Separation of Carbon Black from Silica by Froth Flotation Part 1: Effect of Operational Parameters

Froth flotation can be applied to separate hydrophobic particles from hydrophilic ones in aqueous solution with the use of an appropriate surfactant. In this work, carbon black was separated from silica gel by means of froth flotation. Since the point of zero charge, or PZC, of the carbon black (3.5) is close to that of the silica gel (4.1), a nonionic surfactant (ethoxylated alcohol) was selected as the separating agent. Based on experimental results using a surfactant concentration of 62M or 75% of its critical micelle concentration (CMC), up to 70% of carbon black recovery was achieved with a carbon black enrichment ratio around 3.5. Added electrolyte (NaCl) showed a negligible effect on the separation efficiency. The presence of the surfactant was found to provide both a higher mass transfer surface area and to reduce the coalescence of air bubbles in the froth flotation column.