Improved Cadmium Removal Induced by Interaction of Nanoscale Zero-Valent Iron and Microplastics Debris

Nanoscale zero-valent iron (nZVI) is one of the most prevalently used engineered nanomaterials for heavy metals removal. Microplastics (MPs) have been detected extensively in the environment, such as soil, surface water, groundwater, and water treatment plant. PVC MPs and Cd coexist in a variety of environment, and Cd compounds are often used as stabilizers in PVC production, which increases the likelihood of their coexistence. In this work, the influence of aged PVC MPs on Cd2+ removal with nZVI was evaluated. Spent nZVI after reaction with Cd2+ with and without MPs was characterized with scanning transmission electron microscopy (STEM), energy-dispersive spectroscopy (EDS), scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FTIR), and Brunauer-Emmett-Teller (BET). The results showed that when MPs coexisted, the removal rate of Cd2+ with nZVI increased by up to 73.4%. Spent nZVI has more extensive oxidation, and has looser structure and higher specific surface area in a mixed contamination solution with trace MPs, resulting in high removal efficiency of Cd2+. Interaction between PVC MPs and nZVI shows positive promotion toward removal of Cd2+ with nZVI; thus, nZVI may have great potential for remediation of Cd in the water environment rich in PVC MPs.