Development of Continuous Extraction of Bio-Silica from Rice Husk in Pilot Scale

The use of renewable biomass, instead of petroleum, could be effective strategy to reach to carbon neutral society. Rice husks can be an alternative to silica raw material because it contains 15~20% of silica. Annually, 194 million tons of rice husk was produced worldwide in 2020. The initial step to use silica in rice husks is extracting silica from rice husk. Generally, alkaline extraction was performed at high temperature and pressure condition to extract silica from rice husks. In this study, the continuous extraction of silica from rice husk has developed at 80°C and atmospheric pressure. First, the optimal conditions of NaOH concentration, reaction temperature and time, and solid/liquid ratio were investigated at a lab-scale. The optimal conditions found in the lab-scale were 80°C reaction temperature, 2.5hr reaction time, 10 wt% solid/liquid ration and 0.5M NaOH. Based on the optimal conditions found in the lab-scale, continuous extraction process was operated in the pilot-scale having 20.2kg/d processing capacity. The stability of the continuous process was proved by operating for 190 hr. The process showed stable during the operation and extraction efficiency was maintained about 82%.