Coupling CO2 Capture with Organic Pollutant Removal in an Integrated Indoor Air Treatment System

Abstract Indoor air pollution due to elevated CO2 levels and the presence of volatile organic compounds (VOCs) and biological agents is increasingly considered as a major health concern. Current strategies to ventilate buildings are mainly oriented at CO2 levels, although the importance of the other pollutants are increasingly recognized. The approaches rarely capture the CO2 within the building, leading to considerable heat losses as well as the introduction of outdoor pollutants inside. Here we demonstrate an electrochemically driven indoor-air treatment system that couples CO2 capture with the coremoval of VOCs. First, we generated acid and base from a saline solution using a membrane electrolysis cell, producing 0.97 M H2SO4 and 1.88 M NaOH at 72% efficiency and an energy investment of 4.8 kWh/kg NaOH. The electrochemically generated alkaline solution was circulated through a scrubber for indoor air treatment, achieving a steady-state reduction of indoor CO2 by approximately 49% during continuous operation to reach 253 ppm. Carbon speciation analysis confirmed that absorbed CO2 was successfully converted to carbonate. Dissolved organic carbon accumulated in the scrubbing solution, indicating the cocapture of airborne organics, including acetone, ethyl acetate, xylene isomers, and styrene. The pregnant solution was contacted with the electrogenerated acid to separate the CO2 again in a separate stream from the saline solution containing organics. During subsequent electrochemical regeneration, these captured organics were substantially degraded. Under the investigated conditions, the integrated system achieved CO2 recovery with a minimum energy consumption of 1.13 kWh/kg CO2. Process analysis further suggests that this demand could potentially be reduced to 0.68 kWh/kg CO2 through system optimization. These results demonstrate the feasibility of integrating electrochemical carbon capture with indoor air purification within a single operational cycle.