A low field NMR study of water adsorbed on silica and alumina surfaces

Low field (0.54 T) proton nuclear magnetic resonance spectroscopy (H-1 NMR) was used in order to determine the water adsorbed on porous silica and nano-powder alumina, between 0 and 36% of water content by analyzing free induction decay (FID) and Carr-Purcell-Meiboom- Gill (CPMG) relaxation curves at room temperature. The main objective of this study is to demonstrate the usefulness of NMR relaxation times in characterization of the state of water in silica and alumina, the first results showed that the CPMG sequence detected all added adsorbed water and very probably the few residual water molecules of dry samples. A short apparent transverse relaxation time T-2* of 50 mu s was observed for silica and a very short one of 15 mu s for alumina.