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

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.