Synthesis and surface characterization of ordered mesoporous silica SBA-15

Abstract

Ordered mesoporous silica SBA-15 materials were synthesized using Pluronic P123 (non-ionic triblock copolymer, EO 20PO 70O 20) as a template, under acidic conditions and different heating temperatures and time of the reaction solution. These materials were characterized by nitrogen adsorption–desorption measurements, Fourier-transformed infrared spectroscopy (FT-IR), and determination of points of zero charge and izoelectric points as well as particle diameters. Synthesis at lower temperature (80 °C) and longer time of reaction (48 h) gives samples with higher specific surface area ( S BET = 710 m 2 g −1), mesoporose surface ( S meso = 481 m 2 g −1) and narrower pore size distribution. Material synthesized at higher temperature (100 °C) and shorter time of reaction (24 h) has lower specific surface and mesoporosity ( S BET = 641 m 2 g −1 and S meso = 367 m 2 g −1). At both samples, the presence of micropores was confirmed. The point of zero charge, pH PZC = 5.2 ± 0.2, and the isoelectric point, pH IEP = 2.3 ± 0.1, were not affected by synthesis conditions. Washing of silica samples in a dilute solution of nitric acid shifts the isoelectric point to a higher value (pH IEP = 3.0 ± 0.2) while the point of zero charge remains constant.