Efficient removal of free and nitrilotriacetic acid complexed Cd(II) from water by poly(1-vinylimidazole)-grafted Fe3O4@SiO2 magnetic nanoparticles

Poly(1-vinylimidazole)-grafted Fe 3 O 4 @SiO 2 magnetic nanoparticles (FSPV) were developed to remove both free Cd(II) and nitrilotriacetic acid (NTA) complexed Cd(II) from water. The adsorption capacity of NTA-complexed Cd(II) (42.1   mg/g) was larger than that of free Cd(II) (24.8   mg/g). Free Cd(II) and NTA-complexed Cd(II) could be reduced from 50   μg/L to below 5   μg/L within 10 and 20   min, respectively. FSPV could effectively remove trace free and NTA-complexed Cd(II) over broad pH ranges of 5–10 and 5–11, respectively. Moreover, the presence of seven coexisting ions (up to 100   mM) including four cations (Na + , K + , Ca 2+ , and Mg 2+ ) and three anions (Cl − , NO 3 − , and SO 4 2− ) all slightly promoted the removal of both free and NTA-complexed Cd(II) onto FSPV. The removal of free Cd(II) or NTA-complexed Cd(II) was not obviously affected by the presence of Ni(II) and Co(II) (50   μg/L), humic acid (up to 3   mg/L as TOC) or alginate (up to 8   mg/L as TOC). In addition, FSPV could be regenerated with 10   mM HCl in 10   min, and the removal of both types of Cd(II) maintained above 95% in five consecutive adsorption/regeneration cycles. Therefore, FSPV could be utilized as promising adsorbent for both free and NTA-complexed Cd(II).