| Ammonium perfluorooctanoate (APFO ) is an expensive and poisonous fluorinated surfactant with unique properties, its contamination to environment has attracted world's attention. In order to reduce the contamination, and recovery the costly APFO from waste water, an innovative separation method was put forward in this paper, and experiments were conducted in our lab.The effects of air flux(v), feed liquid flux(u), concentration of APFO(Cf), ratio of the heights of foam vs. liquids(Hb/H1) and pH value of waste water on the separation efficiency were investigated and analyzed. Optimal operating conditions were found out, and the results shows that under optimal operating conditions, separation process can maintain steady state, and the mass transfer in the column is effective, APFO is concentrated in the foam liquid, but the recovery rate is low.Nanofiltration experiment indicated that nanofiltration membrane can condense dilute waste water fastly with high retention rate to APFO(90%), so its suitable to integrate with foam separation to increase recovery rate.Under the optimal operating conditions: Cf=400mg/L , v=0.06m/s , u =8.6×10-3m/s, Hb/H1=1.0, pH=5, nanofiltration operation pressure 0.5Mpa, recoveryexperiment was conducted in integrated apparatus. The results shows that the concentration of APFO in foam liquid reachs to 4152mg/L, that is 9.2 times to the feed waste water; and the content of APFO in the leftover waste water was reduced to 35mg/L, the recovery rate was increased to 88.9%.The integrate method has many advantages, such as high recovery rate, low energy consumption, simplified techniques, without secondary contamination and so on. It's especially effective to recovery APFO from dilute waste waster. It will be broadly used in the future. |
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