Dissolved pollutant transport in tailings ponds

Abstract

Water and dissolved ion transport in mineral tailings was studied at laboratory scale with three different tailings samples. Percolation rate, determined in column experiments, depends mainly on the granulometric distribution of the solid and varies between 3.0 X 10(-4) cm/s for a tailings sample with coarser particles (d(90) > 700 mum) to 4.0 x 10(-5) cm/s for the tailings sample with higher content of fine particles (d(90) < 200 mum). In stationary conditions, the ascending rate of water by capillarity through the solid bed is controlled by the evaporation rate at the top surface of the tailings. Rates between 2.6 x 10(-5) cm/s (2.2 mm/day) and 8.1 x 10(-5) cm/s (7.0 mm/day) have been obtained under forced evaporation at 40 degreesC. Ion transport in the percolation process is mainly controlled by the hydraulic diffusion of the solution through pores in the solid bed. In the capillarity process, ion transport is controlled by chemical diffusion of the dissolved ion in the ascending solution.