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Abstract Brunei, similar to other nations, encounters difficulties in effectively managing solid waste, with 70% of the waste ending up in landfills, 2% through composting, and the remainder being disposed of through conventional methods. The current landfill site is anticipated to reach its maximum capacity in 2025. Energy recovery from waste is crucial for Brunei since it can improve waste management, mitigate environmental consequences, produce economic advantages, bolster energy security, and promote a circular economy. This study aims to identify the potential for energy recovery through landfill gas generated from solid waste disposal in Brunei Darussalam. The study finds that Brunei Darussalam can produce 129 thousand tonnes of CO2e/year landfill gas. Utilising gas to generate electricity of 367 GWh could save 1.6 million USD annually. In addition, it also identifies the strengths and weaknesses of the existing solid waste management in Brunei Darussalam. Furthermore, it formulates a waste management policy in Brunei Darussalam by identifying relevant stakeholders to overcome the weakness. Lastly, the framework for waste management is designed to consider short-, intermediate- and long-term goals and targets, with actions to be taken by respective stakeholders.

Abstract The present work deals with developing a method for revalorizing steel residues to create sunlight-active photocatalysts based on iron oxides. Commercial-grade steel leftovers are oxidized under different combinations of pH and temperature (50–90 °C and 3 ≥ pH ≤ 5) in a low energy-intensive setup. The material with the highest production efficiency (yield > 12%) and magnetic susceptibility (χm = 387 × 10−6 m3/kg) was further explored and modified by diffusion of M2+ (Zn and Co) ions within the structure of the oxide using a hydrothermal method to create ZnFe2O4, CoFe2O4 and combined Co–Zn ferrite. (Co–Zn)Fe2O4 displayed a bandgap of 2.02 eV and can be activated under sunlight irradiation. Electron microscopy studies show that (Co–Zn)Fe2O4 consists of particles with diameters between 400 and 700 nm, homogeneous size, even distribution, and good dispersibility. Application of the developed materials in the sunlight catalysis of black liquors from cellulose extraction resulted in a reduction of the Chemical Oxygen Demand (− 15% on average) and an enhancement in biodegradability (> 0.57 BOD/COD) after 180 min of reaction. Since the presented process employs direct solar light, it opens the possibility to large-scale water treatment and chemical upgrading applications.

Abstract Water contaminated with arsenic presents serious health risks, necessitating effective and sustainable removal methods. This article proposes a method for removing arsenic from water by impregnating biochar with iron oxide (Fe2O3) from brown seaweed (Sargassum polycystum). After the seaweed biomass was pyrolyzed at 400 °C, iron oxide was added to the biochar to increase its adsorptive sites and surface functional groups, which allowed the binding of arsenic ions. Batch studies were conducted to maximize the effects of variables, including pH, contact time, arsenic concentration, and adsorbent dosage, on arsenic adsorption. The maximum arsenic adsorption efficiency of 96.7% was achieved under optimal conditions: pH 6, the adsorbent dosage of 100 mg, the initial arsenic concentration of 0.25 mg/L, and a contact time of 90 min. Langmuir and Freundlich’s isotherms favored the adsorption process, while the kinetics adhered to a pseudo-second-order model, indicating chemisorption as the controlling step. Column studies revealed complete saturation after 200 min, and the adsorption behavior fits both the Adams–Bohart and Thomas models, demonstrating the potential for large-scale application. The primary mechanism underlying the interaction between iron-modified biochar and arsenic ions is surface complexation, enhanced by increased surface area and porosity. This study highlights the significant contribution of iron-modified biochar derived from macroalgae as an effective and sustainable solution for arsenic removal from water.

Abstract Ionic liquids (ILs) are highly effective for capturing carbon dioxide (CO2). The prediction of CO2 solubility in ILs is crucial for optimizing CO2 capture processes. This study investigates the use of deep learning models for CO2 solubility prediction in ILs with a comprehensive dataset of 10,116 CO2 solubility data in 164 kinds of ILs under different temperature and pressure conditions. Deep neural network models, including Artificial Neural Network (ANN) and Long Short-Term Memory (LSTM), were developed to predict CO2 solubility in ILs. The ANN and LSTM models demonstrated robust test accuracy in predicting CO2 solubility, with coefficient of determination (R2) values of 0.986 and 0.985, respectively. Both model's computational efficiency and cost were investigated, and the ANN model achieved reliable accuracy with a significantly lower computational time (approximately 30 times faster) than the LSTM model. A global sensitivity analysis (GSA) was performed to assess the influence of process parameters and associated functional groups on CO2 solubility. The sensitivity analysis results provided insights into the relative importance of input attributes on output variables (CO2 solubility) in ILs. The findings highlight the significant potential of deep learning models for streamlining the screening process of ILs for CO2 capture applications.

Abstract This study evaluated Aloe vera extract as a green inhibitor to prevent corrosion in seawater environments. A. vera extract was produced by maceration with methanol –water at room temperature. Electrochemical techniques were used to evaluate the corrosion inhibitor effectiveness of the A. vera extract. The morphology of the corrosion products was analyzed by FE-SEM equipped with EDS and AFM. FT-IR and LCMS characterized the functional and structural groups in this extract. The electrochemical measurements show that A. vera extract could effectively reduce the corrosion of API 5L steel in seawater environments. Inhibition efficiency (IE) increases with increasing concentration. Optimal corrosion inhibition efficiency of around 83.75% (PDP) and 88.60% (EIS) was obtained by adding 300 mg L−1 of extract at 310 K. Furthermore, the higher the concentration of A. vera extract, the greater the activation energy (Ea), with the highest activation energy being 48.24 kJ mol−1 for the concentration of 300 mg L−1. Conversely, increasing the temperature and exposure duration reduces the corrosion inhibition efficiency (IE) values; the best exposure period was 30 min with 88.34% IE by a concentration of 300 mg L−1 at 300 K. This corrosion inhibition is achieved by the adsorption process of A. vera bioactive on metal surfaces with a mixed inhibitor through a physisorption-chemisorption mechanism. This finding was confirmed by the smoother surface morphology of the steel treated with A. vera extract than without. This unveiling investigation found that A. vera extract has the potential to be an environmentally friendly corrosion inhibitor in the seawater environment.

