Clayey materials as geologic barrier in urban landfills: Comprehensive study of the interaction of selected quarry materials with heavy metals

Interaction studies of clayey materials with heavy metals have been carried out at different experimental conditions to evaluate their suitability as geological barrier of landfills. For this purpose, five raw materials, usually quarried for brick making, having different mineralogical composition and geochemical and physical–chemical properties were selected. The interactions between zinc (II), lead (II), cadmium (II) and chromium (III) ions and the clayey materials were studied in solutions that simulate the characteristics (composition, majority components) and conditions of leachate from municipal solid waste landfills in the acetogenic stage (young leachate) and methanogenic stage (old leachate). Batch experiments were used to study the retention of metals on clayey materials as function of pH in non-competitive and competitive conditions. Moreover, adsorption isotherms for all the assayed metals and materials were calculated. All the clayey materials displayed lower metal sorption capacity in the young leachate conditions. The clayey materials displayed greater sorption capacity for zinc (II) and chromium (III) whereas lower sorption capacity was observed for cadmium (II). The abundance of clay minerals, carbonate content, specific surface area and the presence of smectites control the metal retention capacity of the clayey material. The obtained results showed that the selected clayey materials are suitable as components of the multibarriers in controlled urban landfills.

► Interactions between heavy metals and clayey materials in urban landfill leachates.
► Metal retention is higher in leachates from old landfills.
► Composition and physicochemical properties of clays influence on metal retention.
► Interaction key parameters are phyllosilicate content and type and specific surface.
► Assayed materials are suitable for using as geological barriers of urban landfills.