Fig. 1
From: Remediation of heavy metal contaminated soil by asymmetrical alternating current electrochemistry
Working principle of the AACE method. a Schematic of an AACE remediation system. EDTA solution is recirculated to wash the contaminated soil. The AACE filter recovers heavy metal cations from the washing effluent and recycles the EDTA solution for repeated use. b Illustration drawing of the AACE filter, composed of two parallel Ami-PC electrodes and a separator. c The waveform of the applied bias and the physical process in the AACE filtration. In step I, all the ions are randomly dispersed in the washing effluent. In step II, a bias of 5 V applied, an electrical double layer is established on the surface of the Ami-PC electrode, with anions in the inner layer. The chelation sites will bind heavy metal cations and stabilize the MEDTA2− on the electrode surface. In step III, a bias of −10 V applied, heavy metal cations are electrochemically reduced to zero-valent particles. EDTA anions are repelled by the negative bias due to less affinity with the charge-neutral particles. Soil nutrient elements are reserved in this process because of their lower reduction potential
