Demands for batteries have been increasing each year globally. This results in an enormous number of waste batteries, especially non-rechargeable types. It can pose severe environmental and health hazards if disposed of improperly. The consumers are generally not aware of how waste batteries should be properly disposed, thus, they usually end up in landfills worsening its risks. Hence, determining a more valuable alternative usage is a sustainable solution. In this study, graphite rods from the waste primary (zinc-carbon) batteries were utilized to produce conductive ink. Graphite rods were systematically removed from the spent batteries, cleaned with acetone to remove the plastic coating, and dried. It was then electrochemically exfoliated by applying 10 V and 2 A while submerged in an H₂SO₄ solution (1 M). The resulting powders were filtered, rinsed with distilled water until neutral pH, and oven-dried (80 °C). These were then dispersed in silver-ammonia solution and hydrothermally reacted at 150 °C for 5 h. Sodium silicate solution was used as a dispersing medium for the reduced graphene oxide (rGO) powder producing conductive ink. The ink demonstrated a good surface adhesivity, very low resistivity (<30 μΩ∙m), and consistent even after 500 bending cycles. Also, Ag@rGO powder’s morphology, surface characteristics, and physicochemical properties have been evaluated using XRD, Raman, and FE-SEM.

The research presents the simulation results with Matlab on combining of a type of thin-film photovoltaic module (a-Si), a copper plate heat absorber with thermoelectric generators (TEG) utilizing the standard low-sun spectrum AM1.5G at 0.05, 0.06, 0.07, 0.08, 0.09 and 0.1 Sun as a source of radiation. Amorphous silicon is a type of thin-film solar cell that is more suitable for indoor use so that by using a source of low-intensity light radiation from the sun will still generate electrical energy conversion. Spectrum splitting is used as a cold mirror, which reflects the spectrum of light to the a-Si module in the form of photon energy while transmitting to the TEG module the spectrum of near-infrared light radiation in the form of heat. On the hot side of the TEG, a copper plate was placed to accommodate the heat from light radiation to increase convection heat transfer and temperature differences between the hot and cold sides of the TEG. The simulation results show that the highest efficiency of a-Si module is 3.46% achieved at the lowest spectrum of 0.05 Sun, vice versa TEG is at the highest spectrum at 0.1 Sun and 10.05% its efficiency. This low sun spectrum will be a milestone in the utilization of bulb radiation energy in general domestic needs.

One-step ammonia synthesis under ordinary temperature and pressure has been attempted by introducing a nitrogen source (pure nitrogen gas or air) to hydrogen production reaction field of in-liquid plasma. As a result of the experiment, it was confirmed that ammonia can be synthesized by this method. However, the amount of ammonia synthesized was small. Most of the produced hydrogen is as pure. Also, the introduced nitrogen source is almost released outside of the reactor. This indicates low ammonia selectivity, study is required to improve the selectivity. The findings of this study are that the hydrogen production efficiency (HPE) and the C O balance of the raw materials affect the amount of ammonia synthesized. It was found that the higher HPE the better. A one to one ratio of C and O was found to be the optimal condition.

At present, the two main wastewater treatment methods are biological treatment and coagulation sedimentation treatment. However, wastewater discharged from dyeing factories cannot be adequately treated because it contains persistent organic substances. The purpose of this study is to develop a treatment for dye wastewater using plasma under atmospheric pressure. The decolorization processing characteristics were investigated using a methylene blue (MB) solution as a model for dye wastewater. The study revealed that an MB solution could be decolorized using plasma treatment, and the conversion rate was correlated to the MB concentration. The discharge method and liquid temperature affected the conversion of MB, and the conversion rates and energy efficiencies were compared for each condition. Additionally, flow-type plasma that took in air from the side of the reaction vessel could treat MB the most efficiently and could be stably operated for considerable time. This process may eventually be used to treat dye wastewater discharged from actual dyeing factories.

