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BACKGROUND: Organophosphorus herbicides in water are an increasingly critical environmental problem. Given this challenge, a free-standing 3D reduced graphene oxide (GO) foam supporting Fe 3 O 4 nanoparticles (3D-rGO-Fe 3 O 4 ) was synthesized using GO as a precursor and applied as an efficient persulfate activator for glyphosate (GLY) degradation.RESULTS: The effects of Fe 3 O 4 mass, pH, oxidant dosage, temperature and common ions on GLY degradation were investigated in detail. Analytical techniques using scanning electron microscopy (SEM), Fourier transform infrared analysis (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated that the 3D foam prevented aggregation of the Fe 3 O 4 nanoparticles by in situ uniform formation on GO nanosheets. The addition of Fe was vitally important for activation of the oxidation system. The results of batch-scale experiments illustrated that the GLY degradation efficiency reached 96.8% with initial GLY concentration 30 mg L −1 , graphene:Fe 3 O 4 mass ratio 1:7, solution pH 4 and persulfate mass 48 mg. High temperatures could significantly facilitate GLY degradation. Additionally, the 3D-rGO-Fe 3 O 4 material proved highly stable according to the replicated test results. Furthermore, EPR test results revealed that Na 2 S 2 O 8 catalytic activation by 3D-rGO-Fe 3 O 4 mainly produced •OH and SO 4 − •, and the predominant free radical was SO 4 − • in the current experiment. CONCLUSION:The results indicate that 3D-rGO-Fe 3 O 4 has good catalytic activity and stability, and, accordingly, has high application prospects for the remediation of organophosphorus herbicide-contaminated water.

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Compared with traditional hydrothermal synthesis, microwave-assisted synthesis has the advantages of being faster and more energy efficient. In this work, the MoS2/BiVO4 heterojunction photocatalyst was synthesized by the microwave-assisted hydrothermal method within 30 min. The morphology, structure and chemical composition were characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM). The results of characterizations demonstrated that the synthesized MoS2/BiVO4 heterojunction was a spherical structure with dimensions in the nanorange. In addition, the photocatalytic activity of the samples was investigated by degrading tetracycline hydrochloride (TC) under visible light irradiation. Results indicated that the MoS2/BiVO4 heterojunction significantly improved the photocatalytic performance compared with BiVO4 and MoS2, in which the degradation rate of TC (5 mg L−1) by compound where the mass ratio of MoS2/BiVO4 was 5 wt% (MB5) was 93.7% in 90 min, which was 2.36 times of BiVO4. The active species capture experiments indicated that •OH, •O2− and h+ active species play a major role in the degradation of TC. The degradation mechanism and pathway of the photocatalysts were proposed through the analysis of the band structure and element valence state. Therefore, microwave technology provided a quick and efficient way to prepare MoS2/BiVO4 heterojunction photocatalytic efficiently.