Solidification/stabilization of a tannery waste with blended cement and Wyoming bentonite

The solidification/stabilization of a tannery waste, which has a high chromium content, was studied by thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA). Pastes prepared with water, cement, tannery waste and Wyoming bentonite were analyzed after different setting times during the first 28 days of solidification. In the present work it is clear that Wyoming bentonite combined with waste affects cement hydration, while bentonite alone does not affect it significantly. The presence of the waste results in a small acceleration of the cement hydration reactions, probably due to the presence of extra Ca and alkalinity in the waste. When waste is present in the sample during TG and DTG analysis, it is burned to carbon dioxide, which partially reacts with the calcium hydroxide formed during cement hydration. This results in an underestimate of the calcium hydroxide content of the solidified sample. The greater the degree of hydration of the waste-containing cement sample, the greater the amount of carbon dioxide absorbed.