Upgrading the rice husk char obtained by flash pyrolysis for the production of amorphous silica and high quality activated carbon

• Rice husk char is valorised for the joint production of silica and activated carbons.
• Na2CO3 extraction for the recovery of high amorphous silica rates (88%).
• 15 min activation for BET surface areas of up to 1365 m2 g−1.
• Long activation times cause growth and eventual destruction of micropores.
• Promising results for the viability of rice husk flash pyrolysis.

The overall valorization of rice husk char obtained by flash pyrolysis in a conical spouted bed reactor (CSBR) has been studied in a two-step process. Thus, silica has been recovered in a first step and the remaining carbon material has been subjected to steam activation. The char samples used in this study have been obtained by continuous flash pyrolysis in a conical spouted bed reactor at 500 °C. Extraction with Na2CO3 allows recovering 88% of the silica contained in the rice husk char. Activation of the silica-free rice husk char has been carried out in a fixed bed reactor at 800 °C using steam as activating agent. The porous structure of the activated carbons produced includes a combination of micropores and mesopores, with a BET surface area of up to 1365 m2 g−1 at the end of 15 min.

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