Mesoporous silica nanoparticles are frequently used in catalysis and biomedical applications such as drug delivery. With increasing usage, release of these nanoparticles into the environment becomes increasingly possible. Due to the high specific surface area, these nanoparticles can adsorb different natural ligands present in the environment. Fulvic acid, which is a component of natural organic matter, is one of the most abundant natural ligands in the environment. The adsorption of fulvic acid on amine functionalized and non-functionalized mesoporous silica nanoparticles as a function of pH was studied using attenuated total reflectance Fourier transformation infrared spectroscopy in order to gain an understanding of the mechanisms involved in the adsorption process. According to the results, carboxylic functional groups and the amine functional groups on the functionalized nanoparticles play key roles in the adsorption process. Multiple carboxylic groups present in different chemical environments dictate the speciation of fulvic acid in an aqueous environment whereas amine groups dictate the surface charge of the functionalized nanoparticles. The adsorption was also found to be pH dependent and it also depends on the surface functionality of the nanoparticles. Amine functionalized mesoporous silica nanoparticles show a higher adsorption of fulvic acid compared to the non-functionalized nanoparticles that decreases as a function of pH. Quantitative studies of the adsorption were done using thermogravimetric analysis such that the mass loading and surface coverage of fulvic acid on the mesoporous silica nanoparticles were calculated. Both are higher on functionalized nanoparticles than on non-functionalized nanoparticles at all pH conditions studied. The adsorption of fulvic acid on the surface alters properties of mesoporous silica nanoparticles such as the surface charge. According to the zeta potential measurements, fulvic acid adsorption increase the zeta potential (negative) in both functionalized and non-functionalized nanoparticles under all pH conditions studied which indicates a change in surface charge.

Surface adsorption of Nordic aquatic fulvic acid on amine functionalized and non-functionalized mesoporous silica nanoparticles

255th National Meeting (2018)

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