Novel function for anionic clays: selective transition metal cation uptake by diadochy

Abstract

Here we report for the first time, the extremely high and selective uptake of transition metal cations such as Cu²⁺, Ni²⁺, Co²⁺ and Zn²⁺ by two anionic clays of nominal composition, [Mg₆Al₂(OH)₁₆ ]²⁺[CO₃·4H₂O]^2– and [Mg₂Al(OH)₆ ]⁺[NO₃·2H₂O]^–. We postulate that the principal mechanism of this selective cation uptake is by substitution in the anionic clay structure for mainly Mg through a process known as diadochy. This newly discovered function for anionic clays is useful for the decontamination and immobilization of the above transition metals at room temperature and may find applications in the remediation of metal contaminated soils, filtration of drinking water as well as decontamination of waste waters.