Novel MoS2-based heterojunction as an efficient and magnetically retrievable piezo-photocatalyst for diclofenac sodium degradation

It is a challenging and meaningful task to design a piezo-photocatalyst with excellent performance under mild mechanical stirring conditions rather than ultrasonic irradiation. Herein, a hydraulic-driven piezo-photocatalytic process was proposed, using MoS₂-based heterojunction as catalysts for diclofenac sodium (DCF) degradation. A magnetically retrievable MoS₂/TiO₂/Fe₃O₄ composite was designed and successfully prepared by a facile one-step solvothermal process. Among various heterojunction composites and pure MoS₂, the ternary composite MoS₂/TiO₂/Fe₃O₄ exhibited the strongest piezo-photocatalysis capability, with a DCF degradation efficiency of 99.6% and a pseudo-first-order rate constant of 0.733 min⁻¹. Additionally, the degradation efficiency of DCF was still up to 85.2% in 6 min after 5 cycles by MoS₂/TiO₂/Fe₃O₄. The ternary composite can be easily collected and separated using a magnet. There was an optimum hydraulic gradient value (0.45 s⁻¹) for DCF degradation. ^•OH played a major role in DCF degradation during the hydraulic-driven piezo-photocatalytic process. A satisfactory DCF degradation was found in the actual water media. The results verify the existence of a synergetic effect between piezo and photocatalytic processes. Thereupon, the hydraulic-driven piezo-photocatalysis can be an efficient, sustainable, and energy-saving process for water treatment.