The removal of Cr(VI) from aqueous and saturated porous media by nanoscale zero-valent iron stabilized with flaxseed gum extract: Synthesis by continuous flow injection method

Recently, the in-situ removal of contaminants by iron nanoparticles has been considered due to their non-toxicity, abundance, ease of production, and cost-effectiveness, which can be accomplished by injecting them underground. In this study, nZVI was synthesized using a novel continuous synthesis method using flaxseed glaze as a green, non-toxic, and low-priced coating. The produced nanoparticles were characterized by dynamic diffraction analysis (DLS), field electron microscopy (FE-SEM), X-ray spectroscopy (EDX), and infrared spectroscopy (FTIR) spectroscopy. Batch experiments were conducted to evaluate the effect of Cr(VI) concentration, FG-nZVI dosage, pH, and coexisting components (Total dissolved solids, Humic acid, and NO 3 − ) on Cr(VI) removal. Results of the characterization and identification, and stability tests indicated that nanoparticles synthesized by using this continuous synthesis system were smaller and more regular shaped than those prepared by conventional synthesis. According to the results, the Cr(VI) residual level increased by increasing the initial Cr(VI) concentration and decreased by increasing the nZVI coated with flaxseed glaze (FG-nZVI) dosage. At the Cr(VI) initial concentration of 4 mg L −1 , the Cr(VI) was removed entirely at almost all dosages of FG-nZVI. Optimal amount of FG-nZVI was 62.73 mg L −1 when applied at 4 mg L −1 of Cr(VI) at optimum pH 6.64, resulting in the Cr(VI) residual concentration of 0.05 mg L −1 . The results of saturated porous media showed that injection background solutions enhanced the transfer of nanoparticles in the porous medium, resulting in the adequate removal along the desired radius. The results illustrated that using FG-nZVI can be effective for practical groundwater remediation.