The Influence of Combined Carbonation and Physical Separation on Heavy Metal Elution from Bottom Ash

Abstract

It has been reported that carbonation with CO₂ has the effect of reducing the Pb elution of the bottom ash of general waste in stabilization treatment. Also, the recovery of valuable metals by physical separation via air tables, etc., is performed as well, mainly in Europe. In this study, we investigated the influence of the combined treatment of carbonation and separation (air tables and eddy currents) on the elution characteristics of heavy metals for the purpose of recycling the bottom ash into civil engineering materials. For each sample of treated ash, we measured the Pb, Cr(Ⅵ), and B concentrations of the test solutions obtained by elution testing and testing in a small indoor lysimeter. As a result, the reduction of Pb elution and the increase of Cr(Ⅵ) elution through carbonation were confirmed, but no clear difference was observed in the elution of Pb or Cr(Ⅵ) through separation. On the other hand, it was clarified that the concentrations of B elution in the solution and in the leachate were lower in carbonation after separation than in the reverse order. Also, no clear difference was found in Pb, Cr(Ⅵ), or B elution in either due to the difference in the separation method.