Electrokinetic Recovery of Copper, Nickel, and Zinc from Wastewater Sludge: Effects of Electrical Potentials

Abstract

One of the main obstacles to the agricultural use of the sludge produced in wastewater treatment plants are heavy metals that have accumulated. Electrokinetic treatment can be used to remove these heavy metals, but the process is time consuming, sometimes lasting several days. In this study, the effects of different potential gradients were investigated. Electrokinetic experiments were conducted under constant potential gradients (1 V/ cm, 3 V/cm, and 5 V/cm) with a treatment time of 16 hours. Results showed that the most efficient removal of metals was achieved at a potential gradient of 5 V/cm. Average removal efficiencies of heavy metals were 30.29% for copper, 43.52% for nickel, and 33.38% for zinc. Accumulation of metals occurred at a distance of 7 cm from the anode at a potential gradient of 1 V/cm. Results of the sequential extraction and sludge pH profiles show that an acidic front generated at the anode reservoir flushed across the sludge chamber and that the higher potential gradient increased the migration velocity, which aided the dissociation and desorption of metals. Furthermore, the use of higher potential gradients made it possible to remove heavy metals from sludge cells in a shorter period of time.

Copper removal from sediment by electrokinetic treatment with electrodes in a hexagonal configuration

“…According to Lei et al., [ 47 ] we can expect that a significant amount of Cu will migrate during electrokinetic treatment (metals bound in weak acid soluble and reducible fractions are subject to electromigration and electroosmosis).…”