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Abstract This work aimed to extract silica from combination of rice husk (RH and Rice straw (RS) by optimizing the ash digesting process parameters with the aid of response surface methodology (RSM). The effects of three independent ash digestion process factors like sodium hydroxide concentration (1–3 M), temperature (60–120 °C) and time (1–3 h), for silica production from the mixture of rice husk (RH) and rice straw (RS) were studied. A quadratic model was used to correlate the interaction effects of the independent variables for maximum silica production at the optimum process parameters by employing central composite design (CCD) with RSM. The work indicates that the temperature is the most significant parameter among the model terms, followed by NaOH concentration, then time for digestion of ash for silica production. It may be because of the larger F-value for temperature, which influences to high extent of ash digestion for silica production. The proximate analysis discovered that RH/RS possessed compositions of high ash, volatile matter and fixed carbon content whereas low moisture content, i.e., 20.5 ± 0.46, 67.1 ± 0.78, 15.8 ± 0.35 and, 6.6 ± 0.37 wt.%, correspondingly. The characterization of RH/RS and silica were performed by employing thermogravimetric (TG) and differential thermal (DT), Fourier transforms infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF) and Brunner–Emmet–Teller (BET) for confirmation of the silica production. Hence, this current study concludes that silica materials obtained from RH/RS (with purity > 97.35 wt.%) may be new materials in the Si–C–O system that may be used in construction, ceramics and silica gel that helps to absorb moisture.

Abstract Foodborne illnesses affect 30% of people in developed nations and lead to financial difficulties in less wealthy countries. Insufficient understanding of pathogens and inadequate food safety practices in water bottling facilities impede progress. To prevent illnesses, ensuring clean water, proper sanitation, and good hand hygiene are essential in order to decrease the 829,000 annual deaths related to diarrhea. This study aimed to evaluate the performance of food safety systems in water bottling factories in view of their contextual characteristics. A study was conducted in northwestern Ethiopia at water bottling factories from January 2023 to August 2023. This study used a mixed method approach to collect and analyze data through laboratory testing, observations, interviews, questionnaires, and document analysis. The Kruskal‒Wallis H test was used to compare mean scores of context riskiness and food safety output across four clusters, while the Mann‒Whitney U test was used to compare means between certified and noncertified factories. In our study, 43% of the samples showed positive total plate count. The result also indicated the presence of potentially dangerous by-products of chlorine, trihalomethanes was found in bottled water. On average, the manufacturers operated in a moderate risk context. Inadequate food safety outcomes resulted from lower food safety management systems scores. Factories with insufficient Food Safety Management Systems often face challenges marked by safety protocol discrepancies, leading to higher risks of contamination and non-compliance with regulations. This assessment underscores the need for tailored interventions focusing on specific contextual barriers to improve food safety outcomes in the bottled water industry.

Sustainable technology in energy-related applications will be crucial in the coming decades. As a result, developing new materials for existing processes has presently arisen as a major research priority. Recently, Deep eutectic solvents (DESs) have been expected as low-cost task-specific solvents for zinc-air batteries (ZABs). Here in, initially the various preparation methods of DESs their detection strategies, and the fundamental characteristics of DESs are summarized. Then, the recent utilization of DESs on ZABs has been reviewed. After that, the chemical and physical characteristics of DESs including phase behavior, viscosity, density, ionic conductivity, refractive index, pH, surface tension and stability have been studied. Lastly, the challenges, limitations, and possible upcoming research fields of DESs for ZABs were discussed.

Herein, a facile co-precipitation technique was employed to prepare cobalt oxide (Co3O4) and Co3O4 nanoparticles (NPs) with manganese (Mn) doping. The morphologies and crystalline structures of the as-prepared NPs were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) techniques. XRD measurements showed that Co3O4 (19.42 nm) and Mn-doped Co3O4 (14.02 nm) NPs were successfully synthesized on average, and they exhibit a face-centered cubic crystalline structure. The SEM images also depicted the spherical morphology of Co3O4 NPs, with Mn particles clustering together. FTIR spectroscopy further confirmed the presence of Mn within the doped Co3O4 NPs. TGA/DTA analysis revealed boosted thermal stability in Mn-doped Co3O4 NPs compared to Co3O4 NPs. Moreover, the BET surface areas of Co3O4 and Mn-doped Co3O4 NPs were 534.013 and 712.741 m2/g, respectively, indicating an increase in surface area due to Mn doping. Consequently, Mn doping enhances both surface area and thermal stability, rendering Mn-doped Co3O4 NPs desirable for nanomaterial applications. This study shows that modulating the Mn doping concentration in the Co3O4 NPs offers superior surface area and thermal stability compared to the prepared Co3O4 NPs.

Highlights Design and working mechanisms of rechargeable zinc air batteries. Investigation of various electrolyte systems for rechargeable zinc air batteries. Advances in the electrolyte technologies and stable electrolytes for rechargeable zinc air batteries.

