Electrocoagulation and separation of aqueous suspensions of ultrafine particles

摘要

Conventional methods for the removal of suspended ultrafine particulates in industrial effluents and wastewater treatment frequently involve the bulk addition of inorganic coagulants (e.g. aluminum or ferric salts). This electrolytic dosing is followed by sedimentation to obtain a clarified supernatant liquid. The increased size of the coagulated material facilitates subsequent solid-liquid separation processes such as filtration. An alternative separation treatment for ultrafine particles is electrocoagulation, which involves the in situ formation of ions by electrolysis. This generation of ions is succeeded by the electrophoretic concentration of the particulates in the immediate region surrounding the electrode. The addition of the electrochemically generated reagent can be controlled by adjusting the supplied power, thereby enabling optimization of the process. The effective performance of the electrocoagulation technique was evaluated with kaolinite suspensions, using a batch, stirred cell system, and a continuously flowing suspension through a series of stirred cells. Particular attention was focused on determining the rate constants for the kinetics of the particulate coagulation process. The parameters examined were electrode voltage, residence time, particle concentration, and suspension flow rate. The results showed that the electrocoagulation rate follows a second order relationship, accounting for the electrophoretic movement of the particles toward the anode.