Optimization of Silica Extraction Method from Rice Husk Ash Using Taguchi Method

This study presents a systematic investigation of silica extraction from rice husk ash (RHA) using Taguchi L27 orthogonal array optimization methodology. With global rice production generating 31-39 million tonnes of RHA annually, valorization of this agricultural waste addresses both environmental disposal challenges and sustainable silica production needs. The extraction process involved controlled calcination, acid leaching with hydrochloric acid, alkali solubilization using sodium hydroxide, and acid precipitation to produce high-purity amorphous silica. Three critical process parameters—heating temperature (600-800°C), heating time (2-6 hours), and chemical concentration (1-3 M)—were systematically optimized across 27 experimental runs. Statistical analysis identified optimal conditions of 700°C calcination temperature, 4-hour processing time, and 3 M chemical concentration, achieving maximum silica yield of 7.02 g from 10 g RHA (70.2% extraction efficiency). Main effects analysis revealed chemical concentration as the most influential parameter, followed by temperature exhibiting volcano-shaped behavior with peak efficiency at 700°C, and heating time showing positive linear correlation with yield. Characterization confirmed successful extraction of high-purity silica with white appearance, near-neutral pH, bulk density of 180-200 kg/m³, and 3.1% moisture content. The NaOH/CuSO₄ confirmatory test validated silica presence, while absence of HCl reaction confirmed purity. Results demonstrated superior performance compared to conventional methods, with yields exceeding reported alkali hydrothermal extraction (52.8%) and approaching optimized acid leaching ranges (70-90%). The Taguchi optimization approach reduced experimental requirements by 66% compared to full factorial design while maintaining statistical rigor. This research establishes an efficient, scalable methodology for converting agricultural waste into value-added industrial material suitable for construction, ceramics, and environmental remediation applications, contributing to circular economy principles and sustainable materials development.