Novel insights into ammonia nitrogen removal: TiO2-based photocatalysts and potential of intimate coupling biodegradation

Abstract

Ammonia nitrogen (${\text{NH}}_4^{+}$-N/NH₃-N) is a widespread pollutant in aquatic environments, leading to oxygen depletion and eutrophication, and posing risks to ecosystems and human health. Traditional biological and physicochemical methods for the treatment of ammonia nitrogen wastewater face challenges such as long startup times, high sludge production, and secondary pollution. In contrast, photocatalysis, particularly with titanium dioxide (TiO₂), offers a promising alternative due to high efficiency, low energy consumption, and environmental compatibility. However, the limited utilization of visible light, rapid electron-hole recombination, and challenges with catalyst recovery restrict the practical application of TiO₂-based photocatalysts. This review explores recent advances in the modification of TiO₂ to improve the efficiency removal of ammonia nitrogen, including ion doping, surface sensitization, heterojunction formation, and material loading. Furthermore, the paper highlights the emerging strategy of intimate coupling photocatalysis and biodegradation (ICPB), a synergistic approach that harnesses the strengths of both processes, exploring its advantages and potential in enhancing pollutant removal. This coupling not only enhances the removal efficiency of ammonia nitrogen but also mitigates the drawbacks of each individual method, offering a more robust and energy-efficient solution. By analyzing the mechanisms, limitations, and future research directions of TiO₂-based photocatalysts, this review provides critical insights into the development of effective ammonium nitrogen treatment strategies, paving the way for sustainable water remediation and wastewater treatment technologies.