Construction of plum-branch-like BiOI/NH₂-MIL-68(In) Z-scheme heterojunctions for removal of tetracycline hydrochloride from wastewater via synergistic adsorption-photocatalysis process

The synergistic adsorption-photocatalysis process has been considered as a novel, green and effective way in the field of environmental remediation, in which adsorption would facilitate the photocatalysis process by strengthening the link between the contaminant and the catalyst. In this paper, a series of Z-scheme heterojunction adsorption photocatalysts of BiOI/NH₂-MIL-68(In) with plum-branch-like morphology were designed and constructed. The adsorption process on BiOI/NH₂-MIL-68(In) is heterogeneous and multilayer, and the as-formed chemical adsorption is mainly attributed to the effects of electrostatic attraction, π-π conjugation and hydrogen bonding. Such produced high adsorption capacity would be conducive to the further photocatalytic degradation of tetracycline hydrochloride (TC). The removal efficiency on 1.5-BiOI/NML reaches 90.04 % after an hour dark reaction following 30 min visible light irradiation, which is 5.08 and 8.61 times than that of the original BiOI and NH₂-MIL-68(In). The mechanism of TC removal and the possible pathway of photocatalytic degradation are reasonably proposed. This study provides some enlightenment for the design and construction of visible light responsive adsorbents in the field of wastewater treatment.