Non-catalytic oxidation of water-slurried coal with oxygen: Identification of fulvic acids and acute toxicity

The composition and toxicity of the aqueous oxidation fraction of coal were investigated, to gain information concerning process safety measures and the utilization of the oxidation products as antibacterial agents. Coal was oxidized with oxygen at 180 degrees C under constant pressure (4 MPa). Fractions of the crude filtrate obtained during this process were sublimed, distilled and extracted with ether and ethanol. Almost 50 different acids were identified in these samples using g.c. and g.c.-m.s. analyses. The following groups of acids could be distinguished: (1) all possible unsubstituted acids containing up to four carbon atoms: (2) higher carboxylic acids containing even numbers of carbon atoms, agreeing with occurrence in nature; (3) oxygenated straight-chain or branched acids in the hydroxy or keto form containing up to six carbon atoms; (4) dicarboxylic aliphatic acids containing up to six carbon atoms; and (5) benzoic acid and its monohydroxy derivatives and phthalic acid. No highly toxic compounds could be identified, most of the compounds being common physiological metabolites. Primary acute toxicity studies were carried out on rats, using the crude aqueous solution and the drum-dried product of this solution. Apart from local irritation caused by their acidic nature, neither of these fractions exhibited significant acute toxicity in the test animals. Copyright (C) 1997 Elsevier Science Ltd.