Simultaneous removal of tetracycline hydrochloride and hexavalent chromium by heterogeneous Fenton in a photocatalytic fuel cell system.

In this work, a novel double-chamber system (PFC-Fenton), combined photocatalytic fuel cell (PFC) with Fenton, was constructed for tetracycline hydrochloride (TCH) and hexavalent chromium (Cr(VI)) removal and electricity production. Therein, Zn(OH)(CO)/FeO/BiVO/fluorine-doped SnO (ZIO/BiVO/FTO) and carboxylated carbon nanotubes/polypyrrole/graphite felt (CCNTs/Ppy/GF) were served as photoanode and cathode, respectively. Under light irradiation, the removal efficiencies of TCH and Cr(VI) with the addition of HO (2 mL) could reach 93.1% and 80.4%, respectively. Moreover, the first-order kinetic constants (7.37 × 10 min of TCH and 3.94 × 10 min of Cr(VI)) were 5.26 and 5.57 times as much as the absence of HO. Simultaneously, the maximum power density could be obtained 0.022 mW/cm at a current density of 0.353 mA/cm. Therein, the main contribution of TCH degradation was ·OH and holes in anode chamber. The synergistic effect of photoelectrons, generated ·O, and HO played a crucial role in the reduction of Cr(VI) in cathode chamber. The high-performance liquid chromatography-mass spectrometry indicated that TCH could be partially mineralized into CO and HO. X-ray photoelectron spectroscope and X-ray absorption near-edge structure spectra showed that Cr(VI) could be reduced to Cr(III). After 5 times of cycling, the removal efficiencies of TCH and Cr(VI) were still greater than 70%, indicating the remarkable stability of the PFC-Fenton system. Overall, this system could remove TCH/Cr(VI) and generate power simultaneously without iron sludge formation, demonstrating a promising method to further develop PFC-Fenton technology.