Recent advancements in polymer science and engineering underscore the importance of creating sophisticated soft materials characterized by well-defined structures and adaptable properties to meet the demands of emerging applications. The primary objective of polymeric composite technology is to enhance the functional utility of materials for high-end purposes. Both the inherent qualities of the materials and the intricacies of the synthesis process play pivotal roles in advancing their properties and expanding their potential applications. Polypyrrole (PPy)-based composites, owing to their distinctive properties, hold great appeal for a variety of applications. Despite the limitations of PPy in its pure form, these constraints can be effectively overcome through hybridization with other materials. This comprehensive review thoroughly explores the existing literature on PPy and PPy-based composites, providing in-depth insights into their synthesis, properties, and applications. Special attention is given to the advantages of intrinsically conducting polymers (ICPs) and PPy in comparison to other ICPs. The impact of doping anions, additives, and oxidants on the properties of PPy is also thoroughly examined. By delving into these aspects, this overview aims to inspire researchers to delve into the realm of PPy-based composites, encouraging them to explore new avenues for flexible technology applications.

Abstract This study synthesized a highly efficient KOH-treated sunflower stem activated carbon (KOH-SSAC) using a two-step pyrolysis process and chemical activation using KOH. The resulting material exhibited exceptional properties, such as a high specific surface area (452 m2/g) and excellent adsorption capacities for phenol (333.03 mg/g) and bisphenol A (BPA) (365.81 mg/g). The adsorption process was spontaneous and exothermic, benefiting from the synergistic effects of hydrogen bonding, electrostatic attraction, and stacking interactions. Comparative analysis also showed that KOH-SSAC performed approximately twice as well as sunflower stem biochar (SSB), indicating its potential for water treatment and pollutant removal applications. The study suggests the exploration of optimization strategies to further enhance the efficiency of KOH-SSAC in large-scale scenarios. These findings contribute to the development of improved materials for efficient water treatment and pollution control.

Abstract A numerical analysis of a CdTe/Si dual-junction solar cell in terms of defect density introduced at various defect energy levels in the absorber layer is provided. The impact of defect concentration is analyzed against the thickness of the CdTe layer, and variation of the top and bottom cell bandgaps is studied. The results show that CdTe thin film with defects density between 1014 and 1015 cm−3 is acceptable for the top cell of the designed dual-junction solar cell. The variations of the defect concentrations against the thickness of the CdTe layer indicate that the open circuit voltage, short circuit current density, and efficiency (ƞ) are more affected by the defect density at higher CdTe thickness. In contrast, the Fill factor is mainly affected by the defect density, regardless of the thin film’s thickness. An acceptable defect density of up to 1015 cm−3 at a CdTe thickness of 300 nm was obtained from this work. The bandgap variation shows optimal results for a CdTe with bandgaps ranging from 1.45 to 1.7 eV in tandem with a Si bandgap of about 1.1 eV. This study highlights the significance of tailoring defect density at different energy levels to realize viable CdTe/Si dual junction tandem solar cells. It also demonstrates how the impact of defect concentration changes with the thickness of the solar cell absorber layer.

Abstract Plastic waste is being manufactured for the production of hydrogen. The amount of plastic waste collected annually is 189,953 tonnes from adjacent nations like Indonesia and Malaysia. Polyethylene (PE), Polypropylene (PP), Polyethylene Terephthalate (PET), Polyvinyl chloride (PVC), and Polystyrene (PS) are the five most prevalent forms of plastic found in most waste. Pyrolysis, water gas shift and steam reforming reaction, and pressure swing adsorption are the three main phases utilized and studied. In this research, authors examines the energy consumption on every stage. The plastic waste can be utilized to manufacture many hydrocarbons using the pyrolysis reaction. For this process, fast pyrolysis is being used at a temperature of 500 °C. A neutralization process is also needed due to the presence of Hydrochloric acid from the pyrolysis reaction, with the addition of sodium hydroxide. This is being carried to prevent any damage to the reactor during the process. Secondly, the steam reforming process continues after the water gas shift reaction has produced steam and carbon monoxide, followed by carbon dioxide and hydrogen formation. Lastly, pressure swing adsorption is designed to extract H2S and CO2 from the water gas shift and steam reforming reaction for greater purity of hydrogen. From the simulation study, it is observed that using various types of plastic waste procured (total input of 20,000 kg per hour of plastics) from, Brunei Darussalam, Malaysia and Indonesia, can produce about 340,000 tons of Hydrogen per year. Additionally, the annual profit of the Hydrogen production is estimated to be between $ 271,158,100 and $ 358,480,200. As per the economic analysis, it can be said that its a good to start hydrogen production plant in these regions.

Recent developments in nanomaterials have come to extensive use in various fields, especially in the biomedical industry. Numerous significant obstacles still need to be overcome, particularly those about utilizing nanomaterials in biomedical science, before they can be used for medicinal purposes. Major issues in biomedicine include biological functioning, harmony, toxic effects, and nano-bio surface properties. Thus, researchers may use cutting-edge characterization approaches to study nanomaterials for biomedical applications. Two-dimensional nanomaterials and polymers are crucial components of biological systems. Polymer-based nanomaterials are flexible and more resistant to chemical attack than other NPs. Polymers easily form composite or functionalization with other NPs to improve their performance compared to the traditional NPs. The current review article discussed nanomaterial performance, including carbon nanotubes (CNTs), graphene, MXene and polymers-based biomedical applications. The current state of nanomaterials in the biomedical area is illustrated in this summary article, along with applications and the significance of characterization approaches. The advanced methods for examining the interior geometry, structure, and morphology of nanomaterials are discussed in this piece of writing, including Transmission electron microscopy (TEM), Scanning electronic microscopy (SEM), Atomic Force Microscopy (AFM), Magnetic resonance force microscopy (MRFM) and X-ray diffraction (XRD). Finally, the authors discussed the issues associated with nanomaterials in biomedical applications.

This case report investigates the preventive effect of Tinospora cordifolia extract on biocorrosion induced by Pseudomonas aeruginosa on mild steel API 5L in the simulated seawater medium. Electrochemical techniques, spectroscopic techniques, and surface analysis were employed to investigate biocide performance and corrosion behavior. P. aeruginosa has been shown to enhance iron dissolution in seawater medium. These findings point to the role of P. aeruginosa bacteria in forming differential oxygen, which causes corrosion. Morphology results from atomic Fourier microscopy (AFM) highlight the presence of P. aeruginosa in biotic environments, where the surface is rougher than in abiotic conditions. On the other hand, adding T. cordifolia to the biotic medium resulted in a smoother and more homogeneous surface without any significant deterioration. Electrochemical findings reveal that adding 300 mg L−1 of T. cordifolia extract prevents the microbiologically influenced corrosion (MIC) of steel API 5L, with an optimum effectiveness value of 74.50 % after 21 days of incubation. This protective effect is caused by forming a more compact iron oxide surface layer and the adsorption of phenolic active compounds such as Moupinamide and others on the surface of mild steel API 5L, as detected by liquid chromatography-mass/spectrometry-mass spectrometry (LCMS-MS), Fourier-transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM) techniques.

