Effect of Mechanical Force on Activation Characteristics of a Low-grade Ascharite Ore

Abstract

This is an article in the field of mining engineering. In this article, SEM-EDS, XRD, FT-IR, laser particle size analysis and other means were used to characterize the mechanical activation of boron and magnesium ore powder. The results show that the crystal structure of boraxite changes at the action of mechanical force from the regular and orderly crystal structure to the disorder of the amorphous structure. The particle size distribution of the ore powder is greatly affected by the mechanical force. At the experimental conditions of 200 r/min speed of the ball mill and the ratio of ball to material of 10∶1, the optimal activation time is 6 h, when the particle size of 90% of the ore powder is less than 21.5 μm. The activity of ascharite is related to the number of active bonds after activation. In a certain activation time, the activity of ascharite increases with increasing activation time, but the agglomeration of mineral powder particles at the action of van der Waals force for a long activation time leads to a decrease in activity. The mechanical activation pretreatment can reduce the dependence on sulfuric acid concentration and temperature in the leaching reaction of ascharite, and significantly improve the leaching rate of elements in ascharite. The experiments show that the leaching rate of ascharite after activation for 6 h is 50% higher than that of the raw ascharite under the condition of reaction temperature 25 ℃ and sulfuric acid concentration 1.48 mol/L. And amorphous SiO2 can be prepared at friendly conditions. The apparent activation energy decreases from 23.54 kJ/mol to 9.41 kJ/mol after activation. The diffusion of the solid product layer during the leaching process is the limiting link which affects the reaction of ascharite with sulfuric acid.

Keywords

• mining engineering
• low-grade ascharite
• mechanical activation
• particle size distribution
• activation energy