The Physical And Chemical Properties Of Bulk Nanobubbles In Different Solutions

The existence of bulk nanobubbles are still controversial even though their significance in a large range of applications.Here,we developed a new method of compression-decompression to produce controllably bulk nanobubbles.Then we further investigated the generation of bulk nanobubbles in pure water,acid,alkaline and salt solutions using nanoparticle tracking analysis,respectively.The results indicated that the concentration of bulk nanobubbles depends on the decompression time and would reach to a maximum value when the decompression time is about 30 min for the pure water system.More importantly,we gave a relatively direct evidence of the existence of bulk nanobubbles by measuring the X-ray fluorescence intensity of Kr in acid,alkaline and salt solutions.It was showed that the decrease tendency in intensity of Kr in alkaline solution is similar to that in the concentration of bulk nanobubbles with the deposited time,indicating that the bulk nanobubbles produced are indeed gas inside.Furthermore,the concentration and stability of bulk nanobubbles in the alkaline solution are both greatest comparing with other two solutions regardless of gas types.The concentration of bulk nanobubbles will decrease in an order: alkaline > acid/pure water > salt solutions.We believe that our results should be very helpful for understanding the formation and stability of bulk nanobubbles in different solutions.