Characterization of Flake Boron Nitride Prepared from the Low Temperature Combustion Synthesized Precursor and Its Application for Dye Adsorption

Flake boron nitride (BN) in large yield was successfully synthesized at low temperature from the combustion synthesized precursor. The precursor was prepared by a low-temperature (350 °C) combustion synthesis (LCS) method using nitric acid (HNO3), urea (CO(NH2)2), boric acid (H3BO3), and glucose (C6H12O6·H2O) as starting materials. The precursor consists of B2O3 and amorphous carbon and the morphology is composed of blocks with average diameters of about 10 μm by statistical methods using SEM at different fields. Then BN was synthesized at 900 °C in NH3 at a heating rate of 5 °C min−1. The as-prepared BN possesses a flake morphology and high specific surface area up to 936 m2 g−1. It also has high density structural defects and abundant –NH2/–OH groups. The surface groups improve its water wettability and electronegativity, which contributes to the rapid and selective adsorption performance, especially towards the cationic dyes. When 4 mg of the sample was added into a 100 mL RhB solution with an initial concentration of 5 mg L−1, 95% of the RhB was removed within 1 min and the adsorption capacity is 125 mg g−1. Importantly, the sample can be regenerated by heating at 400 °C in air.