Effect of External Reflux on Foam Fractionation of Poly(Vinyl Alcohol).

The potential of foam fractionation for intra-process recycling of surface active materials is investigated. Batch foam fractionation of poly(vinyl alcohol) (PVA) was carried out with and without external foamate reflux. The effect of PVA concentration on foam fractionation without reflux was firstly investigated. The foam fractionation of PVA without reflux is possible only at initial PVA concentrations below 200 mg/l. At initial PVA concentrations above 300 mg/l, foam fractionation is impossible because almost all the water and PVA are discharged as foamate, of which PVA mean concentration is almost equal to that of the initial solution. Effects of external foamate reflux and temperature on foam fractionation of PVA were then investigated at initial PVA concentration of 1000 mg/l. With rising temperature, the enrichment and separation factor increases, while the removal factor is almost constant. The enrichment and separation factors at 363 K are about 11 and 90, respectively. External foamate reflux is essential for foam fractionation when treating a highly foaming solution.