Hollow Polyaniline Microsphere/Fe3O4 Nanocomposite as an Effective Adsorbent for Removal of Arsenic from Water

Polyaniline hollow microsphere (PNHM)/Fe3O4 magnetic nanocomposites have been synthesized by a novel strategy and characterized. Subsequently, PNHM/Fe3O4-40 (Fe3O4 content: 40 wt.%) was used as an adsorbent for the removal of arsenic (As) from the contaminated water. Our investigations showed 98–99% removal of As(III) and As(V) in the presence of PNHM/Fe3O4-40 following pseudo-second-order kinetics (R2 > 0.97) and equilibrium isotherm data fitting well with Freundlich isotherm (R2 > 0.98). The maximum adsorption capacity of As(III) and As(V) correspond to 28.27 and 83.08 mg g−1, respectively. A probable adsorption mechanism based on X-ray photoelectron spectroscopy analysis was also proposed involving monodentate-mononuclear/bidentate-binuclear As-Fe complex formation via legend exchange. In contrast to NO3− and SO42− ions, the presence of PO43− and CO32− co-ions in contaminated water showed decrease in the adsorption capacity of As(III) due to the competitive adsorption. The regeneration and reusability studies of spent PNHM/Fe3O4-40 adsorbent showed ~83% of As(III) removal in the third adsorption cycle. PNHM/Fe3O4-40 was also found to be very effective in the removal of arsenic (<10 μg L−1) from naturally arsenic-contaminated groundwater sample.