Calcium binding by fulvic acids studied by an ion selective electrode an ultrafiltration method

Mathuthu, A.S.; Ephraim, James H.

doi:10.1016/0039-9140(93)80011-f

Cited by 22 publications

(9 citation statements)

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“…Table 6 presents the Ca 2+ -humic stability constants from the literature, with the log β values at 0.10 m (NaCl) from this work. The latter are in good agreement with the log β values from references [29][30][31]. Higgo et al [32] reported a value at I = 0.01 M (NaCl) of 2.15 ± 0.02; however, their stability constant is expressed in l/g.…”

Section: Resultssupporting

confidence: 84%

“…It has been described as a weak electrostatic association by Mathuthu et al [31], and Lead et al [11] (comparable to Na + -HA interaction), or as an intrinsic/specific association where Ca 2+ is in direct competition for the binding sites with other metallic cations [11,34]. Our values correspond to stronger interactions and indicate that Ca 2+ binding to humics can compete with actinide binding in natural waters which have relatively high Ca 2+ contents.…”

Section: Resultssupporting

confidence: 72%

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Interaction study between Ca²⁺ and humic acids in brine media

Laszak¹,

Choppin²

2001

Radiochimica Acta

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Section: Resultssupporting

confidence: 84%

Section: Resultssupporting

confidence: 72%

Interaction study between Ca²⁺ and humic acids in brine media

Laszak¹,

Choppin²

2001

Radiochimica Acta

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“…It may be noted that FA did not affect the uptake of Ca 2þ by BCES-DGT for the mass ratios of Ca 2þ /FA from 1:1 to 1:50, showing satisfactory ratios of C DGT /C SOLN from 1.012 AE 0.047 to 0.907 AE 0.061. There was a severe interference on Ca 2þ uptake by BCES-DGT after the mass ratio of Ca 2þ /FA 1:50, with low values of C DGT / C SOLN from 0.752 AE 0.045 to 0.237 AE 0.026 due to the tendency for binding between Ca 2þ and FA being dependent on the ratio of Ca 2þ /FA (Mathuthu and Ephraim 1993).…”

Section: Effect Of Famentioning

confidence: 98%

In-situ sampling of available calcium using diffusive gradients in thin-films technique based on benzo-crown ether-functionalised silica as the binding agent

You

Cao

et al. 2018

Environ. Chem.

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Environmental contextLow availability of calcium (Ca2+) in soils is one of the major factors in Ca2+ deficiency of plants and physiological plant disorders. A device based on functionalised silica was developed for in-situ measurement of the available Ca2+ in soils. Application of the proposed device to measure available Ca2+ may help to develop and improve agricultural practices. AbstractCalcium is an ion of particular interest due to its importance in plant nutrition and soil structure. A novel device of diffusion gradients in thin-films (DGT) based on the benzo-crown ether-functionalised silica (BCES) as the binding agent and the polyethersulfone (PES) membrane as diffusive layer (BCES-DGT) was developed for in-situ sampling of available calcium (Ca2+) in freshwater and soil samples. The performance characteristics of the BCES-DGT device were assessed. The BCES was prepared using the sol-gel process and characterised by Fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric analysis and N2 adsorption–desorption. Results evinced that BCES was obtained successfully with a rough wrinkled surface and good specific surface area of 111.3 m2 g−1. The diffusion coefficient of Ca2+ ions in PES membrane was found to be 1.23 × 10−6 cm2 s−1 at 25 °C and was independent of pH in the range of 3–10 and ionic strength (as pNaCl) from 1 to 3. The high binding capacity of BCES binding gel for Ca2+ ions was determined to be 9822.4 ± 452.9 μg Ca2+/disk and was conducive to the deployment of long-term or high concentration. The BCES-DGT device can accurately measure the concentrations of Ca2+ over wide ranges of ionic strengths (1–3 as pNaCl) and pH (5–10). There was no significant interference on the uptake of Ca2+ by the BCES-DGT device at the tolerance limits up to 500 for Mg2+, Li+, HCO3−, H2PO4−, NO3− and SO42−, 250 for Sr2+, 2000 for K+ and 50 for fulvic acid. The results from BCES-DGT device were in excellent agreement with those measured directly using ion selective electrode in several water and soil samples. Field application in river water indicated that a good agreement was obtained between BCES-DGT value and mean grab sample measurements of Ca2+ and that the relative standard deviation of BCES-DGT measurement (4.7 %) was superior to that of grab sample measurements (13.5 %), suggesting that BCES-DGT was reliable for in-situ sampling and measurement of available Ca2+ with good accuracy and precision.

