adsorption. Wet ball milling, with heptane or water in different amounts, and dry ball milling were performed with petcoke under the conditions: particle size 45-90 µm, 5 min to 9 h, 300 rpm, zirconia balls Φ5 mm, 1:20 powder to ball mass ratio. The wet procedure resulted in smaller particles (~3 µm versus ~6 µm) and a narrower size