Experimental Study of Heavy Metal Dispersion through Cohesionless Soil: a Case Study of Cd+

Abstract

In this case study of cadmium metal (Cd+), an experiment has been conducted on the dispersion of heavy metals through flow in porous media. Sandy soil with a specific gravity of 2.65 has been selected as a porous medium for water contaminated with Cd+. A laboratory model has been built from glass box (0.75 m length × 0.10 m width × 0.55 m height, 10 mm thickness) in order to simulate the two-dimensional flow of the polluted water. The box is divided into three zones, namely, inlet zone (upstream), outlet zone (downstream), and sandy zone. In additional, tow adjuster valves are used to control the flow from upstream to downstream direction. Furthermore, eight points are selected in order to study the effect of time/distance ratio and to obtain acceptable results through a wide range of samples. Six of these points, P1, P2, P3, P4, P5, and P6, are fixed on the side of the model, while P7 and P8 represent the sampling points on the soil surface. The experimental model is activated using continuous flow patterns with a constant average initial concentration of Cd+ (5.899 ppm). Sampling is conducted at 5, 10, 20, 30, 40, 50, and 60 min), and the filtered samples are tested using an atomic Adsorption device. The results of the laboratory test are analyzed in order to study the variations in Cd+ concentration with vertical distance (y-axis) and horizontal distance (x-axis) and to determine the effect of hydraulic gradient on Cd+ concentration. Cd+ has higher concentration at the deeper points, so sandy soil adsorbs Cd+ at higher concentrations before reaching stability. Cd+ concentrations in points closer to the upstream zone are greater than the ones in further points due to the proximity distance from the upstream zone where the concentrations represent high values. Additionally, Cd+ concentrations in P3 at the first half are greater than the ones in P5 and P6 because the adsorption process is inactive at the beginning of running the model using continuous flow.