Enhanced Adsorption of Doxycycline Hydrochloride (DCH) from Water on Zeolitic Imidazolate Framework-8 Modified by Cu2+ (Cu–ZIF-8)

In this study, Cu-ZIF-8, zeolitic imidazolate framework-8 surface modified by Cu2+, was synthesized easily in one-pot method with Cu(NO3)2·3H2O addition in ZIF-8 crystal preparation. The Cu-ZIF-8 as-synthesized turned to light pink from white ZIF-8. The Cu-ZIF-8 particles were in good crystal morphology with the uniform size of approximately 400 nm, and Cu-ZIF-8 was a typical microporous material. Cu-ZIF-8 exhibited an excellent adsorption capacity (379.2 mg·g-1) at the initial doxycycline hydrochloride (DCH) concentration of 80 mg·L-1 in aqueous solution at 303 K, which was higher than ZIF-8 (339.2 mg·g-1). The DCH adsorption capacity on Cu-ZIF-8 increased to 481.5 mg·g-1 at the initial DCH concentration of 100 mg·L-1. The adsorption of DCH onto Cu-ZIF-8 was a spontaneous process. The π–π stacking interaction and multi-complexation resulted in the effective adsorption of DCH on Cu-ZIF-8. Cu-ZIF-8 had a stable structure after it was regenerated by ethanol and reused for multiple times. Cu-ZIF-8 can be considered as a suitable candidate for antibiotic removal.