﻿ 柚子皮活性炭对重金属锰离子吸附的研究

柚子皮活性炭对重金属锰离子吸附的研究Study on Adsorption of Heavy Metal Ions by Citron Peel Activated Carbon

Abstract: This paper uses agricultural waste grapefruit skin as raw material to prepare activated carbon (PC-AC), which was successfully used as an adsorbent for removal of Mn(II) ion in waste water. This work investigates the best adsorption conditions, and fits the corresponding kinetic and thermodynamic models. From the results, adsorption capacity of adsorbent (PC-AC) for Mn(II) depends on the initial concentration of manganese ion, the amount of adsorbent, the adsorption temperature, and the adsorption time. Activated carbon adsorption dynamics model accords with the second reaction kinetics model and the thermodynamic models follows Langmuir model. PC- AC as adsorption removes Mn(II) ion in waste water under relatively broad conditions, and the heavy metal wastewater needn’t pretreatment, which can effectively solves the problem of energy consumption.

1. 引言

2. 实验

2.1. 样品制备

2.2. 活性炭表征

2.3. 吸附试验

${q}_{e}=\frac{\left({C}_{0}-{C}_{e}\right)V}{m}$ (1)

Mn(II) 的去除率(Re%)，由以下方程计算：

$Re\left(%\right)=\left(\frac{{C}_{0}-{C}_{e}}{{C}_{0}}\right)×100$ (2)

$\mathrm{ln}\left({q}_{e}-{q}_{t}\right)=\mathrm{ln}{q}_{e}-{K}_{1}t$ (3)

$\frac{t}{{q}_{t}}=\frac{1}{{K}_{2}{q}_{e}^{2}}+\frac{1}{{q}_{e}}t$ (4)

$h={K}_{2}{q}_{e}^{2}$ (5)

$\frac{1}{{q}_{e}}=\frac{1}{{K}_{L}{C}_{e}{q}_{\mathrm{max}}}+\frac{1}{{q}_{\mathrm{max}}}$ (6)

${R}_{L}=\frac{1}{1+{C}_{0}{K}_{L}}$ (7)

KL是朗格缪尔常数，表示吸附能量(L/mg)；qmax表示重金属离子的最大吸附量。RL分离因子，值在0~1之间，表示吸附的难易程度。

Freundlich热力学模型，由以下方程计算：

$\mathrm{ln}{q}_{e}=\mathrm{ln}{K}_{F}+\frac{1}{n}\mathrm{ln}{C}_{e}$ (8)

KF与结合能有关 [5] 。

3. 结果与讨论

3.1. 吸附反应的影响因素

(a) (b) (c) (d)

Figure 1. The influence factors on adsorption capacity: (a) the amount of adsorbent; (b) the adsorption time; (c) the adsorption temperature; (d) initial concentration of manganese ion

3.2. 吸附的动力学模型

3.3. 吸附的热力学模型

PC-AC活性炭吸附模拟废水中的锰离子的热力学模型分析，如图3所示。图3(a)为Langmuir吸附模型，随着Ce的增大，Ce/qe呈线性增长，同时，升高温度Ce/qe明显下降，郎格缪尔系数约为0.72~0.975。图3(b)为Freundlich模型，随着lnCe的增加，lnqe逐渐上升，并且随着温度的升高出现下降趋势，Freundlich系数为0.813~0.9395。从图中可以看出，2种等温模型都能够很好的描述柚皮粉末活性炭对锰离子的吸附，其线性相关系数均大于0.9。但Langmuir方程的线性相关系数更接近于 =1，能够更好的描述柚皮粉末活性炭对锰离子的吸附过程，结果表明PC-AC活性炭吸附模拟废水中的锰离子的吸附热力学的模型满足Langmuir模型 [10] [12] 。

3.4. PC-AC的结构与形貌

(a) (b)

Figure 2. The corresponding kinetic (a) First order reaction kinetics model; (b) Second order reaction kinetics model

(a) (b)

Figure 3. The thermodynamic models: (a) Langmuir model; (b) Freundlich model.

