A green technology for the preparation of high capacitance rice husk-based activated carbon

Rice husk (RH) is a kind of biomass with huge amount in the world. Comprehensive utilization of RH is of great significance for a sustainable society. In this paper, a green technology to produce high capacitance rice husk-based activated carbon (RHC) was developed. High capacitance RHC was prepared by KOH activation of RH. The waste liquid produced in the washing procedure of RHC was transformed into nano-SiO2 by acidification with HCl. The KCl saline solution produced from the preparation of nano-SiO2 was used to obtain water via evaporation and prepare KOH via electrolysis. Importantly, the collected water and KOH was reused in this technology. The obtained RHC possessed a specific surface area as high as 3263 m(2) g(-1), and exhibited a high specific capacitance of 330 F g(-1) in 6 mol L-1 KOH aqueous solution. The nano-SiO2 was amorphous with average diameter of similar to 30-40 nm. In addition, the economic analysis demonstrated a significant gross profit margin of 70.72% for the products. The technology is simple, feasible, low-cost and environmentally friendly for large-scale production. (C) 2015 Elsevier Ltd. All rights reserved.