A Kinetic Model for Dissolution of Zinc Oxide Powder Obtained from Waste Alkaline Batteries in Sodium Hydroxide Solutions

Metallurgical and Materials Transactions B - The determination of individual dissolution behaviors of zinc and manganese in waste alkaline battery powders is an important subject from the points of...     

Investigation of Leaching Kinetics of Copper from Malachite Ore in Ammonium Nitrate Solutions

The production of metallic copper from low-grade copper ores is generally carried out by hydrometallurgical methods. Leaching is the first prerequisite of any hydrometallurgical process. Solutions containing ammonia may allow for selective leaching of the copper from the ore. In this study, the leaching kinetics of malachite, which is an oxidized copper ore, in ammonium nitrate solutions was examined. The effects of some experimental parameters on the leaching process were investigated, and a kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature, and agitation speed, as well as decreasing particle size. It was found that the leaching reaction followed the mixed kinetic controlled model, which includes two different leaching processes including the surface chemical reaction (303?K to 323?K [30?°C to 50?°C]) and diffusion through a porous product layer (323?K to 343?K [50?°C to 70?°C]). The activation energies of these sequential steps were determined to be 95.10 and 29.50?kJ/mol, respectively.     

利用天然二氧化锰吸附铜（英文）

软锰矿的主要成分为MuO2,其可作为一种低成本的吸附剂使用,研究其对废水中铜离子的吸附分离作用。研究Cu(II)离子的初始浓度、溶液初始pH值、吸附剂用量和粒度对吸附过程的影响。结果表明:随着吸附剂的用量增加,吸附铜的比例增大。在不同铜浓度下,溶液的初始pH值为自然状态时的吸附量最大。当初始溶液浓度、初始p H值、接触时间、搅拌速度、粒径大小和吸附剂用量分别为0.0025 mol/L、自然状态、180 min、200 r/min和6 g/L时,软锰矿对铜的吸附率为96.5%。对吸附过程中的等温吸附曲线和动力学进行研究。结果表明:该平衡吸附数据符合Langmuir等温模型,而过程的动力学符合伪二阶动力学模型。     

Abrasive wear behaviour of powder flame sprayed coatings on steel substrates

The main purpose of thermal spraying method is to produce wear resistant surfaces. Easy applicability, very low possibility of metallurgical changes and low distortion of coated parts due to low heat transfer to the substrate and salvation of worn parts are some of the practical advantages of this process. In this study, abrasive wear behaviour of powder flame sprayed coatings on steel substrates has been investigated. Coating was carried out onto both hot and cold substrates by using four types of powders. Prior to the wear tests, the coated specimens were machined on a lathe and surface roughness and hardness measurements were carried out on the machined surfaces. Heating the substrates prior to the coating led to the decrease in the hardness of the coating layers. Abrasive wear resistance of flame sprayed coatings was seen to be dependent on the chemical composition and characteristics of coating materials and coating condition.     

硝酸溶液中氧化铜矿浸出工艺参数优化及动力学模拟

研究Tunceli孔雀石矿物在硝酸溶液中的溶出行为,以评估各种实验参数的影响.研究为分两个阶段.在第一步中,确定浸出过程的最佳条件,而在第二步中,对该过程进行动力学评估.在优化实验中,以硝酸浓度、温度、搅拌速度和固液比为自变量,采用中心组合设计法(CCD)获得实验数据.确定硝酸浓度、温度、固液比和搅拌速度的最佳值分别为...     

Reductive leaching of pyrolusite ore by using sawdust for production of manganese sulfate

Manganese compounds, such as manganese sulfate, can be obtained from pyrolusite, a manganese ore. Low-grade manganese ores is usually treated by hydrometallurgical methods. In this study, the leaching and recovery of manganese from pyrolusite ore in sulfuric acid solutions containing sawdust as reducing agent was investigated. The effects of experimental parameters, such as sulfuric acid concentration, sawdust amount, solid-to-liquid ratio, stirring speed, particle size, reaction temperature, and leaching time, on the manganese extraction from ore were examined. The results showed that the leaching rate of pyrolusite ore increased with an increasing sulfuric acid concentration, sawdust amount, stirring speed, reaction temperature and leaching time, and decreasing in solid to liquid ratio and particle size. The kinetic analysis of leaching process was carried out, and it was determined that the reaction rate was controlled by diffusion through the product layer under the experimental conditions in this work. The activation energy was found to be 22.35 kJ mol^?1. Manganese can be recovered as manganese sulfate by the evaporative crystallization of the purified leach liquor.     

