Nanoarchitecturing TiO₂/NiCr₂O₄ p-n heterojunction photocatalysts for visible-light-induced activation of persulfate to remove tetracycline hydrochloride

Herein, TiO₂/NiCr₂O₄ nanocomposites with p-n heterojunctions were synthesized via a refluxing method and used with peroxydisulfate (PDS) to produce extensive reactive radicals. Textural, optical, photoelectrochemical, structural, and morphological properties of the prepared materials were extensively investigated. After adding 1.48 mM PDS, the removal rate constant of tetracycline hydrochloride (TH) over the TiO₂/NiCr₂O₄ (20%)/PDS system was almost 20.5, 7.24, and 5.91-times as high as the pristine TiO₂, TiO₂/PDS, and TiO₂/NiCr₂O₄ (20%) samples, respectively. Therefore, the synergistic effect of PDS and heterogeneous photocatalysis remarkably impacted the degradation reaction of TH. It was proposed that all h⁺, ^•O₂⁻, ^•OH, and SO₄^•- contributed to the degradation reaction. According to the formation of heterojunction between n-TiO₂, and p-NiCr₂O₄ semiconductors, a plausible mechanism for removal of different contaminants in the TiO₂/NiCr₂O₄/PDS system was discussed.