Zn2+-Silica Modified Cobalt Ferrite Magnetic Nanostructured Composite for Efficient Adsorption of Cationic Pollutants from Water

A Zn2+-silica modified CoFe2O4 (CZFS) nano-structured composite, useful for adsorbing cationic pollutants from water, was prepared by a wet-chemical method. The composite comprises cubic spinel crystallites (average 18 nm size) with amorphous silica clusters decorated on the crystallites-surface. Improved surface area (59.8 m(2)/g) of CZFS over those of Zn2+ modified CoFe2O4, CZF (32.6 m2/g), and CoFe2O4, CF (42.8 m(2)/g), together with its high negative zeta-potential of -35.4 mV (from surface SiO-) provides CZFS with improved adsorption capacity for Methylene blue (MB) over that of CZF and CF. MB adsorption (initial adsorbate concentration C-0 = 5-25 mg/L) conforms to the Langmuir isotherm model, with maximum monolayer adsorption capacity Q(m) = 25.6 mg/g. CZFS exhibits adsorption efficiency A(e) >= 98% for removal of heavy metal ions Cr3+, Cu2+ and Pb2+ (C-0 = 5 mg/L). High A(e) = 99.9% for Pb2+ dropped only to A(e) = 98.8% for higher C-0 = 20 mg/L (Q(m) = 19.8 mg/g). Saturation magnetization of 39 emu/g enables easy magnetic separation of CZFS from water. Good reusability of CZFS adsorbent was observed for up to three cycles. In summary, CZFS efficiently removes MB as well as heavy metal ions (especially Pb2+) from contaminated water.