Evaluation of Copper(II) Binding Abilities of Humic Substances by a Continuous Site-Distribution Model Considering Proton Competition

Fukushima, Masami; Tanaka, Shunitz; Nakayasu, Ken; Sasaki, Keiko; Takagi, Kenji

doi:10.2116/analsci.15.185

Cited by 12 publications

(4 citation statements)

References 13 publications

(26 reference statements)

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“…Carboxylic acids and phenolic hydroxyl groups, oxygen-containing groups, are known to be major binding sites for Fe in natural organic matter, such as humic substances. 14,29,33 The BC value for LMW was significantly larger than those for NMW and HMW, being consistent with the trend in level of acidic functional groups in SWEOM samples (Table S1). Based on the HSBA principle, oxygen-containing groups are classified as hard bases, 14,46 and Fe(II) is classified as a borderline acid.…”

Section: Complexing Abilities Of Sweoms To Form Labile Complexes Withsupporting

confidence: 80%

“…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%

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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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Section: Complexing Abilities Of Sweoms To Form Labile Complexes Withsupporting

confidence: 80%

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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“…14 The characteristics of SWEOM, HA and FA are summarized in Tables S1 and S2 of Supporting Information.…”

Section: Ha and Famentioning

confidence: 99%

Binding Characteristics and Dissociation Kinetics for Iron(II) Complexes with Seawater Extractable Organic Matter and Humic Substances in a Compost

2012

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A steel-slag/compost fertilizer can be useful in supplying complex Fe(II) species to barren coastal regions. Seawater extractable organic matter (SWEOM) was examined for use as a novel chelator of Fe(II) in the compost. The dissociation kinetics for Fe(II)-SWEOM were evaluated, based on the rate of ligand-exchange with ortho-phenanthroline. The ΔH for the Fe(II)-SWEOM (19 kJ mol -1 ) was significantly smaller than the corresponding values for Fe(II) complexes with humic substances (27 kJ mol -1 ), suggesting that the Fe(II)-SWEOM is kinetically less stable.

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“…These results obtained are in conformity with the literature. 22,23 Analytical results of water samples Analyses of the water samples collected from Sultansazlıgı during the months of October 1995 and March 1996 were examined according to a procedure; the details of which were mentioned above (see Fig. 1).…”

Section: Effect Of Phmentioning

confidence: 99%

Speciation and Determination of Heavy Metals in Lake Waters by Atomic Absorption Spectrometry after Sorption on Amberlite XAD-16 Resin

2000

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The trace heavy metals existing in freshwaters are present in various physico-chemical forms, which include simple hydrated ions, hydroxo complexes, inorganic and organic complexes, and colloidal particles. 1 These physico-chemical forms can effectively change their bioavailabilities and toxicities. For example, chromium(III) is an essential element, whereas chromium(VI) is highly toxic and even carcinogenic. Arsenic(III) is much more toxic than arsenic(V).2,3 The heavy metal speciation, therefore, arouses substantial interest in water analysis because the geochemical behavior and biological effects of heavy metals depend greatly on their physicochemical forms. The chemical speciation has been a topic of increasing research interest in geochemical, biological and environmental sciences, and waste water treatment processes.Humic and fulvic acids are also known to interact with various metal ions, hydrated metal oxides, clay minerals and organic compounds. 1 Humic substances, major organic constituents of natural waters, interact strongly with various heavy metals to form humic complexes and affect adsorption-desorption behavior of metals. Physico-chemical forms of metal humic-complexes, however, are complicated because they may exist alone or be adsorbed on other colloidal particles. 4 Up to now, methods such as coprecipitation, 5,6 sorption on adsorbent resins 7-10 and separation by ion exchange resins 4,11,12 have been used in determining metal ions both free and bound to humic substances present in natural and waste waters. Among these techniques used in trace element determination, adsorption is one of the most widely used. For this purpose, commercially available Amberlite XAD copolymers [13][14][15][16] have been widely used as adsorbents suitable for multielement preconcentration from different matrices, because of their purity and good adsorption properties. Amberlite XAD-16 resin is an adsorbent based on polystyrene divinylbenzene-copolymer. It is used in continuous filtration for adsorption of water-soluble substances. XAD-16 has excellent physical resistance, hydraulic characteristics and thermal stability. In addition, it has high porosity, low polarity and the largest surface area (825 m 2 g -1 ) among the XAD series of Amberlite resins. Therefore, it was selected as an adsorbent resin, owing to these high performance characteristics. But it can show little swelling/shrinking upon changing between organic solvent and aqueous media (Rohm and Haas Co.).In the present work, determinations were carried out of metals bound to humic substances and to suspended particles, and of the free metal ions in water samples taken from different regions of Sultansazlıg ı, a wetland and wildlife refuge. Due to very low metal contents of natural water samples to be analyzed, enrichment procedures are often required. A column filled with Amberlite XAD-16 resin as a preconcentration means was used to determine the metals bound to humic substances and free metal ions. The measurements of the metal concentrations were pe...

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Evaluation of Copper(II) Binding Abilities of Humic Substances by a Continuous Site-Distribution Model Considering Proton Competition

Abstract: Humic substances (HSs), which are widely distributed in soils and natural water, are deeply related to the transportation and accumulation of heavy metal ions.

Cited by 12 publications

References 13 publications

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

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

Binding Characteristics and Dissociation Kinetics for Iron(II) Complexes with Seawater Extractable Organic Matter and Humic Substances in a Compost

Speciation and Determination of Heavy Metals in Lake Waters by Atomic Absorption Spectrometry after Sorption on Amberlite XAD-16 Resin

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