Humic sodium salts

Figure 4.12. A basic extract of an organic soil is shown on the left a sample of the sodium salt of humic acid is seen on the right. 

The insoluble material was removed by centrifuging at 5000 rpm for 15 min in a Beckman Model No J-6B centrifuge. This extraction with alkali was repeated twice more and the solutions of sodium salts of acids were collected. Humic acids were precipitated from the combined NaOH solutions by adjusting the pH to 1 with 2N HCl slowly with stirring and the mixture was left overnight. The precipitated humic acids were collected by filtration through Whatman IMM paper and washed with O.IN HCl. The filtrates were extracted three times with ethyl acetate and the extracts dried over sodium sulfate and evaporated, the residue constituting the fulvic acids. Buth fulvic and humic acids (precipitates) were air-dried, and then dried in a vacuum desiccator over phosphorus pentoxide at room temperature. 

Humic acido from ooilo and ligniteo have been examined by ERR spectrometry. All samples showed a stable free organic radical content of about 1018 spins per gram. When these samples were converted to their sodium salts, a marked increase in radical content occurred. This was interpreted to indicate that a quinhydrone moiety exists in the humic acid macromolecule. Synthetic humic acid, prepared by oxidizing catechol in the presence of amino acids, also showed similar ERR spectra, as did selected quinhydrone model compounds. The radical moiety appeared to be stable to severe oxidation and hydrolytic conditions. Reduction in basic media caused an initial decrease in radical species continued reduction generated new radical species. A proposed model for humic acid based on a hydroxyquinone structure is proposed. 

Sodium Salts. The sodium salts of all samples were prepared by dissolving a given weight of humic acid in IN aqueous sodium hydroxide. Adding a tenfold excess of absolute ethanol to the basic solution precipitated the salt which was filtered, washed with ethanol, and dried at room temperature in... 

One of the most striking properties of humic acid is its change in free radical content upon conversion to the solid sodium salt. This change is reversible upon reacidification of the salt, the spin content returns to its original level (28). In general, the line widths increased about 50% on conversion to the salt. Table III illustrates this effect for many different humic acids. These results seem entirely consistent with the known properties of the salts of quinhydrone as shown in Figure 6 (28). 

Cornelius Steelink. It is possible that other systems may give rise to the. radical species. However, one of our models for humic acids is a biradical cr oh whose radical character would not be changed on acetylation. Our humic acids change very little in spin content on methyladon. It IsJw would be interesting to form sodium salts from your coals to see if ho the spin content increased. This would be fairly convincing evidence for oxygen radicals. 

Humic acid (HA). A 100 mg/L solution of the sodium salt of humic acid, to simulate groundwater containing an organic complexing agent. 

The present studies were carried out using commercially available humic acid, obtained as the corresponding sodium salt (EGA HI,675-2) and dissolved in a phosphate buffer (pH - 6.99), and an acetate buffer (pH = 4.47), respectively. The humic acid solutions were dialyzed against pure buffer solution prior to their use in the complex formation experiments in order to remove any low molecular fractions that could pass through the dialysis membrane. 

The study of Lafrance and Mazet [549] not only provided further confirmation of the beneficial effect of cations (Na ) but also clarified its mechanism by analyzing the effect of sodium salt concentration on the zeta potential of a commercial powdered activated carbon (see Section I V.B. 1). The reported uptakes of a commercial. sodium humate remained <100 mg/g (at 10 mg/L). In the study of Annesini et al. [556], even at humic acid concentrations of 20 mg/L the uptake did not exceed 10 mg/g. These uptakes should be contrasted with those reported recently by Newcombe and Drikas [566] and illustrated in Fig. 23 at low pH, when electrostatic repulsive forces (see Section IV.B. 1) are eliminated, the uptake at comparable concentrations can be as high as 200-300 mg/g. 

Humic and flilvic acids are traditionally extracted from soils and sediment samples as the sodium salts by using sodium hydroxide solution. The material that remains contains the insoluble humin fraction (Figure 3). The alkaline supernatant is acidified to pH 2 with HCl. The humic acid precipitates and the fulvic acid remains in solution with other small molecules such as simple sugars and amino acids. These molecules can be separated by passing the solution through a hydrophobic resin, such as the methacrylate cross-linked polymer, XAD-8. The fulvic acids will sorb to the resin while the more hydrophilic molecules pass through the column. The fulvic acid can be removed with dilute base. 

