Cr(VI) sorption/desorption on untreated and mussel-shell-treated soil materials: fractionation and effects of pH and chromium concentration

M Otero,E Álvarez-Rodríguez,A Núñez-Delgado,M Arias-Estévez,J C Nóvoa-Muñoz,L Cutillas-Barreiro,M J Fernández-Sanjurjo

doi:10.5194/se-6-373-2015

M Otero, E Álvarez-Rodríguez + Show 5 more

Open Access

https://doi.org/10.5194/se-6-373-2015

Copy DOI

Abstract

Abstract. We used batch-type experiments to study Cr(VI) sorption/desorption on granitic material, forest soil, pyritic material, mussel shell, and on forest soil and granitic material amended with 12 t ha−1 (1.2 kg m −2) shell, considering the effects of varying Cr(VI) concentration and pH. Sequential extractions were carried out to fractionate adsorbed Cr(VI) and to determine the stability of Cr(VI) retention. The pyritic material had the highest Cr(VI) retention capacity, whereas the granitic material showed the lowest retention potential. When high Cr concentrations were added, some saturation of the adsorbent surfaces became apparent, but Cr release remained low. The highest Cr retention was achieved at a very acid pH value, with release progressively increasing as a function of increasing pH. The amendment with 12 t ha−1 mussel shell did not cause marked changes in Cr(VI) retention. Sorption data were satisfactory adjusted to the Freundlich model. Regarding Cr(VI) fractionation, the soluble fraction (weakly bound) was dominant in mussel shell and in the unamended and amended granitic material, whereas more stable fractions dominated in the pyritic material (residual fraction) and in the forest soil (oxidizable fraction). In conclusion, the pyritic material presented the highest Cr(VI) retention capacity, while the retention was low and weak on the granitic material; mussel shell was not characterized by a marked Cr(VI) retention potential, and it did not cause remarkable increase in Cr(VI) retention when used to amend the granitic material or the forest soil.

Highlights

Mining, industrial, and agricultural activities are the main sources of chromium pollution affecting the environment, notably the water and soil compartments (Alves et al, 1993; Di et al, 2006)
The main objectives of this work are (a) to determine Cr(VI) sorption/desorption when different Cr(VI) concentrations are added to a granitic material, a forest soil, a pyritic material, and fine mussel shell, as well as to the granitic material and the forest soil amended with 12 t ha−1 (1.2 kg m−2) fine mussel shell; (b) to elucidate the influence of varying pH as regards Cr(VI) sorption on such materials; and, (c) to determine the fractions where Cr(VI) is retained in the various solid materials investigated, which affect Cr(VI) release and overall risks of pollution
Fernández-Pazos et al (2013) found that the amendment of pyritic material with mussel shell had no positive effect on Cr(VI) retention, so this combination was discarded in the present study

Summary

Introduction

Industrial, and agricultural activities are the main sources of chromium pollution affecting the environment, notably the water and soil compartments (Alves et al, 1993; Di et al, 2006). Mobilization of Cr(VI), and risks of water pollution and even of transfer to the food chain, are strongly related to retention processes affecting the pollutant (Lilli et al, 2015). Schmuhl et al (2001) found high Cr(VI) sorption on chitosan, with best results at pH 5. Good Cr(VI) sorption results were achieved using algae and cyanobacteria (Park et al, 2006; Gupta and Rastogi, 2008a, b), as well as using waste from the coffee and tea industries (Fiol et al, 2008; Duran et al, 2011)

Objectives

Methods

Results

Conclusion