Bidentate complexation modeling of heavy metal adsorption and competition on goethite

TY - JOUR

T1 - Bidentate complexation modeling of heavy metal adsorption and competition on goethite

AU - Xu, Ying

AU - Axe, Lisa

AU - Yee, Nathan

AU - Dyer, James A.

PY - 2006/4/1

Y1 - 2006/4/1

N2 - Accurate sorption modeling is critical for environmental risk assessment and development of sound remedial technologies. Adsorption to iron oxide phases is one of the important sorption processes regulating the bioavailability and toxicity of metal ions in natural systems. In this study, we used spectroscopically derived bidentate surface species to constrain surface complexation modeling in addressing Ni(II) and Zn(II) adsorption and competition on goethite surfaces. The 2-pKa triple layer model successfully predicted adsorption in single adsorbate systems. The curvature in adsorption isotherms was accurately depicted using two types of sites: high affinity and low affinity, and mononuclear bidentate surface complexes. A constrained set of parameters was found for each metal (log KL = -6.63 and log K H = -2.45 for Ni, log KL = -3.92 and log KH = 2.14 for Zn) that successfully described adsorption over a large range of experimental conditions, covering 6 to 7 orders of magnitude in concentration, ionic strength from 10-3 to 10-2, and environmentally relevant pH range between 4 and 6.5. Adsorption competition was predicted using the bidentate surface species with parameters calibrated using single adsorbate data.

AB - Accurate sorption modeling is critical for environmental risk assessment and development of sound remedial technologies. Adsorption to iron oxide phases is one of the important sorption processes regulating the bioavailability and toxicity of metal ions in natural systems. In this study, we used spectroscopically derived bidentate surface species to constrain surface complexation modeling in addressing Ni(II) and Zn(II) adsorption and competition on goethite surfaces. The 2-pKa triple layer model successfully predicted adsorption in single adsorbate systems. The curvature in adsorption isotherms was accurately depicted using two types of sites: high affinity and low affinity, and mononuclear bidentate surface complexes. A constrained set of parameters was found for each metal (log KL = -6.63 and log K H = -2.45 for Ni, log KL = -3.92 and log KH = 2.14 for Zn) that successfully described adsorption over a large range of experimental conditions, covering 6 to 7 orders of magnitude in concentration, ionic strength from 10-3 to 10-2, and environmentally relevant pH range between 4 and 6.5. Adsorption competition was predicted using the bidentate surface species with parameters calibrated using single adsorbate data.

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U2 - 10.1021/es051916e

DO - 10.1021/es051916e

M3 - Article

C2 - 16646455

SN - 0013-936X

VL - 40

SP - 2213

EP - 2218

JO - Environmental Science and Technology

JF - Environmental Science and Technology

IS - 7

ER -