Pores on Pores: A novel approach to fabricate super adsorbents from used face masks for large CO₂ capture and dye removal

Recently, a profound interest has been developed in preparing adsorbents (mostly carbon-based) for CO₂ capture due to increasing global warming. Unfortunately, the adsorption capacity is still not satisfactory due to inadequate coordination between the surface pores and surface chemistry, the key players in adsorption. This article describes a new strategy to produce highly effective adsorbents, capable of absorbing a large CO₂ from ambient conditions (35 °C, 1atm). The adsorbents were produced from used face masks (FMs), a highly produced medical waste in current times. The high adsorption capacity of the adsorbent was incorporated through a novel surface functionalization process that generates numerous additional hierarchical pores on the pre-designed porous adsorbents, and more effective chemical binding sites, prerequisites for heavy CO₂ capture. Firstly, the FMs were converted into porous activated carbon fibers (ACFs) under controlled conditions and then modified the surface with polydopamine (pDA) assisted tetraethylenepentamine (TEPA) grafting. After modification, the adsorbent (TEPA-pDA-ACFs, 3.89 mmol/g) showed 648% and 24% higher CO₂ adsorption capacity than that of the pristine FMs (0.52 mmol/g) and ACFs (3.14 mmol/g), respectively. The value was found superior to many recent reports based on carbon adsorbents. Moreover, the adsorbent displayed excellent regeneration (>98%) and recycling ability even after several cycles. Interestingly, the adsorbent further showed outstanding multi-dye removal capacities (both cationic and anionic) from aqueous solutions. The removal efficiency remained >94% even after 9 cycles of adsorption-desorption. These results conclude that our attempt for preparing adsorbents from used face masks (TEPA-pDA-ACFs) could be a robust and viable approach for the development of a sustainable earth.