Biosorption of Cr(VI) from natural groundwater and the effect of DOC-rich treated water on Cr dissolving from contaminated soil

Abstract

Brewers draff and grape waste were used as efficient biosorbents for removing Cr(VI) from contaminated groundwater. Additionally, the interactions between the dissolved organic carbon-rich (DOC-rich) treated water and a soil contaminated with Cr(III) was further studied. The breakthrough curves obtained from column (dynamic) adsorption experiments showed higher adsorption efficiency of grape waste compared to brewers draff. The adsorption efficiency was 36.8-40.4% for brewers draff and 56.6-68.3% for grape waste, depending on the initial pH. The detected saturation time was approximately three times higher than in our previous study, where a model solution of Cr(VI) was used. The natural groundwater showed to be rich in dissolved organic matter after the treatment. The consequent interaction of the treated water with the soil led to a partial dissolution of Cr from the contaminated soil (corresponding to < 1% of total soil Cr) in the case of brewers draff, but also to adsorption of the residual Cr from the treated water to the soil in the case of grape waste. The obtained data demonstrated that Cr(III), when abundant in soils, could be potentially mobilized by the DOC-rich solution. On the other hand, the risk associated with this secondary Cr mobilization and its subsequent migration in soils (or sediments) seems to be very low or even negligible.