(586e) Magnetic Catch & Release: Reversible Organic Contaminant Adsorption and Enrichment From Water

There is an increasing
need for fast and efficient extraction methods to remove low concentrated (ppb
levels) organic compounds from water with high adsorbent recyclability. Surface-modified magnetic nanoparticles can be used in extraction processes
as they readily disperse in common solvents and combine high saturation
magnetization with excellent accessibility. Reversible and recyclable
adsorption and desorption through solvent changes and magnetic separation
provide technically attractive alternatives to classical solvent extraction. Carbon-coated
cobalt nanoparticles with a thin polymer layer were tagged with
β-cyclodextrin. The resulting material reversibly adsorbed organic
contaminants in water within minutes. Isolation of the immobilized inclusion
complex was easily carried out within seconds by magnetic separation due to the
strong magnetization of the nanomagnets (metal core). The trapped molecules
were fully and rapidly recovered by filling the cyclodextrin cavity with a
microbiologically well accepted substitute, e.g. benzyl alcohol.
Phenolphthalein was used as a model compound for organic contaminants such as
polychlorinated dibenzodioxins (PCDDs) or bisphenol A (BPA). The nanomagnets
can be regenerated under mild conditions and reused in the next cycle at full
efficiency (16 recycles tested). Tagging cyclodextrins with magnetic, stable nanoparticles
(carbon shell, polymer layer) makes them magnetoresponsive and may lead to a
new generation of adsorbents in separation, contaminant enrichment or drug
delivery. Experiments at ultralow concentrations (160 ppb) underline the high
potential of cyclodextrin modified nanomagnets as a fast, recyclable extraction
method for organic contaminants in large water streams or as an enrichment tool
for analytics.

Reference:

1) R. Fuhrer, I.K. Herrmann, E.K.
Athanassiou, R.N. Grass, W.J. Stark, Langmuir,
2011, 27(5), 1924-9

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