Improvement of soil properties applied to capping and multilayer barriers

Results are presented on the research on the selection of natural clayey materials for the remediation of mill tailings and the possible control of their properties. The following objectives were formulated: a) minimizing of the required soil mass, b) improvement of the material employed. Three methods for the modification of clayey soil were examined: - application of an external electrical field; - hydrolysis by applying strong acids and strong bases; - a combined method. The research focused on two types of clays, on a kaolinite and on a illite/smectite. An electric field of E= 0.2 V/cm was used. The samples were also treated with 0.1 N chloric acid, strong base, peptising agent and an industrial waste solution from an etching processes. Remaining heavy metal concentrations in the solutions were used as a measure for the effectiveness of modification to the clays. Both, the chemical and the electrical method generated similar changes in the clay structures. The electrical method appeared to be simpler in field applications. However, the research showed that the chemical treatment of the clay material was the most efficient. Disappointing results where obtained from the electrical treatment of samples, i.e. the sorptive properties of clays did not improve substantially and the pH change was ambiguous. (author)