Comparative Optimization of Mechanical and Chemical Treatments of Nickel Slag Waste to Produce Silica-Rich Nanomaterials with Potential Anticorrosive Coating Applications

Abstract

Nickel mining and processing in Indonesia is among the largest in the world, concentrated in Sulawesi and Maluku, producing large quantities of nickel slag that are not optimally utilized and that could cause environmental impacts. This study aims to convert waste into resources (waste-to-resource), namely by utilizing it as a silica-rich nanomaterial for anti-corrosion coating applications through mechanical (ball milling, ultrasonic), and chemical (leaching) treatments. This study compared mechanical and chemical treatments and evaluated their complementary effects in reducing particle size, increasing dispersion, and purifying the composition. The results showed that mechanical treatment was effective in modifying the material’s physical properties, with ball milling reducing the size of slag particles from approximately ±1 cm to 100–200 nm. In contrast, ultrasonic treatment via cavitation in a liquid medium significantly reduced particle size, further reducing it to approximately 60–90 nm. The nanoscale particle size improved material dispersion. Leaching treatment increased the silica content up to approximately 69%, accompanied by decreases in dissolved Fe and Mg. In addition, leaching treatment led to the formation of a porous structure in the slag, which can increase surface area and interaction with the coating matrix. These results indicate that the combination of mechanical and chemical treatments effectively transformed nickel slag into silica-rich materials with potential as a functional filler for the development of sustainable anti-corrosion coatings, as well as for supporting waste reduction, resource efficiency, and the development of sustainable materials.