Humic salts

Natural organic polyelectrolytes are some of the most active components of natural soil-water systems entering into physical and chemical reactions with practically all other components of the systems. Most pesticides are strongly sorbed by insoluble natural organic polyelectrolytes, such as humic acid. The soluble humic salts, however, may solubilize insoluble pesticides. Pesticides also enter into chemical reactions with natural organic poly electrolytes. The mechanisms of most of these interactions have not yet been elucidated. Elucidation will require isolation of well-defined, chemically and physically homogeneous natural polyelectrolyte fractions. 

Several authors have noted that the soluble salts of humic acid are surface active however, Wershaw et al. 21) were the first to demonstrate that soluble humic acid salts solubilize insoluble pesticides, such as DDT. Soluble humic salts are present in many soils, and they form in any organic soil on which alkaline fertilizers such as urea or anhydrous ammonia has been applied. Ballard (27) has shown in experiments with agricultural soils that DDT is solubilized by humic acid salts when the soils are fertilized with urea. 

In some systems, such as lake and river waters, the suspended inorganic particles may be coated by biological polymers, termed humic substances, which prevent flocculation by either steric or electrostatic mechanisms. These can also interact with added inorganic salts (31) that can neutralize charged functional groups on these polymers. 

Upland surface water. This is low in hardness salts having run over impervious rocks but will often be high in organic matter, i.e. fulvic and humic acids. 

Color in water (apart from textile dyes, etc.) often is caused by the degradation of natural organic matter, resulting in colloidal humic and fiilvic acids. These are best removed by precipitation with metal salts, but performance may be improved with high-charge cationic polymers. 

Humic acid precipitates at salt concentrations >0.05 M and pH <4, while the fulvic acids are still soluble. Thus, humic acid is hardly ever found in salt water ( O.S M). Titration experiments with alkali indicate that there are consecutive steps of deprotoni-zation. A typical average pka-value would be 7 (26), and for a selected humic acid values of 4 and 9 are given for pk and pk, (27, 28). 31 aZ... 

In addition, a fluid loss additive for oil-based drilling fluids, which consists of fatty acid compounds and lignite or humic acid, an oil-soluble or oil-dispersible amine or amine salt with phosphorie acid, or an aliphatic amide or hydroxyamide [392], has been described. 

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. 

Aliphatic hydrocarbons, triazine, substituted urea type and phenoxyacetic acid types of herbicides, Fluazifop and Fluazifop-butyl herbicides, ethylene diamine tetracetic acid salts in soil, aliphatic and polyaromatic hydrocarbons, phthalate esters, various organosulphur compounds, triazine herbicides, optical whiteners, mixtures of organic compounds and organotin compounds in non-saline sediments, aromatic hydrocarbons, humic and fulvic acids and mixtures of organic compounds in saline sediments and non-ionic surfactants and cobalamin in sludges. 

Photolytic. The photodegradation rate of sulfotepp in water increased in the presence of humic acid. Under simulated sunlight, the half-lives of sulfotepp in water containing 10 and 100 mg/L of humic acid-potassium salt were 38.4 and 12.4 h, respectively (Jensen-Korte et al., 1987). 

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. 

Bad appearance. Turbidity is caused by suspended matter, which may contain disease-causing microorganisms. Discoloration that leaves stains can be caused by dissolved or colloidal iron, tannin, or humic acid from decaying vegetation, and excessive salt content. 

Maximized recovery of as many different organic compounds as possible is a primary goal of the RO concentration process. Potential losses of compounds can occur through (1) the permeate water stream, (2) volatile headspaces, (3) adsorption and absorption onto system components, and (4) binding or coprecipitation to or with other compounds such as humic acids or insoluble inorganic salts. Control of most if not all of these factors can be attained through the manipulation of process variables. 

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