Industrial Chemistry
Open Access

Electric arc furnace dust (EAFD) and waste pickle liquor (WPL); To produce nickel zinc ferrite (NZF), two major steel industry by products with negative effects on the environment were utilized: the crucial magnetic ceramic material with numerous industrial uses. When compared to materials made from pure reagents, the prepared material's structural and magnetic properties were found to be superior, with a high saturation magnetization and low coercivity. EMI suppressors, electromagnet cores, transformer cores, antenna, video magnetic heads, and multiple path communication magnetic heads are just a few of the many uses for Ni–Zn ferrites in science and technology. In contrast, magnetic ferrite nanoparticles can be used in novel ways for therapeutic purposes, particularly in drug delivery systems, as well as for catalytic purposes, magnetic resonance imaging, supercapacitors, and gas sensors. The use of various oxides and dioxides as a sensor material to detect the majority of reducing gases has been extensively studied [1]. The gases that are toxic, explosive, and flammable, like hydrogen sulfide (H₂S) and hydrogen (H₂), as well as vapors of volatile organic compounds and others. create a significant risk to human health and the environment. As a result, the industry and society place a high value on gas analysis, detection, and alarms.

Due to their advantages of high sensitivity, quick response, and ease of integration, metal oxide semiconductor (MO) sensors are thought to be effective solutions for the detection of harmful gases . As materials for detecting gases, single metal oxides have received a lot of attention. Zinc oxide (ZnO), tin oxide (SnO₂), tungsten oxide (WO₃), titanium oxide (TiO₂), and iron oxide (Fe2O3) are a few examples. ZnFe₂O₄ is a typical spinel ferrite semiconductor that has a narrow band gap (1.9 eV) and several excellent properties. It has received a lot of attention for its use in gas sensors , catalyst , magnetic materials , and materials for lithium batteries . Most of the sensing effect occurs on the material's surface; One of the first requirements for improving the humidity sensitivity of the sensor will be the regulation of particle size. Coprecipitation , sol-gel and the template synthesis method are the most common methods used to make ZnFe₂O₄-based gas sensing materials in recent years. These methods can make ZnFe₂O₄ nanomaterials with different morphologies, like nanorods, nanotubes, nano-thin films, and core-shell microspheres. Pure ZnFe₂O₄ nanomaterials, oxide-ZnFe₂O₄ composite materials, and ZnFe₂O₄-doped ZnFe₂O₄ nanomaterials are the most common ZnFe₂O₄-based gas sensing materials [2]. This paper presents zinc ferrite-based gas sensors, a type of semiconductor gas sensor that responds to various reducing gases by converting chemical signals into electrical signals. Zinc ferrite's phase formation, morphology, and electrical properties are all discussed in this work. We were able to correlate these results with sensitivity to various gases and vapours under a variety of conditions thanks to these. Co-precipitation has been used to create the experimental zinc ferrite. Zinc sulfate of A. R. grade and ferrous sulfate were dissolved in the right amounts. The metal salts were then precipitated into hydroxides using a solution of 10% NaOH at a pH of 10 and then oxidized using a solution of 30% H₂O₂ (100 ml). To get rid of sulfate and excess alkali, the precipitate was washed and filtered. The precipitate was sintered for four hours at temperatures ranging from 500 to 900°C before being dried in a vacuum cryostat at 110°C.

Sensing of oscillatory gas

The early discovery and warning of the presence of dangerous feasts have been well studied. We present a study that focuses on some abecedarian parcels of gas detectors for thawed petroleum gas( LPG) using spinel nano-ferrites, videlicet [3]. Other ignitable feasts tested were hydrogen, methane, propane, and butane. Electronic conduction of LPG detectors near achromatism showed simple electrical oscillations that can be attributed to the tone- dissociation of water motes physically adsorbed on the face of the chemisorbed oxygen species due to proton transfer. The oscillatory actions follow oscillations in the operating temperature attributed to heat transfer between the physisorbed water motes and the hot detector face . This depends on the LPG attention because advanced LPG attention gives rise to lesser heat transfer from the detectors. The adsorption and desorption of these water patch multilayers take a many hundreds of seconds at low attention, while the adsorption conformation process takes longer at advanced attention. Other parameters similar as LPG exposure time, bias voltage, relative moisture, ambient conditions, operating temperatures, and temperature of the gas not only affect electrical oscillations and thermal oscillations but also switch the dominant charge carriers from p- to n- type or vice versa. Acetone is one of the poisonous, explosive, and dangerous feasts. It may beget several health hazards issues similar as somnolence and headache. Acetone is also regarded as a crucial biomarker to diagnose several conditions as well as cover the diseases in mortal health. Grounded on clinical findings, acetone attention in mortal breath is identified with numerous conditions similar as asthma, halitosis, lung cancer, and diabetes [4].

X-ray powder diffraction patterns were recorded on a diffractometer (Philips PW 1730) with a microprocessor controller. The two-probe method was used to measure the temperature-dependent change in DC resistivity from RT to 500°C. Measurements of the gas sensing apparatus Our laboratory constructed the gas sensing apparatus in accordance with the design . The pellet-shaped powder was pressed into the gas sensor. At various operating temperatures and concentrations, the gas sensing characteristics were recorded in relation to time. The ratio of the change in electrical resistance in the presence of air and the presence of the test gas is what is referred to as the sensor sensitivity [5-8]. Gas-Sensing Properties Water molecules are adsorbent on semiconductive oxide and depending on whether the oxides are of the n-type or the p-type, the conductivity of the water molecules increases or decreases. This indicates that water molecules appear to transfer electrons to oxides. The interaction between water molecules and the metal oxide's surface, or reactivity, is what determines a metal oxide's capacity to detect water molecules. Adsorbed oxygen species are known to play a significant role in gas detection. The following is a description of the reducing gas's activity on the surface of zinc ferrites.

Hydrothermal Synthesis/Solvothermal Process In hydrothermal synthesis, Zn2+ and Fe3+ are dissolved in water in a ratio of 1:1, and then ethylene glycol or ethanol are added drop by drop while stirring to ensure that the solution is well mixed. In order to dissolve and recrystallize the precursors, the resulting mixture is put into an autoclave and heated to high temperatures. Changing the concentration of the reactants, the hydrothermal temperature, the reaction time, the pH, the amount of surfactant, and other factors can be used to regulate the product's purity, size, saturation magnetization value, and photocatalytic activity. The disadvantages of hydrothermal synthesis include long reaction times, costly autoclave equipment, and difficult crystal growth observation, despite its potential for large-scale ferrite synthesis. The solvothermal method has been developed because several materials utilized in hydrothermal synthesis are insoluble in water but readily soluble in organic solvents. The solvothermal method is similar to hydrothermal synthesis in that the precursor is dissolved in an organic non-aqueous solvent instead of water.

Conclusion

At first, oxygen from the air adsorbs to the ferrite's surface and extracts electrons from its conduction band to form O- species on the surface, lowering the conductance. When reducing gas R is introduced, it reacts with O-(ads) to form RO, and electrons enter the ZnFe₂O₄ conductance band. In conclusion, H₂S decomposes into gaseous SO₂ and water vapor by reacting with the adsorbed O- on ZnFe₂O₄. It is important to note that ZnFe₂O₄ is known to be an absorbent for H2S and oxidizes it to SO₂ and H₂O. The precise mechanism for ZnFe₂O₄'s selectivity toward H2S is unknown, but it may be due to its favorable absorption configuration in comparison to other gases, making it selective toward H₂S.

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