Journal of Science & Sustainable Engineering

Green hydrogen Production from the oxidative reform of clean biogas over Ni/MgO-Nb2O5 catalysts

2023-11-13T13:57:25+00:00

Synthesis gas has a variety of applications ranging from its transformation into Fischer-Tropsch fuels, its processing to produce pure hydrogen, and even its direct combustion to generate energy, among many other applications. The objective of this work was the conversion of a model of biogas (clean biogas) into synthesis gas, H₂ /CO, through oxidative reforming of methane over NiO/MgO/Nb₂O₅ catalysts. The catalysts in this work were prepared by impregnation and calcination (at 750ºC) and subsequently characterized by Energy Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Nitrogen Adsorption-Desorption (BET method) and Temperature Programmed Reduction with H2 (TPR). Finally, these catalysts were tested in the oxidative reform of methane (molar ratio of 1.5CH₄:1CO₂:0.25O₂) at 750 ºC, 100mg of catalyst at a total flow of 110 mL.min^-1, and 1 atm (inside the reactor). According to the results, it was verified that the catalyst composed of the NiO/MgO mixture is composed of the NiO-MgO solid solution, whereas the NiO/MgO/Nb₂O₅ catalysts are also formed by nickel niobate (NiNb₂O₆). All catalysts showed catalytic activity in the oxidative form of biogas, NiMg, Ni60NbMg, and Ni40NbMg catalysts showed the highest conversion value. The efficiency of the catalysts in the oxidative reforming of biogas improved gradually as the %MgO increased in the NiO/MgO/Nb₂O₅ system. The characterization of the catalyst after the reaction demonstrated that the carbon formed is of the filamentous type.

Innovations for the Treatment of Effluents in the Food Industry

2023-08-01T12:24:35+00:00

During the processing phases of the food business, a large amount of water is used, resulting in a large volume of effluents. Raw materials, sanitary water for food processing, transportation, cooking, dissolving, auxiliary water, cooling, cleaning, and so on are all utilized extensively in the business. Traditional anaerobic or aerobic biological wastewater treatment processes can be employed to handle organic compounds found in food sector effluent. However, some hazardous chemicals to a microbial population may be present in the effluent due to varied consumption. The effluent may contain significant levels of suspended particles, nitrogen in various chemical forms, lipids, oils, phosphorus, chlorides, and high organic content. There are traditional and well-established methods for treating effluents in the food industry, such as the coagulation-flocculation process, electrochemical processes, and biological processes, which have proven to be quite effective when used as treatment methods in a variety of industries; however, such methods have limitations. Innovative techniques, such as microbial fuel cells (MFCs), microalgae, water ultrafiltration, nanofiltration, and membrane technologies, can replace or complement traditional methods in the future. The treatment method chosen will be determined by the industry's and its wastewater's characteristics.

Influence of Chemical Cleaning Procedures and Thermal Oxidation Processes on the Uniformity of MOS Gate Oxides on Abrupt Steps on Silicon Surfaces

2023-06-27T16:13:04+00:00

This work analyzes the influence of some chemical steps used in standard cleaning recipes on the surface micro-roughness of silicon wafers. The effect of varying the ammonium hydroxide concentration in the NH₄OH: H₂O₂:H₂O solution was studied and silicon wafer micro-roughness was characterized by atomic force microscopy technique at different scans of 1µmx1µm. Based on the results, it was possible to point the condition to obtain low surface micro-roughness for NH₄OH-based solutions with the lowest NH₄OH content before the growth of gate oxides. Following, it silicon-oxide thin films were grown onto periodic rectangular shapes, 100 nm in height, obtained by localized plasma etching on silicon wafer surfaces. Silicon oxides (SiO₂), about 4.5 nm thick, were grown in ultrapure dry-O₂ or pyrogenic (O₂ + H₂) environments in order to compare the planar uniformity and the grade of coverage at the step edges of rectangular shapes defined onto silicon surfaces. Pyrogenic and conventional oxidation at 850 ^oC allowed one to obtain gate oxides on 100 nm-stepped silicon surfaces with high dielectric breakdown field (>10 MV/cm), good planar uniformity and conformal coverage at the step edges. The impact of this result is now the feasibility of fabricating good-quality gate oxides for surrounding gate transistors (SGT’s) and texturized MOS solar cells.

Microbial Degradation of Heterocycles- A Review

2023-08-01T13:48:38+00:00

Heterocycles are organic compounds that are well-known and distributed in nature; they can be used in the pharmaceutical, agrochemical, and chemical industries. Heterocycles composed of sulfur, nitrogen, and oxygen atoms are harmful toxins and can cause cancers; these substances can persist for years in the environment. One attractive alternative to expensive physical and chemical methods is microbial degradations, which present high potential and low cost, causing minimal environmental impacts. The use of these microorganisms makes use of heterocyclic substances as substrates, removing them efficiently and safely. Some strains of wild and genetically modified microorganisms (bacteria and fungi) have already been used to degrade various pesticides and aromatic compounds. Understanding the biodegradation mechanism of microorganisms will benefit future bioremediation studies, which may prove to be one of the alternatives to solving environmental problems. This review will focus on the microbial degradation of heterocyclic compounds, taking into account the most used techniques and their limitations in future research

Waste treatment and Sustainable Bioelectricity Generation using Microbial fuel cell

2023-08-01T02:12:28+00:00

In the last decade, great attentions have been paid to microbial fuel cells (MFC) due to the possibility to be the solution for the three bigger world project – energy security, climate changes and waste management. Different from all the conventional wastewater treatment which are energy intensive, MFC can use waste as substrate/fuel to directly generate electricity through microbial reactions in anode and microbial/enzymatic/abiotic electrochemical reactions in cathode. In this sense, the MFC is an emerging technology for treat waste and produce wealth products (energy and some added value substance – organic acids, nutrients). Although, there are a large number of research in new materials and operational conditional to improve the MFC performance, as yet there are practical barriers, such as low power generation, expensive electrode materials and the inability to scale up MFC. Therefore, this work summarizes information about the recent advances in MFC research, focused on MFC configurations, material electrodes, and performances. Limitations and challenges in applying MFC to treat waste are also discussed, moreover future perspective pointed the new hot topics to solve these problems.