Removal of environmentally harmful agent and multi-functionalization of water treatment using Microbubbles

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In the contemporary society where people's life style and concept of values are getting more multifaceted with the increase of richness and convenience of life, various kinds of harmful substances are exposed to the environment surrounding us. Especially, water environment is getting worse very rapidly, showing the complicated pollution features depending on the regional or industrial requirements, and this causes serious problems. Hence, the development of the water treatment technology applicable for various kinds of waste water is strongly required. In this study, we investigated the possibility of efficient methods to remove the tiny particles from the foam, which are important in the floatation process to purify the waste water using tiny bubbles (microbubbles). In the floatation process, harmful substances are adsorbed on the bubble surface and they are condensed in the foam layer during the rise and collapse of the foam. Here, we investigated small particle behaviors in the foam layer. These small particles are assumed to behave like the removal substances and they are lifted up with the rising motion of foams. To elucidate the detail particle behaviors in the foam, we conducted series of experiments. We used two kinds of surfactant. One is Casein which has a rigid foam characteristic and the other is Saponin which has the soft one. In the experiments, a thin tank was used and a laser sheet was exposed from the side of the tank. Then, the trajectories of small fluorescent particles were tracked by using the high speed video camera. Aa a results, it was shown that soft and dry foams such as Saponin foam gives the better performance to remove the small particles from the polluted water.