Electrocoagulation for magnetic seeding of colloidal particles

Abstract

Electrocoagulation (EC) was investigated as a magnetic seeding method to be used prior to a high-gradient magnetic separation (HGMS) process. Experimental results showed that particulates with significant magnetic susceptibility were formed by EC with steel electrodes. Magnetite was specifically formed most readily in a sodium chloride solution, in the absence of other ions, but also in surrogate wastewater under controlled conditions. These results suggest that EC could be employed in a magnetic seeding process in which paramagnetic particles are formed and then removed through high-gradient magnetic filtration (HGMF). The effects of applied potential and current on the magnetic susceptibility and composition of particles formed by EC in a pure sodium chloride solution and in a surrogate wastewater solution were investigated by X-ray diffraction analysis, scanning electron microscopy (SEM), and magnetic susceptibility measurements. Results showed that pure magnetite particles of 100-nm diameter were formed in the sodium chloride solution. Various compounds were present in particles produced by the surrogate wastewater solution, indicating that the formation of magnetite particles was hindered by the presence of some cations and anions. Although these particles had a much lower magnetic susceptibility than magnetite particles, their magnetic susceptibility was relatively high and permitted good removal in HGMF. The removal of copper ions from both deionized water and surrogate wastewater by EC followed by HGMF was also investigated. Results obtained at pH 10 and 12 showed a higher copper ion removal from the deionized water solution than from the surrogate wastewater.