Miscible displacement of copper in soil columns using increasing doses of bentonite

Abstract

The objective of this research was to evaluate the effect of applying increasing doses of bentonite to the soil on the miscible displacement of copper, quantifying copper retention in the soil and elimination by leachate, in order to prevent potential risks for environmental contamination. The experiment was conducted on a laboratory using leaching columns filled by a sandy texture soil contaminated with 250 mg kg-1 of copper each. The experimental design was a completely randomized with four doses of bentonite, 0; 30; 60 and 90 t ha-1, and three replications totalizing 12 experimental units. The leaching columns were made with PVC tubes constituted by three rings, overlaid and joined with silicone glue. Each column was filled with 4 kg of Cu contaminated soil, mixed with the doses of bentonite specified by the treatments (0; 45; 90 and 135 g). After the filling of the columns, each one received five pore volumes of distillated water, and left to percolation under a steady state flux. After percolation, the Cu concentrations in the soil and in the percolate, the breakthrough curves of the flux density and the percolation velocity were determined. The results were submitted to variance analyses using the F test and regressions. The increasing doses of bentonite until 90 t ha-1 increased the adsorption of copper by the soil, reducing the percolation of this element around 72%. Bentonite application to the soil decreased the flux density and flux velocity of the copper percolation, diminishing the potential risks for the environment contamination.