytoremediation is depending on the plants species-specific metabolism including air absorption and photosynthesis, diversity of soil microorganisms and heavy metal uptake. Although the use of nanomaterials and compost promote the restoration of plants to the environment, a high dose may have negative impacts on the plants. In order to improve the practicability of the phytoremediation on environmental restoration, further research is needed to study the effects of different kinds of catalysts on the efficiency of phytoremediation. Thus, the present review provides a recent update for development and applications of phytoremediation in different environments including air, water, and soil.
Indoor air pollution with toxic volatile organic compounds (VOCs) and fine particulate matter (PM2.5) is a threat to human health, causing cancer, leukemia, fetal malformation, and abortion. ...Therefore, the development of technologies to mitigate indoor air pollution is important to avoid adverse effects. Adsorption and photocatalytic oxidation are the current approaches for the removal of VOCs and PM2.5 with high efficiency. In this review we focus on the recent development of indoor air pollution mitigation materials based on adsorption and photocatalytic decomposition. First, we review on the primary indoor air pollutants including formaldehyde, benzene compounds, PM2.5, flame retardants, and plasticizer: Next, the recent advances in the use of adsorption materials including traditional biochar and MOF (metal–organic frameworks) as the new emerging porous materials for VOCs absorption is reviewed. We review the mechanism for mitigation of VOCs using biochar (noncarbonized organic matter partition and adsorption) and MOF together with parameters that affect indoor air pollution removal efficiency based on current mitigation approaches including the mitigation of VOCs using photocatalytic oxidation. Finally, we bring forward perspectives and directions for the development of indoor air mitigation technologies.
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•Indoor air pollution is a threat to human health and needs to be removed.•Harmful pollutants comprise formaldehyde, benzene, PM2.5, and flame retardants.•Adsorption and photocatalytic decomposition are the current mitigation techniques.•Parameters that affect the indoor pollution mitigation efficiency are highlighted.
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•Key concepts, mode, operating parameters, and products of current pyrolysis applications are reviewed.•Heat transfer is more efficient in microwave pyrolysis of biomass waste.•Lack ...of top-tier reactor design blocks the commercialization of microwave pyrolysis.•Microwave pyrolysis produces engineered activated biochar with desirable properties.•Engineered activated biochar has wide application in pollution control, catalysis and energy storage.
Biomass waste represents the promising surrogate of fossil fuels for energy recovery and valorization into value-added products. Among thermochemical conversion techniques of biomass, pyrolysis appears to be most alluring owing to its low pollutant emission and diverse products formation. The current pyrolysis applications for valorization of biomass waste is reviewed, covering the key concepts, pyrolysis mode, operating parameters and products. To date, existing types of pyrolysis include conventional pyrolysis (poor heat transfer due to non-selective heating), vacuum pyrolysis (lower process temperature because of vacuum), solar pyrolysis (entirely “green” with solar-powered), and a newly touted microwave pyrolysis. In microwave pyrolysis of biomass, the heat transfer is more efficient as the heat is generated within the core of material by the interaction of microwave with biomass. The plausible mechanisms of microwave heating are dipole polarization, ionic conduction and interfacial polarization. The lack of top-tier reactor design is identified as the main obstacle that impedes the commercialization of microwave pyrolysis in biomass recycling. Based on the existing works, it is surmised that microwave pyrolysis of biomass produces solid biochar as a main product. To confront the great market demand of activated biochar, it is proposed that the solid char could be upgraded into engineered activated biochar with desirable properties for wide application in pollution control, catalysis and energy storage. Hence, the production of engineered activated biochar from microwave pyrolysis process and its applications are reviewed and explicitly discussed to fill the research gap, and the key implications for future development are highlighted.
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•Emerging pyrolysis techniques for valorisation of municipal waste is reviewed.•Focus on key parameters, comparison to conventional technique, concerns, disputes.•Emphasis is then on ...progress and application of co-pyrolysis as recent technique.•Synergistic reaction mechanism in co-pyrolysis valorisation is discussed.•Co-pyrolysis is a promising method to obtain green energy and energy security.
