Preparation Of Biomaterial-Based Gel Adsorbents And Its Application In Rhenium-Molybdenum Separation

Rhenium and molybdenum are strategic metal elements being related to national industrial production and technological development.The enrichment and separation technology of rhenium and molybdenum plays an important role in their metal smelting,recovery,application and detection.Adsorption method is a simple and efficient separation method.It is important to prepare green adsorption materials with high adsorption capacity,good selectivity for the separation of rhenium and molybdenum.In this thesis,two types of biomaterial-based gel adsorbents(CSN and TCC)were prepared,by tuning cross-link of chitosan and/or cellulose biomaterials.These gel adsorbents had a core-shell structure and wrapped N263(methyl trioctyl ammonium chloride)as an extractant.The main contents were as follows.(1)Chitosan-based ionic gel beads wrapping N263(CSN)were successfully fabricated with a simple cross-linking method by using TPP as a cross-linking agent.Highly selective adsorption of Re(VII)from the mixture of Re(VII)and Mo(VI)could be achieved a wide p H range from p H 4 to p H 12,yielding a separation factor as high as 10³–5×10⁴.The results of adsorption experiments and XPS analysis showed that the extractive adsorption of rhenium by CSN gel was closely related to the content of N263,and the maximum adsorption capacity was about 222 mg g^-1.The adsorption mechanism of Re(?)was mainly related to the formation of the association complex R₄N⁺·Re O₄^-.The results of FT-IR and SEM-EDS showed that Mo(VI)was mainly distributed in the surface of the shell,and the shell could block Mo(VI)off,which produces the selective adsorption of Re(VII).(2)TCC was prepared by using chitosan and cellulose as biometrial precursors and encapsulating N263 by corss-linking.In a wide p H range from p H 4 to p H 12,TCC gel exhibited excellent adsorption performance for Re(?)and Mo(?).The maximum adsorption capacity was 350 mg g^-1 for Re(?),and 337 mg g^-1 for Mo(?).It was confirmed that the adsorption of rhenium by TCC gel was closely related to the active substance N263,while the adsorption of Mo(?)could be carried out by the gel shell under acidic conditions.Under the condition of 298 K and p H 3,the adsorption rate of Mo(?)by TCC gel was significantly faster than Re(?).The kinetics data showed that the adsorption process of Re(?)fitted to pseudo-first-order kinetics,while the adsorption process of Mo(?)fitted to pseudo-second-order kinetics.The experimental data of isothermal adsorption showed that the isothermal adsorption process of Re(?)and Mo(?)conforms to the Langmuir isotherm,but chemisorption of Mo(?)was preferred on the adsorbent surface.