The Deposition Characteristics of Coupled Lead Ions and Suspended Silicon Powders Along the Migration Distance in Water Seepage

The deposition characteristics of lead ions (Pb 2+ ) in the presence of silicon powders (i.e., suspended particles, SPs) were investigated in water seepage in a long one-dimensional sand column experiment. The injected SPs possess a very wide particle-size distribution (PSD). The concentrations of deposited Pb 2+ and SPs and the migration distance along the water flow direction were measured by sampling. The PSDs of the deposited SPs in different sections were obtained by laser diffraction after transport test completion, and microstructure photographs were also acquired through metallographic microscopy. The test results show that the presence of SPs may promote or inhibit Pb 2+ migration, which is closely related to the concentration of the injected Pb 2+ , particle size and concentration of the injected SPs, seepage velocity, and change in the absolute zeta potential of the surface charge. The median diameter of the deposited SPs near the injection end is larger than that of the injected SPs and gradually decreases with increasing distance. Overall, the transport of SPs represents a clear particle-separation characteristic and significantly influences the migration progress of pollutants such as heavy metal ions such as Pb 2+ due to their coupling effects.