Magnetic fly-ash geopolymer for heavy metal removal in aqueous solutions.

Novel magnetic geopolymers were manufactured by synthesizing magnetic FeO particles on the surface of prepared geopolymer (Method 1) or by incorporating pre-synthesized magnetic FeO particles into the geopolymer during the manufacture of the geopolymer (Method 2). This study evaluated the effect of the incorporated magnetic FeO on the geopolymer magnetic, physical, and adsorption properties and its separation in aqueous solutions. Based on several preliminary measurements on the synthesized magnetic geopolymers, Method 2 was found to be a better method for producing magnetic geopolymer. Magnetic geopolymer synthesized by Method 2 exhibited ferromagnetic properties comparable to that of magnetic FeO, with a saturation magnetization of 8 emu·g and an intrinsic coercivity of 265 Oe. The magnetic geopolymer was efficiently separated from an aqueous solution within 2 min using a 0.48-T magnetic field. In addition, the magnetic geopolymer has a maximum copper adsorption capacity of 111.1 mg·g, which was similar to the non-magnetic reference geopolymer indicating that the addition of magnetic FeO did not compromise the geopolymer adsorption capacity. The magnetic geopolymer is a promising material with good adsorption and separation properties that can be used for heavy metals removal and recovery in wastewater and metals separation in industrial processes.