Synthesis of Nano-silica from Boiler Ash in the Sugar Cane Industry using the Precipitation Method

Abstract

Boiler ash is a second layer by-product of the combustion of fuel, usually an agro-waste, in any industry. In the sugarcane industry, boiler ash is obtained from the combustion of bagasse. The boiler ash of the sugarcane industry contains 49.69% silica, which can be transformed into nano-silica using the precipitation method, which is easier and cheaper than other methods. Precipitation pH and aging time are the main factors that influence nano-silica’s characteristics. The objectives of this research were to determine the effect of various precipitation pH levels and aging times on the characteristics of nano-silica and to identify the potential applications of nano-silica based on these characteristics. An increase in precipitation pH affected the number of the crystal phase and the intensity of the diffraction peaks. An increase in aging time also affected the intensity of the diffraction peaks and the number of crystal phases. The degree of crystallinity varied from 66.40% to 93.53%, the crystal size ranged from 37.77 nm to 56.87 nm, the particle size ranged from 214.04 nm to 698.24 nm, and the polydispersity index (PDI) ranged from 0.21 to 0.83. The nano-silica in this research had polygonal morphology. Increases in precipitation pH and aging time increased the number of siloxane groups, creating nano-silica dominated by a crystalline form with three crystal phases: tridymite, quartz, and cristobalite. Nano-silica have various potential applications based on their characteristics, including as filler for membranes, composite resin, rubber airbags, and supplementary cementitious material.

Keywords

• boiler ash
• characteristics
• nano-silica
• precipitation
• silica