Superparamagnetic Fe3O4@Al-based metal-organic framework nanocomposites with high-performance removal of Congo red

Abstract

Azo dyes are one of the most widely used synthetic dyes, not only for printing and dyeing textiles, but also for dyeing leather, paper, and food. The removal of azo dyes is a major challenge to the environment. Under certain conditions, azo dyes can generate aromatic amines, which can covalently bind to human DNA bases through activation, causing human lesions and inducing cancer. Among them, Congo red (CR) is the most representative azo anion dyes. In this study, a hydrothermal method assisted by ultrasound was used to create superparamagnetic Fe3O4 @Al-based metal-organic framework (Fe3O4 @Al-MOF) nanocomposite for the removal of CR from water. According to characterization, Fe3O4 @Al-MOF was a stable nanocomposite with high specific surface area (526.73 m2·g−1) and superparamagnetic. The experimental results showed that Fe3O4 @Al-MOF could remove CR efficiently within 10 min and reach equilibrium within 50 min, and the adsorption capacity was as high as 2543.6 mg·g−1 under acidic and 313 K conditions, which was higher and faster than previously reported literature. The adsorption process was consistent with the pseudo-second-order model and the adsorption data were consistent with the Langmuir monolayer adsorption isotherm. After five cycles, the removal efficiency was still up to 83.7%, indicating the commercial potential of Fe3O4 @Al-MOF. The adsorption mechanism was investigated using FTIR and zeta potential, which revealed that the synergistic interplay of electrostatic interaction, π-π interaction, hydrogen bonding, and high porosity (56.7%) is the adsorption mechanism for CR removal by Fe3O4 @Al-MOF. Thus, Fe3O4 @Al-MOF nanocomposite is a promising material for removing CR.