Recovery of surfactant from an aqueous solution using continuous multistage foam fractionation: Influence of design parameters

A multistage foam fractionation column with bubble cap trays was used to recover a surfactant from water at low concentrations. The effects of design parameters—including the number of bubble caps, foam height, and tray spacing—were first investigated under steady state conditions using cetylpyridinium chloride (CPC) as the model surfactant. An increase in bubble caps per tray significantly increased the separation efficiency, both in terms of the enrichment ratio and recovery of the CPC and of the separation factor (ratio of foamate concentration to effluent concentration). The increase in bubble caps per tray also increased the foam production rate, leading to increasing the adsorptive transport. An increase in tray spacing increased both the enrichment ratio and the residual factor of the CPC, whereas the CPC recovery and liquid entrainment in foam were reduced. An increase in foam height produces drier foams, leading to decreasing bulk liquid transport.

► The number of bubble caps per tray is a significant factor affecting CPC recovery.
► Tray spacing should be matched with the ability of surfactant solution to generate foam.
► The increase in foam height is the most significant to reduce the bulk liquid transport.