Humic acids functional group content

TABLE 4.3. Acidic Functional Group Contents of Humic Acids (HAs) and Fnlvic Acids (FAs) Isolated from Cattle Manure (CM), Sewage Sludge (SS), Municipal Solid Waste Compost (MSWC), Liquid Swine Manure (LSM), Soils Amended with 25tha 1yr 1 of CM for 4 Years (SO + CM25), 25,50, and lOOtha yr1 of SS for 4 Years (SO + SS25,... 

Visser, S. A. (1982). Acid functional group content of aquatic humic matter Its dependence upon origin, molecular weight and degree of humification of the material. J. Environ. Sci. Health A 17, 767-788. 

The product of interaction with the herbicides of 3 humic acids of synthetic, coal and peat origin, indicated as synthetic-2, coal-2 and peat-2 in Table 2, will specifically examined in the first part of this paper. The 3 original HA samples do not differ sensibly in their elemental and acidic functional group composition, but they show quite different ash content (Table 2). 

Humic and fulvic acids form both soluble and insoluble complexes with polyvalent cations, depending on degree of saturation. Because of their lower molecular weights and higher contents of acidic functional groups, metal complexes of fulvic acids are more soluble than those of humic acids. Attempts have been made to subdivide humic acids on the basis of molecular weight by fractional precipitation with ammonium sulfate at pH 7 (Theng et al., 1968). 

Second, an even more serious problem with this method is the critical nature of the filtration step (Holtzclaw and Sposito, 1979 Perdue, 1979 Perdue et al., 1980). Any moderately acidic functional groups (pKa 7-10) that are soluble in the equilibrium mixture (pH 6-7) will be titrated along with acetic acid when the filtrate is titrated to pH 9.8 (see Fig. 7). All the functional groups detected in that titration are simply assumed to be carboxyl groups. Thus, while the use of high concentrations of humic substances can lead to underestimation of carboxyl content, the complexation... 

Cameron, D. F., and Sohii, N. L. (1992). Functional group content of soil and sedimentary humic acids determined by CP/MAS NMR related to conditional Zn +and Cd formation constants. Sci. Total Environ. 113, 121-132. 

NMR Spectra of Unreacted Samples. Quantitative liquid phase NMR spectra of the unreacted samples are shown in Figure 2. Peak areas of the spectra are listed in Table I together with elemental analyses. Characteristically, the humic acid has a greater aromatic carbon and lesser carboxylic acid carbon content than the fulvic acid. The naturally occurring nitrogen contents are 2.68% and 4.18% for the fulvic and humic acids, respectively. Overlap of functional groups which may serve as substrate sites for nucleophilic addition by aniline occurs within the major peak areas of the spectra. Quinone carbons (190 to 178 ppm) overlap with ketone carbons from 220 to 189 ppm, amides and esters (174 to 164 ppm) overlap with... 

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