Mechanisms of metal fixation and leaching by cement based fixation processes

The mechanisms of zinc and mercury leaching from cement/silicate stabilization processes has been assessed from extended leaching tests, scanning electron microscopy and powder X-ray diffraction. The results have demonstrated the importance of microstructure not only in metal fixation but also in metal leaching from the cementitious matrix. After an extended leaching period, massive breakdown of the matrix occurs with a subsequent dramatic rise in leachate concentrations. The calcium aluminate hydrate structure, ettringite, has been identified as to be related to the structural integrity of the solidified product. Once this structure has been removed then massive leaching of zinc and mercury can occur.