Preparation of Activated Carbon from Pyrolyzed Rice Husk by Leaching out Ash Content after CO2 Activation

To prepare activated carbons with a high porosity and low ash content from pyrolyzed rice husk, the method of KOH or K2CO3 solution leaching after CO2 activation was investigated. The effects of KOH or K2CO3 concentration and leaching time on the yield, ash content, and textural properties of the activated carbon were studied, and the activated carbon prepared under the best conditions was characterized. The results showed that the best leaching time was 1 h for KOH and K2CO3, and the best concentrations were 1.0 and 4.0 M, respectively. The leaching process was greatly beneficial to the development of the pore structure. The specific surface area of the activated carbon prepared under the most favorable conditions was approximately 1100 m/g, and the iodine values were greater than 1100 mg/g. As a result of the leaching process, the ash content of the sample was notably decreased from 63% to approximately 5%, and the porosity development was attributed to the reaction of the leaching reagents with silica.