Removal of graphene oxide from water and wastewater using coagulation-flocculation

The present study evaluated the removal of graphene oxide (GO) concentrations of 1, 5 and 10 mg L-1 on water and wastewater secondary effluent from conventional activated sludge via coagulation-flocculation with different concentrations of iron chloride and polyaluminum chloride (PAC) as coagulants. UV-Vis spectroscopy was used to measure GO concentrations in the water and secondary effluent solutions before and after the coagulation-flocculation treatment. Fourier transform infrared (FTIR) analyses were used to evaluate the presence of GO in the residual sludge. The results showed that the coagulation-flocculation process was effective in removing GO from both water and wastewater secondary effluents. In DI water solution, iron chloride showed a higher removal, but with high standard deviation values, meaning an instability of results. PAC results were more stable. For the wastewater GO solution, PAC showed better results on all GO concentrations and coagulant concentrations. FTIR results showed the presence of GO in the settled sludge from both water and wastewater solutions; zeta potential analyses showed that metal coagulants ferric chloride and PAC have an impact on zeta potential of GO particles in DI water solution elucidating that the main mechanism for GO removal was sweep flocculation.