Polyacrylic acid functionalized superparamagnetic iron-oxide supraparticles for highly efficient adsorption and removal of contaminants from water

Intensive research efforts have been devoted to remove trace amounts of toxic pollutants such as Ni(II) and Co(II) from water with the intention to provide clean fresh water to households. Iron-based adsorbents have attracted attention in the field of water purification because of their low cost, non-toxicity, and high availability in nature. However, due to their small volume, the recovery of the superparamagnetic iron-based adsorbents after the removal process in acceptably short times remains an unresolved research question. In this paper, we describe the fabrication of environmentally-friendly and superparamagnetic iron-oxide supraparticles optimized for the adsorption and removal of heavy metal ions and dyes from water with high recovery (within 20 s). The super-adsorbent iron-oxide supraparticles exhibited excellent removal efficiencies for Pb(II), Cr(III), Cd(II), Cu(II), Ni(II), Co(II), Li(I), and methylene blue (MB) with maximum adsorption capacities of 500, 446, 417, 366, 315, 294, 286, and 670 mg/g, respectively. Interestingly, the iron-oxide supraparticles with multicore structure revealed a higher saturation magnetization (72 Am2/kg) when compared to the as-synthesized iron-oxide nanoparticles (61 Am2/kg) that were used as starting material, facilitating fast recovery. The outstanding adsorption performance combined with the superparamagnetic properties and the high recovery demonstrates that low-cost iron-oxide supraparticles adsorbents can potentially be employed in water treatment and bioseparation.