Organocation speciation. I. A comparison of the interactions of methylene blue and paraquat with bentonite and humic acid

Guy, Robert D.; Narine, Deoraj R.; deSilva, S.

doi:10.1139/v80-085

Cited by 21 publications

(9 citation statements)

References 16 publications

(23 reference statements)

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“…1 The steep rise of the o6 curve beyond 6 mL g-' 0.1 N NaOH (Fig. 2) Chen et al 1977;' Guy et al 1980;Preston 1984;Preston and Schnitzer 1984). Posner (1964,1966) reported carboxy_l contents mostly from2.…”

Section: Results Ai\d Discussionmentioning

confidence: 92%

Titrations of Organic Soils With Standard Base: Solubility of Ionizable Functional Groups at 25 °c

Gamble¹

1989

Can. J. Soil. Sci.

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The conversion of undissolved acidic functional groups into dissolved carboxylate anions has been monitored during potentiometric titration of a Typic Mesisol Peat at 25 °C. The analytical chemical calculations of total acid functional groups and of H+ dissociation equilibrium functions take the dissolution process into account. With 0.05 g of sample suspended in 20 mL of 0.1 N NaCl, the molarity of carboxylate anions in the external solution ranged from 4.3 × 10−4 M at 1 mL g−1 0.1 N NaOH, to 1.5 × 10−3 M at 6 mL g−1 0.1 N NaOH. The corresponding amounts of undissolved carboxyl groups were 5.2 × 10−4 and 1.0 × 10−4 mol g−1. Differential acid constants (KGA) for the undissolved carboxyls were 7.6 × 10−4 (σ 1.4 × 10−4) for αG < 0.02 (0.016 – 0.02) and 1.4 × 10−5 (σ 0.04 × 10−5) for αG > 0.026 (0.026 – 0.60). A substantial increase in productivity was achieved by means of an automatic titrator and a microcomputer with spreadsheet software. Types of data production and processing that were previously labor intensive have now become much more practical. Key words: Organic soils, organic matter solubility, organic soil carboxyls, organic soil ion exchange, organic soil titration, pH dependent solubility

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Section: Results Ai\d Discussionmentioning

confidence: 92%

Titrations of Organic Soils With Standard Base: Solubility of Ionizable Functional Groups at 25 °c

Gamble¹

1989

Can. J. Soil. Sci.

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“…One of the principal conclusions of the model studies reported in Part B (9) was that as the ionic strength increases significant desorption would occur for MBlHA systems but no desorption for MBIbentonite systems. Figure 3 presents the re- sults of a degradation study as a function of NaCl concentration.…”

Section: Resultsmentioning

confidence: 99%

“…and methylene blue preparations were described in Part I of this series (9). The tryptophan (Eastman Kodak) was dissolved in NaOH and stored in the dark.…”

Section: Introductionmentioning

confidence: 99%

Organocation speciation. II. Methylene blue photosensitization as a model for speciation and toxicity of herbicides

Guy¹,

Narine²

1980

Can. J. Chem.

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Can. J. Chem. 58.555 (1980). A chemical model that employs the photosensitization properties of methylene blue to mimic herbicide toxicity is used to test size separation as a method of chemical speciation. A spectrophotometric study of the dye interactions with the humic colloid indicated that the dye -humic acid complex has a weaker absorption spectrum than the free dye. The absorption spectra suggested that the binding sites on the humic acid are sufficiently isolated to prevent dye-dye interactions on the colloid su~-fxe. The dye photosensitization of tryptophan degradation indicated that only the free methylene blue was active in the presence of humic acid. clay. and polystyrene sulphonic acid. The model suggests that if the pollutant must be in true solution to be biologically active then a size separation by dialysis would be a satisfactory speciation procedure.ROBERT D. GUY et DEORAJ R, NARINE. Can. J. Chem. 58,555 (1980). On a utilisk un modeie chimique qui fait appel aux proprietes photosensibilisatrices du bleu de methylkne dans ia toxicit6 de I'herbicide mimique, pour verifier la separation dimensionnelle comme une methode de determination de i'esptces chimique. Une etude spectrophotornetrique des interactions entre le colorant et le colloide humique icdique que le complexe colorant -acide humique a un spectre d'absorption plus faible que le colorant B l'ltat libre. Les spectres d'absorption suggkrent que les sites de liaison dans l'acide humique sont suffisamment isoles pour prevenir les interactions colorant-colorant a L a surface du colloide. La degradation du tryptophane phoiosensibilisee par le colorant indique que seu! le bleu de methyl&ne est actif en presence d'acide humique, d'argile et de l'acide polystyrene sulfonique. Le modele suggere que si le polluant doib se trouver rkellement en solution pour itre biologiquement actif la separation par dialyse peut &re satisfaisante commr mcthode de determination de I'espece.[Traduit par le journal]

