2000 Volume 26 Issue 6 Pages 877-881
We investigated the phosphate ion removal ability of an adsorbent, which was prepared by baking volcanic ash soil mixed with iron (II) sulfate at 500°C. It is found by batch experiments that the removal rate of phosphate ion is initially rapid, and falls gradually. Several tens of days are required to achieve equilibrium. The lower the solution pH, the higher the removal amount of phosphate ion. Regardless of the initial pH, the solution pH is closer to the neutral along with time. It is thought that the pH rise of acidic solution is due to the release of OH- attached to Al3+ and Fe3+ by ion exchange with phosphate ion, and the pH drop of alkali solution is due to the formation of H+ by the hydrolysis of Al3+ and Fe3+ dissolved from the surface of baked soil. A column experiment was conducted with PO4-P concentration of 3mg/dm3 and SV=2 (1/hr). The effluent PO4-P concentrations remained less than 1mg/dm3 for 65 days for influent pH of 6.00 and for 35 days for that of 7.55, respectively.