Immobilizing lead using loess and nanoscale zerovalent iron (nZVI)-amended loess: Insights from macroscopic and microscopic tests
Shaojie Wen, Wen-Chieh Cheng, Dongfeng Li, Wenle Hu
Abstract
Lead (Pb) can accumulate in organisms causing damage to liver and kidney functions. Preventing Pb2+ migration to surrounding environments is considered of great necessity. This study explored the potential of applying the loess and nanoscale zerovalent iron-amended loess (nZVI-AL) to Pb immobilization. The static equilibrium adsorption analyses showed that the adsorption of Pb2+ by the loess and nZVI-AL was classed as homogeneous monolayer surface adsorption. The nZVI particles provided Pb2+ with more sites for their attachment and prevented their migration using Fe-O and Fe-O-H bonds. Their attachment encouraged the formation of cerussite precipitation, which not only caused the reduction in the diffraction peak of calcite mineral but shifted the peak of adsorption band from around 1430 cm−1 to a lower wavenumber. The unbonded electrons of the functional groups on the surface of quartz mineral coordinated with the empty orbit of Pb2+, leaving the diffraction peak at 3.3429 Å. Further, Ca2＋ distribution of the nZVI-AL sample was not as blurry as that of the loess sample because of the retardant of the depletion of calcite and quartz by the nZVI particles. Moreover, the hydroxyl groups bound via hydrogen bonds were formed by the nZVI amendment, displacing the peak of the adsorption band from 701 cm−1 to 698 cm−1. The hydroxyl groups of clay minerals coordinated with Pb2+ as well to form Pb(OH)+, corresponding to O-H stretching vibrations at 3616 cm−1 and 3430 cm−1 respectively. The nZVI-AL shows its potential in landfills as a bottom liner system.