Regularities in the behaviour of water confined in adsorbents and bioobjects studied by 1H NMR spectroscopy and TSDC methods at low temperatures

Comparative study of water confined in highly disperse and porous adsorbents and bioobjects by 1H NMR spectroscopy and thermally stimulated depolarisation current (TSDC) methods at T < 273 K revealed the presence of several dynamic processes linked to the mobility of (i) polar bonds responsible for dipolar relaxations (TSDC) at 90 < T < 200–220 K when the molecular mobility (diffusion) is absent; (ii) water molecules responsible for the 1H NMR spectra at T > 200 K; (iii) protons and ions resulting in direct current (dc) relaxation (TSDC) at T > 210–220 K. According to the 1H NMR spectra recorded on layer-by-layer freezing-out of bulk and interfacial waters bound in solid adsorbents and bioobjects, there are four types of confined water attributed to strongly (ΔG < − 1 kJ/mol) and weakly (ΔG > − 1 kJ/mol) bound and strongly (δH = 4–5 ppm) and weakly (δH = 1–2 ppm) associated waters. Several factors such as structural, textural and morphological characteristics of adsorbents and bioobjects, partial hydrophilic/hydrophobic surface functionalisation of adsorbents, amounts of water and other co-adsorbates (organic solvents, ions, etc.) affect contributions of the mentioned types of bound water.