Assessment of zerovalent iron nanoparticle (nZVI) efficiency for remediation of arsenic-contaminated groundwater. Two laboratory experiments

Zerovalet iron nanoparticle (nZVI) technology has been found to be promising and effective for soil and groundwater remediation. This paper shows the results of two batch tests (Test A and Test B) carried out to assess the capacity of nZVI to remediate arsenic (As)-contaminated water. Test A, performed with batches of tap water contaminated by arsenic, with a concentration equal to 10 mg*L-1, showed a significant reduction of the As concentrations in solution, with a maximum removal rate up to 98% (Batch 3). Test A lasted 26 h. At the same time, Test B was performed with a sample of arsenic-contaminated sediment, with a concentration equal to 100 mg*Kg-1 (ca). Test B lasted 72 h. Test B also confirmed an excellent reduction of the As concentrations in solution, up to a maximum removal rate of 99% (Batch 3). These results show the effectiveness of nZVI for the remediation of water contaminated by arsenic. However, as the As–nZVI interaction time increased, there was a decrease in the available sites for arsenic immobilization, and so the As concentrations in solution became constant. In fact, as the dose of nZVI (mnZVI) used in the batches increased, the mass concentration of residue As in the solution at the equilibrium decreased (cAse) and therefore the concentration of As absorbed (cAs0–cAse) on the nZVI increased due to the immobilization action of the nanoparticles. The results show concentrations of As absorbed (cAs0–cAse) on the nZVI with a range between 5.10 mg*L-1 (mnZVI = 0.05 g) and 9.54 mg*L-1 (mnZVI = 0.5 g) for Test A, and with a range between 0.029 mg*L-1 (mnZVI = 0.05 g) and 0.058 mg*L-1 (mnZVI = 0.7 g) for Test B. Therefore, these results underline the need to monitor As concentrations during applications in the field, in order to verify the demand for injecting new active nanoparticles for arsenic removal.