Recyclable Amino-Phosphorylated Polyacrylonitrile Fiber for Gd(III) Adsorption in Aqueous Solution

The development of rare earth adsorbents with high adsorption capacity, outstanding selectivity, and excellent reusability is important for the enrichment and recovery of rare earth elements. The adsorption of the rare earth ion Gd(III) by a phosphorylated polyacrylonitrile fiber was investigated. In this work, the adsorbent was synthesized by a simple and cost-effective grafting method using polyacrylonitrile (PAN) fibers as the substrates. The FTIR analysis, SEM, XPS, and TGA indicated the successful synthesis of polyacrylonitrile-phosphite (PAN-Phos) fibers. To evaluate the feasibility of PAN-Phos fibers as the potential adsorbents for Gd(III) removal, a series of adsorption experiments were conducted. The pseudo-second-order kinetic model better illustrated the adsorption of Gd(III) on PAN-Phos fibers, and equilibrium adsorption was achieved within 50 min; the maximum adsorption capacity was 120.9 mg·g–1. The PAN-Phos fibers also exhibited excellent reproducibility after four adsorption cycles. In addition, the results of various analyses indicated that the adsorption mechanism of Gd(III) on PAN-Phos fibers was mainly through the synergistic complexation of secondary amine and phosphoric acid groups. It provided a practicable way for the synthesis and preparation of rare earth adsorbent materials.