Enhancing the Fenton-like degradation of organic contaminants with silicate-iron in aquifer media by ascorbic acid

In this study, silicate-iron (FeSi-ox, FeAlSi-ox) in aquifer media was utilized as an original iron source in groundwater to systematically investigate the effects of ascorbic acid on the degradation of p-nitrophenol (PNP) in the in-situ Fenton-like reaction. Silicate-iron in the aquifer media increased the PNP removal rate by activing H2O2 following the addition of ascorbic acid. The optimal removal rate of PNP was nearly 89% within 40 h, which was 6.8 times higher than that without ascorbic acid. In addition to PNP, some other common pollutants, such as nitrobenzene, trichloromethane, and trichloroethylene, can also be effectively degraded and mineralized. The suitable pH range for the silicate-iron Fenton-like system with ascorbic acid was 5-9, indicating that it is feasible in near-neutral or alkaline groundwater environments. The main functional free radicals were hydroxyl free radicals (center dot OH), which were produced slowly but continuously. In this novel Fenton-like system, dissolved Fe played a major role in H2O2 decomposition and pollutant degradation. The main mechanism underlying the increased strength of the degradation was the ability of ascorbic acid to facilitate the dissolution of surface Fe from aquifer media and accelerate the cycling of Fe(III)/Fe(II) in the liquid phase.