Few-layered boron nitride nanosheets as superior adsorbents for the rapid removal of lead ions from water

Newly few-layered boron nitride (BN-550) nanosheets were developed by a low-temperature synthesis method, which was used to rapidly and efficiently adsorb lead ions (Pb²⁺). The samples were characterized by using XRD, FT-IR, EELS, SEM, TEM, AFM and XPS, revealing that it possessed the large specific surface area (696 m² g⁻¹), ultrathin sheet structure (1.2 nm thickness), and abundant chemical bonds as multiple adsorption sites. The adsorption properties showed that higher adsorption capacity (845 mg g⁻¹) for lead ions and less equilibrium time (15 min) than many adsorbents reported at present. The adsorption kinetics and isotherms of BN-550 belonged to the pseudo-second-order model and Langmuir model, respectively. The easy recyclability and stability of BN-550 were verified by the experiments regeneration and pH. Interference experiments indicated that the adsorbents were strong affinity for Pb²⁺ under the interference of other heavy metal ions such as Ni²⁺, Cu²⁺, and Cd²⁺ ions (their adsorbing capacity individually are 201, 402, and 312 mg g⁻¹). The XPS and FT-IR analysis revealed that the excellent adsorption performances for Pb²⁺ attributed to the chemical binding reactions with the numerous surface functional groups, such as the strong B–O–Pb interactions and –NH₂···Pb complex. The threshold value of Pb²⁺ removal on BN-550 nanosheets was 1080 mL g⁻¹ when Pb²⁺ concentration was 50 mg L⁻¹ in adsorption column. The unique characteristics render ultrathin nanosheets highly promising as an ideal candidate for the removal of lead ions.