Home > Research > Publications & Outputs > Use of DGT to measure cadmium speciation in sol...

Links

Text available via DOI:

View graph of relations

Use of DGT to measure cadmium speciation in solutions with synthetic and natural ligands : comparison with model predictions.

Research output: Contribution to Journal/MagazineJournal articlepeer-review

Published

Standard

Use of DGT to measure cadmium speciation in solutions with synthetic and natural ligands : comparison with model predictions. / Unsworth, Emily; Zhang, Hao; Davison, William.
In: Environmental Science and Technology, Vol. 39, No. 2, 15.01.2005, p. 624-630.

Research output: Contribution to Journal/MagazineJournal articlepeer-review

Harvard

APA

Vancouver

Unsworth E, Zhang H, Davison W. Use of DGT to measure cadmium speciation in solutions with synthetic and natural ligands : comparison with model predictions. Environmental Science and Technology. 2005 Jan 15;39(2):624-630. doi: 10.1021/es0488636

Author

Bibtex

@article{8b160c2250064425a5b37fb1e0d731ff,
title = "Use of DGT to measure cadmium speciation in solutions with synthetic and natural ligands : comparison with model predictions.",
abstract = "The performance of the technique of diffusive gradients in thin films (DGT) was characterized in well-defined systems containing cadmium with chloride and nitrate ions, simple organic ligands (nitrilotriacetic acid and diglycolic acid), and Suwannee river fulvic acid for the pH range 5−8. Cd was fully labile in all Cd, Cl-, and NO3- solutions tested (I = 0.1 and 0.01 M), even at very low Cd concentrations (10 nM), consistent with there being no binding of Cd to the diffusive gel. Diffusion coefficients of Cd−nitritotriacetic acid (NTA) and Cd−diglycolic acid (DGA) species were measured and found to be ca. 25−30% lower than the equivalent coefficient for free metal ions. These values were used to calculate concentrations of labile Cd from DGT measurements in solutions of Cd with NTA or DGA. Cd−NTA and Cd−DGA species were found to be fully DGT-labile. DGT devices that used a diffusive gel with a reduced pore size, which retarded the passage of fulvic acid species through the gel, were used to estimate the proportion of Cd complexed by fulvic acid. These results were compared with predictions of the solution speciation from models with default parameter values. ECOSAT, incorporating the NICA−Donnan model, correctly predicted the magnitude of the binding and its pH dependence, while predictions from WHAM V (with humic ion binding model V) and WHAM 6 (with humic ion binding model VI) were less satisfactory at predicting the pH dependence. Reasonable fits to the data could be obtained from WHAM 6 when the effective binding constant log KMA was changed from 1.6 to 1.5, the value of ΔLK1 from 2.8 to 1.0 to minimize the dependence on pH, and the value of ΔLK2 from 1.48 to1.0 to decrease the strength of the strong bidentate and tridentate binding sites.",
author = "Emily Unsworth and Hao Zhang and William Davison",
year = "2005",
month = jan,
day = "15",
doi = "10.1021/es0488636",
language = "English",
volume = "39",
pages = "624--630",
journal = "Environmental Science and Technology",
issn = "0013-936X",
publisher = "American Chemical Society",
number = "2",

}

RIS

TY - JOUR

T1 - Use of DGT to measure cadmium speciation in solutions with synthetic and natural ligands : comparison with model predictions.

AU - Unsworth, Emily

AU - Zhang, Hao

AU - Davison, William

PY - 2005/1/15

Y1 - 2005/1/15

N2 - The performance of the technique of diffusive gradients in thin films (DGT) was characterized in well-defined systems containing cadmium with chloride and nitrate ions, simple organic ligands (nitrilotriacetic acid and diglycolic acid), and Suwannee river fulvic acid for the pH range 5−8. Cd was fully labile in all Cd, Cl-, and NO3- solutions tested (I = 0.1 and 0.01 M), even at very low Cd concentrations (10 nM), consistent with there being no binding of Cd to the diffusive gel. Diffusion coefficients of Cd−nitritotriacetic acid (NTA) and Cd−diglycolic acid (DGA) species were measured and found to be ca. 25−30% lower than the equivalent coefficient for free metal ions. These values were used to calculate concentrations of labile Cd from DGT measurements in solutions of Cd with NTA or DGA. Cd−NTA and Cd−DGA species were found to be fully DGT-labile. DGT devices that used a diffusive gel with a reduced pore size, which retarded the passage of fulvic acid species through the gel, were used to estimate the proportion of Cd complexed by fulvic acid. These results were compared with predictions of the solution speciation from models with default parameter values. ECOSAT, incorporating the NICA−Donnan model, correctly predicted the magnitude of the binding and its pH dependence, while predictions from WHAM V (with humic ion binding model V) and WHAM 6 (with humic ion binding model VI) were less satisfactory at predicting the pH dependence. Reasonable fits to the data could be obtained from WHAM 6 when the effective binding constant log KMA was changed from 1.6 to 1.5, the value of ΔLK1 from 2.8 to 1.0 to minimize the dependence on pH, and the value of ΔLK2 from 1.48 to1.0 to decrease the strength of the strong bidentate and tridentate binding sites.

AB - The performance of the technique of diffusive gradients in thin films (DGT) was characterized in well-defined systems containing cadmium with chloride and nitrate ions, simple organic ligands (nitrilotriacetic acid and diglycolic acid), and Suwannee river fulvic acid for the pH range 5−8. Cd was fully labile in all Cd, Cl-, and NO3- solutions tested (I = 0.1 and 0.01 M), even at very low Cd concentrations (10 nM), consistent with there being no binding of Cd to the diffusive gel. Diffusion coefficients of Cd−nitritotriacetic acid (NTA) and Cd−diglycolic acid (DGA) species were measured and found to be ca. 25−30% lower than the equivalent coefficient for free metal ions. These values were used to calculate concentrations of labile Cd from DGT measurements in solutions of Cd with NTA or DGA. Cd−NTA and Cd−DGA species were found to be fully DGT-labile. DGT devices that used a diffusive gel with a reduced pore size, which retarded the passage of fulvic acid species through the gel, were used to estimate the proportion of Cd complexed by fulvic acid. These results were compared with predictions of the solution speciation from models with default parameter values. ECOSAT, incorporating the NICA−Donnan model, correctly predicted the magnitude of the binding and its pH dependence, while predictions from WHAM V (with humic ion binding model V) and WHAM 6 (with humic ion binding model VI) were less satisfactory at predicting the pH dependence. Reasonable fits to the data could be obtained from WHAM 6 when the effective binding constant log KMA was changed from 1.6 to 1.5, the value of ΔLK1 from 2.8 to 1.0 to minimize the dependence on pH, and the value of ΔLK2 from 1.48 to1.0 to decrease the strength of the strong bidentate and tridentate binding sites.

U2 - 10.1021/es0488636

DO - 10.1021/es0488636

M3 - Journal article

VL - 39

SP - 624

EP - 630

JO - Environmental Science and Technology

JF - Environmental Science and Technology

SN - 0013-936X

IS - 2

ER -