Use of Rice Husk Hydrolyzed by Subcritical Water to Obtain Silica from Agro-Industrial Waste
Crisleine P. Draszewski, Norton Marozo Silveira, Michel Brondani, Alyson de Souza Cruz, Kátia Rezzadori, Flávio Dias Mayer, Ederson R. Abaide, Márcio A. Mazutti, Marcus V. Tres, Giovani L. Zabot
Abstract
Hydrolyzed rice husk (HRH) obtained from subcritical water hydrolysis at different process temperatures (180°C, 220°C, and 260°C) was investigated as raw material for silica extraction. The composition of fresh RH, HRH, ash, and silica; residual mass HRH structure; thermal properties; and morphology of synthesized silica powder were evaluated using thermogravimetric analysis (TGA), X-ray diffractometer (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). TGA showed a maximum mass loss of 13% until 600°C. Above 600°C, a negligible mass loss was observed for all samples, indicating the thermal stability of extracted silica. XRD analysis revealed the same broad peak of silica for RH and all HRH samples at 2θ = 22°, confirming amorphous silica. FT-IR results indicated the presence of silica–oxygen bonding (Si-O-Si) at 1,070–1,090/cm, while SEM showed similar SiO 2 morphology for silica from RH and HRH processed at 180°C, 220°C, and 260°C.