Significant amounts of oil-containing waste water are discharged in industrial processes

and it is difficult to separate the oil/water mixture. In this paper

a concept of air-lift loop was introduced to traditional flotation process to treat oil-containing water. In the experiment

oil-in-water emulsion was produced by ultrasound

and the flotation agent for this system was optimized first

as poly(acrylamide-co-diallyldimethyl ammonium chloride) (PDA). Then

the effect of different conditions in the loop flotation process was investigated. When air flow rate was 250 L·h-1

liquid flow rate was 10 L·h-1

liquid level was 6 cm

amount of PDA was 20 mg·L-1

oil removal rate was the highest. Concentration of oil was reduced from 900 mg·L-1 to 100 mg·L-1 and the highest efficiency was 90.48%. Compared with the traditional column flotation under the same condition

loop flotation was more effective and quick

with increased oil removal by 10%. The loop flotation concept would have great industrial application value.