Pyrolysis is a potential technology used for the transformation of municipal wastes into energy products such as biofuel. Existing reviews on pyrolysis mainly focus on agroforestry biomass and conventional pyrolysis heating techniques. There is limited literature on the application of recent pyrolysis techniques, types of reactors, key operating parameters, and properties of pyrolysis products from conventional versus recent/novel pyrolysis techniques, and particularly the application of the oil products in fuel engines. Here we focus on the performance of various pyrolysis techniques for valorizing municipal wastes, with an explicit emphasis on the progress and application of co-pyrolysis as a recent technique for value-added products recovery from municipal wastes. We review the main operating parameters of co-pyrolysis, concerns and disputes arisen from the technique, and the resultant liquid fuel properties. In particular, co-pyrolysis using microwave heating shows proficiency to resolve several drawbacks of conventional pyrolysis techniques such as reduced oxygen content and viscosity and increased calorific value of liquid oil, hence promising as a method to generate environmental friendly and sustainable third-generation fuels. Sorting of municipal wastes is recommended as an approach to improve the feasibility of co-pyrolysis by having desired quantity and type of municipal wastes as the feedstock, and more research and development on co-pyrolysis utilizing municipal wastes is necessary to maximize the yield and quality of target pyrolytic products. Thus, we conclude that co-pyrolysis is a feasible and sustainable method for recovering biofuel from municipal wastes to obtain green energy and energy security.
The adsorption of extracellular polymeric substances (EPS) onto soil minerals is an important process for understanding bacterial adhesion to mineral surfaces and environmental cycling of nutrients ...and contaminants. To clarify the molecular level mechanisms and processes of EPS adsorption, the interaction mechanisms between EPS and goethite was explored using two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (CoS) assisted by C 1s near edge X-ray absorption fine structure spectroscopy (NEXAFS). Results show that the amide functional groups of EPS play an important role in its adsorption on goethite, and the adsorption of EPS-proteins on goethite is a function of electrolyte concentration, with increasing adsorption at a higher electrolyte concentration. Results also show that the order in which the EPS functional groups interact and bind with goethite is dependent on electrolyte concentration, where carboxyl and phosphoryl functional groups are the first to adsorb at low electrolyte concentration, while amide groups are the first to adsorb at higher electrolyte concentration. Deconvolution and curve fitting of the amide I band at the end of the adsorption process (~300 min) shows that the secondary structure of proteins is converted from a random coil conformation to aggregated strands, α-helices and turns. This conversion leads to increased adsorption of EPS-proteins and explains the overall adsorption increase of EPS on goethite surfaces with an increasing concentration of electrolyte. Furthermore, the adsorption of the carboxyl functional groups of EPS decreases with increasing electrolyte concentration, likely due to more effective screening of the goethite surface charge with increasing concentration of electrolyte. The integrated results from ATR-FTIR and 2D-CoS allow us to construct a comprehensive overview of EPS-goethite interaction processes at the molecular level, which can be used to improve our understanding of EPS-mineral interactions in the natural environment. These results also provide fundamental information for a better understanding of bacterial biofilm formation on soil and sediment minerals, and facilitate research on the subsequent interaction of nutrients and contaminants with the reactive constituents of biofilms in natural and contaminated environments.
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•2D-FTIR-CoS is used to explore the interaction mechanisms between EPS and goethite.•The adsorption processes can be fit by a pseudo-first-order kinetic equation.•The PO and –COO− functional groups of EPS interact and bind with goethite before the other functional groups of EPS.•The adsorption of carboxyl groups decreases with an increase in NaCl concentration.•The conversion of EPS protein structure with an increase in NaCl concentration affects EPS adsorption on goethite.
Dwindling fossil fuels and improper waste management are major challenges in the context of increasing population and industrialization, calling for new waste-to-energy sources. For instance, ...refuse-derived fuels can be produced from transformation of municipal solid waste, which is forecasted to reach 2.6 billion metric tonnes in 2030. Gasification is a thermal-induced chemical reaction that produces gaseous fuel such as hydrogen and syngas. Here, we review refuse-derived fuel gasification with focus on practices in various countries, recent progress in gasification, gasification modelling and economic analysis. We found that some countries that replace coal by refuse-derived fuel reduce CO
2
emission by 40%, and decrease the amount municipal solid waste being sent to landfill by more than 50%. The production cost of energy via refuse-derived fuel gasification is estimated at 0.05 USD/kWh. Co-gasification by using two feedstocks appears more beneficial over conventional gasification in terms of minimum tar formation and improved process efficiency.
