Effects of geochemical constituents on the zero‐valent iron reductive removal of nitrobenzene in groundwater

Nitrobenzene (NB) was chosen as the model contaminant, and batches lab scale experiments were conducted to investigate the effects of geochemical compositions on reductive removal of nitrobenzene by zero‐valent iron (ZVI) in groundwater. Experimental results showed that the kinetics of nitrobenzene reduction by ZVI was a pseudo‐first order with an observed rate constant, k_obs, of 3.67 × 10^?4/s; the calculated half‐life of nitrobenzene was 1.89 × 10³/s. The geochemical constituents of groundwater have significant influences on ZVI reactivity and nitrobenzene reduction. The presence of high concentration of nitrate, carbonate, sulphate and hardness had detrimental effects on reduction of nitrobenzene and formation of aniline; chloride had a slight positive effect on the nitrobenzene reduction and the formation of aniline. Bicarbonate enhanced the ZVI reactivity initially at lower concentration and inhibited the nitrobenzene reduction at high concentration. Therefore, the performance and reactivity of ZVI were found to be strongly affected by the geochemical constituents of groundwater.