Activated Carbon For Removing Formaldehyde From Air

The simple and convenient granular activated carbon (GAC) adsorption technology will be more widely employed to solve the increasing indoor air contamination of formaldehyde. Selecting the best GAC is difficult due to the highly different adsorptive capacities for formaldehyde of many available GACs prepared from different raw material and manufacture process. This study was performed to investigate the formaldehyde capacities of several different GAC’s (raw material, particle size, and manufacturing process), develop the higher formaldehyde capacity GAC/MnOx by impregnating manganese oxide on the base GAC, and evaluate its enhanced performance of removing formaldehyde from air.The GAC’s formaldehyde capacity vs. equilibrium concentration data was well correlated by the Freundlich isotherm model. The coconut shell based GACs removed more formaldehyde than GACs made from other raw materials. The regeneration runs employing a water bath recovered more formaldehyde capacity than those employing a light bath. The breakthrough data showed that the GAC manufacture process affected its capacity for formaldehyde (i.e., the cylinder-shaped particles were more effective than the crushed particles) and that the formaldehyde removal capability increased with the decreasing particle size, except for the<40mesh GACs (i.e., the formaldehyde capacity of the30-60mesh sample was lower than that of the20-40mesh sample). The MnOx/GAC sample with0.99%manganese was the best with a formaldehyde capacity of6.23mg/g (100%improvement) among all MnOx/GAC samples (0.49-11.46%manganese). The loaded manganese oxide played a role as a catalyst, promoting oxidation of the adsorbed formaldehyde molecules. The performance of formaldehyde removal was dependent on environmental factors; the effectiveness of MnOx/GAC treatment for removing formaldehyde improved with reduced lower temperature and humidity.