Evaluation of Polyurea-Crosslinked Alginate Aerogels for Seawater Decontamination

Polyurea-crosslinked Ca-alginate (X-Ca-alginate) aerogel beads (diameter: 3.3 mm) were evaluated as adsorbents of metal ions, organic solvents, and oils. They were prepared via reaction of an aromatic triisocyanate (Desmodur RE) with pre-formed Ca-alginate wet gels and consisted of 54% polyurea and 2% calcium. X-Ca-alginate aerogels are hydrophobic nanoporous materials (90% v/v porosity), with a high BET surface area (459 m(2)/g(−1)), and adsorb Pb(II) not only from ultrapure water (29 mg/g(−1)) but also from seawater (13 mg/g(−1)) with high selectivity. The adsorption mechanism involves replacement of Ca(II) by Pb(II) ions coordinated to the carboxylate groups of the alginate backbone. After treatment with a Na(2)EDTA solution, the beads can be reused, without significant loss of activity for at least two times. X-Ca-alginate aerogels can also uptake organic solvents and oil from seawater; the volume of the adsorbate can be as high as the total pore volume of the aerogel (6.0 mL/g(−1)), and the absorption is complete within seconds. X-Ca alginate aerogels are suitable for the decontamination of aquatic environments from a broader range of inorganic and organic pollutants.