Our knowledge of fluorine's unique and complex properties has significantly increased over the past 20 years. Consequently, more sophisticated and innovative techniques have emerged to incorporate this feature into the design of potential drug candidates. In recent years, researchers have become interested in synthesizing fluoro-sulphonamide compounds to discover new chemical entities with distinct and unexpected physical, chemical, and biological characteristics. The fluorinated sulphonamide molecules have shown significant biomedical importance. Their potential is not limited to biomedical applications but also includes crop protection. The discovery of novel fluorine and Sulfur compounds has highlighted their importance in the chemical sector, particularly in the agrochemical and medicinal fields. Recently, several fluorinated sulphonamide derivatives have been developed and frequently used by agriculturalists to produce food for the growing global population. These molecules have also exhibited their potential in health by inhibiting various human diseases. In today's world, it is crucial to have a steady supply of innovative pharmaceutical and agrochemical molecules that are highly effective, less harmful to the environment, and affordable. This review summarizes the available information on the activity of Fluorine and Sulphonamide compounds, which have proven active in pharmaceuticals and agrochemicals with excellent environmental and human health approaches. Moreover, it focuses on the current literature on the chemical structures, the application of fluorinated sulphonamide compounds against various pathological conditions, and their effectiveness in crop protection.

Abstract Research studies have been carried out to accentuate Fennel Seed Spent, a by-product of the Nutraceutical Industry, as an inexpensive, recyclable and operational biosorbent for bioremediation of Acid Blue 113 (AB113) in simulated water-dye samples and textile industrial effluent (TIE). The physical process of adhesion of AB113 on the surface of the biosorbent depends on various parameters, such as the initial amount of the dye, amount and expanse of the biosorbent particles, pH of the solution and temperature of the medium. The data obtained was analyzed using three two-parameter and five three-parameter adsorption isotherm models to glean the adsorbent affinities and interaction mechanism of the adsorbate molecules and adsorbent surface. The adsorption feature study is conducted employing models of Weber-Morris, pseudo 1st and 2nd order, diffusion film model, Dumwald-Wagner and Avrami model. The study through 2nd order pseudo and Avrami models produced complementary results for the authentication of experimental data. The thermodynamic features, ΔG 0 , ΔH 0, and ΔS 0 of the adsorption process are acclaimed to be almost spontaneous, physical in nature and endothermic in their manifestation. Surface characterization was carried out using Scanner Electron Microscopy, and identification and determination of chemical species and molecular structure was performed using Infrared Spectroscopy (IR). Maximum adsorption evaluated using statistical optimization with different combinations of five independent variables to study the individual as well as combined effects by Fractional Factorial Experimental Design (FFED) was 236.18 mg g−1 under optimized conditions; pH of 2, adsorbent dosage of 0.500 g L−1, and an initial dye concentration of 209.47 mg L−1 for an adsorption time of 126.62 min with orbital shaking of 165 rpm at temperature 49.95 °C.

Abstract In this study, zeolite Y was synthesised using a novel method. The heat generated from the reaction of H2SO4 with metakaolin was used as a heat source instead of applying external heat for the dealuminated process. The synthesised zeolite Y produced was analysed by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier-infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller (BET). Zeolite Y synthesis was mesoporous because of its pore diameter (30.53 nm), as shown in the BET results. Surface area and pore size decrease after adsorption due to dye deposition on the adsorbent’s surface. FTIR has bonds like O–H, C–H, –CH3, and –COOH responsible for adsorption. The maximum adsorption capacity of eosin yellow (EY) and methyl orange (MO) on to zeolite Y by the Langmuir isotherm was 52.91 mg/g and 20.62 mg/g respectively, at pH 2.5 and 8 for EY and MO dye. The batch adsorption studies were conducted, and the influence of different parameters (i.e., adsorbent dose, adsorption time, initial dye concentration, pH and temperature) was investigated. Experimental data were analysed by two linear model equations (Langmuir and Freundlich isotherms), and it was found that the Langmuir isotherm model best describes the adsorption data for methyl orange and Freundlich isotherm for eosin yellow, respectively. Adsorption rate constants were determined using linear pseudo-first-order and pseudo-second-order. The results showed that MO and EY dye adsorption onto zeolite Y followed a pseudo-second-order kinetic model. Thermodynamic studies show that adsorption was an exothermic reaction (enthalpy

Abstract Recently, most service or product-oriented industries have been focusing on their activities to uphold the green and sustainable environment protocol owing to the increased environmental pollution. Concerning this issue, industries are now concentrating on developing recyclable or waste materials products. This research advocates developing and validating a banana fiber sandwich composite to promote the beneficial usage of bio-waste. The composite sandwich specimens were fabricated with resin-impregnated woven banana fiber mat as a skin, and the core was reinforced with three different weight percentages (5, 7.5 and 10%) of chopped banana fiber. The sandwich specimens were pressed into a three-point bending test to validate the structural integrity. The flexural characteristics like flexural strength and modulus were examined experimentally, whereas the key strength indices like flexural stiffness and core shear modulus were evaluated analytically. Post-fracture surfaces were studied through a scanning electron microscope to investigate the failure mechanism. The experimental and analytical results indicate that 10% banana fiber content in the sandwich core increases the flexural strength and flexural modulus to 225% and 147%, respectively, compared to the neat epoxy core. The numerical simulation was also performed through FEA to validate the experimental findings. The numerical results are in good concurrence with the experimental one.

Pesticides usage has tremendously increased to enhance crop production; however some pesticides are toxic and harmful to human health and the environment. This review discusses the eco-toxicological impacts of pesticides on the environment. This study extensively evaluates various sustainable remediation technologies such as advanced oxidation processes (AOPs), electrochemical processes, membrane separation, and adsorbent types (carbon nanotubes, carbon nanofiber, carbon aerogel, graphene oxide, carbon dot, biochar, biosorbents, polymers, metal-organic framework, and nanocomposite) that are used for removal of toxic pesticides from aqueous bodies. Further, various equilibrium isotherm and kinetic models that are used for understanding the mechanisms along with challenges in the techniques are discussed. From the studies, it is observed that the nanocomposites could degrade and remove pesticides efficiently due to their unique properties, making them promising adsorbents for water and wastewater remediation. This review will be an inclusive paper for readers to easily define research gaps and develop novel treatment methods for removing pesticide-contaminated waters.

