Multifaceted Surface Analysis of Municipal Solid Waste Incineration Fly Ash by Water Repellent Treatment with Fatty Acid

In this study, we aimed to conduct a multifaceted surface analysis of water repellent-treated municipal solid waste incineration (MSWI) fly ash to determine the suppression mechanism of fatty acid elution. The surface of water repellent-treated MSWI fly ash was analyzed using scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analyses. Scanning electron microscopy revealed the absence of needle-shaped crystals but distinct particle agglomeration in the water repellent-treated fly ash. Fourier-transform infrared spectroscopy revealed that the water repellent treatment caused fatty acids to form esters with aluminosilicates in the MSWI fly ash. Crystalline phase analysis of the water repellent-treated fly ash before and after the leaching test via X-ray diffraction revealed the presence of fatty acids on the fly ash surface and retention of the fatty acid coating. Overall, the multifaceted surface analysis revealed that water repellent treatment suppressed heavy metal elution by covering the surface of MSWI fly ash with hydrophobic groups.