Synthesis and characterisation of (Fe, Co, Ni)-polyoxometalates to degrade O, O-diethyl-S-(p-tolyl) phosphorothioate under visible light irradiation

Different metalheteropoly acid salt catalysts were prepared by adding different metal ions (Fe, Co, Ni), and the structure of the materials was characterised by XRD, infrared, ultraviolet, fluorescence, etc., and heteropolyacid salt (TBA)4Hx[PW11M(Q)O39]·nH2O, wherein M = (Fe, Co, Ni) with Keggin-type structure was confirmed. A series of changes in the surface of the material after the addition of metal ions can be seen by scanning electron microscopy. The stability of the material was also experimentally designed and the material showed good stability. The prepared materials were subjected to the degradation of organophosphorus followed by O,O-diethyl-S-(p-tolyl) phosphorothioate as a degradation substrate. The catalytic performance of (TBA)4[PW11Fe(H2O)O39]·2H2O was found better among all synthesised materials, it degraded completely under visible light in 90 min, and degradations performance was analysed by ion chromatography by determining the presence of PO43-. In order to explore its degradation mechanism, ammonium oxalate (AO), isopropanol (IPA) and benzoquinone (BQ) were used to quench holes (h+), hydroxyl radicals (•OH) and superoxide radicals (•O2). It was observed that the important role in the degradation reaction is due to •OH radicals and it was also confirmed through 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin capture electron paramagnetic resonance (EPR) technology validates this conclusion. The prepared photocatalysts (TBA)4[PW11Fe(H2O)O39]·2H2O can be better applied to the degradation of organic phosphorus, which can reduce the environmental pollution caused by the use of organic phosphorus.