Deep eutectic solvents (DESs) have attracted interest due to their unique and favorable electrochemical characteristics. This study reported a novel binary glycerol-zinc salt deep eutectic solvents were prepared with a combination of hydrogen bond donor (glycerol (Gly)) and hydrogen bond acceptor (Zinc nitrate hexahydrate (ZNH)) at different molar ratios of 1:2, 1:3, 1:4, 1:5, and 1:6. The various physicochemical properties including viscosity, refractivity index, conductivity, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance (EIS) were measured. The results showed that among the various combinations tested, DES 1:2 resulted in a low viscosity value of 690, 500, 310, 220, and 160 mPa (mPa s) at shear rate (S −1) values of 20, 30, 60, 100, and 200 respectively. Moreover, DES 1:2 resulted in more electrochemically stable solvents with a lower refractive index value of 1.446, and a higher conductivity (σ) of 4.41 mS/cm. The findings found disclose the features, nature and of properties of prepared DESs as a potential solvents for different electrochemical storage applications.

Through co-precipitation and post-heat processing, nanostructured Fe-doped Co3O4 nanoparticles (NPs) were developed. Using the SEM, XRD, BET, FTIR, TGA/DTA, UV–Vis, and techniques were examined. The XRD analysis presented that Co3O4 and Co3O4 nanoparticles that had been doped with 0.25 M Fe formed single cubic phase Co3O4 NPs with average crystallite sizes of 19.37 nm and 14.09 nm, respectively. The as prepared NPs have porous architectures via SEM analyses. The BET surface areas of Co3O4 and 0.25 M Fe-doped Co3O4 NPs were 53.06 m2/g and 351.56 m2/g, respectively. Co3O4 NPs have a band gap energy of 2.96 eV and an extra sub-band gap energy of 1.95 eV. Fe-doped Co3O4 NPs were also found to have band gap energies between 2.54 and 1.46 eV. FTIR spectroscopy was used to determine whether M–O bonds (M = Co, Fe) were present. The doping impact of iron results in the doped Co3O4 samples having better thermal characteristics. The highest specific capacitance was achieved using 0.25 M Fe-doped Co3O4 NPs at 5 mV/s, which corresponding to 588.5 F/g via CV analysis. Additionally, 0.25 M Fe-doped Co3O4 NPs had energy and power densities of 9.17 W h/kg and 472.1 W/kg, correspondingly.

Ag doped Co3O4 nanoparticles (NPs) were synthesized via a co-precipitation method changing the concentration of Ag. The crystal structure, morphology, surface area, functional group, optical band gap, and thermal property were investigated by XRD, SEM, BET, FTIR, UV–Vis, and TGA/DTA techniques. The XRD results showed the formation of single-cubic Co3O4 nanostructured materials with an average crystal size of 19.37 nm and 12.98 nm for pristine Co3O4 and 0.25 M Ag-doped Co3O4 NPs. Morphological studies showed that pristine Co3O4 and 0.25 M Ag-doped Co3O4 NPs having a porous structure with small spherical grains, porous structures with sponge-like structures, and loosely packed porous structures, respectively. The pristine and 0.25 M Ag-doped Co3O4 NPs showed BET surface areas of 53.06 m2/g, and 407.33 m2/g, respectively. The band gap energy of Co3O4 NPs were 2.96 eV, with additional sub-bandgap energy of 1.95 eV. Additionally, it was discovered that the band gap energies of 0.25 M Ag-doped Co3O4 NPs ranged from 2.2 to 2.75 eV, with an extra sub-band with energies ranging from 1.43 to 1.94 eV for all as-prepared samples. The Ag-doped Co3O4 as prepared samples show improved thermal properties due to the doping effect of silver. The CV test confirmed that the 0.25 M Ag-doped Co3O4 NPs exhibited the highest specific capacitance value of 992.7 F/g at 5 mV/s in a 0.1 M KOH electrolyte solution. The energy density and power density of 0.25 M Ag-doped Co3O4 NPs were 27.9 W h/kg and 3816.1 W/kg, respectively.

To mitigate decades of extreme reliance on fossil fuels that have resulted in an increasingly serious energy shortage and environmental problems, extensive research on new clean renewable energy and energy storage technologies with high effectiveness, low cost, and environmental friendliness is required. Zinc-air batteries (ZABs) are effective tools for converting and storing renewable energy. Unfortunately, the low kinetics of the air cathode, as well as the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the principal drawbacks of ZABs. This necessitates the development of high-performance catalysts to accelerate the reaction rates and improve their efficiency. Cobalt-based carbon is an excellent choice for oxygen electrocatalysts due to its low cost, high activity, and stability. Recent advancements in cobalt-based carbon materials used as electrocatalysts in ZABs, as well as the characterization techniques and synthesis procedures, are covered in this paper. It also introduces and analyzes the fundamental mechanisms of ORR and OER electrocatalysis. Finally, we give a description of the present difficulties and potential future developments in the creation of novel high efficiency and bifunctional electrocatalysts.

