Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter

Ritchie, Jason D.; Perdue, Edward M.

doi:10.1016/s0016-7037(02)01044-x

Cited by 604 publications

(459 citation statements)

References 75 publications

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“…For the SRHA, a binding site concentration of 4.9 × 10 -3 mol g -1 was taken from the literature (18). On the basis of the titration curves, >95% of the polysaccharide binding sites (COOH) were deprotonated under the studied conditions (pH ) 6.0, I ) 5 × 10 -3 M), while for SRHA this proportion was about 80% (32).…”

Section: Resultsmentioning

confidence: 94%

Influence of the Composition of Natural Organic Matter on Pb Bioavailability to Microalgae

Lamelas

Wilkinson

Slaveykova

2005

Environ. Sci. Technol.

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The current work examines the effects of model allochtonous (humic substances) and autochtonous (microbial polysaccharides) natural organic matter (NOM) on Pb speciation and bioaccumulation. The results demonstrated that polysaccharides, in particular alginic acid, had complexing properties and effects on Pb bioaccumulation by the green alga Chlorella kesslerii that were similar to equivalent complexing capacity of humic substances. Pb uptake decreased in the presence of humic, alginic, and polygalacturonic acids with respect to noncomplexed Pb, but accumulated Pb was higher than predicted from measured Pb 2+ concentrations or from previous results obtained in the presence of simple synthetic ligands. An improved fit between experimental observations and Pb speciation was obtained by taking into account the formation of a ternary complex at the algal surface. The contribution of the ternary complexes to Pb bioaccumulation was dependent on the relative binding constants of the Pb to the NOM and to the binding sites on the biological surface. In the presence of the humic acid, a decreased surface charge and increased membrane permeability were considered to be of secondary importance to explain the observation of increased Pb uptake with respect to that predicted on the basis of [Pb 2+ ]. The environmental implications of the results are discussed with respect to the development of site-specific water quality criteria.

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Section: Resultsmentioning

confidence: 94%

Influence of the Composition of Natural Organic Matter on Pb Bioavailability to Microalgae

Lamelas

Wilkinson

Slaveykova

2005

Environ. Sci. Technol.

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“…HS are composed of amorphous, chemically complex and internally structured molecules or molecular aggregates (Avena and Wilkinson, 2002;Sutton and Sposito, 2005) with a polyelectrolyte nature that can be classified as softcolloidal matter (Duval et al, 2005). The charge density of HS depends on the pH and at the pH conditions in most natural waters HS are negatively charged (Milne et al, 1995;Ritchie and Perdue, 2003). The charge density of humic particles is a dominant factor for the interactions of HS with: (1) heavy metal ions (Milne et al, 2003;Koopal et al, 2005;Merdy et al, 2006), (2) oppositely charged polyelectrolytes (Bolto et al, 1999;Kam and Gregory, 2001;Hankins et al, 2006), (3) proteins (Tan et al, 2008(Tan et al, , 2009), (4) cationic surfactants Yee et al, 2006;Ishiguro et al, 2007) and (5) mineral surfaces Filius et al, 2000;Saito et al, 2004;Weng et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Humic substance charge determination by titration with a flexible cationic polyelectrolyte

Tan

Norde

Koopal

2011

Geochimica et Cosmochimica Acta

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“…In terms of the value of the pK 1 of LSLHA, determined [7] to be 3.89, lowering the pH to 2.5 for solubility reversal corresponds to the carboxyl groups of the material being approximately 96% protonated.…”

Section: Ph Adjustmentmentioning

confidence: 99%

“…The pKa of LSLHA was determined by titrating 125 mL of 40 mg/L LSLHA with a carbonate-free 0.04 M NaOH solution, held at 22 ∘ C under nitrogen [7]. After dissolution of the HA sample with a minimal amount of base, the solution was acidified to pH 2.5 with HCl prior to titration.…”

Section: Pkamentioning

confidence: 99%

Temperature Induced Aggregation and Clouding in Humic Acid Solutions

Shaffer

Wandruszka

2015

Advances in Environmental Chemistry

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Humic acids in aqueous solution demonstrate inverse temperature-solubility relationships when solution conditions are manipulated to reduce coulombic repulsion among the humic polyanions. These effects were followed by dynamic light scattering (DLS) measurements of the resulting aggregates, as well as the addition of a polarity sensitive fluorescent probe (pyrene). The humic solutions could be primed for temperature induced clouding by carefully lowering the pH to a point where hydration effects became dominant. The exact value of the cloud point (CP) was a function of both pH and humate concentration. The CPs mostly lay in the range 50-90 ∘ C, but DLS showed that temperature induced aggregation proceeded from approximately 30 ∘ C onward. Similar effects could be achieved by adding multivalent cations at concentrations below those which cause spontaneous precipitation. The declouding of clouded humate solutions could be affected by lowering the temperature combined with mechanical agitation to disentangle the humic polymers.

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Proton-binding study of standard and reference fulvic acids, humic acids, and natural organic matter

Cited by 604 publications

References 75 publications

Influence of the Composition of Natural Organic Matter on Pb Bioavailability to Microalgae

Influence of the Composition of Natural Organic Matter on Pb Bioavailability to Microalgae

Humic substance charge determination by titration with a flexible cationic polyelectrolyte

Temperature Induced Aggregation and Clouding in Humic Acid Solutions

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