A Study of the Mechanism of Atrazine Adsorption by Humic Acid From Muck Soil

Li, Gwo-Chen; Felbeck, George T.

doi:10.1097/00010694-197202000-00010

Cited by 45 publications

(31 citation statements)

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“…Humic and fulvic acids have been observed to favor the hydrolysis of triazine molecules (164). In a recent study, Gamble and Khan (165) obtained experimental results that improved the knowledge of the mechanism of humic substance catalytic action.…”

Section: Adsorption and Degradation Of Organic Chemicalsmentioning

confidence: 99%

Adsorption of Organic Chemicals in Soils

Calvet¹

1989

Environmental Health Perspectives

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This paper presents a review on adsorption of organic chemicals on soils sediments and their constituents. The first part of this review deals with adsorption from gas and liquid phases and gives a discussion on the physical meaning of the shape of adsorption isotherms. Results show that no general rules can be proposed to describe univocally the relation between the shape of isotherms and the nature of adsorbateadsorbent system. Kinetics of adsorption is discussed through the description of various models.Theoretical developments exist both for the thermodynamics and the kinetics of adsorption, but there is a strong need for experimental results. Possible adsorption mechanisms are ion exchange, interaction with metallic cations, hydrogen bonds, charge transfers, and London-van der Waals dispersion forces/ hydrophobic effect. However, direct proofs of a given mechanism are rare. Several factors influence adsorption behavior. Electronic structure of adsorbed molecules, properties of adsorbents, and characteristics of the liquid phase are discussed in relation to adsorption. Such properties as water solubility, organic carbon content of adsorbing materials, and the composition of the liquid phase are particularly important. Evaluation of adsorption can be obtained through either laboratory measurements or use of several correlations. Adsorption measurements must be interpreted, taking into account treatment of adsorbent materials, experimental conditions, and secondary phenomena such as degradations. Correlations between adsorption coefficients and water-octanol partition coefficient or water solubility are numerous. They may be useful tools for prediction purposes. Relations with transport, bioavailability, and degradation are described.

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Section: Adsorption and Degradation Of Organic Chemicalsmentioning

confidence: 99%

Adsorption of Organic Chemicals in Soils

Calvet¹

1989

Environmental Health Perspectives

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“…A review of Stevenson for example (2), presents evidence for this accumulated since 1962 (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). A number of authors have consequently investigated the interactions of organic pesticides with humic materials (5,7,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). The acidic functional groups of humic materials are an important factor (32,(34)(35)(36)(37)(38), 'Contribution NO.…”

Section: Introductionmentioning

confidence: 99%

Atrazine hydrolysis in aqueous suspensions of humic acid at 25.0 °C

Gamble¹,

Khan²

1988

Can. J. Chem.

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. J. Chem. 66,2605Chem. 66, (1988.The acidic properties of a Chemozemic humic acid were determined by equilibrium titration. The number of carboxyl groups is 2.828 (mmol/g) ? 0.5%. The results were used for an investigation of Bronsted acid catalysis of atrazine hydrolysis by a suspension of the humic acid. There is sufficient sorption so that the rates of change of atrazine and product hydroxyatrazine in solution differ both from each other and form the rate of atrazine conversion on the catalytic sites. An important objective of this work was the separate determination of the sorption equilibrium constants for atrazine and hydroxyatrazine, and the rate constant for atrazine conversion on the catalytic sites. All three constants are relevant to environmental research. The apparent rate constants for changes in solution are experimental artifacts however, not useful for such research. calculated-in terms of carboxyl sorption sites in the free acid form, the sorption equilibrium constants were 1.74 X lo2, CJ = 0.03 X 10' and 8.5 x lo2, a = 2.3 X lo2, for atrazine and hydroxyatrazine, respectively. The rate constant for conversion on catalytic sites ranges from 1.8 X lo-' day-' k 20% to 2.9 X lo-' day-' r 20%, for atrazine coverage of sites from 9.0 ( p,mol/g) to 1.0 ( p,mol/g).

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“…Reduced mobility and biocidal activity due to bonding to humic substances are often described (5)(6)(7)(8). It is in some cases supported by various experimental results, that parent molecules or metabolites are bound to the humic matrix either by covalent bonding (9)(10)(11)(12)(13)(14)(15)(16)51), ionic bonding (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28), charge transfer complexes (29)(30)(31)(32)(33), ligand exchange (34,35), hydrogen bonding (23,31,(36)(37)(38)(39)(40), van der Waals forces (22,(41)(42)(43)(44), hydrophobic sorption (45)(46)(47)(48)(49)…”

Section: Comission On Pesticide Chemistrymentioning

confidence: 88%