Magnetic recyclable MoS2/Fe3O4 piezoelectric catalysts for highly efficient degradation of aqueous pollutants

As a new type of advanced oxidation processes, simple and easy to implement with less energy consumption, piezoelectric catalytic degradation technology has attracted much attention in recent years. However, the low degradation activity of piezoelectric catalysts and the problem of recycling limit their wide application in the actual degradation of wastewater. In this work, a series of MoS₂/Fe₃O₄ nanocomposite with different MoS₂ to Fe₃O₄ mole ratios were prepared using a facile two-step hydrothermal-precipitation method. The piezocatalytic performance of the obtained composite was investigated through piezocatalytic degrading azo-dye methylene blue (MB) and diclofenac sodium (DCF) in artificial solution, as well as antibiotic resistance genes (ARGs) in swine wastewater. The optimum mole ratio of MoS₂ to Fe₃O₄ was 1:1, by which MB degradation was completed in 6 min with a pseudo-first-order rate constant as high as 0.445 min^-1, which was about 2.2 times that of pure MoS₂ (0.202 min^-1). Moreover, the hybrid material displayed excellent reusability and good stability. The MoS₂/Fe₃O₄ piezocatalytic system can also efficiently degrade both DCF (100 % removal in 15 s) and ARGs (> 99 % in 8 min).The electron paramagnetic resonance characterization and free radical scavenging experiments display that ^•OH and ^•O₂^– were the major active free radicals in the piezocatalysis process and ^•OH was the dominant species. The piezoresponse force microscopy characterization and electrochemical test demonstrate that MoS₂/Fe₃O₄ has higher piezoelectric response than pure MoS₂, of which a plausible mechanism is proposed.