One-Step Hydrothermal Synthesis of Carbonaceous Spheres from Glucose with an Aluminum Chloride Catalyst and Its Adsorption Characteristic for Uranium(VI)

Hydrothermal carbonization (HTC) of carbohydrates has been widely used for the synthesis of carbon materials. Most of the chemical transformations (e.g., fragmentation, dehydration) of carbohydrates in the HTC synthesis of carbon-rich microspheres need relatively high temperatures. However, the superficial functionalities (e.g., reactive oxygen groups) of the microspheres are susceptible to the synthesis temperature. It synthesis of HTC microspheres with highly abundant reactive oxygen groups is seldom reported at low temperatures. Herein, HTC of glucose was proposed to synthesize carbon materials using AlCl3 as the catalyst at 120–150 °C in this study. The chemical properties and structural characteristics of HTC microspheres were analyzed using Fourier transform infrared, X-ray photoelectron spectroscopy, solution 13C NMR, and scanning electron microscopy. The results showed that the HTC microspheres were successfully synthesized with near single-spherical shapes and smooth surfaces and the size of the diameter in the range of 0.5–5.5 μm. There were cross-linked furanic structure and abundant reactive oxygen groups on the surface of the HTC microspheres. 5-Hydroxymethylfural was detected by solution 13C NMR, which played a key role in the HTC synthesis of carbon-rich microspheres. The HTC microspheres exhibit the maximum adsorption capacity of 163 mg/g for uranium(VI).