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-FeO) modified NaY zeolite (FeO@Y) with bifunction of adsorption and catalysis. The Fe successfully replaced the Na in the β cage of zeolite in the ion exchange process and coordinated with framework oxygens to form magnetic γ-FeO. Therefore, most of the γ-FeO particles were confined in the β cages, which resulted in the high dispersal and stability of the catalyst. The FeO@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 FeO@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-FeO 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 FeO@Y + MNB system. In this work, the FeO@Y was demonstrated as a potentially magnetic adsorbent or MNB catalyst for wastewater treatment.