Abstract Epoxides were primarily derived from petroleum-based sources. However, there has been limited research on optimizing the process parameters for epoxidized palm oil-derived oleic acid, resulting in its underutilization. Therefore, this study aimed to optimize the catalytic epoxidation of palm oleic acid concerning the oxirane content by applying ion exchange resin as a catalyst. Epoxidized oleic acid was produced using in-situ-formed performic acid by combining formic acid as the oxygen carrier with hydrogen peroxide as the oxygen donor. The findings revealed that the optimal reaction conditions for producing epoxidized oleic acid with the highest oxirane content were an Amberlite IR-120 catalyst loading of 0.9 g, a molar ratio of formic acid to oleic acid of 1:1., and a molar ratio of hydrogen peroxide to oleic acid of 1:1.1. By employing these optimal conditions, the maximum relative conversion of palm oleic acid to oxirane was achieved at 85%. The reaction rate constants (k) based on the optimized epoxidized oleic acid are determined as follows: k11 = 20 mol L−1 min−1, k12 = 2 mol L−1 min−1, and k2 = 20 mol L−1 min−1. The findings validated the kinetic model by showing good agreement between the simulation and experimental data.

Abstract A comprehensive understanding of physiochemical properties, thermal degradation behavior and chemical composition is significant for biomass residues before their thermochemical conversion for energy production. In this investigation, teff straw (TS), coffee husk (CH), corn cob (CC), and sweet sorghum stalk (SSS) residues were characterized to assess their potential applications as value-added bioenergy and chemical products. The thermal degradation behavior of CC, CH, TS and SSS samples is calculated using four different heating rates. The activation energy values ranged from 81.919 to 262.238 and 85.737–212.349 kJ mol−1 and were generated by the KAS and FWO models and aided in understanding the biomass conversion process into bio-products. The cellulose, hemicellulose, and lignin contents of CC, CH, TS, and SSS were found to be in the ranges of 31.56–41.15%, 23.9–32.02%, and 19.85–25.07%, respectively. The calorific values of the residues ranged from 17.3 to 19.7 MJ/kg, comparable to crude biomass. Scanning electron micrographs revealed agglomerated, irregular, and rough textures, with parallel lines providing nutrient and water transport pathways in all biomass samples. Energy Dispersive X-ray spectra and X-ray diffraction analysis indicated the presence of high carbonaceous material and crystalline nature. FTIR analysis identified prominent band peaks at specific wave numbers. Based on these findings, it can be concluded that these residues hold potential as energy sources for various applications, such as the textile, plastics, paints, automobile, and food additive industries.

Abstract Discharging untreated dye-containing wastewater gives rise to environmental pollution. The present study investigated the removal efficiency and adsorption mechanism of Acid Red 18 (AR18) utilizing hexadecyl-trimethyl ammonium chloride (HDTMA.Cl) modified Nano-pumice (HMNP), which is a novel adsorbent for AR18 removal. The HDTMA.Cl is characterized by XRD, XRF, FESEM, TEM, BET and FTIR analysis. pH, contact time, initial concentration of dye and adsorbent dose were the four different parameters for investigating their effects on the adsorption process. Response surface methodology-central composite design was used to model and improve the study to reduce expenses and the number of experiments. According to the findings, at the ideal conditions (pH = 4.5, sorbent dosage = 2.375 g/l, AR18 concentration = 25 mg/l, and contact time = 70 min), the maximum removal effectiveness was 99%. The Langmuir (R2 = 0.996) and pseudo-second-order (R2 = 0.999) models were obeyed by the adsorption isotherm and kinetic, respectively. The nature of HMNP was discovered to be spontaneous, and thermodynamic investigations revealed that the AR18 adsorption process is endothermic. By tracking the adsorption capacity of the adsorbent for five cycles under ideal conditions, the reusability of HMNP was examined, which showed a reduction in HMNP's adsorption effectiveness from 99 to 85% after five consecutive recycles.

Abstract Toxic dyes in water bodies and bacterial pathogens pose serious global challenges to human health and the environment. Zinc oxide nanoparticles (ZnO NPs) demonstrate remarkable photocatalytic and antibacterial potency against reactive dyes and bacterial strains. In this work, PVP-ZnO NPs have been prepared via the co-precipitation method using polyvinylpyrrolidone (PVP) as a surfactant. The NPs’ microstructure and morphology were studied using X-ray diffraction (XRD), having a size of 22.13 nm. High-resolution transmission electron microscope (HR-TEM) and field emission scanning electron microscopy (FESEM) analysis showed spherical-shaped PVP-ZnO NPs with sizer ranging from 20 to 30 nm. Fourier Transform Infrared Spectroscopy (FT-IR) confirmed the hybrid nature of the NPs, and UV–Vis spectroscopy showed an absorption peak at 367 nm. The PVP-ZnO NPs exhibited high photocatalytic activity, achieving 88% and nearly 95% degradation of reactive red-141 azo dye with 10 mg and 20 mg catalyst dosages, respectively. The antibacterial properties of the NPs were demonstrated against Escherichia coli and Bacillus subtilis, with inhibition zones of 24 mm and 20 mm, respectively. These findings suggest that PVP-ZnO NPs can be effectively used for water treatment, targeting both dye and pathogenic contaminants.

Abstract A typical ferrite/martensitic heat-resistant steel (T91) is widely used in reheaters, superheaters and power stations. Cr3C2-NiCr-based composite coatings are known for wear-resistant coatings at elevated temperature applications. The current work compares the microstructural studies of 75 wt% Cr3C2- 25 wt% NiCr-based composite clads developed through laser and microwave energy on a T91 steel substrate. The developed clads of both processes were characterized through a field emission scanning electron microscope (FE-SEM) attached with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and assessment of Vickers microhardness. The Cr3C2-NiCr based clads of both processes revealed better metallurgical bonding with the chosen substrate. The microstructure of the developed laser clad shows a distinctive dense solidified structure, with a rich Ni phase occupying interdendritic spaces. In the case of microwave clad, the hard chromium carbide particles consistently dispersed within the soft nickel matrix. EDS study evidenced that the cell boundaries are lined with chromium where Fe and Ni were found inside the cells. The X-ray phase analysis of both the processes evidenced the common presence of phases like chromium carbides (Cr7C3, Cr3C2, Cr23C6), Iron Nickel (FeNi3) and chromium-nickel (Cr3Ni2, CrNi), despite these phases iron carbides (Fe7C3) are observed in the developed microwave clads. The homogeneous distributions of such carbides in the developed clad structure of both processes indicated higher hardness. The typical microhardness of the laser-clad (1142 ± 65HV) was about 22% higher than the microwave clad (940 ± 42 HV). Using a ball-on-plate test, the study analyzed microwave and laser-clad samples' wear behavior. Laser-cladding samples showed superior wear resistance due to hard carbide elements. At the same time, microwave-clad samples experienced more surface damage and material loss due to micro-cutting, loosening, and fatigue-induced fracture.

