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

Abstract

A bio-electrochemical fuel cell reactor with cathodic Fe⁰/TiO₂ generates electricity.

It destroys recalcitrant pollutants in cathode chamber without photocatalysis.

Fe⁰/TiO₂ generates reactive oxygenated species in the dark or under photocatalysis.

Cathodic produced ROS (hydroxy radical/superoxide radical) can degrade tetracycline or dyes.

Electricity generation is enhanced by semiconductor catalyzed cathodic degradation of pollutants.

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 spin-resonance spectroscopy (ESR) study demonstrated that ·OH was formed under visible light, and ·O₂⁻ 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.

Graphical abstract

Keywords

Bio-anode / Photocatalytic cathode / Fe⁰/TiO₂ / ESR / Dye and antibiotics / Advanced oxidation

RIGHTS & PERMISSIONS

Higher Education Press and Springer-Verlag Berlin Heidelberg