Feasibility of removal of graphene oxide particles from aqueous suspensions by DC/AC electrocoagulation

Graphene oxide (GO) particulates offer an inexpensive route for the formation of graphene flakes. Their fine size and high degree of dispensability in aqueous media have raised environmental safety concerns in processing plants. This manuscript describes a novel electrocoagulation based method that enables the removal of GO particles from acidic aqueous suspensions in the form of copper-ion containing GO films. Specifically, copper ions were generated near a copper anode and adsorbed onto negatively surface-charged GO particles, driving the anodic deposition of GO films. The experimental variables included the type of electric field (DC and AC) and the use of a copper-ion induced bulk pre-coagulation step. A direct current (DC) potential gradient of 3 V/cm applied to a baseline suspension with a GO concentration of 0.8 mass percent solids removed approximately 3% of the GO particles in a minute in the form of compact films of thickness ranging from approximately 10 to 50 microns containing copper ions. Use of AC fields led to lower deposition rates and copper content. On the other hand, precoagulation of GO dispersions with copper ions led to films with enhanced copper concentrations. Characterization of GO films using XPS and Raman techniques has shown that copper is present in the bivalent form in GO.