Abstract A limited experimental work was on multi-walled carbon nanotube (MWCNT)—water nanofluid with surfactant in the solar parabolic collector at low volume concentrations. At high-volume concentrated nanofluid, the pressure drop was more due to an increase in the viscosity of the working fluid and an increase in the nanoparticle cost; hence it is not economical. This report attempted to use Sodium Dodecyl Benzene Sulfonate (SDBS) surfactant in the low-volume concentrated MWCNT-water nanofluid to establish effective heat transfer in solar parabolic collector applications. The stable MWCNT-water nanofluid was prepared at 0.0158, 0.0238, and 0.0317 volume concentrations. The experiments were conducted from 10:00 to 16:00 at 6, 6.5 and 7 L/min flow rates concerning ASHRAE Standards. At the 7 L/min flow rate of the working fluid, having a minimum temperature difference between the working fluid and absorber tube leads to better heat transfer. The increased volume concentration of MWCNT in the water enhances the surface area interaction between water and MWCNT nanoparticles. This results in maximum solar parabolic collector efficiency at 0.0317 vol% with a 7 L/min flow rate and 10–11% higher than the distilled water.

Abstract Contamination of water resources by industrial effluents containing heavy metal ions and management of solid waste from agricultural and food industries is a serious issue. This study presents the valorization of waste walnut shells as an effective and environment-friendly biosorbent for sequestrating Cr(VI) from aqueous media. The native walnut shell powder (NWP) was chemically modified with alkali (AWP) and citric acid (CWP) to obtain modified biosorbents with abundant availability of pores as active centers, as confirmed by BET analysis. During batch adsorption studies, the process parameters for Cr(VI) adsorption were optimized at pH 2.0. The adsorption data were fitted to isotherm and kinetic models to compute various adsorption parameters. The adsorption pattern of Cr(VI) was well explained by the Langmuir model suggesting the adsorbate monolayer formation on the surface of the biosorbents. The maximum adsorption capacity, q m, for Cr(VI) was achieved for CWP (75.26 mg/g), followed by AWP (69.56 mg/g) and NWP (64.82 mg/g). Treatment with sodium hydroxide and citric acid improved the adsorption efficiency of the biosorbent by 4.5 and 8.2%, respectively. The endothermic and spontaneous adsorption was observed to trail the pseudo-second-order kinetics under optimized process parameters. Thus, the chemically modified walnut shell powder can be an eco-friendly adsorbent for Cr(VI) from aqueous solutions.

Abstract A reliable and accurate diagnosis and identification system is required to prevent and manage tea leaf diseases. Tea leaf diseases are detected manually, increasing time and affecting yield quality and productivity. This study aims to present an artificial intelligence-based solution to the problem of tea leaf disease detection by training the fastest single-stage object detection model, YOLOv7, on the diseased tea leaf dataset collected from four prominent tea gardens in Bangladesh. 4000 digital images of five types of leaf diseases are collected from these tea gardens, generating a manually annotated, data-augmented leaf disease image dataset. This study incorporates data augmentation approaches to solve the issue of insufficient sample sizes. The detection and identification results for the YOLOv7 approach are validated by prominent statistical metrics like detection accuracy, precision, recall, mAP value, and F1-score, which resulted in 97.3%, 96.7%, 96.4%, 98.2%, and 0.965, respectively. Experimental results demonstrate that YOLOv7 for tea leaf diseases in natural scene images is superior to existing target detection and identification networks, including CNN, Deep CNN, DNN, AX-Retina Net, improved DCNN, YOLOv5, and Multi-objective image segmentation. Hence, this study is expected to minimize the workload of entomologists and aid in the rapid identification and detection of tea leaf diseases, thus minimizing economic losses.

The present study investigates the inhibition potential of Tinospora cordifolia extract in combination with different methanol solvents on the corrosion of carbon steel in artificial seawater environments. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) methods were utilized to evaluate this inhibitor. The measurement data show a positive correlation among inhibition efficiency (%IE), inhibitor concentration, temperature, and time. However, above 320 K, the efficiency has a slight decline, as well as when the exposure duration extends beyond 30 minutes. The highest observed inhibition efficiency was 85.94%, achieved by incorporating 300 mgL−1 of T. cordifolia extract (at 310 K). The inhibition by T. cordifolia extract was suggested to occur through adsorption on the metal surface and complies with the Langmuir adsorption isotherm. The potentiodynamic polarization analysis findings demonstrated that the extract of T. cordifolia mainly acted as a mixed inhibitor. The EIS study suggests that the T. cordifolia extract became effective by increasing the charge transfer resistance (Rct) by adsorbing on the steel surface. The FE-SEM study verified that T. cordifolia extract enhances the surface smoothness of the metal specimen. The adsorption mode of corrosion prevention is validated by the change in the chemical composition of the elemental surface examined by EDX studies. T. cordifolia extract mainly contains numerous aromatic phenolic compounds. FT-IR analysis confirmed the presence of several compounds with N and OH bonds in T. cordifolia extract. It has been established that T. cordifolia extract could be used for carbon steel in a marine environment.

Abstract The use of solar energy is one of the most prominent strategies for addressing the present energy management challenges. Solar energy is used in numerous residential sectors through flat plate solar collectors. The thermal efficiency of flat plate solar collectors is improved when conventional heat transfer fluids are replaced with nanofluids because they offer superior thermo-physical properties to conventional heat transfer fluids. Concentrated chemicals are utilized in nanofluids' conventional synthesis techniques, which produce hazardous toxic bi-products. The present research investigates the effects of novel green covalently functionalized gallic acid-treated multiwall carbon nanotubes-water nanofluid on the performance of flat plate solar collectors. GAMWCNTs are highly stable in the base fluid, according to stability analysis techniques, including ultraviolet–visible spectroscopy and zeta potential. Experimental evaluation shows that the thermo-physical properties of nanofluid are better than those of base fluid deionized water. The energy, exergy and economic analysis are performed using 0.025%, 0.065% and 0.1% weight concentrations of GAMWCNT-water at varying mass flow rates 0.010, 0.0144, 0.0188 kg/s. The introduction of GAMWCNT nanofluid enhanced the thermal performance of flat plate solar collectors in terms of energy and exergy efficiency. There is an enhancement in efficiency with the rise in heat flux, mass flow rate and weight concentration, but a decline is seen as inlet temperature increases. As per experimental findings, the highest improvement in energy efficiency is 30.88% for a 0.1% weight concentration of GAMWCNT nanofluid at 0.0188 kg/s compared to the base fluid. The collector's exergy efficiency increases with the rise in weight concentration while it decreases with an increase in flow rate. The highest exergy efficiency is achieved at 0.1% GAMWCNT concentration and 0.010 kg/s mass flow rate. GAMWCNT nanofluids have higher values for friction factor compared to the base fluid. There is a small increment in relative pumping power with increasing weight concentration of nanofluid. Performance index values of more than 1 are achieved for all GAMWCNT concentrations. When the solar thermal collector is operated at 0.0188 kg/s and 0.1% weight concentration of GAMWCNT nanofluid, the highest size reduction, 27.59%, is achieved as compared to a flat plate solar collector with water as a heat transfer fluid.

