Next Sustainability最新文献

Municipal solid waste incineration fly ash was selected as the alkaline Ca-bearing solid waste, and a series of direct aqueous carbonation experiments using 10% CO₂ gas were conducted to showcase the capability of ultrafine bubbles (UFBs) in enhancing carbonation efficiency. Results from the experiments, conducted using a one-pass water flow system, revealed that carbonation without UFBs increased the CO₂ content of the ash from 59 to 200 mgCO₂/g (an increase of 141 mgCO₂/g), while the presence of UFBs elevated it to 237 mgCO₂/g (an increase of 178 mgCO₂/g). Consequently, the introduction of UFBs led to a 26% increase in CO₂ content in ash [(178−141) / 141]. This improvement was primarily attributed to the enhanced carbonation efficiency for particles ≥ 46 µm. The positive impact of UFBs was more evident (62% increase in CO₂ content in ash) in experiments using a water circulation system, where carbonation proceeded at a faster rate compared to the one-pass water flow system. In terms of the mechanism, X-ray diffraction and scanning electron microscopy analyses indicated that UFBs facilitated the removal of CaCO₃ deposition, which inhibited Ca(OH)₂ dissolution. To the best of our knowledge, this study is the first to demonstrate the favorable influence of UFBs on fly ash carbonation efficiency.

Nanotechnology represents a burgeoning scientific field that focuses on materials within the nanometer size range. Nanoparticles, categorized as incidental, engineered and naturally occurring nanoparticles (NONPs), constitute a critical aspect of nanotechnology. Incidental nanoparticles are inadvertently generated as byproducts, engineered nanoparticles are synthesized by humans for diverse applications and NONPs exist naturally in the environment. NONPs are further categorized based on their location in the environment, such as Naturally Occurring Carbon Nanoparticles, Naturally Occurring Metal Nanoparticles, NONPs present in food, NONPs of biological origin and NONPs present in the aquatic environment. NONPs exhibit ubiquity, spanning the atmosphere, hydrosphere, lithosphere and biosphere. They exhibit distinct properties in comparison to their bulk counterparts, such as a substantial surface area-to-volume ratio, immune-boosting capabilities, scavenger activity, nutritional significance and electron-donor attributes. NONPs have been utilized by humans since ancient times. Owing to these properties, they have been used unknowingly in various fields like medicine, cosmetics, decor, textile and the food industry. NONPs are found in artifacts such as Copper Ruby and the Lycurgus Cup, as well as in medicine, cosmetics and the food industry. Even today, NONPs continue to play pivotal roles in diverse fields such as cancer treatment, biosensors and the food industry. Also they contribute to environmental processes, soil fertility, nutrient transport and bioremediation. This review sheds light on multifaceted significance of NONPs in our evolving scientific landscape and comprehensively explores the history, sources, properties, types and uses of NONPs. It also focuses on the fate of NONPs in water, soil and plants and their environmental and human hazards. A special section on the environmental transformation of NONPs is included.

This study investigates an easy synthesis method of magnetic activated carbon (Fe₃O₄/AC) composites by ultrasonic mechanical blending of Fe₃O₄ particles and activated carbon (AC) powder at different mass ratios. The materials with the best performance were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), specific surface and porosity analyzer (BET), hysteresis loop meter (VSM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS). The as-prepared Fe₃O₄/AC was used to remove the contaminant methylene blue (MB) from solution. The effects of initial solution pH, material dosage, and temperature on MB removal were studied. A series of batch experiments demonstrated that the Fe₃O₄/AC with a mass ratio of Fe₃O₄ to AC = 1:5 showed a higher adsorption capacity of 251.3 ± 2.0 mg/g at 20 °C and pH = 6.5. Isotherm and kinetic studies indicated that the MB adsorption onto Fe₃O₄/AC was exothermic in a chemical monolayer adsorption process. The purification mechanism of Fe₃O₄/AC was investigated, FT-IR results showed that MB molecules adhered to Fe₃O₄/AC after purification. From the results of XPS full spectrum and high resolution spectrum, the possible purification mechanism is inferred as follows: electronic transfer between =N⁺ in MB and CO/C─O in Fe₃O₄/AC, as well as π-π interaction between the skeleton sheet of Fe₃O₄/AC and aromatic ring of MB. This study provides the theoretical reference and experimental basis for recovery and utilization of easily-obtained Fe₃O₄/AC to remove MB from wastewater.

