Study On The Formation And Stability Of Bulk Nanobubbles

Since the concept of nanobubbles was present in 1994,researchers have made lots of efforts about nanobubbles,especially the study of surface nanobubbles.They have already been studied for about 20 years so far.The basic properties and stability mechanism are being revealed.However,the researches of bulk nanobubbles are relatively few.Considering about the broad application prospects of bulk nanobubbles in many fields,such as sewage treatment,mineral flotation,biomedical detection,it is necessary to further study to explore their significant properties.In this paper,we generated bulk nanobubbles based on ethanol-water exchange,a method which is generally used in the studies of surface nanobubbles.The size distribution,the influence of ethanol concentration,the time and temperature on the formation of bulk nanobubbles were further studied by using “Nanosight”(a new type of dynamic light scattering).Our results showed that the concentration of the bulk nanobubbles produced by exchange was about five times than those in the degassed group,which indicated the existence of the bulk gas nanobubbles.For the effects of ethanol/water ratios and temperature on the stability of the bulk nanobubbles,it was found that their numbers will reach to the maximum at the ratio of about 1:10(v/v).We have also studied bulk nanobubbles generated by the bubble generator.Once produced,it is not easy to absorb to the surface,even the hydrophobic surface.Their lifetime of formed bulk nanobubbles is about a few hours,which is very shorter than that of interfacial nanobubbles(such as more than several days).It was showed that the temperature change can induce more interface nanobubbles not bulk nanobubbles.These results are very helpful for the important applications of bulk nanobubbles.