Preparation and application of chelating polymer-mesoporous silica composite for Europium-ion adsorption

Ordered mesoporous silica (MCM-48) functionalized with a carboxymethylated polyethyleneimine (CMPEI) was prepared and applied to adsorb Eu(III) ions. The samples were characterized by SEM, TEM, XRD and N₂ adsorption-desorption experiments. Adsorption studies of Eu(III) onto the MCM-48 and CMPEI-functionalized mesoporous silica, which are denoted as CMPEI/MCM-48, were performed by batch experiments. The adsorption of Eu(III) on the CMPEI/MCM-48 obeyed the Langmuir isotherm model. The CMPEI/MCM-48 exhibited much higher adsorption capacity at pH 3.0 to 5.0 compared to that of the pristine MCM-48. The Eu(III) adsorption of the CMPEI/MCM-48 increased with the pH. This was attributed mainly to a change in the chemical structure of CMPEI, which is strongly dependent on the solution pH. The XPS depth profiles showed that CMPEI was present on the mesopore walls inside the MCM-48 as well as on the surface of the particle, and further showed that a change in the Eu(III) content with etching time was not severe, indicating that the complexation of Eu(III) with CMPEI/MCM-48 occurred uniformly, even inside the CMPEI/MCM-48. The overall results showed that the mesopore surface of MCM-48 was functionalized successfully with CMPEI and the resulting CMPEI/MCM-48 could be used as a proper adsorbent for the recovery of trivalent actinide species.