Removal of uranyl ions from aqueous media by tannic acid-chitosan hydrothermal carbon: equilibria, kinetics and thermody
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Removal of uranyl ions from aqueous media by tannic acid‑chitosan hydrothermal carbon: equilibria, kinetics and thermodynamics Zili Wang1,2 · Zhirong Liu1,2 · Tianzhen Ye1,2 · Yun Wang1 · Limin Zhou1,2 Received: 28 May 2020 / Accepted: 7 October 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract 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. Keywords Hydrothermal carbon · Wastewater-treatment · Uranium(VI) · Adsorption
Introduction Uranium is the main raw material for nuclear energy [1–5], and the global demand for uranium is increasing rapidly. In the process of uranium mining, a large number of harmful radioactive waste water was produced [5–11]. Therefore, it is very important to develop a safe, efficient and economical method to eliminate uranium(VI) from wastewater. Adsorption method has simple process and high removal ratio [12–17]. It is a prospective wastewater treatment technology. The key of adsorption method is to select effective adsorbent. In recent years, various adsorbents for uranium(VI) removal have been reported in literatures [18–21]. Chitosan is a kind of heavy metal adsorbent with good biocompatibility, low toxicity, rich in amino and hydroxyl groups, and has good adsorption performance for a variety of metal ions [22]. However, chitosan is easily soluble in * Zhirong Liu [email protected] 1
State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
School of Chemistry, Biological and Materials Science, East China University of Technology, Nanchang 330013, China
2
weak acid and has poor thermal stability [23, 24]. The instability of chitosan limits its adsorption property. Therefore, the modification of chitosan has become the focus of many scholars [25]. It is found that chitosan can be modified by mixing with other polymers, porous inorganic materials, organic materials or introducing more active adsorption sites into amino (-NH2) and hydroxyl (-OH) groups to improve its stability [26]. Tannic acid is widely distributed in biomass and is also a biocompatibility material. Tannic acid surface has a large number
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