Quantifying rheological and fine particle attachment contributions to coarse particle recovery in flotation

This study focused on the flotation behaviour of very coarse quartz particles in the presence of fine silica and alumina, both of which were used as pulp viscosity modifiers. A decrease in the contact angle of the coarse quartz particles, caused by the attachment of fine particles was believed to be the principal mechanism accounting for the noted depression. Only small surface coverage of attached fine particles may dramatically decrease the quartz particle recovery because the flotation behaviour of the coarse particles was very sensitive to particle hydrophobicity, e.g. less than 5% surface coverage is able to decrease the contact of particles from 83° to 81° and causes a decrease in recovery from 60% to 20%. The effect of removing the fine particles from the pulp, by the process known as desliming, on the flotation behaviour of coarse quartz particles was also investigated. The results showed that desliming is beneficial for the recovery of coarse quartz particles. Furthermore, the recovery of coarse quartz particles attached with fine particles can be restored by conducting flotation in high viscosity medium where glycerol was used as the viscosity modifier.

Effect of fine particles of alumina (2% v/v) and silica (3% v/v) on the recovery of coarse quartz in the size range 600–850 μm. Small decreases in particle contact angle, due to the attachment fine hydrophilic particles, can decrease the contact angle below a critical value depressing flotation.Figure optionsDownload as PowerPoint slideHighlights
► Increased pulp viscosity using fine particles failed to increase coarse particle recovery.
► Attachment of fine particles depressed flotation recovery.
► Desliming successful in restoring recovery due to fine particle detachment.
► Increased recovery of coarse particles with high viscosity medium using glycerol.