Removal of uranyl ions from aqueous media by tannic acid-chitosan hydrothermal carbon: equilibria, kinetics and thermodynamics

The tannic acid-chitosan hydrothermal carbon (TCHC) by hydrothermal carbonization is first used in uranium(VI) adsorption. The characterization of HCTC was investigated by scanning electron microscopy, X-ray diffraction, infrared spectroscopy (FTIR). The effects of pH, adsorbent dosage, initial U(VI) concentration, temperature and contact time on the adsorption of uranium(VI) were expressed in batch experiments. A maximum adsorption capacity 96.99 mg/g has been achieved at pH = 5.5, T = 25 °C and initial concentration of U(VI) solution 80 mg/L. The adsorption data fit well with the Langmuir model and pseudo second order kinetics model, indicating that uranium(VI) was monolayer covered on the surface of the material, and the adsorption process was mainly chemisorption. Thermodynamic data indicates that the immobilization of uranium(VI) to the material surface was spontaneous and endothermic. TCHC in low-cost is a promising adsorbent for uranium(VI) adsorption.