Analysis of Copper Binding in the Ternary System Cu2+/Humic Acid/Goethite at Neutral to Acidic pH

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• 作者：Takumi Saito ; Luuk K. Koopal ; Shinya Nagasaki ; and Satoru Tanaka
• 刊名：Environmental Science & Technology
• 出版年：2005
• 出版时间：July 1, 2005
• 年：2005
• 卷：39
• 期：13
• 页码：4886 - 4893
• 全文大小：158K
• 年卷期：v.39,no.13(July 1, 2005)
• ISSN：1520-5851

文摘

Binding of heavy metal and actinide ions to naturalcolloids, such as humic substances (HSs) and metal (hydr)oxides, plays an important role in the ecotoxicologicalbehavior of these ions. Several thermodynamic models havebeen constructed to predict the speciation of these ionsin metal/HS or metal/oxide binary systems. However, in naturalenvironments the adsorption of HSs on oxides caninfluence the binding of target metals, leading to deviationfrom the additivity of calibrated binary models. In thisstudy binding of copper (Cu²⁺) to the purified Aldrich humicacid (PAHA)/goethite complex in the neutral to acidic pHregion was investigated by measuring Cu²⁺ binding isotherms.The measured isotherms were compared with theresults obtained for the binary systems under similarconditions. The comparison revealed that Cu²⁺ binding inthe ternary system is enhanced with respect to thesum of Cu²⁺ binding in the corresponding binary systems.From the analysis of the charging behavior of the adsorbedPAHA as well as the smeared-out potential profile near thePAHA/goethite interface, the increase of Cu²⁺ binding tothe complex was mainly attributed to the decrease of protoncompetition to the functional groups of the adsorbedPAHA and the change of the electrostatic potential in thevicinity of the goethite surface.