Magnetic Separation Technique Using High Temperature Superconducting Bulk Magnets and Application to Plating Liquid Waste Treatment

概要

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A magnetic separation technique has been conducted to recycle the nickel (Ni) element from the waste fluid of electroless Ni plating processes. The experiment was operated using the face-to-face type electromagnet generating 1.96 T and the data was compared to those in the case of the high temperature superconducting bulk magnet which generates 3.45 T. In the electroless plating processes, the plating fluid containing high concentration of Ni ions is disposed after several turns of the plating cycles when the concentration of phosphite ions exceeds a certain level. In order to extract the Ni element at first, we formed the coarse Ni-sulfate crystals with the sizes over 1 mm from the Ni-phosphite precipitates by controlling the temperature and the pH value. Next, the magnetic separation experiments were operated to collect the Ni-bearing precipitate which carried the weak magnetism. Although the performance of high temperature superconducting bulk magnet is superior to that of electromagnets, as a result, we succeeded in collecting Ni-sulfate crystals preferentially to the Ni-phosphite precipitates soon after the crystal growth began.
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