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摘要: 将改进Hummers法合成的氧化石墨烯(GO)与废茶渣(TW)、Fe3O4进行复合获得废茶渣磁性改性物rGO/Fe3O4/TW,通过FTIR光谱和XRD对产物结构和晶型进行表征。考察溶液pH 值、振荡时间和铀初始浓度对合成产物吸附行为的影响。采用孔结构分析仪和XPS对rGO/Fe3O4/TW吸附前后样品的孔特性和表面结构进行吸附机理分析。结果表明,rGO/Fe3O4/TW不仅具有优良的去铀性能,短时间内可达近100%的去除率,而且负载铀之后通过磁场作用易从液相中快速分离出来。rGO/Fe3O4/TW对铀的吸附过程符合Langmuir 模型和准二级动力学模型。对于初始浓度为10 mg/L的含铀溶液,TW、MTW和rGO/Fe3O4/TW的最大吸附量分别为97.70 mg g−1、79.46 mg g−1和103.84 mg g−1。同时,rGO/Fe3O4/TW具有良好的循环再利用性,经5个吸附-解吸-再吸附循环之后,仍可达到较好的去铀效果,去铀率约为85%。Abstract: Used tea leaves, or tea waste (TW), were crushed into powder and mixed with graphene oxide (GO) in water, followed by adjusting the pH value of the resulting suspension with ammonia to 11, adding FeCl2·4H2O under magnetic stirring, filtration and drying to prepare a rGO/Fe3O4/TW (with mass ratios of 1∶2∶1) hybrid material. The structure and crystalline phases of the material were characterized by FTIR and XRD. Isotherms for uranium adsorption were obtained and its kinetics were measured in a conical bottle that was placed in a shaker. The effects of the pH value of the uranium solution, adsorption time and initial concentration on the uranium adsorption were investigated. Results indicate that the hybrid has a much faster adsorption rate than TW with an uranium removal rate up to nearly 100% in 20 min for an initial uranium concentration of 10 mg L−1. The maximum adsorption capacity of the hybrid is 103.84 mg g−1 while that of TW is 97.70 mg g−1. The hybrid with adsorbed uranium can be easily separated from the solution by applying a magnetic field. The isotherms and kinetics of uranium adsorption on the hybrid are best fitted by the Langmuir isotherm model and the pseudo-second-order model, respectively. The hybrid has good reusability with an uranium removal rate of about 85% after 5 cycles.
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Key words:
- Tea waste /
- Graphene oxide /
- Magnetic modification /
- Adsorption /
- Uranium
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Table 1. Adsorption kinetic model parameters for TW, MTW and rGO/Fe3O4/TW.
Sorbents Pseudo-first-order model Pseudo-second-order model Qe
(mg/g)k1 (g/(mg·
min)R2 Qe (mg/g) k2 (g/(mg·
min)R2 TW 0.5756 0.026 0.9361 19.92 0.233 0.9999 MTW 0.1298 0.018 0.9677 12.35 0.006 0.9945 rGO/Fe3O4/TW 0.2075 0.035 0.9730 20.41 0.027 0.9993 Table 2. Adsorption parameters for langmuir and freundlich isotherm models.
Sorbents Langmuir isotherm Freundlich isotherm Qm
(mg g−1)kL
(L mg−1)R2 n kF (mg1−n Ln g−1) R2 TW 97.70 0.11 0.9899 2.42 16.86 0.9885 MTW 79.46 0.14 0.9969 3.42 21.52 0.8937 rGO/Fe3O4/TW 103.84 0.75 0.9983 4.05 40.27 0.8749 -
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