Frozen-liquid PMR spectra and interactions of water with spherical carbon adsorbents

Abstract

The PMR spectrum from a spherical carbon adsorbent shows separate signals from the water in the pores (δ 2–0 ppm) and outside the granules (δ 5 ppm) at temperatures above 273 K because of the short spin relaxation times in the presence of numerous paramagnetic centers. Below 273 K, the water bound to the carbon after heat treatment above 1273 K may be in two states: A (δA 2–0 ppm) and B (δB −12 to −13 ppm). The enthalpy of (H2O) A ⇄(H2O) B is −50 kJ/mole. State B is associated with the graphitization occurring above 1273 K. It is suggested that the anomalous chemical shifts in states A and B are due to axial coordination in relation to the condensed benzene ring systems at the negatively charged surfaces.