Polymers, humic

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. 

In the area of municipal and iadustrial wastewater treatment, the principal environmental issue is the toxicity of residual flocculating agents ia the effluent. Laboratory studies have shown that cationic polymers are toxic to fish because of the iateraction of these polymers with giU. membranes. Nonionic and anionic polymers show no toxicity (82,83). Other studies have shown that ia natural systems the suspended inorganic matter and humic substances substantially reduce the toxicity of added cationic polymer, and the polymers have been used successfully ia fish hatcheries (84—86). Based on these results, the EPA has added a protocol for testing these polymers for toxicity toward fish ia the presence of humic acids (87). The addition of anionic polymers to effluent streams containing cationic polymers to reduce their toxicity has been mentioned ia the patent Hterature (83). 

Lignite, generally leonardite, and lignite derivatives are appHed in water-based muds as thinners and filtration control agents. Leonardite is an oxidized lignite having a high content of humic acids, which may be described as carboxylated phenoHc polymers (59,60). Litde is known about the chemical stmcture. 

Prepai ative isolation of nonvolatile and semivolatile organic compounds fractions (hydrophobic weak acids, hydrophobic weak bases, hydrophobic neutrals, humic and fulvic acids) from natural and drinking waters in optimal conditions was systematically investigated by solid-phase extraction method with porous polymer sorbents followed by isolation from general concentrate of antropogenic and/or toxic semivolatile compounds produced in chlorination and ozonation processes. 

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 and the corresponding fulvic acid are complex polymers whose structures are incompletely resolved. It is accepted that the structure of humic acid contains oxygenated structures, including quinones that can function as electron acceptors, while reduced humic acid may carry out reductions. These have been observed both in the presence of bacteria that provide the electron mediator and in the absence of bacteria in abiotic reactions, for example, reductive dehalogenation of hexachloroethane and tetrachloromethane by anthrahydroquininone-2,6-disulfonate (Curtis and Reinhard 1994). Reductions using sulfide as electron donor have been noted in Chapter 1. Some experimental aspects are worth noting ... 

C-labeled 2,4-dichlorophenol bound to synthetic or natural humic acids or polymerized by HjOj and peroxidase was mineralized to CO2 only to a limited extent (<10%), and the greater part remained bound to the polymers (Dec et al. 1990). 

Restricted access phases are another approach to exploiting the differences in characteristics of analytes. Large analytes are excluded from an internal surface on which an adsorptive stationary phase is present. A herbicide analysis for Metsulfuron methyl, Bentazone, Bromoxynil, methylchlorophenoxy acid, and Mecoprop in the presence of humic acid was performed on restricted access reversed phase media.52 The cytostatic compound epirubicin and its metabolites were separated from plasma using a Pinkerton GFF II column.53 Gradient separations of polymers on reversed phase and on normal phase represent an alternative to gel permeation chromatography. Polyesters of noncrystalline materials were separated on a variety of such phases.54... 

Since lignins are polymers of phenolics and are major plant constituents with resistance to microbial decomposition, they are the primary source of phenolic units for humic acid synthesis (178, 179). Once transformed, these humic acids become further resistant to microbial attack and can become bound to soils (180) form interactions with other high molecular weight phenolic compounds (ex. lignins, fulvic acids) and with clays (181) and influence the biodegradation of other organic substrates in soils (182, 183). 

Shindo H, Huang PM (1985a) The catalytic power of inorganic components in the abiotic synthesis of hydroquinone-derived humic polymers. Appl Clay Sci 1 71-81... 

Wang MC, Huang PM (1986) Humic macromolecular interlayering in nontronite through interaction with phenol monomers. Nature (London) 323 529-531 Wang MC, Huang PM (1988) Catalytic power of nontronite, kaolinite, and quartz and their reaction sites in the formation of hydroquinone-derived polymers. Appl Clay Sci 4 43-57... 

Kopinke F, Georgi A, Mackenzie K (2001) Sorption of pyrene to dissolved humic substances and related model polymers. 1. Structure-property correlation. Envion Sci Technol 35 2536-2542... 

Chin, Y.-R, Weber, Jr., W.J. (1989) Estimating the effects of dispersed organic polymers on the sorption contaminants by natural solid, 1. A predictive thermodynamic humic substance-organic solute interaction model. Environ. Sci. Technol. 23, 978-984. 

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