Recovery of Th(IV) from acid leaching solutions of bastnaesite at low concentrations

• The PSMA resin is an excellent adsorbent for recovery of low concentrations of Th4 +.
• The adsorbent exhibited a high capacity of 360.14 mg g −1.
• PSMA effectively separated Th4 + from a simulated system containing La3 +.
• PSMA is easily regenerated, low-cost and environmental-friendly.

Low concentrations of Th4 + were recovered using the hydrolysis products of poly(styrene-co-maleic anhydride) (PSMA) to form an amorphous thorium(IV) macromolecular complex. The adsorption behavior and mechanism of the as-prepared PSMA toward Th4 + were investigated. At the optimum pH value and adsorption dosage, the adsorption percentage of Th4 + was 97.93%, and the maximum adsorption capacity of Th4 + was 360.14 mg g −1 at 40 °C within 1.5 h. The adsorption isotherm data were consistent with the Langmuir model, which confirmed the monolayer coverage mechanism of Th4 + onto the PSMA surface. The kinetic data followed a pseudo-second-order model, which suggested a chemisorption process. Through variation of pH values, Th4 + was efficiently enriched and separated from a simulated acid leaching solution of bastnaesite containing La3 + or Mg2 +, and these selectivity coefficients were above 103. Inorganic acid decomposes the Th–PSMA complex easily and the regenerated PSMA resin can be utilized repeatedly.