In this study, hydrogen production by the in-liquid plasma methods reported thus far was compared, to find the optimal method and condition. Because the in-liquid plasma is a type of plasma generated within bubbles in a liquid, an ingredient with a small evaporation enthalpy (EE) is found to be more advantageous. In addition, it is necessary to select an ingredient with a high thermodynamic ideal efficiency (IE), as calculated using the enthalpy of the formation. The actual hydrogen production efficiency (HPE) of water (IE, 0.28 Nm³-H₂/kWh; EE, 44 kJ/mol), methanol (IE, 1.26 Nm³-H₂/kWh; EE, 38 kJ/mol), n-dodecane (IE, 2.99 Nm³-H₂/kWh; EE, 62 kJ/mol), were found to be 0.02, 0.28, and 0.13 Nm³-H₂/kWh, respectively. The highest HPE was obtained for the methanol decomposition, indicating that ingredients with low EE and high IE are advantageous for hydrogen production. Moreover, the HPE reduced because most of the energy of the plasma diffused to the surroundings. Therefore, it is essential to develop efficient heat recovery methods and heat insulation systems.

In this study, mass transfer of ash during bamboo powder combustion on a flat flame is investigated experimentally and numerically. The bamboo powder combustion consisted of volatiles emission, volatiles combustion, char formation, char combustion, and finally ash formation. The mass of ash formed was about 3 wt% that of raw bamboo powder. The mass of ash decreased with the equivalence ratio Φ for flat flame combustion. Part of the ash fused and then adhered to the Inconel mesh for wrapping of bamboo powder as bottom ash, flowing through the mesh. The mass adhered to the Inconel mesh depended strongly on the equivalence ratio Φ. The fusion tendency of the atmospheric oxidization ash agreed qualitatively with Liu’s standard bamboo ash fusion test. On the other hand, as ash fusion started locally in this work, it suggests that the concentration of metal oxides of the atmospheric oxidization ash was not uniform. For the atmospheric oxidization ash at 600 °C, K₂Si₂O₅, KAlSiO₄, Na₂CaP₂O₇, Mg₂SiO₄, K₂SO₄, and Fe₂O₃ were predicted to be the major eutectic materials. At 1120 °C, only Fe₂O₃ remained and the liquid components accounted for about 95%. On the other hand, the major eutectic materials for the combustion ashes of Φ = 0.85 and Φ = 1.0 at 1260 °C were MgO and Fe₂O₃, respectively. Therefore, the predicted eutectic materials of the combustion ash were changed appropriately in comparison with those for the atmospheric oxidization ash because of the fusion and disappearance of some metal oxide components during combustion.

Composites have absorption properties, namely the ability to absorb water at a specific time. The nature of absorption is a problem because this can reduce the mechanical strength of composites. This study aims to determine the effect of seawater immersion on the impact strength of the composite. The composites used are made of epoxy resin as matrices and ramie fiber as reinforcement. Variation in the orientation of the fibers is given, i.e., continuous and woven fibers. Ramie fiber composites are expected to be able to provide consideration for the primary raw material for shipbuilding so that the composite is carried out on a scale-scale seawater immersion to determine the effect of immersion on impact strength, and immersion is carried out for 0, 2, 4, 6, 8 and 10 weeks. Impact strength testing refers to the ASTM D 5942-96 standard. The results obtained show that the impact strength of unidirectional ramie fiber composites decreased by 30.76% and stronger than ramie’s woven strength composites which decreased by 17.08%. Still, the impact strength on unidirectional ramie fiber composites (150.14 kJ/m²) is more when compared to ramie woven composites (83.26 kJ/m²).

Converting the de-oiled cashew nut shell into usable products (e.g. briquettes) will address the problem of waste disposal. The study was conducted to develop an environment-friendly fuel briquette sufficient to resist impact during handling and transport and produce the required heat for domestic cooking and also for industrial application. Piston-type and screw-type briquetting machines and three levels of binding agent were used in the production of de-oiled spent cashew shell-based fuel briquettes. The produced briquettes were subject for physicochemical, mechanical and thermal properties tests. Results showed that the best formulation that is required to produce a good quality de-oiled cashew nut shell fuel briquettes using both piston-type and screw type briquetting machines is 10 % binding agent with briquette density, shatter resistance and compressive strength of 0.87 g/cm³ and 0.83 g/cm³, 99.54 and 99.89 % and 43.97 and 101.82 kPa, respectively. The total electricity consumption is 150.91 kWh per ton of briquettes while LPG consumption is 1.32 kg. It is concluded that the energy values and combustion qualities of the briquettes produced in this study are sufficient enough to produce the required heat for domestic cooking and a potential for industrial application.