Preparation of UiO-66/chitosan and its adsorption mechanism of U(VI)
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摘要: 铀矿开采和冶炼等工艺产生大量低浓度铀废水,危害着生态环境和人类健康,从含铀废水中去除铀(VI)迫在眉睫。本文以UiO-66、壳聚糖(CS)为原料,采用交联法制备UiO-66/CS新型复合材料,通过静态吸附实验,考察不同pH值、吸附剂投加量、吸附时间及铀初始浓度等外部因素对U(VI)去除率的影响。通过SEM、FTIR、XPS等对UiO-66/CS材料进行表征分析,揭示吸附剂去除U(VI)的机制。结果表明:在铀初始浓度为5 mg/L,温度为298 K,pH为5,投加量为0.15 g/L,吸附时间120 min条件下,UiO-66/CS对U(VI)的去除率可达90.24%。吸附过程符合准二级动力学模型和Freundlich等温吸附模型。U(VI)吸附去除机制主要是—NH、—COOH、Zr—O、—OH等官能团与U(VI)发生络合作用。Abstract: Uranium mining and smelting processes produce a large amount of low-concentration uranium wastewater, which endangers the ecological environment and human health. It is urgent to remove uranium(VI) from uranium-containing wastewater. In this work, UiO-66 and chitosan (CS) were used as raw materials to prepare UiO-66/CS new composite materials by cross-linking method. Through static adsorption experiments, different pH values, adsorbent dosage, adsorption time and initial uranium concentration were investigated of the influence of external factors on U(VI) removal rate. The UiO-66/CS material was characterized and analyzed by SEM, FTIR, XPS, etc., revealing the mechanism of adsorbent removal of U(VI). The results show that when the initial uranium concentration is 5 mg/L, the temperature is 298 K, the pH is 5, the dosage is 0.15 g/L, and the adsorption time is 120 min, the removal rate of U(VI) by UiO-66/CS can reach 90.24%. The adsorption process conforms to the quasi-second-order kinetic model and Freundlich isotherm adsorption model. The adsorption and removal mechanism of U(VI) is mainly the complexation of —NH, —COOH, Zr—O,—OH and other functional groups with U(VI).
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Key words:
- UiO-66 /
- chitosan /
- uranium /
- adsorption /
- mechanism /
- quasi-second-order kinetic
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表 1 UiO-66/CS吸附U(VI)的动力学方程拟合参数
Table 1. Fitting parameters of the kinetic equation of UiO-66/CS adsorption of U(VI)
Adsorbent qe,exp/(mg·g−1) Quasi-first-order dynamics model Quasi-second-order dynamics model k1/min−1 qe/(mg·g−1) R2 k2/(g·(mg·min)−1) qe/(mg·g−1) R2 UiO-66/CS 30.078 0.380 18.793 0.986 0.005 31.056 0.999 Notes: qe,exp—Experimental adsorption capacity; qe—Equilibrium adsorption capacity; k1—Quasi-first-order adsorption rate constant; k2—Quasi-second-order adsorption rate constant; R2—Linear correlation coefficient. 表 2 UiO-66/CS吸附U(VI)的动力学方程拟合参数
Table 2. Fitting parameters of the kinetic equation of UiO-66/CS adsorption of U(VI)
Temperature/K Langmuir Freundlich qmax/(mg·g−1) b R2 KF n R2 288 173.310 0.190 0.956 31.592 2.122 0.976 298 179.211 0.246 0.967 37.424 2.228 0.979 308 193.798 0.299 0.963 44.022 2.275 0.987 Notes: qmax—Maximum adsorption capacity; b—Adsorption equilibrium constant of the Langmuir model; KF—Adsorption equilibrium constant of Freundlich model; 1/n—Empirical parameter related to the adsorption strength. -
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