SURFACE CHARACTERIZATION OF ALKALI-TREATED COALS

The surface interactions of alkali with coal and mineral matter have been studied by electron spectroscopy for chemical analysis (ESCA) to establish a basis for predicting the relative reactivity of alkali with sulphur during coal beneficiation processes. The speciation of sulphur in coals doped with various alkali salts was determined and quantified after heating the mixtures to 648 K in air or N2, then washing with water. Organic and pyritic sulphur on the surface react with alkali when heated, and the sulphide or oxidized sulphur product can then be washed from the coal. The extent of reaction between the alkali salt and surface sulphur is governed by the size of the cation and the electronic properties of the anion; larger alkali cations are more effective in promoting the reactivity of surface sulphur, as are anions with stronger nucleophilic properties. © 1990.