Efficient removal of CO2 from indoor air using a polyethyleneimine-impregnated resin and its low-temperature regeneration

Abstract

Aminated adsorbents are efficient in capturing high concentrations of CO2, while their efficiency in air purifier for the removal of low concentrations of CO2 from indoor air remains unclear. In this study, a polyethyleneimine-impregnated resin (PEI-MR10) was prepared and used to remove indoor CO2, and its regeneration at low temperatures was evaluated. PEI loading narrowed the pore size distribution but increased the average pore size of the PEI-MR10. The PEI-MR10 with small particle size (0.250–0.425 mm) exhibited higher adsorption capacity and faster adsorption rate than the bigger one. The PEI-MR10 was able to remove all CO2 during the first 2 h with an initial CO2 concentration of 1000 ppm. Under variable indoor conditions, the adsorbed amounts of CO2 could maintain high values from 90 to 136 mg/g. At a relative humidity of 50%, the adsorbed amount on the PEI-MR10 for 1000 ppm CO2 reached 128.4 mg/g. In consideration of real application in air purifier, a cost-effective regeneration method using ambient air was adopted, and the spent PEI-MR10 was regenerated at low temperatures no more than 70 °C. The desorption efficiency of CO2 increased with increasing temperatures, and the best regeneration was obtained at 70 °C. The adsorbed amount of CO2 on the first-regenerated PEI-MR10 decreased significantly, but the adsorbent maintained stable adsorption capacity of about 80 mg/g after three adsorption-regeneration cycles. This study demonstrated that PEI-MR10 was an effective adsorbent for CO2 removal from indoor air.