Coating Fe3O4 magnetic nanoparticles with humic acid for high efficient removal of heavy metals in water.
Humic acid (HA) coated Fe3O4 nanoparticles (Fe3O4/HA) were developed for the removal of toxic Hg(II), Pb(II), Cd(II), and Cu(II) from water. Fe3O4/HA were prepared by a coprecipitation procedure with cheap and environmentally friendly iron salts and HA. TOC and XPS analysis showed the as-prepared Fe3O4/HA contains approximately 11% (w/w) of HA which are fractions abundant in O and N-based functional groups. TEM images and laser particle size analysis revealed the Fe3O4/HA (with approximately 10 nm Fe3O4 cores) aggregated in aqueous suspensions to form aggregates with an average hydrodynamic size of approximately 140 nm. With a saturation magnetization of 79.6 emu/g, the Fe3O4/HA can be simply recovered from water with magnetic separations at low magnetic field gradients within a few minutes. Sorption of the heavy metals to Fe3O4/HA reached equilibrium in less than 15 min, and agreed well to the Langmuir adsorption model with maximum adsorption capacities from 46.3 to 97.7 mg/g. The Fe3O4/HA was stable in tap water, natural waters, and acidic/ basic solutions ranging from 0.1 M HCl to 2 M NaOH with low leaching of Fe (< or = 3.7%) and HA (< or = 5.3%). The Fe3O4/HA was able to remove over 99% of Hg(ll) and Pb(ll) and over 95% of Cu(II) and Cd(II) in natural and tap water at optimized pH. Leaching back of the Fe3O4/HA sorbed heavy metals in water was found to be negligible.
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
Jing-fu
JF
Liu
Zong-shan
ZS
Zhao
Gui-bin
GB
Jiang
D000327:Adsorption; D002244:Carbon; D052918:Environmental Restoration and Remediation; D005290:Ferric Compounds / Q000737:chemistry*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008280:Magnetics; D019216:Metals, Heavy / Q000302:isolation & purification*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D012996:Solutions; D013055:Spectrophotometry, Infrared; D014867:Water / Q000737:chemistry*
D005290:Ferric Compounds; D006812:Humic Substances; D019216:Metals, Heavy; D012996:Solutions; D014867:Water; C000499:ferric oxide; D002244:Carbon