Rational assembly of GO-based heterocyclic sulfur- and nitrogen-containing aerogels and their adsorption properties toward rare earth elementals

Highlights: • 3D GO-ABT composite was fabricated and used as an efficient adsorbent. • Adsorption mechanisms of GO-ABT composite for REEs were proposed. • GO-ABT composite exhibited relatively better enrichment, recovery and reutilization ability. An aromatic heterocyclic compound, 2-aminobenzothiazole (ABT), was used to decorate graphene oxide (GO) by a facile hydrothermal self-assembly procedure. The developed three-dimensional (3D) GO-ABT composite aerogels could be utilized as high-powered and sustainable adsorbents for the enrichment and recovery of low concentration rare earth elements (REEs) from aqueous solutions. The composition and microstructure of GO-ABT composites were explored various characterization methods. The enrichment properties of GO-ABT composites for REEs were investigated in detail, revealing the existence of S-, N- and –NH₂ in ABT, as well as the carboxyl and hydroxyl groups of GO which might act as the major REE binding sites. The adsorption of GO-ABT composites for low concentration REEs could reach equilibrium in 30 min. Our investigations confirmed that the optimal pH value of GO-ABT composites for REEs was pH 4.0–5.0. For the adsorbent regeneration study, 50.0 mg of GO-ABT_{15:1/120 °C/6 h} composite was used toward 20.0 mL of Er³⁺ solutions. After ten regeneration cycles, the adsorption rates of GO-ABT composites for Er³⁺ remained around 100%, and the desorption rates maintained over 90%. The long-term storage of the adsorbent did not affect its adsorption ability, while desorption rates increased, indicating it possessed relatively higher stability.