Sorption Characteristics Of Rhenium Ions From Aqueous Solutions Using Modified Nano-Al₂O₃

In this paper, we used modified nano-γ-Al₂O₃ as sorbents. The adsorptive capability and mechanism of rhenium on modified nano-γ-Al₂O₃ at different time, amount, pH value, and concentration were studied in thesis. The research contents and experimental results as follows:1. The effect of nano-TiO₂,nano-SiO₂,nano-Al₂O₃,nano-ZnO,micro-Al₂O₃ on the adsorption behaviour for rhenium in aqueous was studied , the recovery were all less then 9%; the modified nano-γ-Al₂O₃ was 93%;but using unmodified nano-γ-Al₂O₃, the recovery was only 8.32% .2. Both adsorption and desorption of modified nano-γ-Al₂O₃ to rhenium ions depended on the initial pH of the solution. The sorption has been optimized with respect to the pH of the solution. A removal percentage （ > 90%） was found for Re（VII） in the pH range of 2.0³.5.The best conditions of static adsorption method are as follows: The adsorption amount 200mg after oscillate 10 min, and the adsorption percentage was closed 93%. 1.5 mL 0.5 mol·L^-1 NaOH was used for the desorption of Re（VII） on modified nano-γ-Al₂O₃, the recovery was 99%. The enrichment factor values of nano-γ-Al₂O₃ was 10, respectively.3. The adsorption of Re（VII） ions on nano-γ-Al₂O₃ properly correlate with the second-order rate equation. The rate constant of second-order adsorption of nanoγ-Al₂O₃ was 14.442 g·mg^-1·min^-1,initial adsorption rate h was 13.006mg·g^-1·min^-1, the activation energy of nano-γ-Al₂O₃ was 10.97 kJ·mol^-1.The internal diffusion coefficient Di was 2.599×10^-9cm²/s,the external diffusion rate kES was 0.0943 min^-1. The overall rate process appears to be complex ,external mass transport and intraparticle diffusion governs the rate-limiting process,at the same time.4. The Langmuir model could describe the adsorption of nano-γ-Al₂O₃ to Re（VII） ions successfully over the whole range of concentration studied. At room temperature, maximum adsorption capacity was 1.94 mg·g^-1. The value of standard enthalpy and standard entropy （ΔH^θ,ΔS^θ>0） may be interpreted as the endothermic adsorption process. The negative value ofΔG? showed the adsorptions of molybdenum by nano-γ-Al₂O₃ were spontaneous process. The adsorption energy of nano-γ-Al₂O₃ was 7.52 kJ·mol^-1（<8）, indicating that the value lie within the energy range for phyical adsorption.5. The detection limits of determining Re（VII） ions with nano-γ-Al₂O₃ as sorbents was 0. 0325 mg·L^-1, respectively, and the relative standard deviations was 2.0%, respectively. Except for Se（IV）, Gr（VI） ,MoO₄（2-） ,other coexisting ions almost didn’t have effects and the allowable volume for these species were large. MoO₄（2-） can removl at pH 6 using modified nano-γ-Al₂O₃ , the amount of Se（IV） and Gr（VI）in certified reference material was less then the max amount of coexisting ions.The proposed method was applied to the determination of trace amount of Re（VII） in certified reference material （GBW07285） and synthetic samples, the determined values were in good agreement with the certified values.