Figure 4. The results of SEM (a) and XRD (b) of PC-AC

PC-AC活性炭吸附模拟废水中重金属离子Mn(II)达到饱和以后，过滤，干燥。从图4(b)中可以看出，在吸附后的PC-AC活性炭XRD谱图中没有观察到明显的锰的化合物衍射峰，这主要是由于吸附锰离子进入孔道中，活性炭的衍射峰覆盖了微小的锰化合物衍射峰。也有可能是负载的锰化合物含量较少且尺寸太小，在吸附剂活性炭表面以无定型锰离子存在，超出XRD仪器检测范围，无法被扫描 [13] 。

4. 结论

Figure 5. The results of (a) SEM of AC/MnOx; (b) EDX of C element; (c) EDX of O element; (d) EDX of Mn element

[1] 熊安晗, 莫文龙, 王君华, 等. 蛭石对模拟废水中镍离子的吸附研究[J]. 合成材料老化与应用, 2015, 44(3): 79-81.

[2] Demiral, H., Demiral, İ., Tümsek, F., et al. (2008) Adsorption of Chromium (VI) from Aqueous Solution by Activated Carbon Derived from Olive Bagasse and Applicability of Different Adsorption Models. Chemical Engineering Journal, 144, 188-196.
https://doi.org/10.1016/j.cej.2008.01.020

[3] Esfandiar, N., Nasernejad, B. and Ebadi, T. (2014) Removal of Mn(II) from Groundwater by Sugarcane Bagasse and Activated Carbon (a Comparative Study): Application of Response Surface Methodology (RSM). Journal of Industrial and Engineering Chemistry, 20, 3726-3736.
https://doi.org/10.1016/j.jiec.2013.12.072

[4] 张军强, 李随勤. 柚子皮的利用研究[J]. 西部皮革, 2016, 38(8): 282.

[5] Kumar, P.S., Ramalingam, S., Kirupha, S.D., et al. (2011) Adsorption Behavior of Nickel (II) onto Cashew Nut Shell: Equilibrium, Thermodynamics, Kinetics, Mechanism and Process Design. Chemical Engineering Journal, 167, 122-131.
https://doi.org/10.1016/j.cej.2010.12.010

[6] Wang, J., Pan, K., He, Q., et al. (2013) Polyacrylonitrile/Polypyrrole Core/Shell Nanofiber Mat for the Removal of Hexavalent Chromium from Aqueous Solution. Journal of Hazardous Materials, 244-245, 121-129.

[7] Chávez-Guajardo, A.E., Medina-Llamas, J.C., Maqueira, L., et al. (2015) Efficient Removal of Cr (VI) and Cu (II) Ions from Aqueous Media by Use of Polypyrrole/Maghemite and Polyaniline/Maghemite Magnetic Nanocomposites. Chemical Engineering Journal, 281, 26-36.
https://doi.org/10.1016/j.cej.2015.07.008

[8] Swain, B., Mishra, C., Park, J.L., et al. (2015) Treatment of Indium-Tin-Oxide Etching Wastewater, Recovery of Semiconductor Grade Indium and Copper Nanopowder: A Commercial Hybrid Green Process. The Asia Pacific Conference on Sustainable Energy & Environmental Technologies, July 2015, University of Seoul, Seoul.

[9] Anirudhan, T.S. and Sreekumari, S.S. (2011) Adsorptive Removal of Heavy Metal Ions from Industrial Effluents Using Activated Carbon Derived from Waste Coconut Buttons. Journal of Environmental Sciences, 23, 1989-1998.
https://doi.org/10.1016/S1001-0742(10)60515-3

[10] Dada, O.A., Adekola, F.A. and Odebunmi, E.O. (2015) Kinetics and Equilibrium Models for Sorption of Cu(II) onto a Novel Manganese Nano-Adsorbent. Journal of Dispersion Science and Technology, 37, 119-133.
https://doi.org/10.1080/01932691.2015.1034361

[11] Shi, P. and Liu, C.-J. (2009) Characterization of Silica Supported Nickel Catalyst for Methanation with Improved Activity by Room Temperature Plasma Treatment. Catalysis Letters, 133, 112-118.
https://doi.org/10.1007/s10562-009-0163-0

[12] Arulkumar, M., Thirumalai, K., Sathishkumar, P., et al. (2012) Rapid Removal of Chromium from Aqueous Solution Using Novel Prawn Shell Activated Carbon. Chemical Engineering Journal, 185-186, 178-186.

[13] Liu, W., Zhang, J., Zhang, C., et al. (2012) Preparation and Evaluation of Activated Carbon-Based Iron-Containing Adsorbents for Enhanced Cr(VI) Removal: Mechanism Study. Chemical Engineering Journal, 189-190, 295-302.

Top