Utilization of bentonite in cementation of Cs-137-contaminated electric arc furnace dust

Cementation was employed to harden the Cs-137-contaminated electric arc furnace dust. The dust and cement were used as cementation binders. Bentonite was added to resist the Cs-137 leaching from the dust-cement-bentonite specimens. The strengths of all specimens exceeded the acceptable level. The specimen strength dropped when the dust and/or bentonite were added. It could decline due to the specimen component leaching. The amount of Cs-137 leached decreased as the bentonite content increased. The leachate Cs-137 concentration was positively correlated with the leachate pH and conductivity. The specimens without bentonite had Cs-137 leachability index (LI) values ranging from 6.2 to 6.8. The LI reduced as the dust content rose. The specimens containing bentonite had better LI values ranging from 6.6 to 9.3. The LI increased as the bentonite content increased, demonstrating that bentonite can be an effective cementation additive for retarding the Cs-137 leaching. The graph slopes revealed that the Cs-137 leaching was caused by diffusion or surface wash-off. However, the multiple mechanisms-based analysis using the 15 leaching models showed that the Cs-137 leaching occurred as a result of the four processes, with the insignificant contribution of diffusion. The contribution proportion of each process depended on the EAFD and bentonite contents.