Process optimization of rice husk-based activated carbon production for water vapor adsorption

Activated carbon is a potential adsorbent for dehumidification. For a large scale, an abundant source and optimum process are needed to produce the activated carbon adsorbent. This work utilized the industrial rice husk carbon (RHC) as an activated carbon source for dehumidification. The RHC was activated using potassium hydroxide (KOH) and sodium hydroxide NaOH. The activation process was designed using a response surface methodology (RSM). The results showed that the activation process cleaned the impurities and reduced the particle size of RHC. N₂ adsorption–desorption results indicated that KOH-activated carbon possessed the highest surface area (138.857 m²/g) and pore volume (0.204 cm³/g). Thus, the adsorption capacity of activated carbon was twofold higher than that of RHC (without activation). According to RSM, the optimum activation time for KOH and NaOH were 12.83 and 7.17 h, respectively. Meanwhile, the optimum concentration for both activating agents was the same, 22.07% w/v. The water vapor adsorption of the activated carbon followed the pseudo-second-order model. The Freundlich isotherm provided the best accuracy in the water vapor sorption isotherm.