Papers by Keyword: Reduction

Abstract: Paper investigates the possibility of producing silicon from silica contained in Shoda-Kedela (Oni-Gebi district, Georgia) quartz deposition. Characterization of silica from Shoda-Kedela quartz rock is carried by its crushing, grinding, thermal analysis, studying composition and density. Metallurgical grade silicon (MG-Si) is obtained by reducing Shoda-Kedela quartz in its reaction with coke in an electric arc furnace at temperature of ~1800°C. The obtained in this way material reveals that Shoda-Kedela silica containing of 99.58% SiO₂ would be useful for developing the silicon high-technology production.

Abstract: This study investigates the electrochemical reduction of quinine (QN) detection using boron-doped diamond electrodes (BDD). Different pulse voltammetry (DPV) of QN in a 0.1 M PB solution exhibits reduction peaks at -0.86 V (vs. Ag/AgCl). Additionally, the effects of pH and scan rate were explored to investigate the reduction mechanism within a potential range of -1.4 V to -0.4 V (vs. Ag/AgCl). Furthermore, a linear calibration curve was observed in the concentration range of 2 μM to 25 μM (R²=0.99) with a detection limit of 0.62 μM (S/B=3).

Abstract: Since electric arc furnace dust (EAFD) contains a certain amount of zinc (Zn), recovery of this metal is important. Many methods have been applied to recover Zn from EAFD so far. Pyro- and hydrometallurgical methods are recommended for this purpose. EAFD was leached using an ammonia carbonate solution, but the leached residue still had an amount of Zn that needed to be recovered. In the present study, the residue was mixed with coke, compressed into pellets, and heated at 1000 - 1200 °C for 30 - 90 minutes to investigate the reducing ability of the Zn compound. The residue was characterized by wet chemical analysis and the XRD method. The Zn content of heated pellets was analyzed to calculate the Zn removal efficiency. The obtained results showed that higher temperatures provided a strongly reducing reaction, the Zn removal efficiency was higher than 90 % for the pellet heated at 1100 °C for 60 minutes. It was concluded that combining the leaching method and carbothermic reduction could recover all amounts of Zn in the EAFD.

Abstract: The article shows the process of preparing an oxide layer on the surface of titanium for use in industrial catalysis. Data from physical and chemical studies are presented, namely microhardness, porosity, thickness, specific surface area, adhesion and thermal stability of the active layer.To determine the physicochemical characteristics of the resulting oxide layer, the following analysis methods were used: X-ray diffraction analysis (XRD), X-ray diffraction phase analysis (XPA), X-ray absorption analysis (XRA), and X-ray fluorescence analysis. The thickness of the oxide layer depending on the duration of anodization was estimated by optical microscopy.

Abstract: Drug resistant microbial strains are becoming continuous dilemma for researchers; hence, some alternates are required to combat this issue. In this way, nanotechnology is fascinating researchers to put forward a step in order to synthesize metals nanoparticles via adopting an ecofriendly, facile, and quick approach using medicinal plants. By means of aqueous extract of Polyalthia longifolia (AEPl), gold nanoparticles (AuPl) were synthesized for the mechanism study of synthesis and antibacterial bahavior. The reddish colored solution was an indicative clue of synthesis showing surface plasmon band at 540nm using UV/Visble spectroscopy. Various functional groups in the extract were identified which participated in the reduction of metal ions to metallic form as indicated from the Fourier Transform Infrared (FTIR) spectra of AuPl. Moving ahead, the synthesized AuPl were characterized through Transmission Electron Microscopy (TEM) showed spherical shape with more or less 50nm size. Besides, Scanning Electron Microscopy (SEM) study revealed some aggregates formation. Further, structural characterization via X-Rays Diffractometry (XRD) displayed crystallline nature of these nanoparticles. Finally, Energy Dispersive X-rays (EDX) analysis described their metallic form. The antibacterial activity at increased concentration when measured; AuPl showed 15 and 18mm bacterial growth inhibition zones against Escherichia coli and Bacillus subtilis at 100μg/mL concentration respectively. In addition, significant least minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of AuPl against these microbes were also observed. In the light of the above knowledge, it is inferred that the biogenic AuPl exhibit strong antibacterial potential enabling them to be a good substitute of antibiotics.

Abstract: Removal of Au(III) on a purified bagasse ash (BA) has been examined. The purified BA adsorbent was prepared through purification of a crude BA obtained from Madukismo sugarcane industry, Yogyakarta, Indonesia, using a mixed solution of HCl 0.1 M and HF 0.3 M and followed by HNO₃ 3 M. The HCl-HF-HNO₃ purified BA contained quartz with silanol (Si-OH) and siloxane (Si-O-Si) functional groups and aromatic component. Removal of Au(III) on the HCl-HF-HNO₃ purified BA was maximum at pH 4.2 with siloxane and silanol functional groups, but not aromatic component, took important role on the removal. At this optimum pH, the removal of Au(III) on the HCl-HF-HNO₃ purified BA fitter to the second order removal kinetics model than the pseudo-first and pseudo-second order kinetics models indicating that adsorption was not the only mechanism for the Au(III) removal. The second order removal rate constants (k₂) of Au(III) by HCl-HF-HNO₃ purified BA was 3.32 x 10² L/mol min. In fact, reduction of Au(III) to Au metal also occurred as an addition to adsorption for the removal of Au(III) from aqueous solution.

