Extraction organic substances, soil

Solvent extraction uses an organic solvent to extract toxic substances from contaminated liquid or solid.67 Examples can be found in the section dealing with the treatment of contaminated soil. 

Pierce RH Jr, Felbeck GT Jr (1972) A comparison of three methods of extracting organic matter from soils and marine sediments. In Povoledo D, Golterman HL (eds) Humic Substances. Center for Agriculture Publication and Documentation, Wageningen, Netherlands, pp 217-232... 

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. 

Mingelgrin U, Gerstl Z (1993) A unified approach to the interactions or small molecules with macrospecies In Beck AJ, Jones KC, Hayes MHB, Mingelgrin U (eds) Organic substances in soil and water. Royal Society of Chemistry, Cambridge, pp 102-128 Mordaunt CJ, Gevao B, Jones KC, Semple KT (2005) Formation of non-extractable pesticide residues Observations on compound differences, measurement and regulatory issues. Environ Pollution 133 25-34... 

Methods for extracting humic substances must take into account the various ways in which organic matter is bound. Free forms of humic and fulvic acids can be recovered by procedures used to displace the soil solution, as well as by extraction with neutral salt solutions or dilute mineral acids. The usual procedure for recovering humic material bound to polyvalent cations is... 

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