Natural rubber latex foam with particulate fillers for carbon dioxide adsorption and regeneration

To reduce the carbon dioxide (CO₂) concentration in the atmosphere, natural rubber (NR) was developed as a rubber foam for CO₂ adsorption. Although the CO₂ adsorption capacity of the NR latex foam produced by mixing with a cake mixer (CM) was higher than that produced with an overhead stirrer (OS), both capacity values were still low. To improve the CO₂ adsorption capacity, the use of unmodified and (3-aminopropyl)triethoxysilane-modified silica particles as fillers in the CM rubber foam matrix was examined. The highest CO₂ adsorption capacity, from a mixed gas flow rate of 100 mL min^-1 at ambient temperature and pressure, was obtained with the CM foam filled with 5 parts by weight per hundred parts of rubber filled with modified silica particles (4.08 mg g^-1). The CO₂ adsorption capacity of this foam was approximately 1.11- and 2.87-fold higher than that of the CM foam filled with unmodified silica particles (3.69 mg g^-1) and unfilled CM rubber (1.42 mg g^-1), respectively. Morphological analysis supported that the cell size and number of pores per cell of the NR latex foam, which were higher in the CM foams than the OS foams, were important factors for evaluating CO₂ adsorption. In addition to physisorption between CM and CO₂, chemisorption between the modified silica particles and CO₂ increased the CO₂ adsorption capacity.