Polymer/iron-oxide nanocomposite adsorbents for cycled magnetically-enabled extraction of aqueous micropollutants

Abstract

We present a facile, low-cost method for the preparation of milli-scale magnetic polymer prints which can be utilized as adsorbents for removal of methylene blue (MB) from aqueous solution. The nanocomposites were prepared by mixing magnetic iron-oxide nanoflowers (NFs) with a multibranched acrylate terminated PEG monomer (Trimethylolpropane ethoxylate Triacrylate, TET). 1 mol% Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) was used as a photoinitiator, enabling very rapid bulk template printing by UV-initiated free radical polymerization. The magnetic adsorbents demonstrated moderate adsorption capacity of 0.75 mg.g -1 , however a 5 wt% adsorbent load could remove over 99% of dissolved MB at concentrations as high as 15 mg.L -1 . The materials were homogeneous and were easily processable into a range of shapes. Full characterization of the magnetic adsorbents was undertaken, including determination of the dependence of adsorption capacity on adsorbent volume and surface area to volume ratio. A morphology (cylinders of d = 3 mm, h = 1 mm) was identified that provided optimal adsorption performance and which enabled rapid magnetic capture/recovery for subsequent regeneration by solvent extraction. Facile capture, as compared with nano-or micro-scale absorbents, offers practical advantages for in-line continuous extraction. The magnetic adsorbent showed excellent stability and could be regenerated at least 5 times without any observed decrease in adsorption efficiency. Evaluation of the performance of the adsorbent with a library of common micropollutants revealed the dominant role of, polymer to MB, n -π interactions in the micropollutant extraction mechanism.