Preparation of Expanded Microcrystalline Graphite and Its Adsorption Behavior of Pb2+
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摘要:
为进一步拓展微晶石墨的应用领域，将其氧化-膨胀获得膨胀微晶石墨，并用于含铅废水处理。通过静态吸附试验考察初始Pb2+浓度、反应时间、pH和温度等因素对膨胀微晶石墨吸附性能的影响。结果表明，微晶石墨经氧化膨胀制备的膨胀微晶石墨颗粒呈"蠕虫"状，含有丰富的网络孔隙结构，孔径集中在2~5 nm。膨胀微晶石墨对Pb2+的吸附行为受初始浓度、时间、pH和温度的影响，吸附量与初始浓度、时间和pH呈正相关，与温度呈负相关。Langmuir等温吸附模型和准一级动力学模型较好地拟合了吸附过程。热力学分析表明，膨胀微晶石墨对Pb2+的吸附为自发进行的放热吸附过程，以物理吸附为主。
Abstract:To further extend the application of microcrystalline graphite, the expanded microcrystalline graphite was prepared by oxidation and expansion, and then was used in the treatment of lead bearing wastewater. The effects of initial Pb2+ concentration, reaction time, pH and temperature on the adsorption properties of expanded microcrystalline graphite were investigated by static adsorption experiments. The results showed that the expanded microcrystalline graphite was worm-shaped and composed of abundant network pores. The pore size was concentrated at 2~5 nm. The adsorption behavior of expanded microcrystalline graphite on Pb2+ was affected by initial concentration, time, pH and temperature. The adsorption capacity of expanded microcrystalline graphite was positively correlated with initial concentration, time and pH, and negatively correlated with temperature. The adsorption process fits well with the Langmuir isotherm model and pseudo-first-order kinetic model. Thermodynamic study revealed that adsorption of Pb2+ on the expanded microcrystalline graphite was primarily due to a spontaneous exothermic reaction, and the process was mainly controlled by physical adsorption.
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Key words:
- microcrystalline graphite /
- oxidation /
- expansion /
- reduction /
- adsorption
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表 1 微晶石墨样品的化学成分分析
Table 1. Chemical composition of microcrystalline graphite sample
成分 C Al2O3 CaO K2O TiO2 MnO SiO2 Fe2O3 MgO Na2O P2O5 LOI 含量/% 81.54 3.95 0.41 0.38 0.21 0.01 7.85 1.06 0.14 0.14 0.05 4.56 注：LOI为烧失量。 
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表 2 膨胀微晶石墨吸附Pb2+的等温模型参数
Table 2. Isothermal model parameters of Pb2+ adsorption on the expanded microcrystalline graphite
T/K 样品编号 Langmuir Freundlich qm kl R2 kf 1/n R2 298.15 HJC-C-1.6P 81.96 0.96 0.999 5 41.28 0.199 0.909 2
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表 3 膨胀微晶石墨吸附Pb2+的动力学参数
Table 3. Kinetic parameters of Pb2+ adsorption on the expanded microcrystalline graphite
样品编号 准一级动力学 准二级动力学 qe k1 R2 qe k2 R2 HJC-C-1.6P 78.36 6.698 0.999 1 80.19 7.58×10-4 0.995 5
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表 4 膨胀微晶石墨吸附Pb2+的热力学参数
Table 4. Thermodynamic parameters of Pb2+ adsorption on the expanded microcrystalline graphite
样品编号 ΔH°/
(kJ·mol-1)ΔS°/
(J·mol-1·K-1)ΔG°/(KJ·mol-1) R2 293 298 303 308 313 HJC-C-1.6P -12.48 -28.16 -4.16 -4.10 -4.02 -3.81 -3.60 0.961 3
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