Rice husk-based activated carbon with high mesoporosity prepared by a combination of CO2 activation and boiling in alkaline solution

A combination of CO2 activation and boiling in an alkaline solution was used to prepare highly mesoporous rice husk-based activated carbons. An orthogonal experimental design was used to investigate the effects of CO2 flow rate, CO2 activation time, NaOH concentration, boiling time and liquid/solid ratio on the porosity of the activated carbons. Results show that an activated carbon with a high mesopore volume of 79% can be obtained under optimized conditions with no need for high temperature treatment with NaOH. The specific surface area, pore volume and yield of the activated carbon can reach 899 m2 g−1, 0.783 cm3 g−1 and 26.2%, respectively.