Sorption properties of polymer-modified bentonite to Pb(Ⅱ) ions
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摘要: 为研究聚合物改性膨润土（简称PMB）对重金属的吸附特性，开展了Batch吸附试验，利用4种吸附动力学模型（准一阶动力学、准二阶动力学、颗粒内扩散和Elovich模型）和4种等温吸附模型（Langmuir、Freundlich、D-R和Temkin模型）研究了钠化钙基膨润土（简称NCB）和PMB对Pb(Ⅱ)离子的吸附行为，并通过BET（Brunauer- Emmett-Teller）试验对膨润土进行了比表面积和孔径分析。结果表明，当溶液pH值为1（强酸）时，PMB对Pb(Ⅱ)离子的吸附率为60%，较NCB提高了33%。膨润土对Pb(Ⅱ)离子的吸附动力学更符合准二阶模型，PMB在初始5 min内可快速吸附Pb(Ⅱ)离子，吸附率达50%。Langmuir吸附等温模型更好地描述了两种膨润土对Pb(Ⅱ)离子的吸附特性，计算所得最大吸附量与试验结果接近。Abstract: To investigate the heavy metal sorption properties of the polymer-modified bentonite (PMB), the batch sorption tests are conducted. The sorption behaviors of the sodium activated calcium-bentonite (NCB) and PMB to Pb(Ⅱ) ions are investigated using four sorption kinetic models (i.e., pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich models) and four isothermal sorption models (i.e., Langmuir, Freundlich, D-R, and Temkin models). Additionally, the specific surface area and pore size distribution of the bentonites are analyzed the through BET (Brunauer-Emmett-Teller) tests. The results indicate that at solution pH = 1 (strong acidity), the sorption efficiency of the PMB to Pb(Ⅱ) ions is 60%, with an improvement of 33% over the NCB. The sorption kinetics of bentonites to Pb(Ⅱ) ions conformes more closely to the pseudo-second-order model, with the PMB rapidly adsorbing Pb(Ⅱ) ions within the first 5 minutes, achieving the sorption rate of 50%. The Langmuir sorption isotherm model provides a better description of the sorption characteristics of both bentonites to Pb(Ⅱ) ions, and the calculated maximum sorption capacity closely matches the testing results.
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Keywords:
- bentonite /
- polymer modification /
- sorption property /
- Pb(Ⅱ) ion
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图 2 Pb(Ⅱ)离子的平衡浓度与溶液中C(H+)的关系曲线
Figure 2. Relationship between equilibrium Pb(Ⅱ) concentration and H+ concentration
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图 5 RL与Pb(Ⅱ)离子初始浓度的关系曲线
Figure 5. Relationship between RL and source Pb(Ⅱ) concentration
表 1 Pb(Ⅱ)离子在膨润土中的吸附动力学参数
Table 1 Kinetic parameters for Pb(Ⅱ) sorption on bentonite
吸附动力学参数 钠化钙基膨润土NCB 聚合物改性膨润土PMB 准一阶模型 qe, cal/(mg·g-1) 94.370 105.72 K1/ min-1 0.1299 0.5702 R2 0.8100 0.4000 0.7231 0.1665 准二阶模型 qe, cal/(mg·g-1) 105.26 109.89 K2/((g·mg-1)·min-1) 0.0013 0.0043 R2 0.9996 0.9999 0.0496 0.0001 颗粒内扩散模型 Kp1/ ((mg·g-1)·min-1/2) 13.426 1.6778 c1 22.029 96.413 R12 0.8838 0.9834 Kp2/ ((mg·g-1)·min-1/2) 2.3715 0.4272 c2 69.031 101.62 R22 0.8917 0.9380 Elovich模型 α/((mg·g-1)·min-1) 365.10 5.6211×1020 β/(g·mg-1) 0.0876 0.4856 R2 0.9004 0.9747 
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表 2 膨润土对Pb(Ⅱ)离子的吸附等温模型参数
Table 2 Predicted isothermal parameters for Pb(Ⅱ) sorption on bentonite
模型 参数 钠化钙基膨润土NCB 聚合物改性膨润土PMB Langmuir模型 qm, cal/(mg·g-1) 103.09 112.36 KL/(L·mg-1) 0.0345 0.0090 R2 0.9998 0.9989 0.0432 0.2685 Freundlich模型 KF/(L·g-1) 4.6520 1.9889 nF 2.1124 1.6875 R2 0.8655 0.9026 D-R模型 qm, cal/(mg·g-1) 311.34 401.57 KD-R/ (mol2·kJ-2) 0.0046 0.0061 E/(kJ·mol-1) -10.426 -9.054 R2 0.9379 0.9592 438.05 810.95 Temkin模型 KT/(L·g-1) 1.0891 0.2771 bT/(J·mol-1) 172.09 139.56 R2 0.9516 0.9423
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表 3 膨润土试样的微观表面特性
Table 3 Comparison of surface characteristics of bentonites
表面特性 具体参数 钠化钙基膨润土NCB 聚合物改性膨润土PMB 比表面积/(m2·g-1) 单点BET比表面积 57.31 4.14 多点BET比表面积 57.67 4.22 Langmuir比表面积 88.31 6.52 孔隙体积/ (cm3·g-1) 总孔体积 0.129 0.022 BJH吸附孔体积 0.127 0.022 BJH脱附孔体积 0.131 0.022 孔径/nm 平均孔直径 8.97 20.98 BJH吸附平均孔直径 10.00 21.30 BJH脱附平均孔直径 8.14 18.18
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