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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