CONICET | Buscador de Institutos y Recursos Humanos

Silica-based Order Mesoporous Materials (OMS), have a number of outstanding features that enable their use as sorbents for various pollutants substances, e.g. high specific surface area, modulable pore sizes and the possibility of increasing its specificity as adsorbent by changing the surface chemical species by using different functionalizing agents [1]. Among the OMS, the amino-functionalized MCM-41 and SBA-15 substrates have been employed as adsorbents of different aqueous contaminants with promising results. However, the bibliographic reports indicate that when pH working values are between 5 and 10, amino groups and the silica mesoporous structure can undergo dissolution at the pore surface, which decreases the durability of the hybrid material [2-3]. In this sense, this work deals with a second surface modification, in addition to the -NH2 functional groups, and the influence of this attachment in the stability of an NH2-OMS solid. Thus, a -CH3 and -NH2 bi-funtionalized sorbent was used toward Cr(VI) adsorption from an aqueous matrix and compared against the -NH2 mono-fuctionalized one. For this purpose, an ordered mesoporous solid with spherical morphology and hexagonal pores arrangements, MCM-41 type material, wassynthesized and surface-modified by the incorporation of aminopropyl groups. Part of the sample was functionalized again incorporating trimetilsil groups. The mono and bi-functionalized samples showed Cr(VI) adsorption capacity of around 60 mg.g-1. In order to evaluate the stability of the samples in the desorption of Cr(VI) (regeneration process), the materials were submerged for 480 min. at pH 10 (sc. NaOH). After that, both samples were used in a new adsorption process. The bi-functionalized sample showed a minor decrease in the elimination capacity of Cr(VI) (6%), while the mono-functionalized fell 22%.