Incorporation of methyl groups as strategy to avoid degradation of aminopropyl-modified mesoporous silica nanoparticles in aqueous media

NICOLÁS FELLENZ; JOSÉ FERNANDO BENGOA; MARÍA FLORENCIA AGOSTO; PEDRO PABLO MARTIN; SERGIO GUSTAVO MARCHETTI

Gramado

Congreso; XVI Brazil MRS Meeting; 2017

Brazilian Materials Research Society (B-MRS),

Incorporation of methyl groups as strategy toavoid degradation of aminopropyl-modifiedmesoporous silica nanoparticles in aqueousmediaNicolás Fellenz1,2, Pedro Pablo Martin1,2, María Florencia Agosto1, José FernandoBengoa3, Sergio Gustavo Marchetti2,31Universidad Nacional de Río Negro, 2Consejo Nacional de InvestigacionesCientíficas y Técnicas, 3Centro de Investigación y Desarrollo en CienciasAplicadase-mail: nfellenz@unrn.edu.arThe characteristics of the MCM-41 structure, i.e. regular array of uniform poreswith sizes between 2-10 nm and the ability to functionalize its surface withseveral organic groups, make this material as an ideal candidate for applicationsin adsorption-based technologies. In particular, it has been proved that aminomodifiedMCM-41 is useful to interact via electrostatic forces with severalspecies, showing high loading capacity and selectivity as sorbent in complexaqueous matrices [1]. On the other hand, mesoporous ordered silicas sufferdissolution and pores collapse, when they are exposed to a neutral or basic pHenvironment due to the dissolution of the silica network which implies the loss ofthe functional groups [2]. These facts limit the application of the amino-modifiedMCM-41 as sorbent. Taking into account these considerations, the aim of thepresent work is improve the stability of an MCM-41-NH2 sorbent by introducing asecond functional group (-CH3) on its surface. Thus, a mono and a bifunctionalizedMCM-41-based sorbents were synthesized and used for Cr(VI)elimination from water at pH= 2. The batch adsorption assays were realizedbefore and after that the sorbents were subjected to a treatment under extremebasic conditions of pH (8 h, pH = 10). The ordered mesoporous structure and thechemical surface characteristics were determined by powder X-ray diffraction(XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM),nitrogen sorption experiments, dynamic light scattering (DLS) and X-rayphotoelectron spectroscopy (XPS). After the basic treatment the adsorptionassays indicated a decrease of about 32% in the chromium elimination capacity ofthe sample MCM-41-NH2, while the MCM-41-NH2-CH3 retained 100% comparedwith the data obtained before the basic treatment. The XPS studies demonstratethat these differences in the adsorption capacities are due to the presence ofmethyl functionalities that avoid the leaching of the amino groups.