Effective removal of the heavy metal ion Cd2+ from the structure of cementitious materials with mineral additives

Abstract

Natural zeolite and bentonite were used as mineral addi-tions to create cement-based building materials that are safe for the environment. This research focuses on the adsorptive qualities of these two clay raw materials, i.e., their propen-sity to immobilize heavy metal ions like Cd2+. The acquired results were examined using kinetic models of pseudo-first and pseudo-second order. The isotherms of Langmuir and Freundlich were examined. Zeolite and bentonite had differ-ent adsorption affinities for Cd2+ cations. Seven cement binders with various mineral additions (fly ash, zeolite, bentonite) underwent a leaching test. The adsorption and hydration mechanisms that immobilized heavy metals within cementitious composites caused leachates obtained on cement samples with the addition of fly ash and clay (either zeolite or bentonite) to contain lower concentrations of Cd2+ ions than leachates obtained on cement samples with fly ash alone.