Abstract: Experimental research on the process of cold tubes drawing was performed in order to obtain important information about the behaviour of the tube material in the drawing tool during the drawing to the required outer diameter of Ø12 mm. The DEFORM-3D simulation software was an important tool for verifying the plastic flow of material in the drawing tool (i.e. drawing die), as well as for optimizing the technological parameters of cold tubes drawing. In the finite element (FE) analysis, emphasis was placed on determining the influence of tool geometry, strain degree, drawing speed and friction on the size of the drawing force and the quality of production of drawn tubes. The paper points out the importance of simulation software for common comparison of results obtained from laboratory experiment and FE analysis of the process of tubes drawing. By comparing the results, the reliability of the used simulation software was proved, as the results were identical for all monitored technological parameters. Computer simulation brings valuable knowledge that is important for the correct design of the drawing tool as well as for the technology of production of tubes with precise dimensions.

Abstract: Simple and low environmental impact methods for producing chemically-stable nanoparticles of metallic zinc (Zn) are asked to be developed, because metallic Zn nanoparticles are easily oxidized in air, and organic solvents, which can be used for the fabrication of metallic Zn particles, give a great environmental impact. The present work focuses on the chemical reaction in protonic solvents containing aqueous solvents, of which the use will give a smaller environmental load, and proposes a method for producing metallic Zn nanoparticles by reduction of Zn ions in the protonic solvent. Two kinds of hydrophilic solvents were examined: water and ethylene glycol (EG). The use of water and EG as the solvents produced Zn oxide. Though the addition of aluminum salt to EG also produced Zn oxide, the crystallinity of Zn oxide was lower than that for with no addition of aluminum salt. In the case of the aluminum salt addition, nanoparticles with a size of 27. 5±13.3 nm were fabricated, and not only bonds of Zn-O-Zn and Zn-OH but also a bond of Zn-Zn were confirmed to be formed, which indicated the production of low crystallinity metallic Zn nanoparticles.

Abstract: Temperature-programmed reduction (TPR) was used to observe the chemical reduction behaviour of molybdenum trioxide (MoO₃) and zirconia (Zr)-doped MoO₃ catalyst by using carbon monoxide (CO) as the reductant. The characterisation of catalysts was performed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscopy (TEM) analyses. The reduction performance were examined up to 700°C and reduction was continued for 60 min at 700°C in a stream of 20 vol. % CO in nitrogen. The TPR profile showed that the doped MoO­₃ catalyst was slightly moved to a higher temperature (580°C) as compared to the undoped MoO₃ catalyst, which began at around 550°C. The interaction between zirconia and molybdenum ions in doped MoO₃ catalyst led to an increase in the reduction temperature. According to characterisation of the reduction products by using XRD, it revealed that the reduction behaviour of pure MoO₃ to MoO₂ by CO reductant involved two reduction stages with the formation of Mo₄O₁₁ as the intermediate product. Meanwhile, MoO₃ catalyst doped with zirconia caused a delay in the reduction process and was proven by the presence of Mo₄O₁₁ species at the end of reactions. Physical analysis by using BET showed a slight increase in surface area of 3% Zr-MoO₃ from 6.85 m²/g to 7.24 m²/g. As for TEM analysis, black tiny spots located around MoO₃ particles revealed that the zirconia was successfully intercalated into MoO₃ particles. This confirmed that formation of intermetallic between Zr-MoO₃ catalyst will give new chemical and physical properties which has a remarkable chemical effect by disturbing the reduction progression of MoO₃ catalyst.

Abstract: The provision of carbon reducing agents for the direct reduction process of iron ore is carried out by immersing the iron ore in a tar solution and then proceeding with the pyrolysis/ carbonization process to obtain carbon deposits on the surface of the iron ore. The purpose of this study is to investigate the characterization and reduction behavior of Fe compounds resulting from impregnation and carbonization processes. In this study, iron ore is immersed in the pine flower tar with immersion time varying from 0 - 12 hours and a fixed ratio of tar / ore 1: 1. The soaking mixture is then carbonized in a vertical tube reactor covered by furnace with N₂ gas flowed during the carbonization/pyrolysis process. The carbonization runs with a temperature variation of 450-550°C, for 1 hour, and a heating rate of 10°C/min. From SEM-EDX-Mapping result shows that the immersion method in tar followed by carbonization caused the carbon content in iron ore to increase by 86.68% in a 1: 1 tar/ore ratio, the impregnating time of 6 hours, and a pyrolysis temperature of 450°C. Effect of impregnation duration evidence that immersion times of 6 and 12 hours are sufficient to produce the magnetite phase after the carbonization process. Furthermore, the 6 hours’ duration provides a more optimal peak intensity. Meanwhile, the effect of temperature on the carbonization process shows that 450°C is the optimal temperature to obtain the magnetite phase in the carbonized ore.