This paper focuses on the functionalization of heterogeneous and highly contaminated waste material, namely bottom ashes (BA) with a particle size ≤ 125 μm that cannot be recycled with conventional treatments. The main goal of this study is to modify this waste into a valuable material that can be used in various applications, especially in the building sector. The complex mineralogical nature of this material was investigated with quantitative XRD, which confirms the presence of crystalline and amorphous phases such as silicates, carbonates, metallic oxides and amorphous glass. A hydrophobic modification was performed by using a fluorosilane grafting agent that utilizes the reactive surface sites of these minerals to form silanol bonds. Results showed that the 2.5% (m/m) of silane made the BA hydrophobic. Moreover, a thorough characterization showed that fluorosilane was well-grafted at the surface of the BA, with more than 60% of the fluorosilane chemisorbed on the surface. Additionally, the hydrophobic modification led to a significant decrease of the leaching of the contaminants (Cr, Cu, Mo and Sb) from the BA particles. Following this methodology, fine fraction of BA could be eventually used as a building material, preventing the landfill of this toxic waste.
The authors would like to acknowledge the financial support provided by NWO ( Nederlandse Organisatie voor Wetenschappelijk Onderzoek ), the Netherlands, under the project number 10019729: “Environmental concrete based on the treated MSWI bottom ashes”. Special thanks to Prof. dr. A. Caballero Martinez from the department of chemical engineering for assisting us with the XPS analysis.
|Nederlandse Organisatie voor Wetenschappelijk Onderzoek
- Coal Ash
- Construction Materials
- Solid Waste
- MSWI bottom Ash
- Surface characterization