The Effect of the Grinding Time on the Mechanical Activation of MnO2 Ore and Tea Plant Waste Carbonization Product

In this study, pyrolusiteore （MnO2） was subjected to mechanical milling with a high-energy mill with carbonized tea plant wastes and the effect of grinding time on the crystal structure of the material was investigated. The ratio of Mn/Fe was 8/1, the ratio of C/（MnO2 ＋ Fe3O4） was 2 and the ratio of ball to ore was 10/1. The samples were mechanically ground at 10, 15, 20, 30, 60, 90 and 120 hours. In the processes performed on the attritor, the rotation speed of the mill shaft was determined to be 350 rpm. The results were characterized by TG-DTA, SEM and XRD analyzes. As a result of the experimental studies, it was observed that the samples subjected to mechanical grinding for 120 hours were gradually reduced due to the increasing grinding time at all the diffraction peaks when the XRD peaks were compared with the grinding times. In the thermogravimetric analysis, the sample milled for 120 hours, 50% weight loss was observed at 470 ℃, weight loss of up to 56% was observed at progressive temperatures.

Optimization of reaction conditions for the electroleaching of manganese from low-grade pyrolusite

In the present study, a response surface methodology was used to optimize the electroleaching of Mn from low-grade pyrolusite. Ferrous sulfate heptahydrate was used in this reaction as a reducing agent in sulfuric acid solutions. The effect of six process variables, including the mass ratio of ferrous sulfate heptahydrate to pyrolusite, mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio, current density, leaching temperature, and leaching time, as well as their binary interactions, were modeled. The results revealed that the order of these factors with respect to their effects on the leaching efficiency were mass ratio of ferrous sulfate heptahydrate to pyrolusite 〉 leaching time 〉 mass ratio of sulfuric acid to pyrolusite 〉 liquid-to-solid ratio 〉 leaching temperature 〉 current density. The optimum conditions were as follows： 1.10：1 mass ratio of ferrous sulfate heptahydrate to pyrolusite, 0.9：1 mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio of 0.7：1, current density of 947 A/m^2, leaching time of 180 min, and leaching temperature of 73°C. Under these conditions, the predicted leaching efficiency for Mn was 94.1%; the obtained experimental result was 95.7%, which confirmed the validity of the model.

Copper adsorption by natural manganese dioxide

The adsorption of copper ions was investigated using pyrolusite ore as a low-cost alternative adsorbent source. Pyrolusite, which contains mainly MnO2, is a manganese ore. The effects of the initial concentration of copper（II） ions, initial pH of solution, adsorbent dosage and particle size on the adsorption process were examined. It was found that the percentage of the adsorbed copper increases with increasing the amount of adsorbent. It was observed that the maximum adsorption occurred at natutral initial pH values for all copper concentrations. While the initial solution concentration, initial pH, contact time, stirring speed, particle size and adsorbent dosage were 2.5 mmol/L, natural, 180 min, 200 r/min, 120μm and 6 g/L, respectively, the efficiency of copper adsorption on pyrolusite ore was 96.5%. The isotherm and kinetic studies relating to this adsorption process were also made. It was determined that the equilibrium data followed the Langmuir isotherm model while the process kinetic could be described by the pseudo-second order kinetic model.