Two reduced graphene oxides (rGO) were synthesized using two carbon sources, namely pristine graphite (rGO-PG), and recovered graphite (rGO-RG) (graphite recovered from spent Li-ion batteries) by modified hummers method and followed by the chemical reduction method to compare their supercapacitive performances. Their supercapacitance is found to be highly competitive and comparable with each other, except for their rate capabilities. The rate capability of rGO-RG is found to be inferior compared to rGO-PG. The supercapacitive behavior of both rGO’s was evaluated using five different aqueous electrolytes. The specific capacitance, specific energy, specific power, and columbic efficiencies exhibited by rGO-RG and rGO-PG were superior in the presence of 1 M H₂SO₄ and are 36 F g¹, 7.1 Wh kg¹, 0.88 kW kg¹ and 96.55 %; and 40 F g¹, 7.9 Wh kg¹, 0.66 kW kg¹ and 97.36 %, respectively. Both the rGOs exhibited no deterioration in their performance up to 10,000 continuous charge and discharge cycles at a current density of 10 A g¹; rather, they exhibited enhancement in their performances with an increase in charge and discharge cycles. The enhancement exhibited by rGO-RG is superior to that of rGO-PG, which is 844 % (272 F g¹) higher than its initial performance (29 F g¹).

In this work, we report the use of spent rooibos tea leaves to fabricate activated carbon and use it to adsorptively remove the toxic Remazol Brilliant Blue R (RBBR) from the aqueous solution. The resulting activated carbon (SRTLAC) was characterized by Brunauer-Emmett-Teller N₂ adsorption/desorption for surface area analysis, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction for morphological, functional group and crystallinity analyses. A Taguchi design approach was employed to determine the optimal conditions for the RBBR adsorption onto SRTLAC. Among the process variables studied, the sorbent dosage, initial concentration, and pH predominantly affected the removal capacity. The maximum removal of 246.5 mg/g was attained at the highest initial RBBR concentration of 120 mg/L, solution pH of 2, sorbent dosage of 20 mg, and agitation time of 110 min. The analysis of variance results showed that RBBR initial concentration contributed the most significant percentage (95.33 %) towards the removal uptake, highlighting its considerable impact. The adsorption data collected at various concentrations (20 – 120 mg/L) were modelled using three non-linear regression isotherms and kinetic models. The Langmuir isotherm model provided the optimal fit for adsorption, suggesting a monolayer and homogenous sorption system with a maximum capacity of 491.38 mg/g. Meanwhile, the pseudo-2^nd order kinetic models accurately elucidated the sorption mechanism. The RBBR species interacted with the SRTLAC functional groups via hydrogen bonding, dipole-dipole interactions, and ion-dipole forces. Therefore, SRTLAC presents a powerful tool for ridding the environment of RBBR dye pollution.

