Facile fabrication of hollow biochar carbon-doped TiO2/CuO composites for the photocatalytic degradation of ammonia nitrogen from aqueous solution

Ammonia nitrogen contaminated wastewater poses a great threat on the safety of water resources. In this work, a series of hollow tubular structure TiO2/hemp stem biochar carbon (HSC) and TiO2-CuO/HSC were successfully fabricated under different calcination temperature and were used as catalysts for the degradation of ammonia nitrogen from aqueous solution. The morphologies and structures of the catalysts were characterized by X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method and UV–vis−DRS spectroscopy (DRS) technique. The effects of the different calcination temperature, the dosage of catalyst, the pH on the ammonia solution, and contact time on the degradation process were investigated. In addition, the comparison of ammonia removal efficiency under sunlight and UV-light were studied, and the degradation mechanism was also discussed. The result indicates that those of as-prepared TiO2/HSC and TiO2-CuO/HSC show excellent photocatalytic activity. The enhanced photocatalytic activity of the nanocomposites can be attributed to the high specific surface area and the reduction of electron-hole pair recombination because of the introduction of HSC and copper oxide. In addition, the removal efficiency of ammonia reached 99.7% under UV light while degraded about of 60.7% under sunlight with TiO2-CuO/HSC. The reusing capability and stability of catalysts were studied, and the results demonstrated that the as-prepared composites showed high stability and excellent recycling performance in aqueous reaction systems. The prepared catalysts are promising for the degradation of ammonia nitrogen from wastewater.