Adsorption performance and mechanism of MnO2/Ti3C2TX composite towards U(VI) in water
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摘要: 针对Ti3C2TX纳米片层易堆叠和吸附位点少的不足,采用水热法制备了MnO2/Ti3C2TX复合剂。通过单因素试验探讨铀的初始浓度、投加量、pH值、时间和共存离子对其吸附U(VI)的影响,利用现代表征手段分析MnO2/Ti3C2TX的表面性质及吸附U(VI)的作用机制。试验结果表明:在U(VI)初始浓度5 mg·L−1、MnO2/Ti3C2TX投加量为0.1 g·L−1、温度303 K、pH值为6时,30 s内U(VI)浓度降至0.41 mg·L−1,30 min后吸附达到平衡,其对U(VI)的吸附率达99.15%,吸附容量为49.58 mg·g−1。经过5次循环后,MnO2/Ti3C2TX对U(VI)的吸附效率仍保持在96.3%,具有良好的可再生利用性。整个吸附过程为自发吸热过程,符合拟二级动力学模型和Freundlich等温线模型。BET分析表明MnO2/Ti3C2TX的比表面积达318.3 m2·g−1,较Ti3C2TX高55.9倍。FTIR和XPS分析表明MnO2/Ti3C2TX对U(VI)吸附主要是表面含氧基团与铀的配位络合。Abstract: To address the shortcomings of Ti3C2TX nanosheets, which tend to stack and have limited adsorption sites, a MnO2/Ti3C2TX composite was prepared using the hydrothermal method. The influence of uranium initial concentration, dosage, pH, time, and interfering ions on U(VI) adsorption was investigated through single-factor adsorption experiments. Modern characterization techniques were employed to analyze the surface properties of MnO2/Ti3C2TX and the mechanism of U(VI) adsorption. Experimental results revealed that with an initial U(VI) concentration of 5 mg·L−1, MnO2/Ti3C2TX dosage of 0.1 g·L−1, and a temperature of 303 K, pH of 6, the U(VI) concentration dropped to 0.41mg·L−1 within 30 seconds. Adsorption equilibrium was reached after 30 minutes, with an adsorption rate of 99.15% and an adsorption capacity of 49.58 mg·g−1. After five cycles, the adsorption efficiency of MnO2/Ti3C2TX remained at 96.3%, demonstrating its potential for regeneration and reuse.The entire adsorption process was endothermic and spontaneous, fitting the pseudo-second-order kinetic model and the Freundlich isotherm model. BET analysis showed that the specific surface area of MnO2/Ti3C2TX reached 318.3 m2·g−1, which is 55.9 times higher than that of Ti3C2TX. FTIR and XPS analyses indicated that the primary mechanism of U(VI) adsorption on MnO2/Ti3C2TX is the coordination complexation between surface oxygen-containing groups and uranium.
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Key words:
- Ti3C2TX /
- MXene /
- MnO2 /
- adsorption /
- U(VI)
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图 10 (a)吸附时间对MnO2/Ti3C2TX吸附不同浓度 U(VI)的影响; (b)拟一级动力学模型拟合曲线;(c)拟二级动力学模型拟合曲线;(d)颗粒内扩散模型拟合曲线
Figure 10. (a) Effect of adsorption time on MnO2/Ti3C2TX adsorption of different concentrations of U (VI); (b) the fitting curve of pseudo-first-order kinetic model; (c) the fitting curve of quasi-second-order kinetic model; (d) the fitting curve of intra-particle diffusion model
qt−Adsorption capacity at t time; qe−Equilibrium adsorption capacity; t−Adsorption time
表 1 MnO2/ Ti3C2Tx与其他吸附剂比表面积对比
Table 1. Comparison of BET surface area between MnO2/ Ti3C2Tx and other adsorbents
表 2 MnO2/Ti3C2TX吸附U(VI)的动力学模型参数
Table 2. Kinetic model parameters of uranium adsorption by MnO2/Ti3C2TX
C0/(mg·L−1) qe.exp/(mg·g−1) Pseudo- first Kinetics model Pseudo- second Kinetics model K1 qe.cal R2 K2 qe.cal R2 5 49.792 0.085 1.923 0.687 0.020 49.751 1 10 99.112 0.099 8.575 0.893 0.010 99.010 1 15 146.825 0.064 24.016 0.972 0.007 147.059 0.999 Notes: qe is the adsorption capacity at equilibrium time; K1 and K2 are reaction rate constants of pseudo-first-order and pseudo-second-order equations, respectively; R2 is the correlation coefficient. 表 3 MnO2/Ti3C2TX吸附等温线模型的相关参数
Table 3. Relevant parameters of MnO2/Ti3C2TX adsorption isotherm model
T/K Langmuir Freundlich qmax/(mg·g−1) b R2 KF n R2 293 372.801 0.853 0.933 162.314 3.058 0.994 303 380.414 1.157 0.941 176.716 3.139 0.994 313 434.837 0.717 0.936 196.977 3.145 0.992 Notes: qmax is Adsorption capacity per unit mass of the adsorbent; b is Langmuir coefficient related to the affinity of binding site; KF , n-Constants that are related to the adsorption capacity and the adsorption intensity, respectively. 表 4 MnO2/Ti3C2TX吸附U(VI)性能与其他吸附剂对比
Table 4. Comparison of MnO2/Ti3C2TX adsorption performance for U (VI) with other adsorbents
Adsorbent pH Temperature/K Equilibrium
time/minMaximum adsorption
capacity /(mg·g−1)References MnO2@BBC 5 298 240 97.40 Chen etal[33](2022) HPC/POSS-OH modified MXene 5 298 90 307.67 Zhao etal[34](2022) Chloroacetic acid modified Ti3C2TX 5 308 150 165.43 Xie etal[35](2022) γ-Fe2O3/CSS 6 298 120 214.1 Fan etal[36](2022) Ti3C2@FeS-PDA/PEI 6 298 240 88.5 Liu etal[37](2023) MnO2/ Ti3C2TX 6 303 30 380.41 This work Notes: MnO2@BBC-MnO2 modified bamboo-derived biochar composite;HPC/POSS-OH- hydroxypropyl cellulose (HPC) and polyhedral oligomeric silsesquioxane (POSS-OH);CSS-corn stalk starch; PDA/PEI-polydopamine and polyethyleneimine 表 5 MnO2/Ti3C2TX吸附U(VI)的热力学参数
Table 5. Thermodynamic parameters of uranium adsorption by MnO2/Ti3C2TX
∆G0/(kJ·mol−1) ∆H0/(kJ·mol−1) ∆S0/(kJ·mol−1) 293 K 303 K 313 K 21.073 119.551 −14.014 −15.038 −16.406 Notes: ΔG0 −Standard free energy change; ΔH0 −Standard enthalpy change; ΔS0 −Standard entropy change. -
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