One-pot synthesis of Aluminum-containing ordered mesoporous silica MCM-41 using coal fly ash for phosphate adsorption

The present study offers an economic one-pot synthesis of Al-containing ordered mesoporous silica MCM-41 from the coal fly ash. The samples were characterized by small-angle XRD, N2 adsorption, TEM, mapping, (27)Al MAS NMR, EDX, and NH3-TPD. The effects of pH values to the final mesostructures have also been investigated. The results show that the material prepared at the pH value of 10 displays the largest pore volume of 0.98 cm(3)/g, the highest BET surface area of 1020 m(2)/g, and the lowest Si/Al molar ratio of 2. Using this material as adsorbent for phosphates, the adsorption capacity reaches 64.2mg/g at 298 K, which is much higher than that of large pore mesoporous silica SBA-15 (53.5mg/g), diatomite (62.7 mg/g), and MCM-41 (31.1 mg/g). In addition, the thermodynamics and kinetics for the phosphate adsorption were also investigated. Our present study shows an economic way to treat phosphates using the industrial solid waste of coal fly ash.