Evaluation of a novel fertilizer-drawn forward osmosis and membrane contactor hybrid system for CO₂ capture using ammonia-rich wastewater

Chemical absorption is widely employed to capture carbon dioxide (CO₂) for addressing climate change. While monoethanolamine (MEA) currently dominates as an absorption solvent, utilizing ammonia-rich wastewater offers advantages such as reduced costs, high absorption capacity, and the generation of ammonium carbamate. This study proposes an innovative fertilizer-drawn forward osmosis (FDFO)-membrane contactor (MC) hybrid system for economically and sustainably mitigating CO₂ emissions using ammonia-rich wastewater. First, ammonia-lean synthetic wastewater was concentrated through an FDFO system, using three fertilizers (KCl, monoammonium phosphate, and diammonium phosphate) as draw solutions. While KCl achieved a 45% ammonia dilution, diammonium phosphate yielded the highest concentration approximately 49%. Also, MCs were assessed for CO₂ absorption under various operational conditions. Increased liquid concentration and flow rates improved CO₂ capture efficiency, whereas higher CO₂ flow rates and concentrations resulted in an adverse effect. Furthermore, a simulation study of a hybrid FDFO-MC system was conducted to evaluate the feasibility and potential of the system. The results indicated that the FDFO-MC hybrid system has the potential to efficiently remove CO₂ if sufficient concentration and flow rate of ammonia-rich solution was secured at the FDFO outlet. This innovation addresses CO₂ emissions and wastewater challenges, adhering to circular economy principles.