Application of stabilized Fe0 nanoparticles for remediation of Cr(VI)-spiked soil

In this study, laboratory batch experiments were conducted on a chromium (Cr)-spiked soil to evaluate the effectiveness of synthesized starch-stabilized iron (Fe0) nanoparticles and compared with Fe0 and Fe3O4 with different particle sizes, and also with decreasing water-extractable Cr(VI). Comparative studies were carried out at a Cr(VI) concentration of 100 mg kg-1 and a Fe materials dosage of 1.5% w/w. Results indicated that stabilized Fe0 nanoparticles had a greater efficiency (100%) to immobilize Cr(VI). The efficiency of the iron materials that we used for immobilization of Cr(VI) was in the following order: starch-stabilized Fe0 nanoparticles > non-stabilized Fe0 nanoparticles > Fe3O4 nanoparticles > Fe0 micro-particles > Fe3O4 micro-particles. Several factors affecting the immobilization of Cr(VI) by stabilized Fe0 nanoparticles, including reaction time, initial Cr(VI) concentration in soil, Fe0 nanoparticles dosage and soil-solution suspension pH, were investigated. The overall rate of the Cr(VI) immobilization process was quick and almost 50% of the immobilization was reached within the first 2 minutes of the reaction. Cr(VI) immobilization percentages decreased from 100 to 54% as the initial Cr(VI) concentration increased from 50 to 1650 mg kg-1. Furthermore, increasing Fe0 nanoparticles dosage from 0.5 to 3% w/w caused a 70% increase in the immobilization efficiency. The results indicated that increasing the soil suspension pH from 5 to 9, in both buffered and unbuffered conditions, did not have any significant effect on the extent of water-extractable Cr(VI).