Freezing Separation of Phosphate and Ammonium Ions and the Adsorption Phenomena on Ice Crystals.

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  • リン酸イオン及びアンモニウムイオンの凍結分離と氷結晶への吸着現象
  • リンサン イオン オヨビ アンモニウムイオン ノ トウケツ ブンリ ト コオリ

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Laboratory experiments were conducted in order to find more effective methods for removing phosphate and nitrogen from lakes, swamps, and inland seas. Employing freezing-dissolution method, these tests examined the possibility of separation or removal of phosphate and ammonium ions from water.<BR>First, inclusion phenomena and behaviour of both ions in ice crystals were observed. This was done by forming spherical ice crystals from a solution containing phosphate and ammonium ions, and by dissolving the crystals. At dissolution, the concentration of both ions in the initially-eluated solution was higher than that in the solution eluated later. This suggested that most of the phosphate and ammonium ions were included near the surface of ice crystals. More concentrated phosphate and ammonium ions were observed just near the surface, when the crystal growth rate of the spherical ice was lowered. When the dissolving methods were altered, a large difference of the concentrations in the eluant was recognized.<BR>Second, phosphate and ammonium ions in the solution adjusted to nearly 0°C were adsorbed on the pure spherical ice crystals, which were prepared with only water. Large adsorption amounts of phosphate and ammonium were observed at a temperature range of 0.2-0.5°C, and the maximum adsorption amount was observed at the contact time of about 10 seconds. The adsorption of phosphate and ammonium ions on ice crystals made it possible to discriminate comparatively the adsorption rate between phosphate and ammonium ions; the former rate was higher than the latter one. This physical adsorption, accompanied with an influence of hydrogen bonds, was of the Langmuir-adsorption type.

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