Electro-Fenton purification of floodwater with a poly(vinyl alcohol)-treated FeNi3@laser-induced 3D-graphene composite anode from Kraft paper

Abstract

Electro-Fenton process has been recognized in recent decade as a useful method for removing water contaminants via electrochemical redox reactions at large scale. Laser-induced graphene (LIG) with 3D porous structure is an electrically conductive carbon material, which can be used as a promising electrode for electro-Fenton water purification. This work presented a straightforward synthesis of LIG electrode by direct CO2 laser scribing on the lignocellulose-based Kraft paper. The magnetic FeNi3 nanoparticles were sandwiched by two LIGs as a Fenton catalyst, which were then coated with poly(vinyl alcohol) (PVA) in cross-linking solution. The resulting PVA-treated FeNi3@LIG electrode exhibited outstanding electrochemical stability, low resistance (29 Ω/Sq), high conductivity (1,013 S/m), and fast electrochemical reaction kinetic (80 mV/dec) suitable for electro-Fenton water purification. Compared to PVA-treated LIG electrode, PVA-treated FeNi3@LIG did effectively remove contaminants in floodwater that sampled from flood-ravaged He’nan Province, China. Notably for degrading organic pollutants, the removal efficiencies of chemical oxygen demand, total nitrogen, ammonia nitrogen, total phosphorous were approximately 86 %, 70 %, 77 % and 96 %, respectively. Meanwhile, the heavy metal ions were adsorbed to cathode and reduced into metal form. The metallic selenium and arsenic ions were also removed via adsorption and precipitation. The concentration of sulfate and nitrate in floodwater decreased rapidly from 76 and 9 mg/L to 54 and 0.5 mg/L, respectively. Due to the oxidation stress and cell death during electro-Fenton process, the number of total bacteria was removed by ∼ 73 %, in particular, the fecal coliform was removed completely. The demonstrated lignocellulose LIG electrode is eco-friendly, facile and cheap (∼ 25 USD/m2), which can be made scalable using existing roll-to-roll papermaking line. This work provided new and efficient technology for floodwater treatment.