Highlights Pure ZnO and Cr–ZnO nanoparticles have been synthesized using a facile and cost effective technique. The as prepared samples of pure ZnO and Cr–ZnO nanoparticles show wurtzite structure. Cr doped ZnO nanoparticles showed a higher surface area than that of un-doped ZnO nanoparticles. The synergetic effect of Cr and ZnO nanoparticles attributed to good thermal stability and high surface area.

Stable and active electrocatalysts preparation for the oxygen reduction reaction (ORR) is essential for an energy storage and conversion materials (e.g. metal-air batteries). Herein, we prepared a highly-active MnO2 and Co3O4/MnO2 nanocomposite electrocatalysts using a facial co-precipitation approach. The electrocatalytic activity was examined in alkaline media with LSV and CV. Additionally, the physicochemical characteristics of the MnO2 and Co3O4/MnO2 composite materials were studied via SEM, XRD, BET, UV-Vis, TGA/DTA, ICP-OES and FTIR. Morphological studies indicated that a pure MnO2 has a spherical flower-like architecture, whereas Co3O4/MnO2 nanocomposites have an aggregated needle-like structure. Moreover, from the XRD investigation parameters such as the dislocation density, micro-strain, and crystallite size were analyzed. The calculated energy bandgaps for the MnO2, Co3O4/MnO2-1-5, and Co3O4/MnO2-1-1 nanocomposites were 3.07, 2.6, and 2.3 eV, correspondingly. The FTIR spectroscopy was also employed to study the presence of M-O bonds (M = Mn, Co). The thermal gravimetric investigation showed that the Co3O4/MnO2 nanocomposite materials exhibited improved thermal stability, confirming an enhanced catalytic activity of ORR for MnO2/Co3O4-1-1 composite materials for ORR. These results confirm that the prepared Co3O4/MnO2 composite materials are promising air electrode candidates for the energy storage and conversion technologies.

This research data set contains data related to experimental dataset on the effect of the electron acceptors in energy generation from brewery wastewater via a microbial fuel cell. The presented data gives information on the generation of electricity and waste minimization as various electron acceptors adopted in microbial fuel cells. Dual-chamber microbial fuel cell (MFC) system was assembled with aluminium mesh electrode as an anode and sulfonated tetrafluoroethylene membrane for proton exchange as a cathode at 500–2000 mg/L chemical oxygen demand (COD). A 0.4 and 0.6 M of Potassium permanganate (KMnO4) and potassium cyanide K3[Fe(CN)6 were used anaerobically as a mediator for electron acceptor in the cathode chamber. Furher more, The pH, COD, total nitrogen, biochemical oxygen demand, total phosphorous, total suspended solid and electrical conductivity for the raw brewery wastewater were measured. Inaddition, the voltage generated and the current density have been obtained for both (KMnO4) and K3[Fe(CN)6 electron acceptors. Moreover, the COD removal efficiency, Columbic efficiency, voltage generation, current, and power density were measured.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most popular conducting polymers and widely used as polymer thermoelectric materials, and its thermoelectric performance could be improved by a variety of post-treatment processes. This paper reported two series of post-treatment methods to enhance the thermoelectric performance. The first series method included pre-treatment of PEDOT:PSS film with formamide, followed by imidazolium-based ionic liquids. The second series method included pre-treatment of PEDOT:PSS film with formamide, followed by sodium formaldehyde sulfoxylate, and finally imidazolium-based ionic liquids. Two series of post-treatment methods significantly improved the power factor of PEDOT:PSS when compared to that of PEDOT:PSS treated with formamide only. For example, using the first series post-treatment method with 40 vol.% ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide, the Seebeck coefficient of the PEDOT:PSS film increased from 14.9 to 28.5 μV/K although the electrical conductivity reduced from 2,873 to 1,701 S/cm, resulting in a substantial improvement in the overall power factor from 63.6 to 137.8 μW/K2m. The electrical conductivity enhancement in the formamide-treatment process was in part ascribed to the removal of the insulating PSS component. Further treatment of PEDOT:PSS film with ionic liquid caused dedoping of PEDOT and hence increased in Seebeck coefficient. In contrast, second series post-treatment method led to the reduction in electrical conductivity from 2,873 to 641 S/cm but a big improvement in the Seebeck coefficient from 14.9 to 61.1 μV/K and thus the overall power factor reached up to ~239.2 μW/K2m. Apart from the improvement in electrical conductivity, the increase in Seebeck coefficient is on account of the substantial dedoping of PEDOT polymer to its neutral form and thus leads to the big improvement of its Seebeck coefficient. The environmental stability of ionic liquid-treated PEDOT:PSS films were examined. It was found that the ionic liquid treated PEDOT:PSS retained more than 70% Seebeck coefficient and electrical conductivity at 75% RH humidity and 70°C for 480 h. The improved long-term TE stability is attributed to the strong ionic interaction between sulfonate anions and bulky imidazolium cations that effectively block the penetration of water and lessen the tendency to take up water from the air.