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“…Fluorescence quenching techniques (McCarthy and Jimenez, 1985) are limited to compounds which are significantly fluorescent, and sorbent fluorescence may interfere with interpretation of results. Equilibrium dialysis has been used (Guy et al, 1980;Suffet, 1982, 1983;McCarthy and Jimenez, 1985) and is limited to HOC which can easily pass through dialysis bags. Landrum et al (1984) report difficulty in obtaining equilibrium in dialysis bags, measured over several days, and dialysis gave higher Koc than those found using reverse-phase liquid chromatography.…”

Section: Sorption Of Hoc To Soil Humic Acidmentioning

confidence: 99%

The role of colloidal organic matter in the marine geochemistry of PCBs

Brownawell¹

1986

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WITHDRAWN AD -sT~i~Bñ~c i~tZ4-2-ABSTRACT Polychlorinated biphenyls (PCBs) were used as model hydrophobic organic compounds (HOC) to study physical-chemical processes which affect the speciation and fate of HOC in coastal environments. The focus of this study is on the sorption of PCBs with colloidal organic matter in seawater, and the influence of this process on the distribution of PCBs in coastal sediments. Laboratory and field experiments were used to make quantitative estimates of PCB-organic matter sorption, and to test predictions of three-phase equilibrium models.A static headspace partitioning method was developed to measure the sorption of several individual chlorobiphenyls with colloidal organic matter enriched from coastal seawater by hollow fiber ultrafiltration. This technique directly measured the dissolved phase fugacity of PCBs in experimental bottles, and avoided uncertain separation techniques often used in isolating various chemical phases. Colloidal organic carbon normalized partition coefficients (Koc) were determined from linear sorption isotherms, and increased from 1.9 x 10' (L/Kg) for 2,4'-dichlorobiphenyl to 3.5 x 10 s for 2,2',3,4,5'-pentachlorobiphenyl. Sorption tended to increase with increasing octanol-water partition coefficients (Kow) of the sorbate, and values of Koc were within a range of those reported in other experimental sorption studies with sediments and dissolved humic substances. Experimental partitioning results support the hypothesis that HOC-organic colloid sorption is similar to HOC sorption by sediment organic matter.PCBs were measured in the interstitial waters and sediments of three box cores obtained from New Bedford Harbor and Buzzards Bay, Massachusetts. The three sites studied had a wide range of sediment PCB concentrations, and reducing conditions provided environments containing high concentrations of colloidal organic matter. Dissolved organic carbon (DOC) and total sediment organic carbon (TOC) were measured in two cores to test the role of organic matter on the observed partitioning of PCBs. PCB concentrations, particularly those of less soluble chlorobiphenyls, were highly elevated in interstitial waters compared to water column concentrations at all three sites. The measured apparent distribution coefficients (K'd) of individual chlorobiphenyls did not increase with hydrophobicity (Kow) and indicate that a large fraction of PCBs in interstitial waters must be sorbed to organic colloids. A three-phase equilibrium sorption model, in which dissolved PCBs are in a dynamic equilibrium with colloidal and sediment organic matter, accounts for many aspects of the field data. There is good agreement of observed partitioning at New Bedford Station 67 and Buzzards Bay Station M with model calculations based on predictions derived from laboratory experiments of HOC sorption with sediments and organic colloids, but model calculations underpredict K'd at Station 84 in New Bedford Harbor.-3-The sediment-interstitial water results were contrasted with a study of PCB pa...

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Organocation speciation. I. A comparison of the interactions of methylene blue and paraquat with bentonite and humic acid

Cited by 21 publications

References 16 publications

Titrations of Organic Soils With Standard Base: Solubility of Ionizable Functional Groups at 25 °c

Titrations of Organic Soils With Standard Base: Solubility of Ionizable Functional Groups at 25 °c

Organocation speciation. II. Methylene blue photosensitization as a model for speciation and toxicity of herbicides

The role of colloidal organic matter in the marine geochemistry of PCBs

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