UC Irvine

Arsenic (As) is widely distributed in soil in the United States and around the world, highly toxic, and not efficiently remediated by existing traditional methods. Nanoscale zero-valent iron (nZVI)-based remediation is an emerging technology that has successfully been used to immobilize metals and metalloids due to nZVI’s high surface area and strong reducing ability. However, immobilization efficiency of nZVI decreases over time due to its oxidation under natural conditions. Modification of nZVI via sulfidation, to produce sulfide-modified nZVI (SnZVI), has been shown to overcome some of the shortcomings of nZVI. The main objective of this study was to compare the immobilization performance of nZVI and SnZVI for As in soil and determine if the toxicity of nZVI is influenced by sulfidation. The immobilization efficiency of nZVI and SnZVI (0.3, 1, and 5 wt.%) for As (50 ppm) in soil was monitored for 112 days under aerobic and anoxic conditions. The aerated soil also contained earthworms (Eisenia fetida) to evaluate the toxic impacts of the nanoparticles-based remediation. In general, SnZVI had a slower reaction kinetics, leading to lower As immobilization efficiency than nZVI after 7 days at 0.3 and 1% group. However, after 112 days, sulfidation was found to inhibit the corrosion of nanoparticle under aerobic conditions and the immobilization efficiency was similar to that of nZVI at all nanoparticle dosage concentrations. Both nanoparticles were toxic to E. fetida, but SnZVI was remarkably less toxic than nZVI. This study demonstrates the potential of SnZVI for effective and sustainable remediation.