Contribution of Calcium to Phosphorus Removal by Using Electric Furnace Slag

Abstract

The removal of phosphorus by using the electric furnace slag was studied. Tabular slag sample was made of a mixture of the fine slag and Kibushi clay. Chemical component and mechanism for the removal of phosphorus were examined with sample dipped in KH₂PO₄ solution.
Removal ratio of phosphorus of slag sample showed over 90%. High removal of phosphorus can be explained in terms of the calcium of slag. Under the great concentration of calcium of 2.49mmol/L and the pH range from 8 to 11, the precipitate was formed. The precipitate was analyzed with X-ray diffraction and ion chromatography, then it was identified as hydroxylapatite, and both calcium and phosphorus were detected in it. Therefore, dissolved calcium in solution from slag contributed to the removal. Undissolved calcium on slag surface also contributed to it. Phosphorus adsorption of Kibushi clay effectively exerted influences on the removal. Amount of phosphorus adsorption depended on pH and concentration of phosphorus.