IMMOBILIZATION AND ELUTION BEHAVIOR OF CrO₄^2－ IN AFm PHASE

Abstract

The immobilization of CrO₄^2－ into the tricalucium aluminate mono-sulfate hydrate（AFm）was examined, moreover, the elution behavior of CrO₄^2－ from AFm-type hydrate including CrO₄^2－ and/or SO₄^2－ was investigated.
In the range of low mixing ratio of CaCrO₄・nH₂O/AFm in molar, below ca.0.50, CrO₄^2－ was fixed into AFm by the anion-exchange reaction with SO₄^2－ and concentration of chromium in liquid phase was less than 1.0×10^－4 mol/L. As the mixing ratio of that was 0.75 or more, on the other hand, the ettringite including CrO₄^2－ was formed and chromium in liquid phase was 1.0×10^－3 mol/L or more.In the dipping test of the hydrate, the concentration of chromium eluted was increased with an increase in the CrO₄^2－ content of AFm-type hydrate. In addition, an AFm-type hydrate containing SO₄^2－ of 5mol％ or more showed that the concentration of chromium eluted was 1/4 or less compared with the SO₄^2－ free hydrate and the fixation effect of the CrO₄^2－ was large.