Insoluble organic matter characteristics

Machihara, T. and Ishiwatari, R. (1981). Characteristics of insoluble organic matter in lake sediments as revealed by alkaline potassium permanganate oxidation. Ver. Internal. Verein. Limnol. 21, 244-247. 

Organic matter extracted from earth materials usually is fractionated on the basis of solubility characteristics. The fractions commonly obtained include humic acid (soluble in alkaline solution, insoluble in acidic solution), fulvic acid (soluble in aqueous media at any pH), hymatomelamic acid (alcohol-soluble part of humic acid), and humin (insoluble in alkaline solutions). This operational fractionation is based in part on the classical definition by Aiken et al. (1985). It should be noticed, however, that this fractionation of soil organic matter does not lead to a pure compound each named fraction consists of a very complicated, heterogeneous mixture of organic substances. Hayes and Malcom (2001) emphasize that biomolecules, which are not part of humic substances, also may precipitate at a pH of 1 or 2 with the humic acids. Furthermore, the more polar compounds may precipitate with fulvic acids. 

Humic Materials. Humic materials are divided into three fractions based on their solubility in aqueous solutions as a function of pH humic acid, which is soluble in an alkaline aqueous solution fulvic acid, which is soluble in an aqueous solution regardless of pH and humin, which is insoluble in water at any pH value (and contains the OMN in soil organic matter). The chemical characteristics of humic acid and fulvic acid (e.g., Stevenson, 1994 Orlov, 1985 Rashid, 1985 Aiken et al., 1987 Hayes et al., 1987) and humin (Hatcher et al., 1985 Rice, 2001) are described in numerous reviews. 

The British Pharmacopoeia, 1948 revision, includes standards for total ash, acid-insoluble ash, and starch and foreign organic matter. It requires certain identification tests— for instance, that no pink color is produced when tragacanth is treated with ruthenium red and that the characteristic copper reduction of alkaline copper tartrate solutions is produced to indicate the sugar character of the gum. 

Humin s insolubility obviates its presence in a dissolved organic matter aquatic sample. In aquatic systems, the operational definitions of humic and fulvic acids are stated somewhat differently [4]. Humic acid and fulvic acid are defined by the aqueous solution pH necessary to desorb them from XAD-8 resin fulvic acid can be desorbed with water humic acid is desorbed with an alkaline aqueous solution. However, the defining operational characteristic, solubility in an aqueous solution as a function of pH, is consistent in both operations. Thus, the use of the term fulvic acid in this paper refers to the humic substance fraction soluble in aqueous solution at any pH value, and the term humic acid refers to the humic substance fraction soluble in alkaline aqueous solution but insoluble under acidic conditions. 

The organic chemical industry, the food processing industry, the pulp and paper industry, the textile industry, and the petroleum industry are important industries that produce organic process wastes. Unlike inorganic process wastes, they contain dissolved and insoluble matter in the main wastewater stream thus, they are more difficult to handle for disposal. They have its characteristic biological problems and spontaneous interaction with the surrounding environment, particularly, under high solar radiation. 

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