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 al cohol) (PVA) was carried out with and without external foamate reflux. The effect of PVA concentration on foam fractionation without reflux was firstl y investigated. The foam fractionation of PVA without reflux is possible on ly at initial PVA concentrations below 200 mg/l. At initial PVA concentrati ons above 300 mg/l, foam fractionation is impossible because almost all the water and PVA are discharged as foamate, of which PVA mean concentration i s 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 en richment and separation factor increases, white the removal factor is almos t constant. The enrichment and separation factors at 363 K are about 11 and 90, respectively. External foamate reflux is essential for foam fractionat ion when treating a highly foaming solution.