Removal of heavy metals in wastewater in a clay soil matrix using electro‐osmosis

Abstract

Abstract The feasibility of using electro‐osmosis for removal of heavy metals (Cd, Cu, and Pb) contained in aqueous solutions was examined using soil cores formed from Randall clay — a clay found in Playa lake basins in the High Plains of West Texas. Initially, sorption tests were conducted with the clay dispersed in the metal solutions of interest to determine if adequate sorption would take place. The retention capacity of the clay for Cd was found to be 0.0083 mg/mg of soil. (10 5 kilograms of Cd could be removed in top one‐meter depth of a hectare of Randall clay with a bulk density of 1.4 g/cm 3 ). Electro‐osmosis was found to increase the permeability of the clay but was found to be both a slow rate system (up to 225 days to remove one pore volume of water through a m 3 of soil) and energy intensive (1.44 × 10 5 kJ to 8.1 × 10 5 kJ per m 3 of drained water). Problems noted during the test that need solution before further experimentation with this procedure include selection of less corrodible materials for electrodes, prevention of electrolysis of water at potential gradients needed to move the waters being treated through the soil matrix, and control of ion gradients from the anode to the cathode reservoir to prevent backflow episodes from reversing flow from the cathode to the anode region.