Manganese Doping of Magnetic
Iron Oxide Nanoparticles:
Tailoring Surface Reactivity for a Regenerable Heavy Metal Sorbent
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Abstract
A method for tuning the analyte affinity of magnetic,
inorganic
nanostructured sorbents for heavy metal contaminants is described.
The manganese-doped iron oxide nanoparticle sorbents have a remarkably
high affinity compared to the precursor material. Sorbent affinity
can be tuned toward an analyte of interest simply by adjustment of
the dopant quantity. The results show that following the Mn doping
process there is a large increase in affinity and capacity for heavy
metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements
were carried out for the removal of cadmium from river water and showed
significantly higher loading than the relevant commercial sorbents
tested for comparison. The reduction in Cd concentration from 100
ppb spiked river water to 1 ppb (less than the EPA drinking water
limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped
iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were
able to load ∼1 ppm of Cd followed by complete stripping and
recovery of the Cd with a mild acid wash. The Cd loading and stripping
is shown to be consistent through multiple cycles with no loss of
sorbent performance