Removal of Heavy Metals from Aqueous Systems with Thiol Functionalized Superparamagnetic Nanoparticles

TLDR

The thiol‑functionalized Fe₃O₄ nanoparticles are highly dispersible, stable, possess a large surface area (114 m² g⁻¹) and high thiol density (1.8 mmol g⁻¹), and can be magnetically separated from solution within a minute using a 1.2 T field. Their chemical affinity, capacity, kinetics, and stability were benchmarked against conventional resin (GT‑73), activated carbon, and nanoporous silica (SAMMS) sorbents across river water, groundwater, seawater, and human blood/plasma. DMSA‑Fe₃O₄ achieved a Hg capacity of 227 mg g⁻¹—30‑fold higher than GT‑73—and removed 99 wt % of 1 mg L⁻¹ Pb within a minute, outperforming Chelex‑100 and GT‑73, which required 10 and 120 min, respectively, while also effectively binding Ag, Pb, Cd, Tl, and As.

Abstract

We have shown that superparamagnetic iron oxide (Fe3O4) nanoparticles with a surface functionalization of dimercaptosuccinic acid (DMSA) are an effective sorbent material for toxic soft metals such as Hg, Ag, Pb, Cd, and Tl, which effectively bind to the DMSA ligands and for As, which binds to the iron oxide lattices. The nanoparticles are highly dispersible and stable in solutions, have a large surface area (114 m2/g), and have a high functional group content (1.8 mmol thiols/g). They are attracted to a magnetic field and can be separated from solution within a minute with a 1.2 T magnet. The chemical affinity, capacity, kinetics, and stability of the magnetic nanoparticles were compared to those of conventional resin based sorbents (GT-73), activated carbon, and nanoporous silica (SAMMS) of similar surface chemistries in river water, groundwater, seawater, and human blood and plasma. DMSA-Fe3O4 had a capacity of 227 mg of Hg/g, a 30-fold larger value than GT-73. The nanoparticles removed 99 wt % of 1 mg/L Pb within a minute, while it took over 10 and 120 min for Chelex-100 and GT-73 to remove 96% of Pb.