Enhanced effects of reducing agent on oxalate chelated Fe(II) catalyzed percarbonate system for benzene degradation

The addition of hydroxylamine hydrochloride (HAH), ascorbic acid (ASC), sodium ascorbate (SAS) to the OA-Fe(II)/SPC system could promote the generation of HO center dot by accelerating Fe(II)/Fe(III) recycles and H2O2 decomposition. The enhancement of HAH on HO center dot generation surpasses ASC and SAS in the OA-Fe(II)/SPC system. The generation of O-2(center dot-) was also enhanced by HAH, ASC and SAS, and more significant promotion of O-2(center dot-) generation was observed with ASC and SAS addition. More effective benzene removal was achieved in OA-Fe(II)/SPC system with suitable HAH, ASC and SAS addition, compared to the parent system. Excessive HAH, ASC or SAS had a negative effect onbenzene removal. Results of scavenger tests showed that HO center dot is indeed the dominant free radicals for benzene removal in every system, but the addition of HAH, ASC and SAS increased the contribution of O-2(center dot-) to benzene degradation. HAH, ASC and SAS enhanced OA-Fe(II)/SPC systems could be well utilized to acidic and neutral conditions, while HCO3-, high concentration of HA and alkaline conditions were not favorable to benzene removal. Moreover, the addition of HAH, ASC and SAS are conducive to benzene removal in actual groundwater, and HAH was the optimal reducing agent for the enhancement of OA-Fe(II)/SPC system.