Locusts differ from ordinary grasshoppers in their ability to swarm over long distances and are among the oldest migratory pests. The ecology and biology of locusts make them among the most ...devastating pests worldwide and hence the calls for actions to prevent the next outbreaks. The most destructive of all locust species is the desert locust (Schistocerca gregaria). Here, we review the current locust epidemic 2020 outbreak and its causes and prevention including the green technologies that may provide a reference for future directions of locust control and food security. Massive locust outbreaks threaten the terrestrial environments and crop production in around 100 countries of which Ethiopia, Somalia and Kenya are the most affected. Six large locust outbreaks are reported for the period from 1912 to 1989 all being closely related to long-term droughts and warm winters coupled with occurrence of high precipitation in spring and summer. The outbreaks in East Africa, India and Pakistan are the most pronounced with locusts migrating more than 150 km/day during which the locusts consume food equivalent to their own body weight on a daily basis. The plague heavily affects the agricultural sectors, which is the foundation of national economies and social stability. Global warming is likely the main cause of locust plague outbreak in recent decades driving egg spawning of up to 2–400,000 eggs per square meter. Biological control techniques such as microorganisms, insects and birds help to reduce the outbreaks while reducing ecosystem and agricultural impacts. In addition, green technologies such as light and sound stimulation seem to work, however, these are challenging and need further technological development incorporating remote sensing and modelling before they are applicable on large-scales. According to the Food and Agriculture Organization (FAO) of the United Nations, the 2020 locust outbreak is the worst in 70 years probably triggered by climate change, hurricanes and heavy rain and has affected a total of 70,000 ha in Somalia and Ethiopia. There is a need for shifting towards soybean, rape, and watermelon which seems to help to prevent locust outbreaks and obtain food security. Furthermore, locusts have a very high protein content and is an excellent protein source for meat production and as an alternative human protein source, which should be used to mitigate food security. In addition, forestation of arable land improves local climate conditions towards less precipitation and lower temperatures while simultaneously attracting a larger number of birds thereby increasing the locust predation rates.
Highlights
An ultralight and flexible supercapacitor is developed by an effective 3D fabrication method that uses MXene to fabricate waste denim felt through needling and carbonization.
The ...electrodes have a maximum specific capacitance of 1748.5 mF cm
−2
and demonstrate remarkable cycling stability with more than 94% after 15,000 galvanostatic charge/discharge cycles
The loaded more MXene onto
Z
-directional fiber bundles results in enhanced specific capacitance, energy density and power density of supercapacitors.
MXene, a transition metal carbide/nitride, has been prominent as an ideal electrochemical active material for supercapacitors. However, the low MXene load limits its practical applications. As environmental concerns and sustainable development become more widely recognized, it is necessary to explore a greener and cleaner technology to recycle textile by-products such as cotton. The present study proposes an effective 3D fabrication method that uses MXene to fabricate waste denim felt into ultralight and flexible supercapacitors through needling and carbonization. The 3D structure provided more sites for loading MXene onto Z-directional fiber bundles, resulting in more efficient ion exchange between the electrolyte and electrodes. Furthermore, the carbonization process removed the specific adverse groups in MXenes, further improving the specific capacitance, energy density, power density and electrical conductivity of supercapacitors. The electrodes achieve a maximum specific capacitance of 1748.5 mF cm
−2
and demonstrate remarkable cycling stability maintaining more than 94% after 15,000 galvanostatic charge/discharge cycles. Besides, the obtained supercapacitors present a maximum specific capacitance of 577.5 mF cm
−2
, energy density of 80.2 μWh cm
−2
and power density of 3 mW cm
−2
, respectively. The resulting supercapacitors can be used to develop smart wearable power devices such as smartwatches, laying the foundation for a novel strategy of utilizing waste cotton in a high-quality manner.
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