CHARACTERIZATION OF HUMIC ACIDS FROM UNCOMPOSTED AND COMPOSTED SEWAGE-SLUDGE BY DEGRADATIVE AND NON-DEGRADATIVE TECHNIQUES

Humic acids extracted from a composted and uncomposted mixture of sewage sludge and grape debris were studied by non-degradative (FT-IR and C-13 NMR) and degradative techniques (oxidation by persulfate or permanganate). The GC-MS of the products of humic acids oxidation by persulfate or permanganate showed the predominance of aliphatic structures over aromatic ones (large quantity of fatty acids against small quantity of benzenepolycarboxylic acids); more polycondensed humic acids after composting were not detected by this technique. The FT-IR spectrum of humic acids from the composted mixture when compared with that of those extracted from the uncomposted material showed a decrease in the intensity of the absorption peaks corresponding to aliphatic compounds, amides and carbohydrates. C-13 NMR detected an increase, although slight, of the aromaticity percentage with composting (from 21.54 to 28.29%).