Photocatalytic performance of biochar-modified TiO (C/TiO) for ammonia-nitrogen removal.

Biochar-modified TiO (C/TiO) was prepared by a sol-gel method in this study to improve the photocatalytic capacity for ammonia-nitrogen (NH-N) removal from aqueous solutions. The results showed that biochar was successfully modified on TiO and helped improve its photocatalytic performance for pollutant degradation. The removal capacity of ammonia-nitrogen on the synthesized photocatalyst performed well at pH 10 with 1 g L C/TiO under both 60 (12.25 mg g) and 120 min (16.31 mg g) irradiation (xenon lamp, AM1.5, 25 A). Characterization of C/TiO through scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectrometry (FT-IR) analyses showed the successful introduction of biochar on TiO. SEM-EDS and BET analyses displayed that C/TiO had a larger surface area and more pores than the raw materials. XRD spectroscopy illustrated that C/TiO had typical characteristic peaks of anatase-TiO and presented a good photocatalytic degradation performance. It was confirmed from XPS and FT-IR analyses that -COOH groups were present in C/TiO and originated from biochar modification, and these enhanced the photocatalytic performance. Through radical quenching experiments, it was found that superoxide radicals (˙O) played a dominant role in NH-N photocatalytic reactions with hydroxyl radicals (˙OH) and valence band holes (h) playing a synergistic role. N was the main degradation product after 6 h NH-N photocatalytic degradation, which was much larger than NO/NO (both almost undetected) and NH ( 2 times lower than N). The new composite C/TiO has potential for ammonia-nitrogen degradation in wastewater treatment and favorable for treating sewage sludge.