Enhanced nitrate removal using in situ reactive zone with reduced graphene oxide supported nanoscale zero-valent iron

Nitrate pollution in groundwater is becoming more serious, which is harmful to human health. The reduced graphene oxide supported nanoscale zero-valent iron (nZVI/rGO) composite prepared in this paper can effectively remove nitrate in groundwater. In situ remediation of nitrate-contaminated aquifer was also studied. The results showed that NH4+-N was the main product of NO3--N reduction, and N-2 and NH3 were also produced. When the dosage of rGO/nZVI was more than 0.2 g/L, there was no accumulation of intermediate NO2--N during the reaction process. NO3--N was removed by rGO/nZVI mainly through physical adsorption and reduction process with the maximum adsorbing ability of 37.44 mg NO3--N/g. After the slurry of rGO/nZVI was injected into the aquifer, a stable reaction zone could be formed. NO3--N could be removed continuously within 96 h at the simulated tank, and NH4+-N and NO2--N were as the main reduction products. Moreover, the concentration of TFe near the injection well increased rapidly after rGO/nZVI injection, and could be detected at the downstream end, indicating that the reaction range was large enough for NO3--N removal.