Abstract Mg–Al–Zn alloys are widely preferred in many applications by considering their excellent properties of high stiffness-to-weight ratio, lightweight, high strength-to-weight ratio, low density, castability, high-temperature mechanical properties, machinability, high corrosion resistance, and great damping. Improving the properties of such alloys is challenging due to their hexagonal crystal structure and other alloying limitations. This study aims to synthesize Mg–Al–Zn alloy by incorporating the alloying elements 8.3 wt% Al, 0.35 wt% Zn on pure magnesium (Control specimen). Then synthesize Mg–Al–Zn/BN/B4C hybrid composite by reinforcing B4C at three weight proportions (3 wt%, 6 wt%, 9 wt%) along with constant solid lubricant BN (3 wt%) through a stir casting process. The hybrid composite samples were characterized and compared with the performances of the control specimen. The results reveal that 9 wt% B4C reinforced samples outperformed through recording the improvement of tensile strength by 28.94%, compressive strength by 37.89%, yield strength by 74.63%, and hardness by 14.91% than the control specimen. Apart from this, it has reduced the corrosion area (37.81%) and noticed negligible changes in density (increased by 0.03%) and porosity (decreased by 0.01%) than the control specimen. The samples were characterized using SEM, XRD, and EDAX apparatus.

Abstract The presence of metal with microwave irradiation has always invited controversial arguments as the metal will catch on fire easily. But interestingly, researchers found that arc discharge phenomena provide a promising way for molecule cracking to synthesize nanomaterials. This study developed a single-step yet affordable synthesis approach that combines microwave heating and arcing in transforming crude palm oil into magnetic nanocarbon (MNC), which can be considered a new alternative for the palm oil sectors. It involves synthesizing the medium at a partial inert condition with constant coiled stainless steel metal wire (dielectric media) and ferrocene (catalyst). This approach successfully demonstrates heating at a temperature ranging from 190.9 to 472.0 °C with different synthesis times (10–20 min). The produced MNC shows formations of spheres with average sizes of 20.38–31.04 nm, mesoporous structure (SBET: 14.83–151.95 m2/g), and high content of fixed carbon (52.79–71.24wt%), and the ratio of the D and G bands (I D/I G) is 0.98–0.99. The formation of new peaks in the FTIR spectra (522.29–588.48 cm−1) supports the appearance of the FeO compounds from the ferrocene. The magnetometer shows high magnetization saturation (22.32–26.84 emu/g) in ferromagnetic materials. The application of the MNC in wastewater treatment has been demonstrated by evaluating their adsorbent capability with Methylene Blue (MB) adsorption test at a different concentrations varying between 5 and 20 ppm. The MNC produced at synthesis time (20 min) shows the highest adsorption efficiency (10.36 mg/g) compared to others, with 87.79% removal of MB dye. As a result, the value for Langmuir is not promising compared to Freundlich, with R 2 being around 0.80, 0.98, and 0.99 for MNC synthesized at 10 min (MNC10), 15 min (MNC15), and 20 min (MNC20), respectively. Hence, the adsorption system is in a heterogeneous condition. The microwave-assisted arcing thereby presents a promising approach to transforming CPO into MNC that could remove the hazardous dye.

Abstract Selenium in wastewater is of particular concern due to its increasing concentration, high mobility in water, and toxicity to organisms; therefore, this study was carried out to determine the removal efficiency of selenium using iron and manganese-based bimetallic micro-composite adsorbents. The bimetallic micro-composite adsorbent was synthesized by using the chemical reduction method. Micro-particles were characterized by using energy-dispersive X-ray spectroscopy for elemental analysis after adsorption, which confirms the adsorption of selenium on the surface of the micro-composite adsorbent, scanning electron microscopy, which shows particles are circular in shape and irregular in size, Brunauer–Emmett–Teller which results from the total surface area of particles were 59.345m2/g, Zeta particle size, which results from average particles size were 39.8 nm. Then it was applied to remove selenium ions in an aqueous system. The data revealed that the optimum conditions for the highest removal (95.6%) of selenium were observed at pH 8.5, adsorbent dosage of 25 mg, and contact time of 60 min, respectively, with the initial concentration of 1 ppm. The Langmuir and Freundlich isotherm models match the experimental data very well. The results proved that bimetallic micro-composite could be used as an effective selenium adsorbent due to the high adsorption capacity and the short adsorption time needed to achieve equilibrium. Regarding the reusability of bimetallic absorbent, the adsorption and desorption percentages decreased from 50 to 45% and from 56 to 53%, respectively, from the 1st to the 3rd cycle.

Abstract A continuous mode fixed-bed up-flow column adsorption analysis was conducted utilizing Acacia nilotica sawdust activated carbon (ASAC) as an adsorbent for the adsorption treatment of toxic Indigo Carmine Dye (ICD). The effect on the adsorption characteristics of ASAC of the influent ICD concentration, flow rate, and column bed depth has been investigated. According to the column study, the highest efficiency of ICD removal was approximately 79.01% at a preliminary concentration of 100 mg/L with a flow rate of 250 mL/h at a bed depth of 30 cm and adsorption power of 24.67 mg/g. The experimental work confirmed the dependency of break-through curves on dye concentration and flow rate for a given bed depth. Kinetic models were implemented by Thomas, Yoon–Nelson, and Bed-depth-service-time analysis along with error analysis to interpret experimental data for bed depth of 15 cm and 30 cm, ICD concentration of 100 mg/L and 200 mg/L and flow rate of 250 mL/h, and 500 mL/h. The analysis predicted the breakthrough curves using a regression basin. It indicated that all three models were comparable for the entire break-through curve depiction. The characteristic parameters determined by process design and error analysis revealed that the Thomas model was better followed by the BDST and Yoon–Nelson models in relating the procedure of ICD adsorption onto ASAC. B-E-T surface area and B-E-T pore volume of ASAC were 737.76 m2/g and 0.2583 cm3/g, respectively. S-E-M and X-R-D analysis reveal the micro-porous and amorphous nature of ASAC. F-T-I-R spectroscope indicate distinctive functional assemblies like -OH group, C–H bond, C–C bond, C–OH, and C–O groups on ASAC. It could be computed that the ASAC can be used efficiently as an alternative option for industrial wastewater treatment

Abstract This paper studies an adjacent accumulation discrete grey model to improve the prediction of the grey model and enhance the utilization of new data. The impact of COVID-19 on the global economy is also discussed. Two cases are discussed to prove the stability of the adjacent accumulation discrete grey model, which helped the studied model attain higher forecasting accuracy. Using the adjacent accumulation discrete grey model, non-renewable energy consumption in G20 countries from 2022 to 2026 is predicted based on their consumption data from 2011 to 2021. It is proven that the adjacent accumulation exhibits sufficient accuracy and precision. Forecasting results obtained in this paper show that energy consumption of all the non-renewable sources other than coal has an increasing trend during the forecasting period, with the USA, Russia, and China being the biggest consumers. Natural gas is the most consumed non-renewable energy source between 2022 and 2026, whereas hydroelectricity is the least consumed. The USA is the biggest consumer of Nuclear energy among the G20 countries, whereas Argentina consumed only 0.1 Exajoules of nuclear energy, placing it at the end of nuclear energy consumers.

