g-C3N4 Enhanced Fe3+/ Fe2+ Cycling to Activate PMS for Pharmaceuticals Degradation Under Solar Irradiation

Since Peroxymonosulfate (PMS) is readily available and can produce sulfate radicals with a stronger oxidation capacity, the Fenton-like system Fe2+/PMS has gradually replaced Fe2+/H2O2 system in organic pollutants degradation. However, the Fe3+/PMS system has almost no degradation effects, with the conversion of Fe2+ to Fe3+ being the rate-limiting step in the Fe3+/PMS system. In this paper, graphite-like phase carbon nitride (g-C3N4) was employed to activate PMS using trace amounts of Fe3+ for the treatment of water pollution under sunlight, and the Fe3+/g-C3N4/PMS system demonstrated the ability to rapidly degrade a wide range of difficult-to-degrade organic pollutants. The Fe3+/g-C3N4/PMS system was able to completely degrade carbamazepine (CBZ) within 30 min under sunlight. The fundings indicated that this system effectively improved the stringent limitations typically associated with Fenton process regarding the feed ratio of metal ions to oxidants, and could efficiently degrade CBZ across a broad pH range. In addition, the Fe3+ concentration of 6.17 x 10(-6) M was used in the experiments to avoid the generation of large amounts of "iron sludge". The trap burst experiments, DMSO oxidation experiments and electron paramagnetic resonance spectroscopy experiments indicated that O-2<middle dot>(-) and O-1(2) exerted the major effectiveness in the photocatalytic degradation reaction of CBZ, and SO4<middle dot>(-) and <middle dot>OH jointly promoted the CBZ degradation.