Key Engineering Materials Vol. 962

Abstract: The wide applicability of proton exchange membrane fuel cells (PEMFCs) is hindered by their dependency on the Nafion membrane as a state-of-the-art electrolyte. Nafion membranes can only operate at relatively low temperatures, up to 80°C. Therefore, any application of the fuel cell above this temperature would cause the PEMFC to lose its proton conductivity and mechanical integrity. For this reason, the development of Nafion-free membranes for PEMFCs has been studied extensively through the corporation of several additives over polymer substrates. The charge transfer abilities of metal-organic frameworks (MOFs), among other properties, make them one of the possible additives. The objective of this work is to synthesize Nafion-free membranes based on graphene oxide, MOFs, ionic liquids, polyethylene glycol, and zirconium phosphate over PTTFE membrane as an alternative to Nafion membranes. The preliminary results gave proton conductivities in the range of 10^-4 S/cm up to 150°C with graphene oxide MOF addition to all samples.

Abstract: Fuel cells are preferred to operate at high temperatures, i.e., more than 100°C, due to their numerous advantages, that range from improved kinetics and better water management. Unfortunately, Nafion cannot operate above 80°C as it dehydrates, so its proton conductivity decreases significantly. Therefore, in this work, a new polymer electrolyte membrane is developed. It is based on solid proton conductors-Zirconium phytate (ZrPA) and Silicotungstic acid. Ionic liquids are used as structure-directing agents. ZrPA/Silicotungstic acid/IL composite membranes were fabricated and supported on polytetrafluoroethylene (PTFE). The composite membranes were evaluated for their proton conductivity. High proton conductivity of 0.0911 S/cm was achieved at room temperature when a 7.26 wt.% ionic liquid (1-Hexyl-3- methylimidazolium tricyanomethanide) was used. The proton conductivity kept its value at 0.0066 S/cm even at a higher temperature of 150°C.

Abstract: Microbial Fuel Cells (MFCs) are attracting attention for their application in simultaneous energy production and waste treatment, as innovative biochemical reactors. They usually operate under adiabatic conditions, utilizing microorganisms to treat wastewater compositions using mainly carbon-based electrodes as anodes and cathodes. During the past years, various anodic and cathodic electrodes with plenty of variations were used in MFC configurations. On the anode side metal-based electrodes are used while on the cathode, ceramic electrodes are currently introduced. In this study, a stainless steel anode is used in a single chamber MFC. Ceramic cathodic electrodes are used, coated with Fly Ash (FA). The mixed transition oxides of FA are tested as potential cathodic catalysts in the operation of the MFC. The FA powder was deposited by two methods: an ultrasound-assisted method and a conventional brush coating. Tannery liquid waste is used as the waste/substrate to be treated in the single-chamber MFC. The configuration with ultrasound-assisted Fly-Ash produced cathodic electrodes, led to the highest power output in batch operation modes and a high degree of simultaneous COD decrease of the tannery waste reaching the values of 0.44 mW/g_cat and 85.6% COD removal respectively.

Abstract: Microbial Fuel Cells (MFCs) are electrochemical devices that exploit microbes for wastewater treatment with simultaneous power production. Concerning reactor design, electrode materials and operation modes, great achievements have been reported with an emphasis on developing anode materials to improve overall MFC performance. Anode materials (carbon cloth, carbon veil, carbon sponges) and their properties such as biocompatibility, electrical conductivity, surface area and efficient transport of waste play a very important role in power generation in MFCs. Despite their low cost, they present structural-based disadvantages eg. Fragility, and low conductivity issues. Additive manufacturing of Fused Deposition Modelling (FDM) due to its tailoring properties, has employed various polymer-based materials such as Polylactic Acid (PLA) and Acrylonitrile Butadiene Styrene (ABS) for manufacturing applications. In addition, carbon-based composites and hybrid materials eg. electrically conductive PLA and ABS have already been fabricated and are commercially available to exploit good electrical conductivity and structural rigidness. In this research, FDM was used to fabricate custom-sized electrodes made of a laboratory-produced electrically conductive ABS filament. A parametric study of conductivity and biocompatibility properties of these electrodes in correlation to 3D printer parameters was investigated and reported. Furthermore, treatment with a combination of thermal, mechanical, and chemical procedures was performed to improve the crucial parameters of anodes for MFCs.

Abstract: Biodiesel is produced by an esterification process with hygroscopic chemicals, otherwise the biodiesel is very easy to produce water, and the hydrocarbon compounds were easily oxidized, causing corrosion in the stockpiling process such as in storage tanks and distribution pipes. Antioxidants have been shown to reduce the formation of water in the biodiesel stockpiling process. While the demulsifier plays a role in helping to separate water and oil. In this study, the addition of an acrylate-based demulsifier in the accumulation of biodiesel-containing antioxidants was carried out. The antioxidant used in the form of tertiary butylhydroquinone with a concentration of 0.5 M has been able to play an active role in inhibiting the formation of water in the biodiesel stockpiling process. However, the stability of the water and oil emulsion has not been achieved properly, therefore the addition of an acrylate-based demulsifier with a volume of 2 mL, 5 mL, and 10 mL into 100 mL biodiesel can separate oil and water well. The biodiesel that has been added with a demulsifier is evaluated at storage times of 24 hours, 48 hours, and 72 hours. The result is that the storage for 72 hours is more effective in separating water and oil than storage for 24 hours and 48 hours. To evaluate the water content in the biodiesel stockpiling process out using 831 KF Coulometric and Fourier-Transform Infrared Spectroscopy analysis.