The presence of heavy metal, chromium (VI), in water environments leads to various diseases in humans, such as cancer, lung tumors, and allergies. This review comparatively examines the use of several adsorbents, such as biosorbents, activated carbon, nanocomposites, and polyaniline (PANI), in terms of the operational parameters (initial chromium (VI) concentration (Co), temperature (T), pH, contact time (t), and adsorbent dosage) to achieve the Langmuir's maximum adsorption capacity (qm) for chromium (VI) adsorption. The study finds that the use of biosorbents (fruit bio-composite, fungus, leave, and oak bark char), activated carbons (HCl-treated dry fruit waste, polyethyleneimine (PEI) and potassium hydroxide (KOH) PEI-KOH alkali-treated rice waste-derived biochar, and KOH/hydrochloric acid (HCl) acid/base-treated commercial), iron-based nanocomposites, magnetic manganese-multiwalled carbon nanotubes nanocomposites, copper-based nanocomposites, graphene oxide functionalized amino acid, and PANI functionalized transition metal are effective in achieving high Langmuir's maximum adsorption capacity (qm) for chromium (VI) adsorption, and that operational parameters such as initial concentration, temperature, pH, contact time, and adsorbent dosage significantly affect the Langmuir's maximum adsorption capacity (qm). Magnetic graphene oxide functionalized amino acid showed the highest experimental and pseudo-second-order kinetic model equilibrium adsorption capacities. The iron oxide functionalized calcium carbonate (IO@CaCO3) nanocomposites showed the highest heterogeneous adsorption capacity. Additionally, Syzygium cumini bark biosorbent is highly effective in treating tannery industrial wastewater with high levels of chromium (VI).

Abstract Owing to the high toxicity of cerium toward living organisms, it is necessary to remove cerium from aqueous solutions. In this regard, the extraction of cerium (Ce (III)) from nitrate media by Cyanex 572 under different operating conditions was examined in this study. The effect of contact time, pH, extractant concentration, and nitrate ion concentration were investigated to characterize the extraction behavior of cerium and based on these outcomes, an extraction mechanism was suggested. The analysis of infrared spectra of Cyanex 572 before and after the extraction of cerium indicated that cerium extraction was performed via a cation-exchange mechanism. Then, the predictive models based on intelligent techniques [artificial neural network (ANN) and hybrid neural-genetic algorithm (GA-ANN)] were developed to predict the cerium extraction efficiency. The GA-ANN model provided better predictions that resulted higher R2 and lower MSE compared to ANN model for predicting the extraction efficiency of cerium by Cyanex 572. The interactive effects of each process variable on cerium extraction were also investigated systematically. pH was the most influential parameter on cerium extraction, followed by extractant concentration, nitrate ion concentration and contact time. Finally, the separation of cerium from other rare earth elements like La (III), Nd (III), Pr (III), and Y (III) was conducted and observed that the present system provides a better separation of cerium from rare heavy earth than light rare earths.

Abstract Wastewater consisting of different pharmaceuticals and drug residues is quite challenging to treat and dispose of. This situation poses a significant impact on the health aspect of humans and other biotic organisms in the environment. The main concern of hospital wastewater (HWW) is the resistivity towards treatment using the different conventional methods. For the treatment of HWW, this study was performed using an electro bioreactor using hospital wastewater. The electro reduction overcomes the effect of toxic elements in hospital wastewater, and biodegradation removes organic matter and nutrients from wastewater. This study investigated electro bioreactor performance for treating hospital wastewater connected with tubesettler. The parameters of chemical oxygen demand, nitrate, and phosphate concentration were analyzed to evaluate an influent and effluent from electro bioreactor and tubesettler. Also, Kinetic modelling for chemical oxygen demand, nitrate, and phosphate removal was done. The chemical oxygen demand was reduced by 76% in electro bioreactor, and 31% in tubesettler, 84%. The nitrate and phosphate were reduced within permissible discharge limits with a final effluent concentration of 1.4 mg L−1 and 3 mg L−1. Further studies are required to assess the impact of pharmaceutical compounds in hospital wastewater on the system's performance.

Water is one of the major sources that spread human diseases through contamination with bacteria and other pathogenic microorganisms. This review focuses on microbial hazards as they are often present in water and wastewater and cause various human diseases. Among the currently used disinfection methods, sonochemical reactors (SCRs) that produce free radicals combined with advanced oxidation processes (AOPs) have received significant attention from the scientific community. Also, this review discussed various types of cavitation reactors, such as acoustic cavitation reactors (ACRs) utilizing ultrasonic energy (UE), which had been widely employed, involving AOPs for treating contaminated waters. Besides ACRs, hydrodynamic cavitation reactors (HCRs) also effectively destroy and deactivate microorganisms to varying degrees. Cavitation is the fundamental phenomenon responsible for initiating many sonochemical reactions in liquids. Bacterial degradation occurs mainly due to the thinning of microbial membranes, local warming, and the generation of free radicals due to cavitation. Over the years, although extensive investigations have focused on the antimicrobial effects of UE (ultrasonic energy), the primary mechanism underlying the cavitation effects in the disinfection process, inactivation of microbes, and chemical reactions involved are still poorly understood. Therefore, studies under different conditions often lead to inconsistent results. This review investigates and compares other mechanisms and performances from greener and environmentally friendly sonochemical techniques to the remediation of microbial hazards associated with water and wastewater. Finally, the energy aspects, challenges, and recommendations for future perspectives have been provided.

