Influence of mussel shell on As and Cr competitive and non-competitive sorption-desorption kinetics in a mine soil: stirred flow chamber experiments

Objective: The objective of this work was to study the effects of amending a pyrite-derived mine soil with mussel shell (MS) on As and Cr adsorption/desorption. Methods: The methodological approach consisted in using stirred flow chamber experiments to elucidate competitive and non-competitive As and Cr adsorption/desorption kinetics, both in un-amended and MS-amended mine soil samples. Results: The results of the experiments indicate that, in non-competitive trials, the MS amendment caused no effect on Cr adsorption, but increased As adsorption, which would be due to the formation of Ca-mediated cationic bridges between As and functional groups present in the negatively-charged soil colloids; whereas, in competitive trials, the MS amendment caused an increase in adsorption for both As and Cr. Additionally, desorption was low for both amended and non-amended soil, showing curves that correspond to fast and slow binding sites, thus differing from adsorption, which were characterized by presenting one-slope curves. Conclusion: In conclusion, MS amendment could be used to increase As and Cr adsorption when both pollutants are present in pyrite-derived mine soils, or to increase As adsorption when this element is present in the mine soil in the absence of Cr, but the MS amendment could not give further Cr adsorption in this medium when As is not present. Practice: These conclusions could be made effective in pyrite-derived mine soil environments. Implication: The achievements of this study could be useful to diminish As and Cr pollution in these environments. (C) 2014 Elsevier B.V. All rights reserved.