Boehmite is a mineral of aluminum oxyhydroxide widely used as a catalyst support, adsorbent for dyes, and a key component in producing advanced optical and electronic devices. This study focuses on the synthesis of boehmite using recycled metallic aluminum through acid digestion (HCl) and subsequent precipitation by pH correction (NaOH). The aluminum source used was can seals, which were characterized using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). XRD analysis confirmed a boehmite-like phase of the recycled aluminum oxyhydroxide powder. SEM analysis revealed that the synthesized boehmite-like powder consisted of agglomerate plates, which influences its thermal and optical behavior, resulting in a lower dihydroxylation temperature and smaller band gap (∼3.7 eV) compared to the literature value (∼5.5 eV) for boehmite. The boehmite-like powder derived from recycling was used as a precursor for the synthesis of manganese aluminate (MnAl₂O₄). XRD analysis confirmed the formation of the MnAl₂O₄ galaxite phase, with XPS and absorbance spectroscopy in the visible region indicating the presence of mainly Mn²⁺ ions. The resulting brown manganese aluminate powder exhibited stability in harsh chemical environments, with a color change imperceptible to the human eye. Moreover, a near-infrared (NIR) reflectance of approximately 50% was achieved, superior to other brown pigments reported in the literature. These findings suggest that recycled aluminum can seals in aluminate have potential applications as pigments for coatings.

Nowadays the replacement of cement with pozzolanic materials is becoming a very hot topic as a result of CO₂ emission challenges during cement production. Pore structures of pozzolanic materials allow understanding of their effects on pore parameters of cement-based composites. In this study, analytical solutions of surface porosity of waste brick powder (WBP) specimens generated from varying milling conditions were constructed using segmentation, watershed, and threshold algorithms. Scanning electron microscopy was combined with simulations of pore structures from Gwyddion leading to multi-scale driven surface porosity solutions. These methods for surface porosity characterisation of pozzolans can be boiled down to calls for sustainable construction. By implementing analytical methods, the porosity properties of WBP subjected to various milling conditions are successfully observed for the first time. Overall, the presented simulations using all the three methods proved that increasing the mass of clay bricks fed in ball mill reduced the fineness levels of WBP and increased the surface porosity values. It was shown that the porosity values from all the three methods ranged from 17% to 51%. The watershed simulations were noticed to underestimate the surface porosity values in comparison with threshold and segmentation simulations. The results on mean pore areas, number of pores, pore densities, pore volumes and mean pore sizes of WBP specimens were quite different from surface porosity results as variations became more evident for all three methods. The results from this research have highlighted that the proposed analytical solutions are fast and efficient in evaluating the overall behaviour of WBP in cement-based composites and represent reference points for engineering researchers involved in studies on supplementary cementitious materials.

The increasing consumption of fossil fuels and petroleum products leads to high prices, depletion of natural resources, and increased global warming. Therefore, there is a critical need for an alternative, greener fuel that could replace fossil fuels. Biodiesel derived from plant-based oil or biomass is a renewable and non-toxic energy source and has emerged as an alternative to diesel. Today, biodiesel may be manufactured from a range of feedstock using a variety of catalysts and recovery processes thanks to advances in catalytic chemistry technology. Recently, metal oxide-based heterogeneous catalysts have been promising materials for the (trans)esterification reactions of oils to produce biodiesel. The review briefly describes the recent advances in heterogeneous catalysts based on metal oxides for biodiesel production. The pros and cons of various techniques and the mechanism of biodiesel synthesis by heterogeneous catalysts are discussed to understand the topic better. Lastly, the scope of future research and challenges are also presented.

The working-age population is essential to the process of economic growth, and there is growing interest in understanding the demographic dividend's role in sustainable development, particularly in response to the challenge of environmental sustainability. The routes, however, via which the demographic dividend is likely to affect environmental sustainability, are poorly understood. This paper has provided a new case for a better understanding of the asymmetric effects of demographic dividend on environmental sustainability in African countries. To this end, we employed Driscoll-Kraay standard error and Instrumental Variable Generalized Method of Moments (IV-GMM) for a panel dataset of 32 African countries from 1996 to 2018. The empirical findings show that demographic dividend deteriorates environmental sustainability via an increase in the ecological footprint. The results also show that urbanization, globalization and renewable energy reduce ecological footprint. However, economic growth and ICT increase ecological footprint. Lastly, our findings highlight that economic growth, ICT, urbanization and FDI are channels through which demographic dividend affects environmental sustainability. Therefore, although supporting economic growth, Africa's working-age population also contributes to some degree to environmental pressure.