Abstract: This study aims to: (1) activate rice husk ash (ASP), coconut shell ash (ATK), and wood charcoal (AK) to become adsorbents and characterize them; (2) purify waste cooking oil (WCO) using ASP, ATK, and AK adsorbents; (3) making biodiesel from the purified WCO and characterizing their quality. This work uses experimental techniques, starting with preparing adsorbents by activating with KOH and characterizing activated ASP, ATK, and AK adsorbents using SEM and FTIR. The adsorbents were then used to purify WCO. Biodiesel was made from purified WCO by transesterification using an H₂SO₄ catalyst in ethanol. The process was carried out at 60°C for 12 hours. Then biodiesel layer was heated to 70°C to evaporate the ethanol. The biodiesel products were tested according to Indonesian National Standard (SNI). The results showed that peaks of the activated ASP, ATK, and AK adsorbents have alcohol groups (-OH), and other functional groups. Activated adsorbents have many pores when compared to adsorbents before activation. Biodiesel synthesized using activated ASP adsorbent has a higher flash point than using activated ATK and AK adsorbents and fulfils SNI specifications.

Abstract: Recent advances in the fields of artificial intelligence and machine learning have paved a way in solving the unsolved problems embarking into a new dimension, especially, when there is increase in complexity of molecules. Reports have shown the necessity to employ these techniques to address the environmental problems. Herein we report the CO₂ sequestration process by means of artificial intelligence (AI) and machine learning (ML) tools. The AI and ML approaches adopted enhance the accuracy of the results and at the same time give scope to explore new strategies in understanding the CO₂ sequestration process. Herein we considered the reported active compounds observed in traditional medicinal plants like Oscimum, Azadiracta, Psidium and Ficus leaves and Curcuma and, their interactions with CO₂. The crystal structures of the active compounds, collected from NCBI portal, are used for all the calculations. To understand the probable interactions of CO₂ with active components AI tool IBMRXN was used and the properties of molecules are evaluated. ML techniques are employed using density functional theory method. Keeping in view the complexity of the molecules, optimization of the molecules is carried out at M062X/6-31G(d) level of theory. HOMO-LUMO energy gaps and binding energies are calculated at M062X/6-311+G(d,p)//M062X/6-31G(d) level of theory.

Abstract: The presence of residual antibiotics in soil and water ecosystems has harmful effects on the environment, ecological food chain, and human health. It is also a driving factor for bacterial antibiotic resistance. Erythromycin is an antibiotic found in the water bodies in several countries due to improper disposal or inefficient wastewater treatment. Biochar is an adsorbent material prepared by the pyrolysis of discarded waste items including food and garden waste that could provide a cost-effective and efficient method for eliminating antibiotics from wastewater. This study evaluated whether biochar is successful in removing the antibiotic erythromycin from an aqueous environment through adsorption. It also investigated whether various factors such the pH of the aqueous environment or the concentration of erythromycin impacted its adsorption. Lastly, it was compared to commercially available activated charcoal to determine which material adsorbs erythromycin more effectively. The biochar is obtained from the pyrolysis of solid domestic waste including food, paper, and garden waste at 300°C. All experiments were conducted over three hours at neutral pH and the adsorption onto 1.0 g (±1 mg) of biochar was calculated in mg/g. The solutions were continuously stirred at 200 rpm and the temperature was set to 23°C. Samples were analysed using reverse-phase high-performance liquid chromatography (HPLC) at 210 nm using a mixture of methanol-water at alkaline pH (80:20, v/v) as a mobile phase. It was found that the highest concentration of erythromycin, 100 mg/L showed a better adsorption capacity (3.71 mg/g) compared to samples at a concentration of 50 mg/L (1.90 mg/g) and 25 mg/L (0.95 mg/g). In addition, samples obtained from the neutral (pH 7) solution showed slightly greater drug adsorption in comparison to samples obtained from the acidic (pH 5) and alkaline (pH 9) solutions. Lastly, biochar was more effective than activated charcoal in adsorbing erythromycin where a 1.0 g of biochar adsorbed almost twice the amount of the drug. Overall, this study suggested the use of a biochar prepared from discarded materials as a simple cost-effective additional method for removing erythromycin from water which could be further optimised or combined with another method achieve a full elimination.

Abstract: The geochemical analysis of the middle Z precious metallic trace elements of the charnockite mineral composition was obtained by using proton induced X-ray emission at 3 MeV with a Si (Li) detector. Compared with other experimental nuclear analytical techniques like EPMA, XRF, and NAA, proton induced X-ray emission is used to detect with good accuracy and precision in the case of trace precious metals like Mo, Nb, Ru, Rh, and Ag, etc., in charnockite mineral composition due to the cross-sections with 3 MeV protons and good agreement. But peak resolution problems of K-X-rays of low Z and L-X-rays of the above elements which were presented in charnockite analysis must be solved and also change the detector parameters to obtain exact values in traces of the above elements in parts per million.