Implementing a sustainable photochemical step to produce value-added products in flue gas desulfurization

Coal consumption has led to a worrying surge in flue gas emissions, aggravating health and environmental issues worldwide. Therefore, novel approaches supported by sustainable technologies are needed to exploit flue gas emissions effectively. Here, we evaluate an ammonia-based flue gas desulfurization process based on the photochemical capture of CO2 and SO2 for producing hydrogen and ammonium-based fertilizers. The kinetics and mechanistic pathways for sulfite photooxidation are examined, while process feasibility and environmental relevance are evaluated by process simulation and life cycle assessment. Results show that increasing the initial sulfite concentration results in faster reaction rates, following first-order kinetics with an activation energy of 32.9 kJ/mol. Moreover, kinetics is ascribed to two competing photoinduced radical-mediated reaction pathways. Finally, powering the process by renewable energy leads to positive human health, ecosystems, and resources scores in life cycle assessment, supporting the sustainability of the process. Overall, this approach offers essential insights for large-scale hydrogen production through the photooxidation of captured flue gas emissions.