Efficient degradation of naproxen in wastewater using Ag-deposited ZnO nanoparticles anchored on a house-of-cards-like MFI-type zeolite: Preparation and physicochemical evaluations of the photocatalyst

Abstract

We utilized Pr6-diquat-5 as an organic structure-directing agent (OSDA) to synthesize hierarchically intergrown ZSM-5 (HI-ZSM-5) as a catalytic support. ZnO particles were deposited onto HI-ZSM-5 via precipitation to remediate naproxen (NPX) in wastewater, while Ag was photo-deposited onto ZnO to prevent electron-hole pair recombination. XRD analysis revealed crystalline structures and particle sizes influenced by synthesis temperatures, and FT-IR confirmed ZnO and Ag deposition onto HI-ZSM-5 surfaces. Based on N2 adsorption-desorption isotherms, all samples exhibited Type I and IV isotherms with H4-type hysteresis loops, indicating the presence of both micro- and mesopores within HI-ZSM-5. XPS analysis confirmed the presence of peaks indicating Zn in ZnO and metallic Ag interacting with ZnO. TEM analysis identified aggregated Ag/ZnO nanoparticles in the photocatalysts, while EDX confirmed uniform element distribution. FE-SEM images revealed a uniform distribution of ZnO and Ag on HI-ZSM-5 with “house-of-cards” morphologies. PL analysis indicated reduced electron-hole recombination and an extended lifespan. NPX photodegradation experimental results showed that the reaction rate constant of the 3 %AZ composite was 2.8 times higher than that of ZnO/HI-ZSM-5 (0.0163 vs. 0.059 min−1, respectively). Evaluation of influential operating parameters demonstrated 90.8 % elimination of NPX under optimum conditions: a catalyst dosage of 1.5 g L−1 at pH 5 within 120 min. The impact of common anions on NPX decontamination and the catalyst's capability for COD and TOC removal (up to 62.6 and 53.4 %, respectively) was also discussed. The 3 %AZ optimum catalyst could be recycled for 5 cycles with remarkable reusability, maintaining 80.1 % removal efficiency after five regeneration cycles.