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    A Kinetic Model for Dissolution of Zinc Oxide Powder Obtained from Waste Alkaline Batteries in Sodium Hydroxide Solutions
    (Springer, 2019) Demirkiran, Nizamettin; Ozdemir, Gulistan Deniz Turhan
    The determination of individual dissolution behaviors of zinc and manganese in waste alkaline battery powders is an important subject from the points of the leaching yield, design of leaching reactor, and separation and recovery steps of hydrometallurgical process. In the current study, we investigated the dissolution kinetics of zinc oxide powder. Zinc oxide was obtained from waste alkaline batteries, and sodium hydroxide solutions were used as solvent. In the experiments, the effects of solution concentration, reaction temperature, stirring speed, solid-to-liquid ratio, and particle size on the dissolution of zinc oxide were investigated. It was demonstrated that the dissolution increased with the increasing concentration, reaction temperature, and stirring speed, and with the decreasing solid-to-liquid ratio and particle size. In consequence of the kinetic analysis performed, it was found that the dissolution kinetics of zinc powder obeyed the Avrami model. Activation energy for the process was determined to be 19.42 kJ/mol. Zinc ions in the resulting solution after dissolution process was recovered in the form of hydroxy-carbonate product by precipitation method. Zinc oxide was produced by isothermal decomposition of hydroxy-carbonate product.
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    Leaching Kinetics of Manganese Oxides Obtained from Waste Alkaline Batteries in Sulfuric Acid Solutions Containing Molasses
    (Springer, 2022) Ozdemir, Gulistan Deniz Turhan; Demirkiran, Nizamettin
    In this study, the leaching kinetics of manganese oxide powder supplied from spent alkaline batteries was investigated in H2SO4 solutions including molasses. Waste battery powder containing manganese oxides was prepared by separating manually from the other components of the collected waste alkaline batteries. The leaching experiments were carried out in a batch reactor. The effects of H2SO4 concentration, stirring speed, solid-to-liquid ratio, reaction temperature, particle size, and amount of molasses on the leaching rate of manganese were studied. It was determined that molasses used as the reducing agent had an important effect on the leaching rate. By adding molasses to the leaching media, it was found that almost all manganese in waste battery powder transferred to the solution. It was observed that the leaching rate increased with an increase in the solution concentration, stirring speed, reaction temperature, and amount of molasses, and with a decrease in the particle size and solid-to-liquid ratio. While the concentration of H2SO4, stirring speed, solid-to-liquid ratio, reaction temperature, particle size, amount of molasses, and reaction time were 1 M, 500 rpm, 2/500 g/mL, 60 degrees C, 0.348 mm, 2 g, and 120 min, respectively, the amount of the dissolved manganese was found to be approximately 98%. A mathematical model represented that the leaching kinetics was elaborated. It was determined that the leaching kinetics followed the mixed kinetic model. The activation energy value for the process was calculated to be 52.31 kJ/mol. After the leaching treatment, Mn (II) ions in the solution were recovered in the form of MnCO3 using NaHCO3 solution. MnCO3 was calcined isothermally at 400 degrees C for 4 h, and MnO2 was produced. [GRAPHICS] .
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    Optimization by response surface method of dissolution of metallic zinc obtained from waste Zinc-Carbon batteries in nitric acid solutions
    (Consejo Superior Investigaciones Cientificas-Csic, 2021) Demirkiran, Nizamettin; Senel, Merve; Ozdemir, Gulistan Deniz Turhan
    In this study, the interactive effects of the process variables containing the concentration of nitric acid, the amount of zinc, and the reaction time on the efficiency of the dissolution of metallic zinc in nitric acid solutions were investigated by applying response surface methodology (RSM). It was found that the dissolution efficiency increased with an increase in the concentration of nitric acid, and the reaction time, and with a decrease in the amount of zinc. The multiple regression analysis to the experimental data was applied to observe the interactive effects of the experimental parameters. The second-order polynomial equation was obtained. The optimal experimental conditions were determined by using the optimization module in Design-Expert software, and different solution points were found.