Obtaining pyritic waste nanoparticles through high-energy milling for application in effluent treatment

Mineral coal is a primary energy source in many countries, and to enhance its quality, a beneficiation process is used to remove impurities like pyrite. Given its properties and potential applications such as photovoltaic cells and effluent treatment, this study focused on producing pyrite nanoparticles from coal mining waste through a high-energy wet milling process. The waste underwent three milling stages with varying sizes of milling elements in a high-energy mill. The influence of parameters such as mill rotation speed and milling time on the final particle size was analyzed. A rotation speed of 2,500 rpm reduced the particle size without significantly affecting the crystallinity of the pyrite phase, achieving nanometric dimensions after 390 min of processing and with greater size uniformity among the particles. The reduction in particle size led to a change in the material's composition. The process resulted in crystalline particles with a specific surface area of 29.5 m²/g, an increase of 26.0 m²/g. Due to their high specific surface area, nanoparticles exhibit much higher efficiency in reducing the color of a real textile effluent compared to microparticles.