Removal of furfural in wastewater by Al-MIL-53 prepared in various solvents

Abstract

Furfural is a typical biomass-derived chemical with great industrial applications. Its increasing production has put forward strong concern on its emission control, especially the removal of low concentration furfural in wastewater. Efficient and environment-friendly strategies for the adsorption/recovery of furfural in diluted aqueous solution are highly required. In this work, we have synthesized several Al-MIL-53 materials in different commonly used solvents, i.e. water (H2O), N,N’-dimethylformamide (DMF), ethanol (EtOH) and methanol (MeOH). The adsorption capacities of furfural on these materials have been investigated to illustrate the effect of solvents used in the synthesis on the furfural adsorption behavior of the obtained Al-MIL-53. We found that the solvents used in this work result in Al-MIL-53 with different morphology, porosity and performance of furfural adsorption. When water was used as a solvent, a framework with good crystallinity was obtained. The specific surface area and the pore volume were 1073 m2 g−1 and 0.58 cm3 g−1, respectively. The adsorption rate of furfural on Al-MIL-53 (H2O) was the fastest and the adsorption capacity could reach 774 mg g−1 at the furfural concentration of 14.34 g L−1, which is 11%, 16% and 25% higher than those on Al-MIL-53 (DMF), Al-MIL-53 (EtOH) and Al-MIL-53 (MeOH) under the identical condition, respectively. The high adsorption property of Al-MIL-53 (H2O) can be due to its better structural crystallinity and porosity. Al-MIL-53(MeOH) has the poorest structural crystallinity and porosity, however, showing the highest furfural adsorption capacity based on surface area (3.3 mg m−2). The characterization results suggest that Al-OH defect sites in crystallites with poor porosity may also favor the interaction between furfural and MOFs.