Effect of adsorbents on the leachability of cement bonded electroplating wastes

This study is aimed at the determination of pore solution composition of hardened cement pastes prepared with the addition of chromium-, cadmium- and nickel-salts. Due to the high pH-value of the pore water of cement paste, cadmium and nickel were transformed into insoluble hydroxides and precipitated practically quantitatively. Chromium, added as Na 2Cr 2O 7.2 H 2O, which is soluble in a highly alkaline medium, was partly bound. It is not clear yet, whether chromium was adsorbed and/or incorporated in hydration products. The use of clinker instead of cement caused a more intensive bond. Adsorbents (silica fume, fly ash and activated carbon), with the exception of fly ash did not improve this bonding.