Improving the performance of heterogeneous Fenton catalysts via enhanced mass transfer and accelerated Fe cycle: Insights from the degradation of typical hydroxamic acids by MoS2-based micromotors

Abstract

Low Fe (II) generation and limited mass transfer are key challenges in the heterogeneous Fenton process. Toward addressing these challenges, we rationally design MoS<inf>2</inf>-based micromotors as heterogeneous Fenton catalysts, leveraging the self-propulsion of micromotors for enhanced mass transfer and the electron-donating property of MoS<inf>2</inf> to accelerate Fe(III) reduction. The tubular C/Fe<inf>3</inf>O<inf>4</inf>/MoS<inf>2</inf>/MnO<inf>2</inf> (CFMM) micromotors are prepared via a simple hydrothermal and impregnation method using hollow kapok fiber templates. Typical hydroxamic acids (HAAs) are used as model pollutants due to their refractory nature, physiological toxicity and widespread presence in mineral-processing wastewater. Incorporation of MoS<inf>2</inf> increases the removal efficiency by 36.92 %, which is attributed to that the electron transfer between MoS<inf>2</inf> and Fe<inf>3</inf>O<inf>4</inf> accelerates the Fe cycle, as confirmed by density functional theory (DFT) calculations and experimental results. Compared to the static counterpart, self-propulsion elevates the removal efficiency by 37.80 % due to enhanced mass transfer. The dual functions of prepared micromotors contribute to the generation of more •OH, •O<inf>2</inf>⁻, and ¹O<inf>2</inf>, leading to over 90 % removal efficiencies for different types of HAAs. The typical degradation pathways of HAAs are also analyzed based on the intermediates obtained in the process. Overall, through the introduction of the proposed scalable micromotor design, this work provides insight for improving the catalytic performance of heterogeneous Fenton catalysts via enhanced mass transfer and accelerated Fe cycle.