Mpg-CN-ZIF-8 composites for the degradation of tetracycline hydrochloride using visible light.

It was found that mesoporous graphite carbon nitride (mpg-CN) prepared using melamine as the precursor and ammonium chloride as the bubble template, has good photocatalytic activity under visible light irradiation. In order to improve the photocatalytic performance of mpg-CN, it was combined with metal-organic framework ZIF-8. Taking tetracycline hydrochloride (TC) solution as a model pollutant, the photocatalytic activity of composites was studied to select the optimal composite ratio and pH value. The initial concentration of hydrogen peroxide and active oxidation species were also investigated. The results showed that when the loading of ZIF-8 was 40 wt%, the removal efficiency was the best and 74.8% of TC could be removed. The degradation efficiency of TC was negatively affected under extreme pH conditions, but the composite photocatalyst mpg-CN-ZIF-8 had a relatively higher degradation efficiency on TC at mild pH values (4-8). The removal efficiency was the best at pH 8, and 75.1% of TC could be removed; the adsorption capacity was 430.7 mg·g and the photodegradation capacity was 548.6 mg·g. The order of active species affecting the photocatalytic degradation of TC by mpg-CN-ZIF-8 was hole > superoxide radical > hydroxyl radical.