Preparation of lotus-leaf-like carbon cathode for the electro-Fenton oxidation process: Hydrogen peroxide production, various organics degradation and printing wastewater treatment

To develop an electro-Fenton (EF) oxidation process for highly efficient organics degradation, a carbon cathode with lotus-leaf-like super-hydrophobic surface was prepared using ordinary graphite powder as an electro-catalyst material, polytetrafluoroethylene (PTFE) as an adhesive agent, boric acid (H3BO3) as a pore-forming agent, and using copper wire meshes to shape the surface morphology. The obtained results show that the carbon cathode with a lotus-leaf-like morphology led to an evident increase in hydrophobicity, which greatly enhanced hydrogen peroxide (H2O2) production performance. In the air-aerated Na2SO4 solution (pH = 2.8), the cathode prepared under optimized conditions yielded 527.5 mg L−1 H2O2 within 60 min with an observed current efficiency (CE) of 35.1 %. The developed EF oxidation process exhibited the strong oxidation ability for the degradation of several organics including rhodamine B (RhB), methylene blue trihydrate (MBT), p-nitrophenol (p-NP) and tetracycline (TC). What's more, the treatment of one real printing wastewater by this EF system presented the chemical oxygen demand (COD) removal of 76.8 % and the total organic carbon (TOC) removal of 73.5 %, and concurrently enhanced the biodegradability evidently. In addition, it was found that chloride ion (Cl−) might have an adverse effect on organics degradation due to the meaningless H2O2 consumption caused by HClO and ClO−. The results of this study indicate that the developed EF process can be used not only for the efficient removal of organic pollutants, but also as a pre-treatment before biological treatment for the enhancement of biodegradability.