Molecular weight distribution,analytical and spectroscopic characterization of humic fractions sequentially isolated by organic solvents from a brown coal humic acid |
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| Authors: | Nicola Senesi Sandor Sipos |
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| Institution: | 1. Institute of Agricultural Chemistry, University of Bari, Bari, Italy;2. Institute of Colloid Chemistry, J. Attila University, Szeged, Hungary |
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| Abstract: | A sequential fractionation procedure employing a series of selected mild organic solvents of different polarity has been applied for the isolation of chemically different organic fractions from a brown coal humic acid. Elemental composition, molecular weight distribution, i.r. and electron spin resonance analysis were carried out on the isolated humic fractions. They were characterized by: (a) a low polydispersity, (b) a decreasing aliphatic and increasing aromatic character along the series, (c) very different molecular weight which significantly correlated with E4/E6 ratios (particle aggregation and molecular association) and free radical concentrations (chemical and biochemical activity). Significant correlations were found between physico-chemical parameters of the isolated humic fractions, i.e. Mn, Mw, E4/E6 ratios, spins/g contents and the dielectric constants of the solvents used. This suggested the efficiency of the applied procedure in isolating chemically different organic fractions from the bulk, original humic acid. |
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| Keywords: | humic fractions organic solvents molecular weight infrared analysis electron spin resonance |
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