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Purpose This study aims to consider environmental sustainability, a global challenge under the preview of sustainable development goals, highlighting the significance of knowledge economy in attaining sustainable aggregate demand behavior globally. For this purpose, 155 countries that have data available from 1995 to 2021 were selected. The purpose of selecting these countries is to test the global responsibility of the knowledge economy to attain environmental sustainability. Design/methodology/approach Results are estimated with the help of panel quantile regression. The empirical existence of aggregate demand-based environmental Kuznets curve (EKC) was tested using non-linear tests. Moreover, principal component analysis has been incorporated to construct the knowledge economy index. Findings U-shaped aggregate demand-based EKC at global level is validated. However, environmental deterioration increases with an additional escalation after US$497.945m in aggregate demand. As a determinant, the knowledge economy is reducing CO2 emissions. The knowledge economy has played a significant role in global responsibility, shifting the EKC downward and extending the CO2 reduction phase for every selected country. Further, urbanization, energy intensity, financial development and trade openness significantly deteriorate the environmental quality. Originality/value This study contains the empirical existence of aggregate demand-based EKC. The role of the knowledge economy is examined through an index which is calculated by using four pillars of the knowledge economy (technology, innovations, education and institutions). This study is based on a combined panel of all the countries for which the data was available.

The importance of the sustainability concept has gained increasing attention from scholars and practitioners. In this context, the aim of this study was to examine the determinants of intention to continue to use the new Metro in Qatar, which is considered a sustainable mode of travel. Therefore, in this paper, a special attention was paid to certain variables, such as environmental concern, perceived quality, and perceived benefits. A quantitative method approach was employed, in which data were collected based on self-administered questionnaires. A total of 1334 Qatar residents responded to the survey questionnaire, and Structural Equation Modeling (SEM) was used for hypothesis testing. The results confirmed the direct effects of perceived behavioral control, social influence, and attitudes on the intention of residents to continue to use the Metro network in their travel. Moreover, perceived behavioral control was found to play a mediating role, enhancing the indirect relationship between perceived benefits and intention to continue to use the Metro network. More importantly, environmental concerns significantly and positively affected the attitudes and perceived behavioral control of travelers; furthermore, these variables presented a mediated influence—through service quality—on the intention to continue to use the Metro network. This study enriched the sustainability behavior literature by examining the influences of crucial factors. Thus, this study is considered of great value for policy-makers who hope to maximize the awareness level of environmental sustainability among the population, in order to encourage them to embrace changes in their lifestyle towards becoming more environmentally responsible.

Pollution is a significant problem in both industrialized and developing countries, as well as in some developed countries. Heavy metal pollution poses a crucial concern for communities due to its detrimental impact on human health and the long-term well-being of the planet. Heavy metals, such as cadmium, chromium, arsenic, lead, and mercury, do not degrade and can enter the food chain, leading to significant health risks. Therefore, it is essential to monitor and take necessary steps to eliminate heavy metal residues that may be present in food, beverages, and the environment. Although the exact role of nanomaterials in pollution cleanup is still unclear, nanotechnology holds promise as a future solution. In the first part of this comprehensive review, a brief overview of nanoremediation is provided. The subsequent sections delve into various nanomaterials and their potential applications in different pollution cleanup scenarios. Following that, critical analysis is conducted on different nano-remediation methods, including oxidation, adsorption, chemical precipitation, filtration, ion exchange, coagulation-flocculation, and photo-catalysis. Lastly, further suggestions are put forward regarding the future utilization of nanotechnology for more effective and enduring pollution cleanup, particularly in eliminating heavy metals.

Owing to the growing interest of bioconvection flow of nanomaterials, many investigations on this topic have been performed, especially in this decade. The bioconvection flow of nanofluid includes some novel significance in era of biotechnology and bio-engineering like bio-fuels, microbial enhanced oil recovery, enzymes, pharmaceutical applications, petroleum engineering, etc. The current analysis aims to explore the various thermal properties of Sutterby nanofluid over rotating and stretchable disks with external consequences of variable thermal conductivity, heat absorption/generation consequences, activation energy and thermal radiation. The considered flow problem is changed into dimensionless form with convenient variables. The numerical structure for the obtained non-dimensional equations is numerically accessed with built-in shooting technique. The consequences of various physical parameters are observed for enhancement of velocity, temperature, concentration and motile microorganism. It is noted that both axial and tangential velocity components decrease with Reynolds number and buoyancy ratio parameter. The nanofluid concentration improves with activation energy and concentration Biot number. Moreover, an improved microorganisms profile is noticed with microorganism Biot number and bioconvection Rayleigh number.

Abstract The variation of properties with temperature have many practical applications in the area of chemical engineering and metallurgy, in the process of extrusion, the materials moving between a feed roll and on carrier belt. Here our intention is to explore the consequences of temperature dependent viscosity and variable thermal conductivity on flow of nanoliquid in a rotating system. Fluid between parallel plates is taken. Energy expression incorporates the exponential heat source. This analysis also explores the attributes of modified Arrhenius energy function with chemical reaction. Boundary layer problems have been computed via NDSolve approach. The obtained solutions are sketched for various estimations of embedded variables of interest. Results pointed out that both axial and transverse velocities show decaying behavior for higher rotation parameter. Thermal field boosts up with an enhancement of thermophoretic and space dependent heat source variables. Moreover the rate of mass transport decays through dimensionless activation energy.

