Conversion of municipal solid waste incineration bottom ash to sorbent material: Effect of ash particle size

Conversion of municipal solid waste incineration bottom ash (IBA) to sorbent material can provide an alternative route for the re-utilization of IBA and improve the sustainability of waste incineration technology. Alkaline hydrothermal treatment was adopted in this study for IBA conversion with an emphasis on the effect of IBA particle size. The converted product was determined to contain sodium aluminum silicon phosphorus oxide hydrate (Na₁₃Al₂₄Si₁₃P₁₁O₉₆(H₂O)₁₆), katoite (Ca₃Al₂(SiO₄)(OH)₈), and other unconverted materials. It is found that IBA of small particle size contains low Si content and promotes the conversion reaction. The presence of high surface area in small particles also facilitates the contact with reagent solution and favors conversion. A reduction in particle size and an increase in surface area were found after hydrothermal conversion. The converted product was adopted as sorbent material and demonstrated promising performance for pollutants (organic dye and heavy metal ions) removal from water. An increase in the surface area of the converted product favored dye adsorption, while an increase in exchangeable cations was found to improve the heavy metal ion removal efficiency. Sorbent converted from IBA in the size range of 0.212–0.6 mm was found to show the highest dye removal efficiency, while sorbent obtained from IBA having particle size < 0.212 mm performed the best for heavy metal ions adsorption. The adsorption of pollutants was also investigated by isotherm study. The adsorption process was found to follow Langmuir model, indicating that the process was dominated by chemisorption.