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).

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A novel adsorbent of mesoporous carbon with high specific surface area was successfully prepared by hydrothermal and template method, using sodium lignosulfonate (LSs) as a raw material and cetyltrimethylammonium bromide (CTAB) as a template agent. The mesoporous carbon was characterized by SEM, TEM, BET, FTIR, and XPS. The formation mechanism of the mesoporous carbon was analyzed. The adsorption of uranium(VI) on the mesoporous carbon from the simulated aqueous solution and actual radioactive wastewater was respectively investigated. The optimum conditions for U(VI) adsorption were determined by studying experimental variables including pH, contact time, sorbent dose, initial concentration, and temperature. The results indicated that the maximum adsorption capacity of the mesoporous carbon for U(VI) in the simulated aqueous solution and actual radioactive wastewater was respectively 109.46 mg/g at pH 5.5 and 328.15 K and 195.6 mg/g at pH 5.5 and the initial U(VI) concentration of 189.75 mg/L. The adsorption data could be well described by the pseudo-second-order model and Freundlich isotherm model. The adsorption of U(VI) on the mesoporous carbon was an endothermic and spontaneous process. The adsorption mechanism may be a complex chemical reaction between uranium and the oxygen-containing functional groups on the mesoporous carbon.

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