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“…30 Indeed, pH and ionic strength both have a dramatic effect on the speciation of dissolved metal ions in the presence of dissolved organic matter, such as humic acids. 11,[31][32][33][34][35] Therefore, the determination of labile species of Fe(II)-SWEOM complexes under seawater conditions (pH 8, I = 0.7) is needed to realistically evaluate contributions of the fertilizer to their bioavailability. FZ colorimetry has been employed for the analysis of Fe(II) in seawater after reducing the total iron to ferrous forms and adjusting the pH to 4 -6.…”

Section: Introductionmentioning

confidence: 99%

Determination of Labile Fe(II) Species Complexed with Seawater Extractable Organic Matter Under Seawater Conditions Based on the Kinetics of Ligand-exchange Reactions with Ferrozine

2013

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Barren ground is a phenomenon associated with the depletion of seaweed in coastal areas. The development of barren ground has been attributed to a lack of soluble Fe (<1 nM), 1 which is an essential micronutrient for the growth of algae. 2,3 In macroalgae, the uptake of soluble iron is required for the gametophyte to produce an oogonium or an antheridium, 4-7 and a sporophyte is formed from the matured gametophyte. 3 Thus, a lack of dissolved Fe in coastal area seawater can lead to seaweed depletion. It is known that natural organic matter plays an important role in the mobility, solubility and bioavailability of trace metals in terrestrial and aquatic environments. 2,[8][9][10][11][12] In seawater, the majority of dissolved ferric (Fe(III)) and ferrous (Fe(II)) species are present in the form of complexes with dissolved organic matter. 2,[13][14][15] Based on this, a fertilizer comprised of a steel slag and compost was tested for its ability to supply dissolved Fe to barren coastal areas, and this attempt was successful and resulted in the restoration of seaweed beds. 16 In this technique, seawater extractable organic matter (SWEOM) from the compost serves as a chelator of Fe and allows for its elution from the steel slag. 17,18 Fe(III)-oxides are found on the surface of the steel slag, 19 and can be reduced to soluble Fe(II) species in the presence of dissolved organic matter. 20 It has been reported that all of the reduced Fe(II) species are complexed with dissolved organic matter. 21 Therefore, the nature of the complex produced between SWEOM and Fe(II) need to be evaluated to better understand the performance of such fertilizers.On the other hand, estimating the bioavailability of a metal to aquatic biota is an important approach. 22,23 The kinetic stability of complexes is a key factor in determining the bioavailability of metal species. 2,3,22,24,25 Readily dissociable complexes (labile species) are the likely primary source of soluble iron for algae. 2,19,[26][27][28] A key factor in the uptake of Fe(II) involves ligand-exchange reactions between dissolved organic matter and receptor proteins on the cell-membrane. 2 The kinetics of ligand-exchange reactions of Fe(II)-humic acid complexes have been investigated using ortho-phenanthroline or ferrozine (FZ) as models of receptor proteins, 17,29 although the conditions (pH 3.6 or 5, I = 0.02) were far from those for seawater (pH 8, I = 0.7). To investigate the contribution of SWEOM as a chelator of Fe, it should be examined that the complexation ability under the conditions of seawater. However, it is difficult to determine both free and complex species of Fe(II) at higher pH and ionic strength levels because Fe(II) is readily oxidized to insoluble Fe(III)-hydroxides, which precipitates from the solution. 30 Indeed, pH and ionic strength both have a dramatic 2013 © The Japan Society for Analytical Chemistry † To whom correspondence should be addressed. Experimental MaterialsAmmonium iron(II) sulfate hexahydrate (Fe(SO4)2(NH4)2·6H2O), tris(hydroxymethyl)ami...

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Calcium binding by fulvic acids studied by an ion selective electrode an ultrafiltration method

Cited by 22 publications

References 12 publications

Interaction study between Ca²⁺ and humic acids in brine media

Interaction study between Ca²⁺ and humic acids in brine media

In-situ sampling of available calcium using diffusive gradients in thin-films technique based on benzo-crown ether-functionalised silica as the binding agent

Determination of Labile Fe(II) Species Complexed with Seawater Extractable Organic Matter Under Seawater Conditions Based on the Kinetics of Ligand-exchange Reactions with Ferrozine

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Calcium binding by fulvic acids studied by an ion selective electrode an ultrafiltration method

Cited by 22 publications

References 12 publications

Interaction study between Ca2+ and humic acids in brine media

Interaction study between Ca2+ and humic acids in brine media

In-situ sampling of available calcium using diffusive gradients in thin-films technique based on benzo-crown ether-functionalised silica as the binding agent

Determination of Labile Fe(II) Species Complexed with Seawater Extractable Organic Matter Under Seawater Conditions Based on the Kinetics of Ligand-exchange Reactions with Ferrozine

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Interaction study between Ca²⁺ and humic acids in brine media

Interaction study between Ca²⁺ and humic acids in brine media