Enhanced activation of peroxymonosulfate by multivariate ZnxCoy-ZIF for efficient pharmaceutical degradation in water

Abstract

The pervasive occurrence of micropollutants in aquatic environments, characterized by their trace-level concentrations, persistent nature, and bioaccumulative potential, poses significant threats to ecological safety and public health. Addressing this challenge requires developing advanced oxidation processes capable of effective contaminant elimination. Herein, we report a series of bimetallic Zn_xCo_y-ZIF catalysts synthesized via a facile one-pot method and comprehensively characterized. These multivariate metal–organic frameworks (MOFs) demonstrated exceptional peroxymonosulfate (PMS) activation capacity for pharmaceutical degradation, with sulfadimidine (SDM) serving as a model contaminant. Key operational parameters including initial contaminant concentration (5–40 mg L⁻¹), solution pH (5–9), catalyst dosage (50–125 mg L⁻¹) and PMS concentration (0.1–0.6 mM) were systematically optimized. The Zn_0.25Co_0.75-ZIF/PMS system achieved complete SDM removal within 50 min, exhibiting 79.4 and 2.13 times enhancement over monometallic ZIF-8 and ZIF-67 references, respectively. Quenching experiments and ESR spectroscopy confirmed the involvement of both radical (SO₄˙⁻ and ·OH) and non-radical (¹O₂) pathways. XPS analysis demonstrated enhanced Co³⁺/Co²⁺ redox cycling in the Zn_xCo_y-ZIF/PMS system, while LC-MS analysis revealed potential degradation intermediates and pathways. The catalyst maintained >87% removal efficiency with minimal metal leaching (Zn 0.10 mg L⁻¹, Co 0.26 mg L⁻¹) after five consecutive cycles, demonstrating remarkable stability. This work advances the rational design of tunable MOF catalysts for persulfate activation while establishing a sustainable strategy for water purification.