Uniformly formed copper-modulation ZIF-8 pellets for efficient removal of tetracycline from wastewater

Removal tetracycline (TC) from wastewater is necessary due to its excessive use and environmental hazards. Herein, Cu-modulation zeolite imidazolate frameworks-8 powders (Cu-ZIF-8) and the shaped pellets composite with chitosan (CS-1Cu-ZIF-8) were successfully fabricated to adsorb TC. All Cu-ZIF-8 samples well preserved the structure of the original ZIF-8 and 1Cu-ZIF-8 sample had the excellent performance with TC adsorption capacity up to 213.8 mg/g. Besides, 0.5CS-1Cu-ZIF-8 pellets retained excellent TC adsorption capacity (203.6 mg/g), with almost no decrease compared to the powders. The powders and pellets adsorbents both fitted well with pseudo-second-order and Langmuir models, suggesting that chemisorption was dominant during adsorption process. Adsorption thermodynamic studies implied that the adsorption process was spontaneous and exothermic. Besides, the mechanism for TC adsorption was revealed to be hydrogen bonding, π-π interactions and electrostatic interactions between TC and adsorbents. Furthermore, the 1Cu-ZIF-8 powder and 0.5CS-1Cu-ZIF-8 pellets both displayed outstanding catalytic performance in complex water environments and had great reusability yet water stability. This work provided a facile and efficient strategy to fabricate MOFs-based adsorbent for water purification.