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摘要:
以膨润土为原料采用超声剥离-自组装-冷冻干燥法制备了膨润土纳米片基水凝胶，并采用X射线衍射仪（XRD）、傅立叶变换红外光谱仪（FT-IR）、场发射扫描电子显微镜（SEM）、比表面积测试（BET）对制备的凝胶进行表征。表征结果显示该凝胶属于微孔和介孔共存材料，且保留了膨润土纳米片表面的含氧官能团。铅离子吸附试验表明：该凝胶吸附铅离子的最佳pH值范围为4~5，吸附过程较好的符合拟二级动力学方程和Langmuir等温吸附模型，且吸附过程比较容易进行。此外，与膨润土或膨润土基复合材料相比，膨润土纳米片基水凝胶具有丰富的孔隙结构和较大的最大饱和吸附量，在废水处理方面具有较好的应用前景。
Abstract:Bentonite nanosheet based hydrogel was prepared by ultrasonic stripping, self-assembly and freeze-drying with bentonite as raw material. The hydrogel was characterized by X-ray diffraction (XRD), fourier transform infrared spectrometer (FT-IR), field emission scanning electron microscopy (SEM) and specific surface area measurements (BET). The characterization results showed that the hydrogel was the microporous and mesoporous material coexisting materials keeping the oxygen-containing functional groups on the surface of bentonite nanosheet. The lead ion adsorption test showed that the maximum adsorption capacity was obtained at the pH range of 4 to 5. The adsorption process was in good agreement with the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model, and the adsorption process was relatively easy to carry out. In addition, compared with bentonite or bentonite-based composites, bentonite nanosheet based hydrogel had rich pore structure and large maximum saturated adsorption capacity. Therefore, it has good application prospects in wastewater treatment.
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Key words:
- bentonite /
- bentonite nano-sheet based hydrogel /
- lead ion /
- adsorption /
- wastewater treatment
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表 1 试验所用试剂列表
Table 1. Lists of reagents used in the experiments
Sample names Specifications Manufacturer Poly (vinyl alcohol) Alcoholysis degree: 98% 99% Shanghai Aladdin Bio-Chem Technology Co., LTD Sodium alginate Chemically pure Tianjin Kemiou Chemical Reagent Co., Ltd. chitosan Biochemical reagents Sinopharm Chemical Reagent Co., Ltd Sodium hydroxide Analysis of pure Luoyang Chemical Reagent Factory Nitric acid Analysis of pure Luoyang Chemical Reagent Factory Anhydrous calcium chloride Analysis of pure Tianjin Kemiou Chemical Reagent Co., Ltd. Boric acid Excellent level of pure Sinopharm Chemical Reagent Co., Ltd Lead nitrate Analysis of pure Tianjin Kemiou Chemical Reagent Co., Ltd. 
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表 2 试验仪器
Table 2. Lists of instruments and equipments used in the experiments
Instrument name Type/specification Manufacturer Atomic absorption spectrophotometer TAS-990 Beijing's General Instrument Co., LTD High-speed centrifuge JW-2017H Anhui Jia Instrument Equipment Co., LTD Small vertical mine dust tester M5L Yancheng ranch yu da Experiment Instrument Plant Intelligent magnetic stirrer ZNL-BS Gongyi city Instrument Co., LTD in China Desktop full temperature oscillator TQZ-312 Shanghai jing macro Laboratory Equipment Co., LTD Ultrasonic cell crushing apparatus JY92-IIN Ningbo xingzhi Biotechnology Co., LTD Infrared spectrometer Nicolet iS5 The game's fly the world's Science and Technology Co., LTD Freeze drying machine SJIA-5FE Ningbo Jia Instrument Co., LTD Ultrasonic cleaning machine SYU-10-200D Zhengzhou Born yuan Instrument Co., LTD Electronic balance FA2004B Shanghai on Instrument Co., LTD pH tester PHS-3E Shanghai on Instrument Co., LTD
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表 3 膨润土纳米片水凝胶的孔性质
Table 3. Pore properties of the bentonite nanosheet based hydrogel
Sample SBET/(m2·g-1) Pore volume /(cm3·g-1) Average pore diameter /nm Hydrogel 6.866 5 0.054 568 31.479 98
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表 4 凝胶吸附铅离子拟一级和拟二级吸附动力学参数
Table 4. Kinetic parameters of the pseudo-first- and pseudo-second-order adsorption forthe adsorption of Pb2+ on the bentonite nanosheet based hydrogel
pseudo-first-order kinetics pseudo-second-order kinetics α1 (min-1) qe(mg/g) R2 α2 (min-1) qe(mg/g) R2 0.027 32 13.59 0.973 9 0.001 82 16.37 0.982 2
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表 5 凝胶对铅离子吸附等温线模型常数及相关参数
Table 5. Adsorption isotherm model constants and related parameters of Pb2+ by the bentonite nanosheet based hydrogel
Temperature Langmuir model Freundlich model qm(mg/g) b(mg/L) R2 k n R2 20 ℃ 524.60 2.45×10-4 0.995 5 0.21 1.11 0.993 2 30 ℃ 133.97 8.33×10-4 0.999 4 0.39 1.36 0.998 0 40 ℃ 80.63 1.27×10-3 0.995 6 0.53 1.54 0.990 6
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