Effective adsorption of thorium ion by novel self-crosslinking polyamide acid-grafted magnetic nanocomposites

A novel self-crosslinking polymer-coated magnetic nanosorbent (Fe3O4@PAA) was prepared to remove thorium ions from aqueous solutions. The grafting-polymerization method was employed to graft polyamide acid (PAA) onto amino-activated magnetic nanoparticles (Fe3O4@SiO2-NH2) via an amidation reaction using pyromellitic dianhydride (PMDA) and tris(2-aminoethyl)amine (TA) as monomers. The adsorption results show that the adsorption process of Th(IV) by Fe3O4@PAA is significantly pH-sensitive, and the theoretical maximum adsorption capacity can reach 122.5 mg/g at pH 3.0. Furthermore, Fe3O4@PAA exhibits a high adsorption rate and the adsorption equilibrium could be reached within 60 min. After 5 cycles of reuse, the adsorption capacity was still retained at more than 80 % of the initial value. In addition, the extraction mechanism of Fe3O4@PAA for Th (IV) ions was analyzed in detail by FT-IR and XPS. This work provides valuable insights into the design and preparation of novel, acid-resistant, easily separable and fast magnetic separation adsorbents for the highly effective separation of Th () from aqueous solutions.