Magnetic hydrogel composites based on cross-linked poly (acrylic acid) used as a recyclable adsorbent system for nitrates

We propose an innovative magnetic separation technique to separate a very important toxic inorganic pollutant (nitrate) from wastewater, using a recyclable magnetic adsorbent system. Our recyclable adsorbent system is a novel magnetic hydrogel composite, based on cross-linked polyacrylic acid (MNP-pAAc). The as-synthesized magnetic hydrogel composite has very well controlled properties related to the thicknesses (each particle is individually covered with a thin layer of cross linked poly acrylic acid shell) which offer a relatively high surface area and a high level of saturation magnetization. The maximum separation efficiency was relatively high, between 80 and 90% while the magnetization value, around 60 emu/g, was considered high for polymeric composite material. This characteristic makes the as-synthesized material a potential material for future water purification device but which is more important is that the material can be recycled, washed and reused which is not reported in the literature for similar kinds of materials. The recyclability was demonstrated in five subsequent adsorption-desorption cycles and maintenance of adsorption capacity over altogether 5 adsorption/desorption cycles to so high levels represents an important advantage and a novel idea over single-use materials. Using this kind of recycling material for effective depollution of nitrate by water we offer a new solution to avoid secondary pollution.