Abstract
In this study, a novel polystyrene-poly(hydroxamic acid) copolymer was synthesized as an effective adsorbent for the treatment of rare earth elements. Through the use of elemental analysis as well as FTIR, SEM, XPS, and Brunauer-Emmett-Teller (BET) surface area measurement, the synthesized polymer was found to have a specific surface area of 111.4 m2·g−1. The adsorption performances of rare metal ions were investigated under different pH levels, contact times, initial concentrations of rare earth ions, and temperatures. The adsorption equilibrium for La3+, Ce3+, and Y3+ onto a polystyrene-poly(hydroxamic acid) copolymer is described by the Langmuir model, which confirms the applicability of monolayer coverage of rare earth ions onto a polystyrene-poly(hydroxamic acid) copolymer. The amount of adsorption capacities for La3+, Ce3+, and Y3+ reached 1.27, 1.53, and 1.83 mmol·g−1 within four hours, respectively. The adsorption process was controlled by liquid film diffusion, particle diffusion, and chemical reaction simultaneously. The thermodynamic parameters, including the change of Gibbs free energy (∆G), the change of enthalpy (∆H), and the change of entropy (∆S), were determined. The results indicate that the adsorption of resins for La3+, Ce3+ and Y3+ was spontaneous and endothermic. The polymer was also used as a recyclable adsorbent by the desorption experiment.
Highlights
Rare earth elements, known as the vitamins of modern industry, are important non-recoverable strategic resources
Adsorption kinetics data were fitted using liquid film diffusion, particle diffusion, and chemical reaction, which are expressed as Equations (3), (4), and (5) [31,32], respectively:
We reported the synthesis of polystyrene-poly(hydroxamic acid) copolymer by suspension polymerization
Summary
Known as the vitamins of modern industry, are important non-recoverable strategic resources. To solve the problem of efficient enrichment and separation of rare earth elements, many studies have been conducted and methods developed, including redox precipitation [7,8], crystallization [9,10], ion exchange adsorption separation [11,12,13,14], and solvent extraction methods [15,16]. Hydroxamic acid chelating resins have double ligands of hydroxyl and oxime groups These ligands enable them to chelate with various metal ions and form stable heterocyclic complexes, providing good adsorption performances [22]. The copolymerization of polystyrene with hydroxamic acid forms spherical resin, and possesses higher hydroxamic acid content This method can improve the adsorption performance and application performance of the resin at the same time. The kinetic and isothermal adsorption equations of resin were established
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