Dissolution kinetics of colemanite in HCl solutions by measuring particle size distributions

Dissolution kinetics of colemanite in hydrochloric acid solutions was investigated in this study. Particle size distribution data was, for the first time in the literature, utilized to investigate dissolution kinetics of colemanite. The size distribution of colemanite particles was measured in the reaction vessel during reaction, and the kinetic models were applied to particle size data. For comparison, the kinetic models were also fitted to the fractional conversion data, calculated from Ca concentration of the medium. Additionally, electrical conductivity and pH of the reaction medium were also recorded while measuring particle size distribution. Among the heterogeneous and pseudo-homogeneous models, Avrami model was found to be the best model to fit the particle size and fractional conversion data.     

Dissolution kinetics of calcined ulexite in ammonium carbonate solutions

The leaching kinetics of calcined ulexite in ammonium carbonate was studied in this work. The effect of parameters of ammonium carbonate concentration, solid/liquid ratio, stirring speed, calcination temperature and reaction temperature was determined in the experiments. It was found that the conversion rate increased with increasing ammonium carbonate concentration, reaction temperature and decreasing solid/liquid ratio. However, the effect of stirring speed on the conversion rate was insignificant. The experimental data practised the heterogeneous and homogeneous models, and an acceptable model for the conversion rates of ulexite was determined to be a first-order pseudohomogeneous reaction model. The activation energy of dissolution process was determined to be 35.3 kJ/mol.     

Effect of monolithic zirconia on the degree of conversion of two resin cements analyzed by FT-IR/ATR spectroscopy

Objective: This study aimed to evaluate the degree of conversion (DC) of two different resin cements polymerized under the monolithic zirconia specimens in different thicknesses and colors.

Material and methods: Partially stabilized monolithic zirconia blocks (inCoris TZI) were cut into three different thicknesses (0.5, 1.0, and 2.0 mm) and the specimens were divided into four color groups (A1, A2, A3, and A4). The light transmittance of each specimen was measured. Panavia F 2.0 or Variolink N resin cement was applied into teflon mold and irradiated using the light emitting diode curing unit for 20 s under monolithic zirconia specimen (n = 10). The resin cement specimens were stored at room temperature under dry conditions. The DC of each specimen was measured by Fourier transform infrared-attenuated total reflection (FT-IR/ATR) spectroscopy after the 1st and 10th day. Data were analyzed with two-way analysis of variance (ANOVA), two-way repeated measures ANOVA, three-way repeated measures ANOVA, and the Tukey least significant difference (LSD) tests (α = 0.05).

Results: The light-cure resin cement groups showed higher DC than the dual-cure resin cement groups (p < 0.05). The DC of both resin cements reduced with an increase in the thickness and darkening of the color of monolithic zirconia specimens. There was a statistically meaningful increase in the 10th-day values for dual-cure resin cement (p < 0.05), whereas there were no significant differences between the 1st- and 10th-day values for light-cure resin cement (p > 0.05).

Conclusion: The use of light-cure resin cement can be suggested for the luting of monolithic zirconia restorations.     

Investigating dissolution of colemanite in sulfuric acid solutions by particle size measurements

Dissolution properties of colemanite and gypsum formation in sulfuric acid were investigated by measuring size distribution of particles in the reaction cell with time. After termination of the reaction, the remained material in the cell was analyzed to find out unreacted and reacted fractions. The results showed that the reaction of colemanite particles with sulfuric acid led to reduction in particle sizes and the degree of reduction depended on acids concentration and reaction time. The dissolution period and point of gypsum formation were clearly distinguished and marked on particle size plots.