Enhanced removal of ethidium bromide (EtBr) from aqueous solution using rectorite

Ethidium bromide (EtBr) is an intercalating agent commonly used as nucleic acid fluorescent tag in various techniques of life science field. It is considered as a serious biohazard due to its mutagenicity and carcinogenicity. As such, developing high efficiency and low cost materials as cleanup kits is in urgent need although many methods have already been developed. In this study we take use of the affinity of organic cations for clay minerals of high cation exchange capacity (CEC) and large specific surface area (SSA) and tested the removal of EtBr using rectorite, a type of clay mineral made of 1:1 regularly mixed layers of illite and montmorillonite. Our results showed that the uptake of Et⁺ on rectorite could be as high as 400 mmol/kg and the removal of Et⁺ was extremely fast. Desorption of inorganic cation Ca²⁺ and sorption of counterion Br⁻ revealed that cation exchange was the dominating mechanism of Et⁺ removal using rectorite. Thermal analyses revealed that the EtBr could be thermally destructed inside the interlayer of rectorite and the material could be thermally regenerated. Thus, clay minerals could have a great potential to be fabricated into cleanup kits for the removal of EtBr in case of spill.