Fractionation and trace metal content of a commercial humic acid

Gaskill, Alvia; Byrd, James T.; Shuman, Mark S.

doi:10.1080/10934527709374738

Cited by 5 publications

(9 citation statements)

References 7 publications

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“…The results showed a more adverse effect of hydrophobic HA on Fe precipitation in the As(V) system (Supplementary Figure S1B) than in the As(III) system (Supplementary Figure S1A). Our findings are consistent with those of previous studies [2,35] which suggested that a stronger inner sphere complexation of anionic ligands molecules with active Fe surface sites may enhance the Fe solubility in solution. In the current study, the As(V) system showed increased Fe solubility, which is related to its anionic ligand characteristics (H 2 AsO 4 − , HAsO 4 2− ) and the presence of negatively charged organic ligand molecules at neutral pH condition [2,36,37,38,39].…”

Section: Resultssupporting

confidence: 93%

“…The presence of various functional groups in hydrophobic/hydrophilic organic ligands may be responsible for such discrepant binding behavior of As species with HA and SA [9,34]. The existence of a trace amount of cationic metals in organic substances may also contribute toward a great variability in binding affinity of As(III, V) with organic molecules via ternary binding mechanisms [28,35]. Moreover, the speciation of As may also influence the complexation ability, since inorganic As(III) and As(V) species at the pH studied here (7.0 ± 0.1) exist in the forms of As(OH) 3 and (H 2 AsO 4 − , HAsO 4 2− ), respectively [2].…”

Section: Resultsmentioning

confidence: 99%

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Interaction of Arsenic Species with Organic Ligands: Competitive Removal from Water by Coagulation-Flocculation-Sedimentation (C/F/S)

et al. 2019

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The co-occurrence of arsenic (As) and organic ligands in water bodies has raised environmental concerns due to their toxicity and adverse effects on human health. The present study aims to elucidate the influences of hydrophobic/hydrophilic organic ligands, such as humic acid (HA) and salicylic acid (SA), on the interactive behavior of As species in water. Moreover, the competitive removal behaviors of As(III, V) species and total organic carbon (TOC) were systematically investigated by coagulation-flocculation-sedimentation (C/F/S) under various aqueous matrices. The results showed the stronger binding affinity of As(V) than As(III) species, with a higher complexation ability of hydrophobic ligands than hydrophilic. The media containing hydrophilic ligands require smaller ferric chloride (FC) doses to achieve the higher As(III, V) removal, while the optimum FC dose required for As(III) removal was found to be higher than that for As(V). Moreover, hydrophobic ligands showed higher TOC removal than hydrophilic ligands. The pronounced adverse effect of a higher concentration of hydrophobic ligands on the removal efficiencies of As(V) and TOC was observed. The adsorption of As(V) on Fe precipitates was better fitted with the Langmuir model but the Freundlich isotherm was more suitable for As(III) in the presence of hydrophilic SA. Moreover, TOC removal was substantially decreased in the As(V) system as compared to the As(III) system due to the dissolution of Fe precipitates at higher As(V) concentrations. The results of FC composite flocs demonstrated that the combined effect of oxidation, charge neutralization and adsorption played an important role in the removal of both toxicants during the C/F/S process. In summary, the findings of the present study provide insights into the fate, mobility and competitive removal behavior of As(III, V) species and organic ligands in the water treatment process.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Interaction of Arsenic Species with Organic Ligands: Competitive Removal from Water by Coagulation-Flocculation-Sedimentation (C/F/S)

et al. 2019

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“…22,23 Similarly, the separation and removal of HA using ion-exchange resins through an ultrafiltration system or the fractionation technique on the formation of complexes under the same mechanism have been shown. 24,25 Because of its complex structure and various functional components, such as carboxylate and phenolate groups, its adsorption-oriented application has been implemented in carboxyl-containing pesticides, biogenic amines in acetonitrile, and pesticides containing phosphorus in hexane. 26,27 Adsorption is regarded as occurring mainly because of complexation, π−π stacking between humic fraction (HF) and analyte, acid−base type of interaction in the case of an amine, and enhanced dipole−dipole interaction in hexane.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Because it contains various components (structurally), including quinone, phenol, catechol, and sugar moieties, numerical benefits, such as crop production and micronutrient transfer, exist and were proven experimentally and in the field . The application of HA for the removal of ions by forming chelate complexes has been shown. , Similarly, the separation and removal of HA using ion-exchange resins through an ultrafiltration system or the fractionation technique on the formation of complexes under the same mechanism have been shown. , Because of its complex structure and various functional components, such as carboxylate and phenolate groups, its adsorption-oriented application has been implemented in carboxyl-containing pesticides, biogenic amines in acetonitrile, and pesticides containing phosphorus in hexane. , Adsorption is regarded as occurring mainly because of complexation, π–π stacking between humic fraction (HF) and analyte, acid–base type of interaction in the case of an amine, and enhanced dipole–dipole interaction in hexane.…”

