Fabricating an adsorbent and micro-nano bubble catalyst through confining maghemite in the β cage of NaY zeolite

Abstract

This work reports the ion exchange fabrication of maghemite (γ-Fe₂O₃) modified NaY zeolite (Fe₂O₃@Y) with bifunction of adsorption and catalysis. The Fe³⁺ successfully replaced the Na⁺ in the β cage of zeolite in the ion exchange process and coordinated with framework oxygens to form magnetic γ-Fe₂O₃. Therefore, most of the γ-Fe₂O₃ particles were confined in the β cages, which resulted in the high dispersal and stability of the catalyst. The Fe₂O₃@Y could remove methylene blue (MB) model pollutants up to 59.02 and 61.47% through the adsorption and catalysis process, respectively. The hydrogen bond between the OH^- ions around the Fe₂O₃@Y surface and the N and O presented in the MB molecules enabled the chemical adsorption to MB, which accorded with the pseudo-second-order kinetic model. Further, the H⁺ existed in the solution and the β cage of zeolite promoted the collapse of micro-nano bubbles (MNBs). Then, the γ-Fe₂O₃ catalyst would be activated by high temperature and oxidated OH^- to produce hydroxyl radicals for pollutant degradation. Thus, pollutant removal was attributed to the combined effects of adsorption and catalysis in the Fe₂O₃@Y + MNB system. In this work, the Fe₂O₃@Y was demonstrated as a potentially magnetic adsorbent or MNB catalyst for wastewater treatment.

Keywords: Integrated adsorbent and catalyst; Ion migration; Maghemite; Methylene blue; Micro-nano bubble; NaY zeolite.