Magnetically Recyclable Wool Keratin Modified Magnetite Powders for Efficient Removal of Cu(2+) Ions from Aqueous Solutions

The treatment of wastewater containing heavy metals and the utilization of wool waste are very important for the sustainable development of textile mills. In this study, the wool keratin modified magnetite (Fe(3)O(4)) powders were fabricated by using wool waste via a co-precipitation technique for removal of Cu(2+) ions from aqueous solutions. The morphology, chemical compositions, crystal structure, microstructure, magnetism properties, organic content, and specific surface area of as-fabricated powders were systematically characterized by various techniques including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), thermogravimetric (TG) analysis, and Brunauer–Emmett–Teller (BET) surface area analyzer. The effects of experimental parameters such as the volume of wool keratin hydrolysate, the dosage of powder, the initial Cu(2+) ion concentration, and the pH value of solution on the adsorption capacity of Cu(2+) ions by the powders were examined. The experimental results indicated that the Cu(2+) ion adsorption performance of the wool keratin modified Fe(3)O(4) powders exhibited much better than that of the chitosan modified ones with a maximum Cu(2+) adsorption capacity of 27.4 mg/g under favorable conditions (0.05 g powders; 50 mL of 40 mg/L CuSO(4); pH 5; temperature 293 K). The high adsorption capacity towards Cu(2+) ions on the wool keratin modified Fe(3)O(4) powders was primarily because of the strong surface complexation of –COOH and –NH(2) functional groups of wool keratins with Cu(2+) ions. The Cu(2+) ion adsorption process on the wool keratin modified Fe(3)O(4) powders followed the Temkin adsorption isotherm model and the intraparticle diffusion and pseudo-second-order adsorption kinetic models. After Cu(2+) ion removal, the wool keratin modified Fe(3)O(4) powders were easily separated using a magnet from aqueous solution and efficiently regenerated using 0.5 M ethylene diamine tetraacetic acid (EDTA)-H(2)SO(4) eluting. The wool keratin modified Fe(3)O(4) powders possessed good regenerative performance after five cycles. This study provided a feasible way to utilize waste wool textiles for preparing magnetic biomass-based adsorbents for the removal of heavy metal ions from aqueous solutions.