Ionogels are hybrid materials comprising an ionic liquid confined within a polymer matrix. They have garnered significant interest due to their unique properties, such as high ionic conductivity, mechanical stability, and wide electrochemical stability. These properties make ionogels suitable for various applications, including energy storage devices, sensors, and solar cells. However, optimizing the electrochemical performance of ionogels remains a challenge, as the relationship between specific capacitance, ionic conductivity, and electrolyte solution concentration is yet to be fully understood. In this study, we investigate the impact of electrolyte solution concentration on the electrochemical properties of ionogels to identify the correlation for enhanced performance. Our findings demonstrate a clear relationship between the specific capacitance and ionic conductivity of ionogels, which depends on the availability of mobile ions. The reduced number of ions at low electrolyte solution concentrations leads to decreased ionic conductivity and specific capacitance due to the scarcity of a double layer, constraining charge storage capacity. However, at a 31 vol% electrolyte solution concentration, an ample quantity of ions becomes accessible, resulting in increased ionic conductivity and specific capacitance, reaching maximum values of 58 ± 1.48 μS/cm and 45.74 F/g, respectively. Furthermore, the synthesized ionogel demonstrates a wide electrochemical stability of 3.5 V, enabling diverse practical applications. This study provides valuable insights into determining the optimal electrolyte solution concentration for enhancing ionogel electrochemical performance for energy applications. It highlights the impact of ion pairs and aggregates on ion mobility within ionogels, subsequently affecting their resultant electrochemical properties.

Abstract Electrochemical stability of energy storage devices is one of their major concerns. Polymeric binders are generally used to enhance the stability of the electrode, but the electrochemical performance of the device is compromised due to the poor conductivity of the binders. Herein, 3D binder-free electrode based on nickel oxide deposited on graphene (G-NiO) was fabricated by a simple two-step method. First, graphene was deposited on nickel foam via atmospheric pressure chemical vapour deposition followed by electrodeposition of NiO. The structural and morphological analyses of the fabricated G-NiO electrode were conducted through Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS). XRD and Raman results confirmed the successful growth of high-quality graphene on nickel foam. FESEM images revealed the sheet and urchin-like morphology of the graphene and NiO, respectively. The electrochemical performance of the fabricated electrode was evaluated through cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) in aqueous solution at room temperature. The G-NiO binder-free electrode exhibited a specific capacity of ≈ 243 C g−1 at 3 mV s−1 in a three-electrode cell. A two-electrode configuration of G-NiO//activated charcoal was fabricated to form a hybrid device (supercapattery) that operated in a stable potential window of 1.4 V. The energy density and power density of the asymmetric device measured at a current density of 0.2 A g−1 were estimated to be 47.3 W h kg−1 and 140 W kg−1, respectively. Additionally, the fabricated supercapattery showed high cyclic stability with 98.7% retention of specific capacity after 5,000 cycles. Thus, the proposed fabrication technique is highly suitable for large scale production of highly stable and binder-free electrodes for electrochemical energy storage devices.

Hydrothermal liquefaction (HTL) is a thermochemical depolymerization technology, also known as hydrous pyrolysis, that transforms wet biomass into biocrude and valuable chemicals at a moderate temperature (usually 200–400 °C) and high pressure (typically 10–25 MPa). In HTL, water acts as a key reactant in HTL activities. Several properties of water are substantially altered as the reaction state gets closer to the critical point of water, which can result in quick, uniform, and effective reactions. The current review covers the HTL of various feedstocks, especially lignocellulosic and high protein-containing feeds with their in-depth information of the chemical reaction mechanisms involved in the HTL. Further, this review gives insight and knowledge about the influencing factors such as biomass pretreatment, process mode, process conditions, etc., which could affect the efficiency of the hydrothermal process and biocrude productivity. In addition, the latest trends, and emerging challenges to HTL are discussed with suitable recommendations.

Transformer oil is refined electrical insulating oil, which is extremely stable at high temperatures and possesses excellent electrical insulating properties. These special types of oils are widely used in high voltage apparatus such as power transformers, high voltage capacitors and circuit breakers. Traditionally, mineral oils have been most commonly used as a coolant or as electrical insulation medium. However, the main concern related to mineral oil is overheating, overloading, short circuits that reduce the shelf life of the transformer unit and restrict its function as a reliable coolant. Moreover, other factors such as high electrical insulation requirements, safety and economic aspects need to be considered for the development of new insulating liquid material. Nanofluids have become the one of the alternatives for the existing products available in the market because of its high thermo-physical and good dielectric properties. This review focuses on the status of nanofluids, the effect of different nanoparticles to enhance the dielectric as well as its heat transfer properties of nanofluids. The thermo-physical properties of the newly developed transformer oil based nanofluids reported in comparison with different oils. Finally, future directions and challenges need to be addressed.

We studied the reinforcing effects of treated and untreated nanohydroxyapatite (NHA) on poly-lactic acid (PLA). The NHA surface was treated with three different types of chemicals; 3-aminopropyl triethoxysilane (APTES), sodium n-dodecyl sulfate (SDS) and polyethylenimine (PEI). The nanocomposite samples were prepared using melt mixing techniques by blending 5 wt% untreated NHA and 5 wt% surface-treated NHA (mNHA). Based on the FESEM images, the interfacial adhesion between the mNHA filler and PLA matrix was improved upon surface treatment in the order of mNHA (APTES) > mNHA (SDS) > mNHA (PEI). As a result, the PLA-5wt%mNHA (APTES) nanocomposite showed increased viscoelastic properties such as storage modulus, damping parameter, and creep permanent deformation compared to pure PLA. Similarly, PLA-5wt%mNHA (APTES) thermal properties improved, attaining higher Tc and Tm than pure PLA, reflecting the enhanced nucleating effect of the mNHA (APTES) filler.

The process parameters of microwave-induced hydrothermal carbonization (MIHTC) play an important role on the hydrothermal chars (hydrochar) yield. The effect of reaction temperature, reaction time, particle size and biomass to water ratio was optimized for hydrochar yield by modeling using the central composite design (CCD). Further, the rice straw and hydrochar at optimum conditions have been characterized for energy, chemical, structural and thermal properties. The optimum condition for hydrochar synthesis was found to be at a 180 °C reaction temperature, a 20 min reaction time, a 1:15 weight per volume (w/v) biomass to water ratio and a 3 mm particle size, yielding 57.9% of hydrochar. The higher heating value (HHV), carbon content and fixed carbon values increased from 12.3 MJ/kg, 37.19% and 14.37% for rice straw to 17.6 MJ/kg, 48.8% and 35.4% for hydrochar. The porosity, crystallinity and thermal stability of the hydrochar were improved remarkably compared to rice straw after MIHTC. Two characteristic peaks from XRD were observed at 2θ of 15° and 26°, whereas DTG peaks were observed at 50⁻150 °C and 300⁻350 °C for both the materials. Based on the results, it can be suggested that the hydrochar could be potentially used for adsorption, carbon sequestration, energy and agriculture applications.