Remediation of soils contaminated with chromium using citric and hydrochloric acids: the role of chromium fractionation in chromium leaching

Abstract

Acid washing is a common method for soil remediation, but is not always efficient for chromium-contaminated soil. Both soil particle size and the forms of chromium existing in the soil affect the efficiency of soil washing. Laboratory batch and column dissolution experiments were conducted to determine the efficiencies of citric and hydrochloric acids as agents to extract chromium from soils contaminated with chromium. The effects of soil particle size and chromium fractionation on Cr leaching were also investigated. About 90% of chromium in the studied soil existed either in residual form or bound to iron and manganese oxides, and Cr fraction distributions were similar for all soil particle sizes. Almost all exchangeable and carbonate-bound chromium was removed by washing once with 0.5 M HCl, whereas organic chromium was more effectively removed by washing with citric acid rather than with HCl solution of the same concentration. For chromium fractions that were either bound to Fe-Mn oxides or existed as residual forms, the efficiencies of acid washing were usually 20% or less, except for 0.5 M HCl solution, which had much higher efficiencies. Separation of the soil sample by particle size before the separate washing of the soil fractions had little improvement on the chromium removal.

Evaluation of Cr(VI) Reduction Using Indigenous Bacterial Consortium Isolated from a Municipal Wastewater Sludge: Batch and Kinetic Studies

“…B9. The inhibition of Cr(VI) removal by some heavy metals at elevated concentrations maybe due to the suppression of microbial activity by metal toxicity, and the destruction of protein structures by heavy metals [14].…”

Comparison of chromium mobility at naturally enriched and anthropogenically polluted sites: A column leaching experiment

“…In an oxic environment, Cr exists as Cr(VI), while in an anoxic environment Cr(VI) is readily reduced to Cr(III) by ferrous oxides and ferric oxyhydroxides as ferrihydrite (Fe 2 O 3 •0.5H 2 O), goethite (FeOOH) and hematite (Fe 2 O 3 ) due to their abundant occurrence and large surface area. Besides ferrous oxides, Cr(VI) can be naturally reduced to Cr(III) by various other reducing agents such as S 2ions, organic matter, and by microbial communities (Banks et al 2006;Cheng et al 2011). The oxidation of Cr in the soil can be caused by low molecular mass organic acids (citric acid, gallic acid, etc.)…”

Efficiency of EDTA and TWEEN 80 for the Removal of Chromium using Soil Washing Technologies

“…For surfactants, it has been reported that this type of agent has good potential for removing metals in soil. However, popular surfactants are the cationic, anionic and nonionic types that can be used for washing (Mulligan et al, 1999) such as TWEEN 80, Triton X-100, Brij-35 (nonionic surfactant), SDS, AOT, SDBS (anionic surfactant) and hydrochloric acids (Kos and Lestan, 2004;Cheng et al, 2011;Xuhui et al, 2015;Min et al, 2017). According to the findings in many studies, filling surfactants in contaminated soil could enhance the emission and dissolution of contaminated organic matter because the solvent as cooled water needs to have a low Critical Micelle Concentration (CMC) related to a low value of toxic microbes (Cheng and Wong, 2006).…”