Here, Zn ferrite is synthesized along with reduced graphene oxide (rGO) by a facile one-step hydrothermal method. The difference between the synthesized nanocomposites with those in other reported work is that the reaction conditions in this work are 160 oC for 12 h. The synthesized products are characterized by field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and attenuated total reflection. Further, the adsorption property of rGO–Zn ferrite (rGZF) nanocomposite is studied after confirming its successful synthesis. The adsorption capacity of rGZFs toward rhodamine B (RB) is ˃ 9.3 mg/g, whereas that of bare ZF nanoparticles is 1.8 mg/g in aqueous media. The efficiencies of rGZF and bare ZF to remove RB are 99 % and 20 %, respectively. Employing rGZF, 60 % of RB is decomposed within 5 min. The kinetic study reveals that the adsorption process of removing RB by bare Zn ferrite follows pseudo-firstorder kinetics. However, after zinc ferrite is incorporated with rGO, the kinetics changes to pseudo-second-order. Furthermore, the Langmuir isotherm is accomplished by the adsorption process employing rGZF, indicating that a monolayer adsorption process occurs. The thermodynamic parameters of the process are also calculated.

Feasibility is investigated for reduction of chromium ore by Si sludge with mixed silicothermic and carbothermic reaction. The reduction behavior of chromium ore using Si sludge is investigated precisely to determine the effects of carbon addition, reaction time, and reaction temperature. The pellets are dropped into the furnace after temperature stabilized. As the amount of C addition increases, the amounts of CO and CO2 gas generation increase. After the dropping of the pellets, the pellets are heated and the reaction starts at about 1,573 K or higher. The pellets maintain their shape until 10 min after the drop, and then melted. As the holding time increased, the size of the reduced metal particles increased. The chromium ore is rapidly reduced by the Si sludge, and the slag penetrated into the chromium ore and reduction progressed inside. As the reduction temperature increased, the reaction initiation time is shortened and the reaction fraction of the reduction reaction increased. As the reaction temperature increased, agglomeration of reduced ferrochrome metal is promoted.

Abstract In this study, Fe-Ni slag, converter slag and dephosphorization slag generated from the steel industry, and fly ash or bottom ash from a power plant, were mixed at an appropriate mixing ratio and melted in a melting furnace in a massproduction process for glass ceramics. Then, glass-ceramic products, having a basalt composition with SiO₂, Al₂O₃, CaO, MgO, and Fe₂O₃ components, were fabricated through casting and heat treatment process. Comparison was made of the samples before and after the modification of the process conditions. Glass-ceramic samples before and after the process modification were similar in chemical composition, but Al₂O₃ and Na₂O contents were slightly higher in the samples before the modification. Before and after the process modification, it was confirmed that the sample had a melting temperature below 1250 ℃, and that pyroxene and diopside are the primary phases of the product. The crystallization temperature in the sample after modification was found to be higher than that in the sample before modification. The activation energy for crystallization was evaluated and found to be 467 kJ/mol for the sample before the process modification, and 337 kJ/mol for the sample after the process modification. The degree of crystallinity was evaluated and found to be 82% before the process change and 87% after the process change. Mechanical properties such as compressive strength and bending strength were evaluated and found to be excellent for the sample after process modification. In conclusion, the samples after the process modification were evaluated and found to have superior characteristics compared to those before the modification.

Fe-Si-Cr ferroalloy is predominantly produced by carbothermic reduction. In this study, silicothermic and carbothermic mixed reduction of chromite ore to produce Fe-Si-Cr alloy is suggested. As reductants, silicon and silicon carbide are evaluated by thermochemical calculations, which prove that silicon carbide can be applied as a raw material. Considering the critical temperature of the change from the carbide to the metallic form of chromium, thereduction experiments were carried out. In these high temperature reactions, silicon and silicon carbide act as effective reductants to produce Fe-Si-Cr ferroalloy. However, at temperatures lower than the critical temperature, silicon carbide shows a slow reaction rate for reducing chromite ore. For the proper implementation of a commercial process that uses silicon carbide reductants, the operation temperature should be kept above the critical temperature. Using equilibrium calculations for chromite ore reduction with silicon and silicon carbide, the compositions of reacted metal and slag were successfully predicted. Therefore, the mass balance of the silicothermic and carbothermic mixed reduction of chromite ore can be proposed based on the calculations and the experimental results.