Removal of chromium from aqueous solutions by treatment with porous carbon electrodes: Electrochemical principles

The possibility of removing hexavalent chromium from waste water by electrochemical treatment using a graphite felt electrode and synthetic electrolytes is investigated. It is suggested that the process proceeds in two steps: electrochemical reduction of the hexavalent chromium to chromic ion followed by the formation of an insoluble chromic hydroxide in an electrochemically generated high pH environment. The chromic hydroxide adheres to the electrode surface as a charged colloidal particle. The electrochemical dissolution of the hydroxide layer by potential inversion is also discussed as a possible regeneration procedure. It is concluded that these steps can be included within a single separating column provided that the feed pH and the column voltage are carefully controlled.