Pulsed discharge plasma assisted with Z-scheme graphene-TiO2-MnFe2O4 for simultaneous removal of atrazine and Cr (VI): Performance and mechanism

Abstract

Simultaneous removal of atrazine (ATZ) and Cr (VI) by pulsed discharge plasma (PDP) coupled with Z-scheme graphene-TiO2-MnFe2O4(GTM) photocatalyst was investigated. The structural morphology, bandgap structure, and photoelectrochemical properties of the prepared catalysts were systematically characterized by various characterization methods. The results showed that GTM was hybridized and exhibited high separation efficiency of electron-hole pairs. PDP can remove ATZ and Cr (VI) simultaneously, and the addition of GTM significantly enhanced the removal efficiencies of ATZ and Cr (VI) in PDP system, which can be attributed to higher separation efficiency of charge carriers and strong redox ability in the Z-scheme system. At Cr (VI) and ATZ initial concentrations of 10 mg/L, discharge power of 7 W, electrode gap of 10 mm, air flow rate of 4 L/min, graphene content of 5 %, catalyst dosage of 0.2 g/L and pH of 3.1, the highest removal efficiencies of ATZ and Cr (VI) reached 96.2 % and 79.8 %, which were 27.3 % and 32.1 % higher than those in single PDP system, respectively. Meanwhile, the energy efficiencies of ATZ and Cr (VI) also reach the maximum (440.0 mg/kWh and 216.8 mg/kWh), which are 2.3 and 2.0 times that of single PDP system, respectively. ·OH and h+ play a key role in the ATZ degradation. eaq, ·H, H2O2, e- and Fe2+ work in the Cr (VI) removal. The possible degradation pathways of ATZ were deduced according to the intermediates determined by LC-MS. Finally, the ecotoxicity of intermediates was evaluated by a quantitative structure–activity relationship (QSAR).