Research on Nitrate Removal by Graphene Loaded With Iron Nanoparticles for Groundwater Remediation

Nitrate is one of the most frequent pollutants of groundwater, and in some areas, nitrate pollution is becoming a serious problem. Seeking new material and methods for improved efficiency of groundwater nitrate removal is a hot topic of environmental research. While graphene has been widely used in the processing of heavy metal ions in aqueous solution, its role in nitrate removal remains largely unexplored. In this study, we loaded micrometer-sized graphene with nanoscale iron particles (G-Fe) by liquid-phase reduction. The characteristics of nitrate reduction by the G-Fe composites were determined under different conditions using static experiments to reveal the reaction mechanism of G-Fe in removing nitrates. Results showed that the optimal load ratio of graphene with nanoscale iron was 5:1. Lower initial pH improved nitrate removal efficiency (NRE) to varying degrees and 100 % removal was obtained at pH 2.15. Dissolved oxygen (DO) had no effect on NRE. The effect of coexisting anions on NRE descended as follows: PO43−, SO42−, and Cl−. Kinetic studies showed that the reaction order between G-Fe and nitrate was about 0.45, indicating that the reaction involved complex redox reactions and adsorption/desorption processes, other than a simple first-order reaction. This study demonstrates the effectiveness of G-Fe composites in nitrate removal and establishes an advanced technology for groundwater remediation.