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

Liu, Dechen, Zhang, Wenli, Lin, Haibo, Li, Yang, Lu, Haiyan, Wang, Yan
Journal of cleaner production 2016 v.112 pp. 1190-1198
acidification, activated carbon, aqueous solutions, biomass, capacitance, economic analysis, electrolysis, evaporation, hydrochloric acid, potassium chloride, potassium hydroxide, profits and margins, rice, rice hulls, sodium chloride, surface area, sustainable communities, sustainable technology, washing
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 m² 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 ∼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.