Wet mechanochemical surface modification of calcite employing an integration of conventional design and analytical hierarchy process

Abstract

The demand for ultra-fine mineral powders from various industries requires the applications of wet grinding and surface modification. In this study, wet mechanochemical surface modification of micronized calcite (d50 = 4.92 μm) with stearic acid [CH3(CH2)16COOH] was carried out in a planetary ball mill. The seven parameters were specified: ball filling ratio (%), ball size distribution ratio (10 and 15 mm, %), micronized calcite filling ratio (%), pulp solid ratio (wt%), mill speed (rpm), stearic acid dosage (% of micronized calcite) and modification time (min). Then, these parameters were optimized using a conventional experimental design when maximizing the active ratio (%) as a significant value for coated calcite. Besides, the analytical hierarchy process was applied to observe the importance of each parameter. Stearic acid dosage, mill speed, and micronized calcite filling ratio are the top three parameters affecting the active ratio. Next, size distribution, XRF, XRD, SEM, FTIR, TGA-DTA, contact angle, and whiteness measurements were performed on the micronized calcite (MC) and coated micronized calcite (CMC) samples. The final CMC product had a 99.90% active ratio, 2.49 μm mean (d50) particle size, and 101.66o contact angle. Finally, CMC obtained by the surface modification can be used as a filler mineral.