Rapid adsorption of tetracycline in aqueous solution by using MOF-525/graphene oxide composite

By improving the synthesis process of MOF-525, MOF-525 was grown on the surface of graphene oxide (GO), and thus the MOF-525/GO composite was obtained for the adsorption of tetracycline (TC) in water. MOF-525 and GO can be identified on the surface of MOF-525/GO, and the BET surface area measured is up to 444.49 m2 g−1. MOF-525 and GO are bonded by coordination bonds, and the lattice structure of MOF-525 is retained in the composite. Both GO and MOF-525 have good adsorption properties, the maximum adsorption capacity is 236.7 mg g−1 and 371.5 mg g−1, respectively. The maximum adsorption capacity of MOF-525/GO reaches 413.6 mg g−1, indicating that GO does not weaken the adsorption performance of MOF-525, but further strengthens. The initial adsorption rate of MOF-525/GO for TC was very fast (the adsorption removal rate reached 47% within 2 min), and the adsorption removal amount is almost unchanged after 360 min. Elovich model and Sips model fitted the adsorption process well, revealing that the adsorption process was exothermic reaction dominated by chemisorption and the maximum adsorption capacity was 436 mg g−1. In addition, MOF-525/GO carries a negative charge, and the adsorption performance gradually decreases with the increase of pH value. The adsorption capacity of MOF-525/GO was mainly derived from π-π stacking and hydrogen bonding, and the complexation between Zr and TC was also involved in the rapid adsorption stage.