Novel ZnWO4 yolk–shell microspheres: interface regulation and high removal efficiency for Pb2+

Abstract

Nanoflake-assembled ZnWO₄ yolk–shell microspheres (NFYM-ZnWO₄) with a diameter of 1.5–2 μm and a wall thickness of about 300 nm have been rationally designed and prepared by a facile one-pot method, were composed of numerous nanoflakes (NFs) with a thickness of 10–15 nm and possessed large specific surface areas. The controlled experiments demonstrated that the novel NFYM-ZnWO₄ were induced by the synergistic effects of ligands (L-aspartic acid, L-Asp) and mixed solvents (ethylene glycol, EG). Combined with the morphological evolution process, a rational mechanism was proposed to describe the nucleation, self-assembly and Ostwald ripening associated with the formation of NFYM-ZnWO₄. Benefiting from yolk–shell features and large specific surface areas, the as-synthesized NFYM-ZnWO₄ were evaluated as adsorbents. With a maximum adsorption capacity of 321.2 mg g⁻¹, NFYM-ZnWO₄ exhibited a high efficiency for Pb²⁺ removal in aqueous solution, which was over 5 times higher than the nanoparticle-assembled ZnWO₄ yolk–shell microspheres (NPYM-ZnWO₄).