Physical Properties and Leachability of MLW Stream Containing Cr, Ni and Cd Immobilized in a Cement Matrix

Abstract

ABSTRACTCement samples containing variable amounts of Cr(III) or Ni(II) or Cd(II) as chloride admixtures present in a MLW stream from reprocessing of spent fuel were prepared under established procedure. Due to the high pH generated in the cement clinker hydration, respective metal hydroxides are formed and improve the physical characteristics of the cement matrix. An increase in the value of the compressive strength was observed when about 7% of the above elements were blended in cement. The increase depends on the nature of the element in the sequence Cr >Ni >Cd.The leach tests confirm the formation of insoluble hydroxide presenting a low concentration in the leachate corresponding to 0.05, 0.004 and 0.052 mg.L−1 for Cr, Ni and Cd, respectively. On the other hand, the hydro-lyzed chloride ions seem to react with calcium with consequent increased degradation of the cement matrix.