Humic matter exchange capacity

Strongly basic anion exchange resins are sensitive to organic matter (particularly humic substances), with attendant decreases in their ion exchange capacity, pH, and active depth, as well as with increases in the amount of water required for the washing operation, and in the conductivity of the final solution. 

Both clay and organic matter contribute to the cation-exchange capacity (CEC) of the soil. The contribution from humic and fulvic acids is due largely to the ionization of COOH groups, although some contribution from phenolic OH and NH groups is expected. 

Humic substances constitute the bulk of the organic matter in most terrestrial soils. The functions they perform are multiple and varied and include the weathering of rocks and minerals, mobilization and transport of metal ions, and formation of stable aggregates by combination with clay minerals. Humic substances make a significant contribution to the cation-exchange capacity of the soil, and they are involved in the sorption of organic molecules applied to soils as pesticides. 

Our results show that the adsorption on suspended matter is increased in the presence of suspended humic acid (Figure 10). This is supported by the finding of other authors (53,54) showing that organic flocculant coatings greatly affect the cation exchange capacities of sediment and suspended matter. 

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