ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis of nanosilica from rice husk: characterization and silicon release pattern in soil

Bekkam Rakesh, T. Chitdeshwari, S. Maragatham, D. Jeya Sundara Sharmila, A. Senthil, and N. Chitra

Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore, India

E-mail: chithukesh@gmail.com

Received: 27 February 2024  Accepted: 10 November 2024

Abstract:

Rice husk is a bulky by-product from rice milling industries and its disposal is a major environmental concern. It is a rich source of silica which can be exploited to develop newer silicon products besides alleviating environmental contamination. Chemical synthesis of silica nanoparticles from ethyl or methyl orthosilicates is costly, toxic and environmentally not sustainable. Hence, the present study was aimed to synthesize nanosilica particles from rice husk via thermal decomposition (500–700 °C) and characterized through FESEM-EDAX, TEM, XRD and FTIR. Nanosilica obtained from rice husk calcined at 700 °C showed spherical morphology with little agglomeration, siloxane bonding, amorphous nature and high purity (99%). It also has comparatively lesser pH, electrical conductivity (EC), bulk density, solubility and higher reactivity than the products obtained at 500 °C and 600 °C. An incubation experiment was conducted by incubating varied levels (0, 5, 10, 15, 30, 30, 40 mg kg⁻¹) of newly synthesized nanosilica for 80 days and found a linear increase in available silicon with increasing levels of nanosilica addition. Application of nanosilica at 40 mg kg⁻¹ registered higher release of available silicon content in soil up to 60 days with a slight decrease at 80 days. The data obtained on the silicon release from synthesized nanosilica over a period of incubation time in soil were fitted in various kinetic equations and observed that pseudo-second-order equation describes the silicon release in a better way than other models (R² = 0.99). In conclusion, rice husk-derived nanosilica proves to be a sustainable and efficient silicon source, which enhanced the silicon availability in soil through slow release for more than 60 days.

Keywords: Rice husk; Calcination temperature; Nanosilica; Characterization; Release pattern

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-024-03805-8

Chemical Papers 79 (2) 685–697 (2025)