Development of Water Purification System by Magnetic Separation Technique and Its Application to the Education for Environment on the Course of Learnbydoing Program

A superconducting permanent magnet system capable of generating strong magnetic fields has been constructed by using bulk high temperatures superconductors HTS. The magnetic field in the open space between the face­to­face settled magnetic poles has exceeded 3 T when they were activated at 30 K. We have investigated the magnetic separation technique with respect to Fe ions in the waste water drained from the university laboratories. The performances of bulk magnet system closely came to those of 5 T superconducting solenoid with a ratio over 90 % under the flowing rate of 3 liter/min in spite of the narrower space of strong field. The result attributes to the fact that the bulk magnet system has the steepest gradient among them. This suggests that the magnetic separation by using bulk magnets is effective for the practical water purification systems. The students of Niigata University take various parts in the actual R&D processes that were incorporated as a course of their educational curricula. It is important for the university students to learn the environmental issues by resolving the practical problems surrounding them. In the study, the water purification system has been adapted to the education course to carry out as a project­based learning. We expect that students would acquire strong motivation to learn sciences through the course. Keywords; water purification, magnet separation, superconductor, practical education Introduction The environmental issues have gradually changed the pollution standards toward less value than those of the past in concentration of heavy metallic ions, arsenic, boron, BOD/COD and so on for the surrounding water. For instances, an importance of water purification by separating toxic heavy metallic ions from the waste water which is drained from the university laboratories has been also referred. Since a large amount of additives containing Fe compounds have been used to throw them away, the reduction of additives in the process is needed to reduce the treatment cost. Since the waste water is ordinary purified through various processes in the vast water pools or tanks, it is necessary for us to develop more compact and easier way than usual. As follows in equation (1), the magnetic force Fm applied to the magnetic particles is given by the product of three elements such as volume of particles, susceptibility and applied magnetic field. We note that the presence of steep gradient is necessary to obtain high magnetic force in addition to the field strength [1].