Hierarchical γ-BaB2O4 hollow microspheres: surfactant-assisted hydrothermal formation, phase conversion, optical properties and application as adsorbents

摘要

Three-dimensional (3D) hierarchical metal borate nanoarchitectures have attracted extensive interest for their wide use owing to their versatile compositions and unique properties, and their rational design and facile synthesis with high uniformity and complex interiors have long remained a great challenge. In this contribution, hierarchical γ-BaB _(2) O _(4) hollow microspheres assembled from one-dimensional (1D) nanorods were successfully synthesized by a facile ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal method (180 °C, 12 h), using Ba(OH) _(2) ·8H _(2) O and H _(3) BO _(3) as the raw materials. The effects of process parameters were investigated in detail, based on which a feasible formation mechanism was proposed. The hierarchical γ-BaB _(2) O _(4) hollow microspheres exhibited a specific surface area of 46.25 m ~(2) g ~(?1) . The subsequent mild phase conversion (700 °C, 3.0 h) led to β-BaB _(2) O _(4) hollow microspheres with a well-preserved spherical morphology and high crystallinity, indicating hierarchical γ-BaB _(2) O _(4) and β-BaB _(2) O _(4) hollow microspheres of excellent thermostability. Both the hierarchical γ-BaB _(2) O _(4) and β-BaB _(2) O _(4) hollow microspheres exhibited a transparent characteristic from the ultraviolet to the visible region. Moreover, when employed as adsorbents, the hierarchical γ-BaB _(2) O _(4) hollow microspheres presented satisfactory adsorption properties for the removal of Pb ~(2+) from mimic waste water, suggesting the great potential applications of the 3D hierarchical porous or hollow nanoarchitectures of metal borates in the future.