Removal Kinetics of Chromium by Nano-Magnetite in Different Environments of Groundwater

Chromium (Cr) is a toxic contaminant and ubiquitously present in the environment. This study was conducted to investigate the removal of Cr by nano-magnetite (nano-Fe3O4) in different biogeochemical environments of groundwater. Size of nano-Fe3O4 used was in the range of 50-100 nm, and it contained Fe (58.88%) and O (31.13%). Removal rates of total Cr (Cr-T) by nano-Fe3O4 were significantly improved (0.40-0.84 min(-1)) as the concentrations of nano-Fe3O4 were increased (0.25-3.75g/L). However, removal rates of Cr-T by nano-Fe3O4 were decreased (1.52-0.66 min(-1)) as the concentrations of Cr-T increased (0.5-1.5mg/L). In addition, the removal rate of Cr-T by nano-Fe3O4 was significantly increased (0.56-1.63 min(-1)) as the pH increased (pH 5.5-pH 9). Removal rates of Cr-T by nano-Fe3O4 were significantly decreased (0.93-0.28 min(-1)) as the concentrations of humic acid (HA) increased (0.25-3.75 g/L). This study revealed that the reactive surface of nano-Fe3O4 plays an important role to enhance maximum removal of Cr-T. The surface charge of nano-Fe3O4 with or without Cr-T is directly related to the reactive surface area of nano-Fe3O4, which has not been well reported in the literature. Chemisorption reaction mechanisms may occur during the removal kinetics of Cr-T by nano-Fe3O4. Experimental findings from this study proved that nano-Fe3O4 has the capability to remove Cr-T and provided fundamental knowledge on the potential reaction mechanisms of Cr-T removal by nano-Fe3O4. (C) 2019 American Society of Civil Engineers.