Modification of Silicon Dioxide Isolated during Acid Processing of Nepheline Concentrate

Abstract—The surface of amorphous silicon dioxide isolated from nepheline concentrate is modified. The modification is carried out with 3-aminopropyltriethoxysilane and oleic acid for targeted change of physicochemical and structural-surface properties of the surface of initial silica. Studies of the samples of initial and modified silica using scanning electron microscopy, X-ray spectral microanalysis, and physical adsorption of gases near the boiling point of the adsorbate are carried out. The difference in the surface morphology of the samples is shown, as well as a significant change in the structural and surface properties (the specific surface area of modified SiO2 in relation to initial silica (467 m2/g) decreases by 96% when using 3-aminopropyltriethoxysilane as a modifier, and it decreases by 23% when using oleic acid as a modifier), and in the specific surface charge determined by the acid-base potentiometric titration (the point of zero charge for the initial silica is 5.0, modified with 3-aminopropyltriethoxysilane is 9.9, and modified with oleic acid is 4.4). The presence of grafted functional groups on the surface of modified silicas is proven by IR spectroscopy: characteristic vibrations typical of chemical bonds of the modifiers are found in the spectra of the obtained samples, namely, –N–H, –C–N, –C–H, and –C–C–. Possible ways for using the obtained modified silicas are proposed.