Silica nano particles synthesized from boiler spent ash: Value addition to an industrial waste

Abstract

Large quantities of biomass ash are generated everyday by the spice industries and are currently disposed off as landfill. However, this could transform into an environmental pollutant unless alternative techniques are developed for its disposal or value addition. Here in this study, the waste ash from biomass combustion wassuccessfully converted into silica nanoparticles with potential for application in several fields. The highly alkaline nature of the ash and presence of unburned carbon warrants a pretreatment which includes digestion and acid treatment. The synthesized silica was characterized in terms of morphology, specific surface area, crystallinity, surface functional groups and size. Alkaline extraction of the pretreated ash followed by acid precipitation yielded an amorphous structure with minimum mineral contaminants, high surface area, and a narrow size distribution (8-10 nm range) characteristic of nano silica. Studies thus indicate that the waste ash and the extraction process could be fine tuned for the large scale production of amorphous silica and could be of use to solve the problem of boiler ash pollution.

Keywords: biomass ash, boiler ash, nano silica, value addition to waste, amorphous silica