In-situ synthesis of 3D GA on titanium wire as a binder- free electrode for electro-Fenton removing of EDTA-Ni.

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. The three-dimensional (3D) macroporous graphene aerogels (GA), which was in-situ assembled by reduced graphene oxide (rGO) sheets on titanium wire as binder-free electrode, was presented as cathode for the degradation of EDTA-Ni in Electro-Fenton process. The X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and Brunauer-Emmett-Teller (BET) results indicated 3D GA formed three dimensional architecture with large and homogenous macropore structure and surface area. Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV) and Rotating Ring-disk Electrode (RRDE) results showed that the 3D GA cathode at pH 3 displayed the highest current density and electrochemical active surface area (ECSA), and better two-electron selectivity for ORR than other pH value, confirming the 3D-GA cathode at pH 3 has the highest electrocatalytic activity and generates more HO. The factors such as pH, applied current density, concentration of Fe, NaSO and aeration rates of air were also investigated. Under the optimum conditions, 73.5% of EDTA-Ni was degraded after reaction for 2h. Mechanism analysis indicated that the production of OH on the 3D GA cathode played an important role in the removal of EDTA-Ni in the 3D GA-EF process, where the direct regeneration of Fe on the cathode would greatly reduce the consumption of HO. Therefore, it is of great promise for 3D-GA catalyst to be developed as highly efficient, cost-effective and durable cathode for the removal of EDTA-Ni.