Microbial fuel cell (MFC) has received much attention in the last decade as a promising technology to simultaneously generate electricity and decontaminate wastewater. This study aims to quantitatively review the published literature on MFC, published in the period of 1970–2020, based on the Web of Science (WoS) database. For the first time in literature, a comprehensive quantitative review of MFC has been conducted by employing the technique of bibliometric and content analyses. A total of 11,397 publications have been retrieved from WoS, out of which 81.6% are research articles. The evaluation in the field of MFC has been mapped in various categories, such as publication history, publication distribution, subject category distribution, leading journals, leading countries and leading organizations in MFC research. Additionally, content analysis has been conducted to unearth the research trends in MFC; and some hot research topics in MFC have been spotted. Results depict that the period 2011–2020 has been the most appreciating era for MFC research, as it contributed 87% of the total publications. Among the subject categories, energy fuel and microbiology lead with contributions of 26.5% for each, butthe overall growth of the energy fuel category in the last decade has been the highest. Out of 1,147 journals publishing MFC research, Bioresource Technology is the leading one; and countries like China, USA and India are the main hub of MFC research with 26.47%, 16.95% and 7.69% contributions in publications, respectively. The hottest topics in MFC research are nanoparticles, catalysts, air electrodes, graphene electrodes, power enhancement, air cathode and nitrogen removal. Moreover, major research areas are engineering, energy fuels and biotechnology with each contribution 26.5% of the total publications.

AbstractThe present studies report the use of an ecofriendly biomass Ficus religiosa in untreated (UFR) and xanthate treated (XFR) forms for the Cd (II) ions removal in a fixed bed column. FTIR, SEM‐EDS, BET surface area, and elemental analysis (CHNS) techniques were used to characterize the biosorbents. The acquired data supported FTIR findings regarding the nature of functional groups present in the materials. Packed bed continuous flow studies explored the effects of various parameters such as Cd (II) ion concentration (100 mg/L–300 mg/L), bed heights (5 cm–30 cm), pH (3–5), at a constant linear flow rate (~1.13 cm/min). The obtained S‐shaped breakthrough curves indicated the efficiency of the packed bed for the Cd (II) removal. Breakthrough time and exhaust times increased (67.5 min–390 min and 292.5 min–1852.5 min) (97.5 min–442.5 min and 345 min–1920 min) for unmodified and modified respectively with bed heights. The BDST, Thomas, and Yoon‐Nelson models were used to evaluate the experimental results. The Yoon‐Nelson model describes the breakthrough data more efficiently compared to other models. Under similar conditions, the modified material exhibited 400% increased capacity (55.20 mg/g) than that of unmodified material (13.33 mg/g). Thus, xanthate modification significantly enhanced the capacity for Cd (II) ions from aqueous solutions.Practitioner Points Xanthate modification of Ficus religiosa is an environmentally friendly process. Modified and unmodified materials were utilized for Cd (II) removal in fixed bed column process which is industrially viable process. Low inlet Cd (II) concentration at pH 5 and higher bed height favored the continuous flow process at fixed flow rate. Modification caused an increase of about 400% in the capacity of material.

Abstract Liquefaction of poly-isoprene based rubber (PIR) was performed using ethanol as a solvent for the production of liquid fuel and chemicals. An autoclave batch reactor was used to perform the ethanolysis of PIR at different temperature ranges (250–375 °C), with different ethanol to PIR ratio (0.5:1 to 4:1), and at different reaction times (15–75mins). The experimental results showed that a maximum yield of 86 wt % was achieved at temperature of 325 °C, ethanol to PIR ratio 1/1, and reaction time of 30 min. This liquid oil yield is about 14% higher than the yield obtained from the pyrolysis of PIR at 500 °C and about 10% higher than the yield obtained from hydrothermal liquefaction of PIR at 375 °C. Moreover, the utilization of ethanol in the process was also incorporated and product yields were redefined. Furthermore, ethanol contributed to enhance the quality of liquid-oil, particularly in term of viscosity, acidity, and energy density. Furthermore, the FTIR analysis showed methyl and methylene were most dominating functional groups found in the liquid product and GCMS analysis identified that they were presented by alkenes, aromatics, and alkyls.

The paper aims to analyse the relationship between energy prices (biodiesel, crude oil) and food commodities - vegetable oils used also as feedstock for biodiesel production. The econometric technique of price transmission, such as unit root test, cointegration test and vector error correction model, is applied to assess the interdependencies between energy prices and vegetable oil prices in Germany. Results suggest close price linkages between prices of vegetable oils and biodiesel and confirm that the vegetable oil prices drive the price dynamics of biodiesel. However, the simultaneous relationship is only revealed between biodiesel and soybean oil prices. The increase in crude oil prices is found to lead to an upward trend in the vegetable oils used for biodiesel production, thus influencing biodiesel prices as well.