Optimization of Potassium Silicate Fertilizer Production from Fly Ash: Effect of KOH Concentration and Extraction Time

Abstract

Fly ash, a byproduct of coal combustion in power plants, contains a high concentration of silica, making it a valuable and underutilized raw material for synthesizing potassium silicate fertilizer. Potassium silicate is known for its ability to enhance plant resistance to abiotic stresses such as drought and salinity, thereby improving overall crop health, productivity, and yield. This study aims to determine the optimal synthesis conditions of potassium silicate from fly ash by varying potassium hydroxide (KOH) concentrations and extraction times. The experimental design involves extracting silica using five different KOH concentrations (7, 9, 11, 13, and 15 N) and five time intervals (60, 90, 120, 150, and 180 minutes). Results indicate that increasing KOH concentration leads to higher silica extraction efficiency; however, it concurrently decreases potassium content in the final product. This is attributed to increased solubility and subsequent loss of potassium during extraction. Among the tested conditions, the optimum synthesis was achieved using 15 N KOH for 120 minutes, producing a potassium silicate compound with 57.5% silica and 39.4% potassium, as confirmed through compositional analysis. These findings highlight the potential of converting fly ash into a high-value agricultural input, supporting waste valorization and sustainable fertilizer development. Despite these promising results, further research is recommended to evaluate field application efficacy, environmental impact, and economic feasibility in comparison with conventional commercial fertilizers.