HUMIC ACID SODIUM SALT FULVIC ACID SODIUM SALT... 

Humic Acid Source Acid Form (spins/g) X 10> Sodium Salt (spins/g) X 10 ... 

The free radicals in humic substances appear to be remarkably stable with respect to time and chemical attack (Steelink and Tollin, 1962 Steelink et al., 1963 Steelink, 1964). This stability has led some workers to suggest that humic substances comprise a free radical, or mixture of free radicals, of the semiquinone type (Steelink and Tollin, 1962 Steelink et al., 1963 Atherton et al., 1967). The increase in spin concentration upon converting humic acids to the sodium salts led Steelink (1964) to propose that the radical species in humic acid is a semiquinone co-existent with a quinhydrone species. Steelink (1964) also suggests that a free radical is an integral part of the humic macromolecule. The stability of this radical has been attributed to the delocalization of the unpaired electron over an aromatic system (Theng and Posner, 1967), or a shielding effect on the free radical due to the macromo-lecular network (Steelink, 1964). 

The carbonates are mainly calcite, dolomite, or siderite. The occurrence of calcite is frequently bimodal. Some calcite occurs as inherent ash, while other calcite appears as thin layers in cleats and fissures. Iron can be present in small quantities as hematite, ankorite, and in some of the clay minerals such as illite. In addition to the more common minerals, silica is present sometimes as sand particles or quartz. The alkalies are sometimes found as chlorides or as sulfates but probably most often as feldspars, typically orthoclase and albite. In the case of lignites, unlike bituminous and subbituminous, sodium is not present as a mineral but is probably distributed throughout the lignite as the sodium salt of a hydroxyl group or a carboxylic acid group in humic acid. Calcium, like sodium, is bound organically to humic acid. Therefore, it too is uniformly distributed in the sample [10]. 

La France, P. and Mazet, M. (1989). Adsorption of humic substances in the presence of sodium-salts. J. Am. Water Works Assoc., 81, 155-62. 

Humic acid, sodium salt. See Sodium humate Humulus americanus Humulus americanus oil. See Hops (Humulus lupulus) oil Humulus lupulus Humulus lupulus extract. See Hops (Humulus lupulus) extract Humulus lupulus oil. See Hops (Humulus lupulus) oil... 

Several extractions were also conducted on 2.0-mg/L humic acid solutions. These solutions were prepared by dissolving a known quantity of humic acid (Fluka, further purified by USEPA pesonnel) in 0.20 M sodium hydroxide followed by dilution with water to a 0.02 M sodium hydroxide solution. Subsequent neutralization to pH 7.0 with 0.100 M HC1 and dilution with water containing the salts noted earlier gave a... 

Stabilization of a radical anion of humic acid may be caused by an adsorption effect. Bijl (3) observed that solid barium hydroxide octahydrate turned blue when placed in a solution of quinhydrone the blue solid was highly paramagnetic. Under the conditions we used for preparing these salts, insoluble sodium humate (with a large surface area) could have stabilized the anion radical by adsorption from the basic solution. Weiss and McNeil (18) observed a similar phenomenon with base soluble xanthenes, and proposed that biradicals may be formed in such a system. His compounds, however, do not appear to have the structural requirements to satisfy such a stabilized system. The recent report by Weber (29) on the spin content increase associated with the basification of a naphthoquinone-naphthohydroquinone system seems to parallel our observations quite closely. 

The best extractants in the above list of salts form complexes with the polyvalent metals that neutralize charges on the humic substances and link them to the inorganic soil colloids. These polyvalent ions are replaced by sodium ions from the salts. The efficiency of each solvent system will depend on the extent to which the resident cations are exchanged and removed from humic structures. Diffusion of the salts to the interior of solid humic substances is slow. Some channeling can take place, but extensive penetration would probably require the opening up from the outside of the macro-molecular structures. It would be necessary for these structures to remain open to allow exchange from the interior to take place. 

Data for the tropical soils provide information about differences in the behavior of DMSO (Table 9). The adsorbance values show, as would be predicted, that sodium hydroxide extracted most organic materials from the H -exchanged soils, and that 0.1 A/ base was generally better than 0.5M base. exchanging had little influence, as might be predicted, and excess salt suppressed solubilization. Again, the addition of acid to DMSO increased solubilization of the colored humic substances. Furthermore, the addition of acid dispenses with the need to H+-exchange the soils prior to extraction with the solvent. 

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