MCM41 functionalized with ethylenediaminetriacetic acid for ion-exchange chromatography

Abstract

Synthesis of ED3A–MCM41 hybrid material is reported. ED3A organic moiety is an ethylenediaminetriacetic group and functionalised mesoporous silica is obtained through a “one-pot” synthesis procedure, yielding –COOH groups available on the surface without any further modification. The product has been characterized using different techniques (XRD, N₂ sorption, SEM, DTG, XRF, FTIR). Due to its chemical structure, ED3A–MCM41 has been tested for on-line chromatographic application in ion exchange of probe metal ions of environmental importance (Cd²⁺, Cu²⁺ and Zn²⁺). In order to identify the mechanisms acting (cation-exchange and chelation) during the separation of metal ions on ED3A–MCM41, the retention behaviour with non-complexing (methanesulfonic acid) and complexing (oxalic and pyridine-2,6-dicarboxylic acids) eluents was investigated. The study revealed that the chelation mechanism is dominant in the retention of Zn²⁺ and Cu²⁺, while for Cd²⁺ the cation-exchange mechanism is prevailing. The different mechanisms acting on the retention of the three metal ions allowed optimizing a gradient for their separation. The chelating properties of the ED3A–MCM41 phase suggest its use for the analysis and preconcentration (and/or removal) of metal ions in highly saline matrix (synthetic sea water). Examples of separations of metal ions in this matrix are shown.