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| The adsorption of Cd to iron oxide/water interface: The CD-MUSIC modeling |
| Received:May 07, 2018 |
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| KeyWord:iron oxide;goethite;hematite;Cd adsorption;CD-MUSIC model;speciation distribution |
| Author Name | Affiliation | E-mail | | XIONG Juan | College of Environment and Resoure, Huazhong Agricultural University, Wuhan 430070, China | | | YANG Cheng-feng | College of Environment and Resoure, Huazhong Agricultural University, Wuhan 430070, China | | | CHEN Xin-rui | College of Environment and Resoure, Huazhong Agricultural University, Wuhan 430070, China | | | WANG Ming-xia | College of Environment and Resoure, Huazhong Agricultural University, Wuhan 430070, China | wangmx@mail.hzau.edu.cn | | TAN Wen-feng | College of Environment and Resoure, Huazhong Agricultural University, Wuhan 430070, China | |
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| Abstract: |
| In this study, the effect of pH and Cd concentration on the adsorption of Cd to the goethite and hematite was investigated by the pH-edge adsorption experiments and the CD-MUSIC modeling with the calculation of speciation distribution. The results showed that the amount and density of the Cd adsorption to the goethite was higher than that to the hematite, and with the increasing of the pH and Cd concentrations it increased for both goethite and hematite. The CD-MUSIC model taking into account the species (FeOH)2Cd+1 and (FeOH)2CdOH0 could describe the adsorption of Cd to the iron oxide satisfactorily. The affinity constant of the (FeOH)2Cd+1 and (FeOH)2CdOH0 were 7.3, 12.8 and 6.1, 11.0 for goethite and hematite, respectively. The calculation of the CD-MUSIC model indicated that the speciation distribution of Cd depended on the pH significantly. At pH 5.0 and 7.0, the speciation distribution of Cd for goethite was similar with that of the hematite. It was independent of the Cd concentrations and the (FeOH)2Cd+1 was the primary species. At pH 9.0, higher than 80% of the Cd was bound by the goethite with the species (FeOH)2CdOH0. For the adsorption of Cd to the hematite, at low Cd concentration, the primary contribution of the species was the (FeOH)2Cd+1. With the increasing of the Cd concentration, the fraction of these two species closed to 50% gradually and the contribution of the (FeOH)2CdOH0 become more important and dominate to the hematite. |
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