Fulvic acid exchange acidity

In this work a novel five-step leaching scheme for HM has been developed addressing exchangeable, acid soluble (carbonate), easily reducible (bound to Mn oxides), easily oxidizable (bound to humic and fulvic acids), and moderately reducible (bound to amorphous Ee oxides) fractions extractable by 0.05 M Ca(N03), 0.43 M CH3COOH, 0.1 M NH,OH-HCl (non-acidified), 0.1 M K/,03 (pH 11), and 0.1 M (NH4),C,04 (pH 3), respectively. The sequence of extractants was chosen according to recent studies on the selectivity of leachants toward dissolved phases of soils. 

The first attempts employing two Cjg columns showed that the selectivity was not high enough, although this improved when the first column was substituted by a 5 p.m GFF n internal surface rcversed-phase material. This is known as a restricted-access-material (RAM) column which, since it restricts some compounds because of their size and includes rcversed-phase interaction and ionic exchange, is very useful for analysing herbicides in samples with high contents of humic and fulvic acids (54). 

About half of the dissolved organic carbon may appear in humic or fulvic acids. These are high-molecular weight organic compounds of a composition which is somewhat uncertain. They contain aromatic hydroxyl and carboxyl groups which have the ability to bind to metal ions. Rivers and estuaries typically contain 10 mg/liter of acid with an exchange capacity of 5-10 mmol/g, mainly due to carboxylic... 

LDHs are also promising materials as sorbents for anionic organic contaminants via both ion-exchange and reconstruction reactions. There have been a large number of reports of the use of LDHs for removal of species such as aromatic carboxylic acids, phenols, pesticides, and humic or fulvic acids. Recently, Cardoso et al. [152] found that the sorption process of terephthalate anions from aqueous solutions by calcined Mg/Al - CO3 LDHs takes place by reconstruction of the LDHs and involves the intercalation and adsorption of terephthalate anions. Calcined Mg/Al - CO3 LDHs were found to be capable of removing 40 to 85 % of the benzoate from solutions in the concentration... 

Figure 6. Standards recovered from 10 mL of distiUed-deionized water containing 5 mg/L carbon as fulvic acid on a strong-anion-exchanger packed precolumn. Peak identities 2, 0.87 pg of phenoxyacetic acid 2, 1.2 pg of p-chlorobenzoic acid 3,0.33 pg of 2-naphthalenesulfonic acid 5,0.20 pg of pentachlorophenol and 12,0.055 pg of pyrene. Conditions for concentration, analytical separation, mobile-phase gradient, and detection were the same as in Figure 3. (Reproduced with permission from reference 18.)...

Step 5. Adjust pH to 1.0 with HC1 to precipitate humic acid. Separate humic and fulvic acids by centrifugation. Rinse humic-acid fraction with distilled water until AgN03 test shows no Cl . Dissolve humic acid in 0.1 N NaOH and hydrogen saturate by passing solution through cation-exchange resin in H-form. 

Step 7. H-saturate fulvic acid fraction by immediately passing 0.1 N NaOH eluate through cation-exchange resin in H-form. Continue cation-exchange process until final concentration of Na+ is less than 0.1 ppm. 

Fulvic acid [479-66-3] -accumulation m anion-exchange resins [ION EXCHANGE] (Vol 14)... 

Dissolved organic compounds may compete with arsenic for adsorption and ion-exchange sites on a variety of sorbents (Stollenwerk, 2003), 89. Specifically, fulvic acid is known to interfere with As(V)... 

Waite, T. D., and F. M. M. Morel. 1984b. Ligand exchange and fluorescence quenching studies of the fulvic acid-iron interaction. Analytica Chemica Acta 162 263-274. 

Larive, C. K., Rogers, A., Morton, M., and Carper, W. R. (1996). 113Cd NMR binding studies of Cd-Fulvic acid complexes Evidence of fast exchange. Environ. Sci. Technol. 30, 2828-2831. 

Ryan, D.K, Ventry, L.S., Cabaniss, S.E. and Shuman, M.S. (1990) Exchange of comments on fluorescence quenching measurements of copper-fulvic acid binding. Anal. Chem., 62,1523-1528. 

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