Effects of Leaching Agents on Pb and Cd Immobilization in Battery Waste Contaminated Soils Amended with Bare and Stabilized Zero-Valent Iron Nanoparticles

Abstract

This study compared the effectiveness of bare zero-valent iron nanoparticles (B-nZVI) and starch-stabilized zero-valent iron nanoparticles (S-nZVI) in immobilizing Pb and Cd from lead-acid battery waste soils. Both B-nZVI and S-nZVI were prepared in almost identical manner using the technique of reducing ferric chloride with sodium borohydride. X-ray diffraction (XRD) and dynamic light scattering (DLS) analyses confirmed that polydisperse B-nZVI and S-nZVI were synthesized. XRD and DLS analyses showed that B-nZVI and S-nZVI had different surface properties. To assess the immobilization capability of B-nZVI and S-nZVI, a composite soil sample was collected from an automobile lead-acid battery waste dumpsite. The soil sample had a pH of 3.85 and Pb and Cd levels of 16,674 mg/kg and 41 mg/kg, respectively. Single extraction procedures using 0.01M CaCl2, 0.1 M HCl, and 0.05 M EDTA were used to simulate phytoavailable Pb and Cd in the soil studied. Batch immobilization analysis showed that Cd was mobile in the control but immobile in B-nZVI and S-nZVI treated soils. Pb was however not immobile in either the control or treated soils. The mobility of Pb however decreased with increasing doses of S-nZVI and 0.003 g of S-nZVI was needed to make Pb completely immobile in soil. Batch immobilization also showed that S-nZVI was 1.8-2.49 times more efficient in immobilizing Pb than B-nZVI. Simulated phytoavailability of Pb was in the order of EDTA > HCl > CaCl2 > H2O while simulated photoavailable Cd was in the order of HCl > EDTA > H2O > CaCl2.