Interfacial behavior of concentrated HCl solution and water clustered at a surface of nanosilica in weakly polar solvents media

Low-temperature 1H NMR spectroscopy was used to study water and concentrated hydrochloric acid solution clustered at a surface of silica A-300 initial and mechanochemically activated (MCA) with the bulk density ρb = 0.045 and 0.394 g/cm3, respectively. Hydrochloric acid solution in contact with silica powder placed in nonpolar (CCl4) or weakly polar (CDCl3) media forms clusters of two types (with different content of HCl and water) in interparticle voids in aggregates of silica nanoparticles. This differentiation is stronger in the system with MCA silica because of enhanced confinement effects in narrower pores (voids) between adjacent nonporous nanoparticles. Obtained results are of importance for deeper insight into the mechanism of the influence of nanosilica used as an oral sorbent on the gastric juice properties.