Unveiling the mechanism of visible light-assisted peroxymonosulfate activation and carbamazepine degradation using NH2-MIL-125(Ti)@MIL-53(Fe/Co) heterojunction photocatalyst

Abstract

Herein, a facile hydrothermal synthesis method was used to create the visible light-responsive heterojunction composite NH₂-MIL-125(Ti)@MIL-53(Fe/Co) (AMIL@MIL). This composite catalyst was investigated for the mineralization of carbamazepine (CBZ) in aqueous solution with a visible light-assisted activation of peroxymonosulfate (PMS). CBZ (initial concentration: 10 mg L⁻¹) could be totally degraded by 0.05 g L⁻¹ of composite containing 10 wt% NH₂-MIL-125(Ti) (AMIL(10)@MIL) and 0.25 g L⁻¹ of PMS within 1 h reaction under visible light. The enhanced degradation of CBZ was attributed to the efficient activation of PMS, and subsequently the generation of SO₄˙⁻, ˙OH and O₂˙⁻ radicals, together with the remarkable light harvesting and spatial charge separation in the direct Z-scheme heterojunction configuration. The composite catalyst could effectively treat contaminated surface and groundwater samples, overcoming the minimal to moderate inhibitory effects of coexisting ions and organics, while also exhibiting good reusability and structural integrity. The adsorbed PMS molecules are activated by several surface-confined redox cycles, including Fe²⁺/Fe³⁺, Co²⁺/Co³⁺ and Ti³⁺/Ti⁴⁺, aiding in the production of reactive radicals in the medium and efficient charge transfer during the reaction. A thorough study on the intermediates was carried out to determine the plausible CBZ mineralization and degradation pathway in the AMIL(10)@MIL/PMS/vis system. Overall, the suggested catalytic method is applicable and feasible for the remediation of contaminated surface and groundwater when exposed to visible light radiation.