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

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.

Mechanism and modeling of hexavalent chromium interaction with a typical black soil: the importance of the relationship between adsorption and reduction

“…Additionally, Cr(III) is less harmful compared with Cr(VI), which even act as an essential trace element for human bodies, and thus reducing Cr(VI) into less mobile and toxic Cr(III) is regarded as one of the most effective strategies for Cr(VI) contaminated soil and groundwater remediation. [18][19][20][21] The natural reduction of Cr(VI) on soil particles is mainly inuenced by pH condition, redox potential, and inorganic and organic electron donors. 22,23 For Cr(VI) adsorption, pH condition mainly determines the soil particle variable charge character according to zero point of charge (ZPC), but for Cr(VI) reduction, pH condition mainly determines the proton concentration, which is a necessary element participating in this reaction.…”

Wheat Straw as a Bio-Sorbent for Arsenate, Chromate, Fluoride, and Nickel

“…The same was observed by Fernández-Pazos et al [25] studying chromium sorption and by Seco-Reigosa et al [11] studying arsenic sorption. This behavior may occur when the samples adsorb Cr(VI) and As(V) predominantly by electrostatic attraction between the adsorbent surface and the anionic species of these elements, releasing OH − and causing an increase in pH [10,34,35]. In the present study, some pH increases took place even when 3 and 6 mmol L −1 As(V) were added (with no As(V) sorption taking place on straw for these added concentrations), suggesting that additional causes could contribute to raising pH.…”

“…Ni 2+ showed notable sorption and an opposite trend to that of F − , with sorption percentage increasing when the highest Ni 2+ concentrations (3 and 6 mmol·L −1 ) were added. We have previously studied [10][11][12][13][25][26][27][28]] the effects of different concentrations, pH, incubation time, and other variables on As(V), Cr(VI), F − , and/or Ni 2+ retention on other sorbent materials, but it should be also performed for wheat straw in future works.…”

“…To fight heavy metal, metalloid, and F − pollution, different waste and by-products have been studied as bio-sorbents [8,9], including mussel shell [10][11][12] and wood industry waste [13]. As indicated by Malik et al [14], some cellulosic materials (as wheat straw) can be effective low-cost sorbents.…”

Cadmium and Lead Sorption/Desorption on Non-Amended and By-Product-Amended Soil Samples and Pyritic Material

“…In fact, Fu and Wang [1] reviewed the sorption capacities of agricultural and industrial waste and by-products, as well as of various types of natural substances, finding promising results. In this regard, in the last years we have studied several sorbents for the removal or retention of cationic heavy metals (Cd, Cu, Hg, Ni, Pb, Zn) [16][17][18][19][20], and anionic pollutants (Cr(VI) and As(V)) [21][22][23][24][25][26][27][28]. However, as far as we know, no previous study has dealt with Cd and Pb retention on forest soil, vineyard soil, and pyritic material samples, as well as on fine mussel shell, oak ash, hemp waste and pine bark samples, differentiating between results corresponding to the individual materials and those corresponding to the soils and pyritic material amended with the by-products.…”