### Abstract

The diffusion coefficients of aquo metal ions (M^{z+}) and their EDTA complexes (M-EDTA^{(z-4)+}) were compared to understand the effect of EDTA complexation on the diffusion of metal ions by the diffusion cell method for Co^{2+}, Ga^{3+}, Rb^{+}, Sr^{2+}, Ag^{+}, Cd^{2+}, Cs^{+}, Th^{4+}, UO_{2}
^{2 +}, and trivalent lanthanides. Most studies about ionic diffusion in water have dealt with free ion (hydrated ion). In many cases, however, polyvalent ions are dissolved as complexed species in natural waters. Hence, we need to study the diffusion behavior of complexes in order to understand the diffusion phenomenon in natural aquifer and to measure speciation by diffusive gradient in thin films (DGT), which requires the diffusion coefficients of the species examined. For many ions, the diffusion coefficients of M-EDTA^{(z-4)+} are smaller than those of hydrated ions, but the diffusion coefficients of M-EDTA^{(z-4)+} are larger than those of hydrated ions for ions with high ionic potentials (Ga^{3+} and Th^{4+}). As a result, the diffusion coefficients of EDTA complexes are similar among various metal ions. In other words, the diffusion of each ion loses its characteristics by the complexation with EDTA. Although the difference is subtle, it was also found that the diffusion coefficients of EDTA complexes increase as the ionic potential increases, which can be explained by the size of the EDTA complex of each metal ion.

Original language | English |
---|---|

Pages (from-to) | 4416-4424 |

Number of pages | 9 |

Journal | Geochimica et Cosmochimica Acta |

Volume | 71 |

Issue number | 18 |

DOIs | |

Publication status | Published - Sep 15 2007 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Geochemistry and Petrology

### Cite this

*Geochimica et Cosmochimica Acta*,

*71*(18), 4416-4424. https://doi.org/10.1016/j.gca.2007.07.009

**Effect of the formation of EDTA complexes on the diffusion of metal ions in water.** / Furukawa, Kenji; Takahashi, Yoshio; Sato, Haruo.

Research output: Contribution to journal › Article

*Geochimica et Cosmochimica Acta*, vol. 71, no. 18, pp. 4416-4424. https://doi.org/10.1016/j.gca.2007.07.009

}

TY - JOUR

T1 - Effect of the formation of EDTA complexes on the diffusion of metal ions in water

AU - Furukawa, Kenji

AU - Takahashi, Yoshio

AU - Sato, Haruo

PY - 2007/9/15

Y1 - 2007/9/15

N2 - The diffusion coefficients of aquo metal ions (Mz+) and their EDTA complexes (M-EDTA(z-4)+) were compared to understand the effect of EDTA complexation on the diffusion of metal ions by the diffusion cell method for Co2+, Ga3+, Rb+, Sr2+, Ag+, Cd2+, Cs+, Th4+, UO2 2 +, and trivalent lanthanides. Most studies about ionic diffusion in water have dealt with free ion (hydrated ion). In many cases, however, polyvalent ions are dissolved as complexed species in natural waters. Hence, we need to study the diffusion behavior of complexes in order to understand the diffusion phenomenon in natural aquifer and to measure speciation by diffusive gradient in thin films (DGT), which requires the diffusion coefficients of the species examined. For many ions, the diffusion coefficients of M-EDTA(z-4)+ are smaller than those of hydrated ions, but the diffusion coefficients of M-EDTA(z-4)+ are larger than those of hydrated ions for ions with high ionic potentials (Ga3+ and Th4+). As a result, the diffusion coefficients of EDTA complexes are similar among various metal ions. In other words, the diffusion of each ion loses its characteristics by the complexation with EDTA. Although the difference is subtle, it was also found that the diffusion coefficients of EDTA complexes increase as the ionic potential increases, which can be explained by the size of the EDTA complex of each metal ion.

AB - The diffusion coefficients of aquo metal ions (Mz+) and their EDTA complexes (M-EDTA(z-4)+) were compared to understand the effect of EDTA complexation on the diffusion of metal ions by the diffusion cell method for Co2+, Ga3+, Rb+, Sr2+, Ag+, Cd2+, Cs+, Th4+, UO2 2 +, and trivalent lanthanides. Most studies about ionic diffusion in water have dealt with free ion (hydrated ion). In many cases, however, polyvalent ions are dissolved as complexed species in natural waters. Hence, we need to study the diffusion behavior of complexes in order to understand the diffusion phenomenon in natural aquifer and to measure speciation by diffusive gradient in thin films (DGT), which requires the diffusion coefficients of the species examined. For many ions, the diffusion coefficients of M-EDTA(z-4)+ are smaller than those of hydrated ions, but the diffusion coefficients of M-EDTA(z-4)+ are larger than those of hydrated ions for ions with high ionic potentials (Ga3+ and Th4+). As a result, the diffusion coefficients of EDTA complexes are similar among various metal ions. In other words, the diffusion of each ion loses its characteristics by the complexation with EDTA. Although the difference is subtle, it was also found that the diffusion coefficients of EDTA complexes increase as the ionic potential increases, which can be explained by the size of the EDTA complex of each metal ion.

UR - http://www.scopus.com/inward/record.url?scp=34548549047&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34548549047&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2007.07.009

DO - 10.1016/j.gca.2007.07.009

M3 - Article

AN - SCOPUS:34548549047

VL - 71

SP - 4416

EP - 4424

JO - Geochmica et Cosmochimica Acta

JF - Geochmica et Cosmochimica Acta

SN - 0016-7037

IS - 18

ER -