Reductive transformation of p-nitrophenol by Fe(II) species: The effect of anionic media

Electron exchange between aqueous Fe(II) and structural Fe(III) of iron minerals has been illustrated for understanding the reduction of nitroaromatic compounds (NAC). However, factors influencing Fe(II)-induced the reduction of NAC still remain elusive. In this paper, p-nitrophenol (1.5 mM) was selected to explore the effects of pH, the stabilizing ligands (Cl−, SO42−) of ferrous ions and the extra addition of iron hydroxide on the reduction of NAC via Fe(II) species. The results indicate that the reduction degree of is much lower in SO42− medium than that in Cl− medium at pH 7.6. p-Nitrophenol reduction increased in SO42− medium and slightly decreased in Cl− medium when Fe hydroxide was extra added. Cl− strength (0.01-0.1 mol L−1) has no obvious effect on p-NP reduction. SO42− species and its dosage have markedly inhibitory effect on p-NP reduction due to the selective adsorption of SO42− and the formation of sulphated surface complexes on the fresh Fe hydroxide.