Synthesis of chitosan-modified magnetic metal-organic framework and its adsorption of Congo red and antibacterial activity

Although various nano-adsorbent have been developed for sewage treatment, only a few adsorbents possess antibacterial activities. We aimed to synthesis a double-purpose nano-adsorbent with adsorption and antibacterial activity. Magnetic composite materials (Fe 3 O 4 @ZIF-8@SiO 2 ) with a porous crystalline state and large specific surface area were synthesized. Chitosan (CS) with broad-spectrum antimicrobial activity was used to functionalize the magnetic metal-organic framework nanocomposites. Fe 3 O 4 @ZIF-8@SiO 2 @CS were produced of low cost, mild conditions without any calcination step. Fourier transform infrared spectroscopy, scanning electron microscopy, the Brunauer-Emmett-Teller method, transmission electron microscopy, vibrating sample magnetometry, thermogravimetric analysis, X-ray diffractometry and X-ray energy dispersive spectrometry presented evidence that a new porous adsorbent Fe 3 O 4 @ZIF-8@SiO 2 @CS is rich in –NH 2 and C S and have specific surface area of 420.58 m 2 /g. Fe 3 O 4 @ZIF-8@SiO 2 @CS has loose crystals, thermodynamically stable and well-defined structures, which are used for Congo red (CR) adsorption and bacterial cell killing. We determined optimal adsorption conditions by adjusting adsorption time, pH and ionic strength. Fe 3 O 4 @ZIF-8@SiO 2 @CS shows a good adsorption capacity of CR, reaching 310.4 mg/g at 298 K. The adsorption kinetics and adsorption isotherm obeyed the General-order kinetic (GO model) and Liu model, respectively. The Fe 3 O 4 @ZIF-8@SiO 2 @CS can remove dyes from simulated dye effluent, and it can be reproduced easily without centrifugation or filtration, with the adsorption efficiency exceeded 70% even after five cycles. Fe 3 O 4 @ZIF-8@SiO 2 @CS exhibited antibacterial activity against Staphylococcus aureus and Bacillus subtilis . Double-purpose Fe 3 O 4 @ZIF-8@SiO 2 @CS can be a potential material for wastewater treatment. • The chitosan composite of Fe 3 O 4 @ZIF-8@SiO 2 @CS synthesized shows exceptional porosity, thermal stability and recyclability. • Fe 3 O 4 @ZIF-8@SiO 2 @CS was prepared by a layer-wise self-assembly method without any calcination step. • The adsorption capacities for Congo red (CR) were 310.4 mg/g. • The Fe 3 O 4 @ZIF-8@SiO 2 @CS exhibited an outstanding reusability and excellent antimicrobial performance. • Electrostatic interaction, Hydrogen bonding, π-π stacking interaction and pore filling were proposed as possible mechanisms for the removal of dyes.