An electrochemical process that uses an Fe0/TiO2 cathode to degrade typical dyes and antibiotics and a bio-anode that produces electricity

Abstract

In this study, a new water treatment system that couples (photo-) electrochemical catalysis (PEC or EC) in a microbial fuel cell (MFC) was configured using a stainless-steel (SS) cathode coated with Fe0/TiO2. We examined the destruction of methylene blue (MB) and tetracycline. Fe0/TiO2 was prepared using a chemical reduction-deposition method and coated onto an SS wire mesh (500 mesh) using a sol technique. The anode generates electricity using microbes (bio-anode). Connected via wire and ohmic resistance, the system requires a short reaction time and operates at a low cost by effectively removing 94% MB (initial concentration 20 mg∙L–1) and 83% TOC/TOC0 under visible light illumination (50 W; 1.99 mW∙cm–2 for 120 min, MFC-PEC). The removal was similar even without light irradiation (MFC-EC). The E Eo of the MFC-PEC system was approximately 0.675 kWh∙m–3∙order–1, whereas that of the MFC-EC system was zero. The system was able to remove 70% COD in tetracycline solution (initial tetracycline concentration 100 mg∙L–1) after 120 min of visible light illumination; without light, the removal was 15% lower. The destruction of MB and tetracycline in both traditional photocatalysis and photoelectrocatalysis systems was notably low. The electron spinresonance spectroscopy (ESR) study demonstrated that ∙OH was formed under visible light, and ∙O 2 – was formed without light. The bio-electricity-activated O2 and ROS (reactive oxidizing species) generation by Fe0/TiO2 effectively degraded the pollutants. This cathodic degradation improved the electricity generation by accepting and consuming more electrons from the bio-anode.