Section: Introductionmentioning

confidence: 99%

Adsorption and Desorption of Plasticizers with Humic-Fraction-Immobilized Silica Gel in Hexane: A Facile Approach to Pre-concentration

Lai

Chen

2013

J. Agric. Food Chem.

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Humic fraction (HF) collected under acidic conditions and used as an adsorbent for various phosphate-based plasticizers in hexane is immobilized on silica gel. Most plasticizer analytes examined in this study under the same conditions achieved adsorption percentages above 90% in 1 h based on the difference in peak area. The Fourier transform infrared (FTIR) spectroscopy results indicate that the interaction leading to the adsorptions between the functional moieties of the analyte and HF (e.g., the carboxylate group of analyte against the carboxyl group of HF) is specific, reversible, and dipole-dipole-oriented. Moreover, it is significantly enhanced by hexane. However, the π−π interaction (even hydrogen bonding in all cases) was either not as significant or absent in hexane and, therefore, contributed little or nothing to the percentage of adsorption. The interaction is highly affected by the acidic or basic origin of the additive introduced to the liquid phase of the matrix, and it is subject to the steric hindrance effect caused by the bulky alkyl groups attached to ether linkages and the relative position of the two ether bonds on the aromatic moiety of the analyte. The pre-concentration of the analyte and, thus, the recycle of the adsorbent can be achieved by adsorbing and, subsequently, desorbing it in a different solvent, such as acetonitrile. Furthermore, the adsorption process is surface-oriented because of its dependence upon both time and the amount of adsorbent.

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“…HA ●− can react with molecular oxygen by electron transfer to generate O 2 ●− , which can undergo disproportionation in water to generate hydrogen peroxide (H 2 O 2 ), Equation (1) [ 29 ]. Hydrogen peroxide can react with Fe(II) within HA materials [ 30 ] via Fenton and Fenton-like reactions to generate the hydroxyl radical (•OH), Equation (2) [ 31 , 32 ]. Although the formation of •OH can occur through photolysis via HA as shown in Equation (3), this pathway is typically not significant [ 24 , 27 , 29 , 31 , 32 , 33 ].…”

Section: Introductionmentioning

confidence: 99%

Removal of As(III) from Water Using the Adsorptive and Photocatalytic Properties of Humic Acid-Coated Magnetite Nanoparticles

et al. 2020

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The oxidation of highly toxic arsenite (As(III)) was studied using humic acid-coated magnetite nanoparticles (HA-MNP) as a photosensitizer. Detailed characterization of the HA-MNP was carried out before and after the photoinduced treatment of As(III) species. Upon irradiation of HA-MNP with 350 nm light, a portion of the As(III) species was oxidized to arsenate (As(V)) and was nearly quantitatively removed from the aqueous solution. The separation of As(III) from the aqueous solution is primarily driven by the strong adsorption of As(III) onto the HA-MNP. As(III) removals of 40–90% were achieved within 60 min depending on the amount of HA-MNP. The generation of reactive oxygen species (•OH and 1O2) and the triplet excited state of HA-MNP (3HA-MNP*) was monitored and quantified during HA-MNP photolysis. The results indicate 3HA-MNP* and/or singlet oxygen (1O2) depending on the reaction conditions are responsible for converting As(III) to less toxic As(V). The formation of 3HA-MNP* was quantified using the electron transfer probe 2,4,6-trimethylphenol (TMP). The formation rate of 3HA-MNP* was 8.0 ± 0.6 × 10−9 M s−1 at the TMP concentration of 50 µM and HA-MNP concentration of 1.0 g L−1. The easy preparation, capacity for triplet excited state and singlet oxygen production, and magnetic separation suggest HA-MNP has potential to be a photosensitizer for the remediation of arsenic (As) and other pollutants susceptible to advanced oxidation.

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Fractionation and trace metal content of a commercial humic acid

Cited by 5 publications

References 7 publications

Interaction of Arsenic Species with Organic Ligands: Competitive Removal from Water by Coagulation-Flocculation-Sedimentation (C/F/S)

Interaction of Arsenic Species with Organic Ligands: Competitive Removal from Water by Coagulation-Flocculation-Sedimentation (C/F/S)

Adsorption and Desorption of Plasticizers with Humic-Fraction-Immobilized Silica Gel in Hexane: A Facile Approach to Pre-concentration

Removal of As(III) from Water Using the Adsorptive and Photocatalytic Properties of Humic Acid-Coated Magnetite Nanoparticles

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