Soil treated with cement for sorption of Pb ²⁺ , Cd ²⁺ , Cr ^3+, and As ⁵⁺ in permeable reactive barriers

ABSTRACT

Environment contamination originates mainly from the exploitation of natural resources and industrial production, with the generation of waste generally disposed on the soil or in the water. One of the solutions for the contaminated groundwater remediation is the isolation of the region (plume) with reactive permeable barriers. In this context, this work aimed to evaluate the sorption of lead (Pb²⁺), cadmium (Cd²⁺), chromium (Cr³⁺), and arsenic (As⁵⁺) by two soils with doses of 1, 2 and 4% of Portland cement. Batch equilibrium assays were performed with monospecific solutions of Pb²⁺, Cd²⁺, Cr³⁺, and As⁵⁺. Sorption isotherms were obtained from equilibrium concentration values of solute in solution (Ce) and mass of solute sorbed by soil mass (S), according to the Langmuir and Freundlich models. The data collected after models adjustment were submitted to regression analysis to evaluate the effect of the cement doses. The pH increase caused by the cement addition made it impossible for most elements in both soils to adjust the theoretical models of Freundlich or Langmuir due to the predominant precipitation of metals. The analyzed sorghum that best satisfied the sorption conditions, for both arsenic and lead, was sandy soil with 2% cement addition. As for cadmium, it was the clay soil with 1% cement. For chromium, it was not possible to establish the best cement dose due to the total metal precipitation at all doses evaluated.

Keywords:
heavy metals; contamination; soil treated with cement