Preparation of Humic Acid/l-Cysteine-Codecorated Magnetic Fe(3)O(4) Nanoparticles for Selective and Highly Efficient Adsorption of Mercury

[Image: see text] Humic acid and l-cysteine-codecorated magnetic Fe(3)O(4) nanoparticles (HA/LC-MNPs) were synthesized using a coprecipitation method. Humic acid fractions abundant with carboxyl and hydroxyl groups can be selectively coated on the surface of MNPs during synthesis. HA/LC-MNPs with abundant heteroatoms (N, S, and O) show excellent removal capacity, great selectivity, and also fast trapping of Hg(2+) in a wide pH range. The adsorption capacity of HA/LC-MNPs for Hg(2+) can reach 206.5 mg/g, and the chemisorption was attributed to the major adsorption form. In competitive adsorption, HA/LC-MNPs preferentially adsorbed Hg(2+) with an affinity order of Hg(2+) > > Pb(2+) > Cu(2+) ≫ Zn(2+) > Cd(2+). In total, 93.91% of Hg(2+) can be quickly captured in the presence of a 6000 times higher concentration of competing metal ions (Pb(2+), Cu(2+), Cd(2+), and Zn(2+)) within 30 min. The adsorption mechanism was analyzed using X-ray photoelectron spectroscopy (XPS). It suggested that the HA/LC-MNPs enhanced the adsorption capacity of Hg(2+) because of the complexing abilities of the multiple thiol, amino, and carboxyl groups in sorbents with Hg(2+), the ion exchange ability of the carboxyl group, and the negative charge surface. All in all, HA/LC-MNPs are a potentially useful and economic material for the selective removal of Hg(2+) from polluted water.