Wall effect on rising foam drainage and its application to foam separation

• The effect of column wall on the rising foam drainage was investigated.
• The wall effect on the performances of foam separation was investigated.
• The foam separation column with the cross internal was developed.
• An increase in wall area of foam phase enhanced rising foam drainage.
• Enrichment ratio of crystal violet was increased by the insertion of cross internal.

A novel and structurally simple foam separation column with the cross internal was developed for investigating the effect of the column wall on the drainage of rising foam, using sodium dodecyl sulfate (SDS) as a foam agent. The cross internal enhances significantly wall effect due to an increase of wall contact area in the foam phase. Furthermore, the performances of foam separation column with the cross internal were assessed using crystal violet (CV) as the model system and SDS as the collector. The insertion of the cross internal significantly decreased the liquid holdup of the foam out of the column and increased the bubble size. The results showed that an increase in wall contact area in the foam phase could enhance the drainage of rising foam due to the higher drainage velocity between the bubbles and the column wall than that between the adjacent bubbles. Under the suitable operations conditions, the enrichment ratio of CV was 16.5 by using the column with the cross internal and it was nearly four times higher than the column without the cross internal. The better performances indicated that an increase of wall contact area in the foam phase is a simple and effective method to enhance foam drainage and improve enrichment of foam separation.