Inertisation of Cd²⁺ ions by using blended cement pastes

The inertisation of cadmium (Cd²⁺) ions in various cement matrices is investigated using the solidification/stabilisation technique. The different cement pastes used in this study are neat Portland cement and Portland cement blended with 20 and 40% blast furnace slag or metakaolin. Two ratios of heavy metal ion, namely 1·0 and 2·0% by weight of solid, are used. The hydration characteristics of the cement pastes are tested by way of determination of the combined water content, phase composition, compressive strength and X-ray diffraction analysis at different time intervals up to 90 d. The metal salt used causes a retarding effect on the hydration of all the investigated cement pastes. The degree of immobilisation of the added Cd²⁺ ions is evaluated by determining the leached ion concentration after time intervals extended up to 90 d. The leachability experiments are carried out by using the static mode leaching process. It is observed that Cd²⁺ ions show a high degree of immobilisation for the cement pastes investigated.