Evaluation of the Affinity of Some Toxic Elements

Authors: Tetsushi Nagano Nobuyuki Yanase Yukiko Hanzawa Morio Takada Hisayoshi Mitamura Tsutomu Sato Hirochika Naganawa

Publish Date: 2010/07/06

Volume: 216, Issue: 1-4, Pages: 153-166

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Abstract

In order to evaluate fixation potential of schwertmannite for fluvial transport of various toxic elements we examined bottom precipitates and stream waters collected from the rivers contaminated with acid mine drainage AMD which arose from the abandoned Nishinomaki mine Shimonita Gunma Japan Mineralogical and morphological observations revealed that schwertmannite was the main mineral of the precipitates The affinity of various toxic ions to schwertmannite was evaluated on the basis of 1 apparent solid–liquid partition coefficients K d’s between precipitates and stream waters 2 coprecipitation behaviors during schwertmannite formation in a laboratory test and 3 consideration on coprecipitation processes using partial charge model PCM As a result oxyanions of V As Mo and Sb K d’s of which were relatively large 104 ml g−1 were considered to be immobilized by schwertmannite precipitates A laboratory test also demonstrated that these ions except Mo coprecipitated with schwertmannite In addition partial charges and average electronegativities predicted on the basis of PCM suggested that the oxyanions of V As Mo and Sb could create stable inner sphere complexes with schwertmannite embryos which results in their high affinity to schwertmannite On the other hand cationic ions of Mn Cu Zn Sr Cs and U K d’s of which were relatively small 104 ml g−1 were thought to have a tendency to flow downstream without uptake by schwertmannite precipitates All these results suggested that schwertmannite has high fixation potential for fluvial transport of various toxic oxyanions in AMDcontaminated rivers

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