Insight into adsorption performance and mechanism of Congo red dye onto ZnFe2O4@ZIF-8 nanocomposite in water

Nowadays, the water contamination of organic dyes generated from the textile industries is increasingly considered an alarming situation. Because dyeing wastewaters are toxic and carcinogenic, it is important to remove textile dyes by feasible techniques, typically adsorption. Herein, we report the production of zinc ferriteloaded zeolitic imidazolate framework-8, or ZFO@ZIF-8 by a tunable hydrothermal method and use this composite as an adsorbent to purify water containing Congo red dye (CR). Well-defined ZFO@ZIF-8 possessed a SBET of 145.9 m2 g-1, a total mesoporous volume of 0.54 cm3 g-1 and an average pore size of 14.4 nm. The adsorption of CR over ZFO@ZIF-8 was investigated under contact time (0-180 min), concentration (5-30 mg L-1), dosage (0.1-1.0 g L-1), pH (3-11). The highest removal efficiency, nearly 95 % was obtained at a CR concentration of 5 mg L-1, a ZFO@ZIF-8 dosage of 0.5 g L-1, pH 5, and 180 min. CR adsorbed by ZFO@ZIF-8 was a mono-layer process, giving a maximum value of 66.45 mg g-1. A FTIR examination confirmed the involvement of electrostatic, pi-pi, and H bonding interactions in the CR adsorption. Interestingly, the ZFO@ZIF-8 composite was reusable at least 6 cycles, remaining an efficiency of 84 % in the final cycle. Therefore, this composite should be a promising adsorbent against organic textile dyes.