Preparation of amino-functionalized fly ash based tobermorite for enhanced removal of Cr(VI)

Amino-functionalized fly ash based tobermorite (NH₂-FAT) was prepared via a two-step process including a hydrothermal preparation of fly ash based tobermorite (FAT) from fly ash (FA) and the impregnation of 3-aminopropyltriethoxysilane (APTES). The characteristics of FA, FAT, and NH₂-FAT were systematically measured. The removal capacity of Cr(VI) by FAT and NH₂-FAT were comparatively studied. The results indicated that the NH₂-FAT presented excellent removal efficiency towards Cr(VI) in the condition of pH of 2. The adsorption capacity of Cr(VI) by NH₂-FAT in this study was up to 498.39 mg/g resulted from Langmuir model, which was more superior to that of FAT, other reported FA based adsorbents and most amino-functionalized adsorbents. Furthermore, the removal mechanisms of Cr(VI) by NH₂-FAT were ascribed to both electrostatic attraction and reduction to Cr(III) by amino groups. Overall, this work indicates the NH₂-FAT is a promising adsorbent for treating wastewater containing Cr(VI), and provides a new utilization method of FA.