Coating Fe₃O₄ Magnetic Nanoparticles with Humic Acid for High Efficient Removal of Heavy Metals in Water

Abstract

Humic acid (HA) coated Fe 3 O 4 nanoparticles (Fe 3 O 4 /HA) were developed for the removal of toxic Hg(II), Pb(II), Cd(II), and Cu(II) from water. Fe 3 O 4 /HA were prepared by a coprecipitation procedure with cheap and environmentally friendly iron salts and HA. TOC and XPS analysis showed the as-prepared Fe 3 O 4 / HA contains ∼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 Fe 3 O 4 /HA (with ∼10 nm Fe 3 O 4 cores) aggregated in aqueous suspensions to form aggregates with an average hydrodynamic size of ∼140 nm. With a saturation magnetization of 79.6 emu/g, the Fe 3 O 4 /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 Fe 3 O 4 /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 Fe 3 O 4 /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 (e3.7%) and HA (e5.3%). The Fe 3 O 4 /HA was able to remove over 99% of Hg(II) and Pb(II) and over 95% of Cu(II) and Cd(II) in natural and tap water at optimized pH. Leaching back of the Fe 3 O 4 /HA sorbed heavy metals in water was found to be negligible.

Speciation analysis of silver sulfide nanoparticles in environmental waters by magnetic solid-phase extraction coupled with ICP-MS

“…However, the color of IOMPs changed from black to brown, and the saturation magnetization of the aged IOMPs (64.4 emu g À1 ) was slightly lower than that of the pristine IOMPs (64.9 emu g À1 ), suggesting that part of the Fe 3 O 4 was oxidized to a-Fe 2 O 3 under heating in air. 32,33 Nevertheless, the saturation magnetization is high enough to ensure their separation from the aqueous solution in a few minutes with a permanent hand-held magnet. The DLS analysis showed that the zero point charge pH (pH pzc ) of the aged IOMPs was between 6 and 7 ( Fig.…”

Study of modification of magnetically labeled yeasts Saccharomyces cerevisiae for copper cations Cu2+ removal

“…Nanosized magnetite [11], which is used to create magnetically labeled cells [12], also absorbs cations of metals on the surface. For example, in [13] showed that the magnetite is an effective sorbent, but the downside is coagulation of particles that impairs its industrial use. Industrial application of yeasts S. cerevisiae is already seen as a real technology for wastewater treatment [14].…”

Arbuscular Mycorrhizal Fungi Alleviate the Negative Effects of Iron Oxide Nanoparticles on Bacterial Community in Rhizospheric Soils

“…Similarly, Martineau et al (2014) find that CuO or ZnO was non-toxic to microorganisms in root washes of exudates extracted from plants. Fe 3 O 4 NPs have the most active surface sites (mainly the Fe-OH site), with high affinity for organic compounds (Liu et al, 2008). Because of this property, some Fe 3 O 4 NPs or their released irons might be immobilized and resulting decreased direct toxicity to microbes caused by the relatively greater amount of organic material available in the soil in AMF-inoculated treatments than that in non-AMFinoculated treatments (Figure 2).…”