Synthesis of Ag3PO4 immobilized with sepiolite and its photocatalytic performance for 2,4-dichlorophenol degradation under visible light irradiation

• A novel Ag3PO4-sepiolite composite photocatalyst was first synthesized.
• Enhanced photocatalytic activity and stability of 2,4-DCP over the composite were achieved.
• Photodegradation conditions of 2,4-DCP was optimized by the response surface methodology.
• OH, O2·− and h+ are the most active species for 2,4-DCP degradation inferred from free radical capture experiments.

A novel Ag3PO4-sepiolite composite photocatalyst was first synthesized using the liquid deposition method. And its characteristics were measured by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) analysis, X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface, UV–vis diffuse spectra and photoluminescence (PL). Moreover, the photocatalytic performance of Ag3PO4-sepiolite was tested for 2,4-DCP degradation under visible light irradiation, and enhanced photocatalytic activity and stability were achieved. Besides, the response surface methodology based on Box–Behnken design (BBD) was employed to investigate the effects of different reaction conditions on the removal of 2,4-DCP. The optimum conditions for 2,4-DCP degradation were as follows: solution pH value of 4.01, H2O2 concentration of 35.24 mM and catalyst dosage of 0.36 g L−1. Under these conditions, the experimental values for 2,4-DCP and TOC removal efficiencies were of 84.50% and 64.39%, which consisted with the predicted values of 84.65% and 64.48%, respectively. Furthermore, the free radical capture experiments indicated that reactive species of OH, O2·− and h+ were the main participants for oxidizing 2,4-DCP. The reaction intermediates were also identified by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometer (GC-MS) technique.

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