Effect of 3-D distribution of ZVI nanoparticles confined in polymeric anion exchanger on EDTA-chelated Cu(II) removal.

Millispherical nanocomposites are promising for water decontamination combining the high reactivity of the confined nanoparticles and the excellent hydrodynamic properties of the supporting host. However, the effect of three-dimensional (3-D) distribution of the nanoparticles inside the host on the performance of the nanocomposite was highly dependent on the specific decontamination process. In this study, four D201-ZVI nanocomposites from peripheral to uniform 3-D distributions of nZVI were prepared to evaluate the effect of 3-D distribution of the confined nanoparticles inside the host beads on the removal of EDTA-chelated Cu(II). The performance of Cu(II) removal increased with the 3-D distribution tailoring towards the peripheral region, which was also validated under various solution chemistry conditions in terms of initial pH, DO, and coexisting sulfate. The mechanism underlying the 3-D distribution effect may be ascribed to three perspectives. First, the dissolution of Fe was also higher from the peripherally distributed nZVI nanocomposites compared with the uniform ones. In addition, SEM-EDS analysis revealed the immobilization of Cu occurred at limited depth from the outermost surface of the composite beads, leading to the low spatial utilization of the inner core region. Furthermore, XRD and XPS analyses demonstrated the higher chemical utilization of nZVI for the outer-distributed nanocomposites owing to the shortened pathway for mass transfer. This study shed new light on the design and development of tunable nanocomposites of improved reactivity for water decontamination processes.