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

Abstract

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 (CrT) by nano-Fe3O4 were significantly improved (0.40–0.84 min−1) as the concentrations of nano-Fe3O4 were increased (0.25–3.75 g/L). However, removal rates of CrT by nano-Fe3O4 were decreased (1.52–0.66 min−1) as the concentrations of CrT increased (0.5–1.5 mg/L). In addition, the removal rate of CrT by nano-Fe3O4 was significantly increased (0.56–1.63 min−1) as the pH increased (pH 5.5–pH 9). Removal rates of CrT 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 CrT. The surface charge of nano-Fe3O4 with or without CrT 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 CrT by nano-Fe3O4. Experimental findings from this study proved that nano-Fe3O4 has the capability to remove CrT and provided fundamental knowledge on the potential reaction mechanisms of CrT removal by nano-Fe3O4.