Durable and Low-Cost Chitosan Decorated Fe/MOF-5 Bimetallic MOF Composite Film for High Performance of the Congo Red Adsorption

The auspicious merits of polysaccharides make them eminent choices in numerous fields, particularly water remediation. Nonetheless, polysaccharides like chitosan (CTS) suffer from low adsorbability. Meanwhile, the recent revolution in material science has produced substances with supreme adsorbability, such as metal-organic frameworks (MOFs). Consequently, the Fe/MOF-5@CTS composite film was synthesized by doping a low amount (5 wt%) of Fe/MOF-5 into the CTS film. The crystallinity, morphology, composition, and surface charge of the Fe/MOF-5@CTS composite film were identified using multiple characterization analyses. Furthermore, the adsorption property of Fe/MOF-5@CTS was examined for the removal of Congo red (CR). Surprisingly, the Qmax of CR onto Fe/MOF-5@CTS reached 219.78 mg/g. Additionally, the composite film only lost 18.54% of its capacity after ten cycles. The selectivity test demonstrated the higher selectivity of the positively charged-rich composite film towards anionic dyes, especially CR, compared to the cationic dyes. Based on the practical experiments and analysis tools, the adsorption mechanism of CR onto Fe/MOF-5@CTS is presumed to occur via electrostatic, host-guest, pi-pi interaction, and coordination bonds.