Nano-silica from rice husk for environmental remediation: Synthesis, characterization, and application in heavy metal removal

¹ Department of H&S, CVR College of Engineering, Vastunagar, Mangalpalli, Ibrahimpatnam, Ranga Reddy- 501510, India
² Department of Botany, SRR Government Arts and Science College (Autonomous), Karimnagar- 505001, India

^* Corresponding author: y.seeta@cvr.ac.in

Published online: 7 January 2026

Abstract

Rice husk is a byproduct that will tend to amass following harvesting, yet the agricultural waste possesses viable prospects as a nano- silica sustainability source. In this experiment we treated rice husk with acid treatment and alkaline extraction and then treated it with microwave-assisted sol-gel to extract amorphous nano-silica. We analyzed the resulting material using FTIR, XRD, BET, and SEM, and found that it consisted of non- crystalline silica nanoparticles, 0.5 0.5 0.5 m in size with a surface area of 185 m 2/g. We considered its adsorption capacity towards Pb(II) and Cd(II) ions to determine its performance. We changed pH (3 to 7), contact time (until three hours), and metal ion concentrations (10- 100mg/L). The Langmuir isotherm model was best fitting the data. Our silica impregnated 102.4 mg/kg of lead and 87.5 mg/kg of cadmium. It retained more than 85 percent of the original efficiency even after four adsorptiondesorption cycles. The overall yield was about 70%. Traditional methods presuppose more energy and chemicals than the process itself. In total, rice husk silica is a cheap and friendly to the environment adsorbent that is suitable in the removal of heavy metals in water.