The influence of polyelectrolyte modification on nanoscale zero-valent iron (nZVI): Aggregation, sedimentation, and reactivity with Ni(II) in water

• SEM, XRD, FT-IR were used to characterize modified-nZVI.
• APAM modification made nZVI aggregate aggressively in water.
• CMC-modified nZVI had better colloidal stability.
• nZVI modified by APAM and CMC had the slow oxidation rate.
• The Ni2+ removal efficiency with nZVI decreased after CMC modification.

Polyelectrolyte modification on the surface of nanoscale zero-valent iron (nZVI) particles could affect colloidal stability, aggregation, mobility, oxidation as well as reactivity. In this article, two anionic polyelectrolytes with different molecular weight (MW), anionic polyacrylamide (APAM, MW = 3 million) and carboxymethylcellulose sodium (CMC, MW = 300–800) were modified on the surface of nZVI. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and X-ray diffraction (XRD) were used to characterize the polyelectrolyte-modified nZVI. Results from UV–vis spectrophotometer (UV) and sedimentation tests showed that APAM modification led to the aggregation of nZVI in suspension, CMC modification made nZVI disperse well. XRD results indicated that polyelectrolyte modification made the slow oxidation of nZVI under ambient conditions. APAM-modified nZVI had much lower Ni2+ removal efficiency than that of bare nZVI while CMC-modified nZVI had higher Ni2+ removal efficiency after 1.5 hours (h). The study provided the information on the modification effect of nZVI on the colloidal stability and aggregation, sedimentation, reduction and sorption of heavy metal ions in the environment.