海藻酸钠-羧甲基纤维素-氧化石墨烯复合气凝胶的制备及其对Pb(II)的吸附

田甜; 付义乐; 关丽; 王溢源; 周军

doi:10.13801/j.cnki.fhclxb.20230314.001

海藻酸钠-羧甲基纤维素-氧化石墨烯复合气凝胶的制备及其对Pb(II)的吸附

西安建筑科技大学　化学与化工学院，西安 710055

基金项目: 国家自然科学基金(21807086)；陕西省自然科学基础研究计划项目(2022JM-096)

详细信息

通讯作者:
付义乐，博士，副教授，硕士生导师，研究方向为功能材料的制备及性能研究　E-mail: fuyile@xauat.edu.cn

中图分类号: X703；TQ424
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出版历程
- 收稿日期: 2022-11-28
- 修回日期: 2023-02-19
- 录用日期: 2023-03-02
- 网络出版日期: 2023-03-14
- 刊出日期: 2023-10-14

Preparation of sodium alginate-carboxymethyl cellulose-graphene oxide composite aerogel for adsorption of Pb(II) ion

School of Chemistry and Chemical Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China

Funds: National Natural Science Foundation of China (21807086); Natural Science Basic Research Program of Shaanxi (2022JM-096)

摘要

摘要: 目前，开发具有优异吸附性能、可持续使用和绿色环保的吸附剂仍然是水污染治理领域的焦点问题。因此，本文以海藻酸钠(SA)、羧甲基纤维素(CMC)和氧化石墨烯(GO)为原料，通过简单的溶胶-凝胶法结合冷冻干燥，构建了具有三维多孔网络结构的SA-CMC-GO复合气凝胶。利用SEM、FTIR、XRD等对SA-CMC-GO复合气凝胶的微观形貌、官能团结构等进行表征分析。以水中Pb²⁺为吸附对象，通过一系列间歇吸附实验，探究了各种因素(pH、介质温度、接触时间等)对吸附剂去除水体中Pb²⁺的影响。结果表明：在pH值2~5的范围内，复合气凝胶对Pb²⁺的吸附量随着pH的升高而升高；复合气凝胶对于Pb²⁺的吸附过程属于自发放热过程并遵循Langmuir吸附等温模型，其最大吸附量为272.5 mg·g⁻¹；动力学研究表明，SA-CMC-GO复合气凝胶对Pb²⁺具有较快的吸附速率，可在60 min内达平衡并符合准二级动力学模型；此外，经过5次吸附-脱附试验，复合气凝胶仍对Pb²⁺保持较高的吸附性能。SA-CMC-GO复合气凝胶可以作为一种高效、快速的吸附剂用于从水体中去除Pb²⁺。
- 气凝胶 /
- 海藻酸钠 /
- 羧甲基纤维素 /
- 氧化石墨烯 /
- 吸附
Abstract: Exploiting adsorbents with excellent adsorption activity, good durability and environment friendly is still the core focus of water pollution treatment. Herein, in this study, sodium alginate (SA), carboxymethyl cellulose (CMC), and graphene oxide (GO) were used as raw materials to frame a SA-CMC-GO composite aerogel with a 3D network structure by a sol-gel and freeze-drying method. The functional group structure and microstructure of SA-CMC-GO composite aerogel were tested and analyzed by SEM, FTIR and XRD. Various parameters affecting the removal of Pb²⁺ such as pH, temperature and contact time were optimized by using a series of batch adsorption experiments. The results show that the adsorption amount of Pb²⁺ by the composite aerogel increases with the increase of pH=2-5. The adsorption process is a spontaneous exothermic process and the experimental data of the adsorption process are more fitted to Langmuir isotherm, the theoretical maximum adsorption capacity of Pb²⁺ on SA-CMC-GO composite aerogel is 272.5 mg·g⁻¹. Adsorption kinetics studies indicate the adsorption of Pb²⁺ by the SA-CMC-GO composite aerogel shows rapid uptake rates and reaches equilibrium within 60 min. The pseudo-second-order kinetic model coincides with the adsorption behavior of the composite aerogel. Furthermore, the composite aerogel exhibited better reusability for five adsorption and desorption cycles with highly adsorption properties. The results imply that the new SA-CMC-GO composite aerogel could be potentially applied as an effective and rapid adsorbent for Pb²⁺ removal from aqueous solutions.
- aerogel /
- sodium alginate /
- carboxymethyl cellulose /
- graphene oxide /
- adsorption

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图 1 海藻酸钠-羧甲基纤维素-氧化石墨烯(SA-CMC-GO)复合气凝胶制备流程

Figure 1. Preparation process of sodium alginate-carboxymethyl cellulose-graphene oxide (SA-CMC-GO) composite aerogel

T—Temperature; t—Time

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图 2 ((a), (b)) CMC-GO复合气凝胶的SEM图像；SA-CMC-GO复合气凝胶的SEM图像((c), (d))和EDS能谱(e)

Figure 2. ((a), (b)) SEM images of CMC-GO composite aerogel; SEM images ((c), (d)) and EDS mapping (e) of SA-CMC-GO composite aerogel

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图 3 CMC、GO、SA、SA-CMC-GO复合气凝胶的FTIR图谱

Figure 3. FTIR spectra of CMC, GO, SA and SA-CMC-GO composite aerogel

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图 4 CMC气凝胶和SA-CMC-GO复合气凝胶的XRD图谱

Figure 4. XRD patterns of CMC aerogel and SA-CMC-GO composite aerogel

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图 5 SA-CMC-GO复合气凝胶的XPS图谱：(a) 全谱；(b) C1s；(c) O1s

Figure 5. XPS spectra of SA-CMC-GO composite aerogel: (a) Full spectrum; (b) C1s; (c) O1s

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图 6 溶液pH与SA-CMC-GO复合气凝胶吸附Pb²⁺去除率和吸附量的关系

Figure 6. Relationship between solution pH and removal rate and adsorption capacity of Pb²⁺ by SA-CMC-GO composite aerogel

q_e—Equilibrium adsorption capacity

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图 7 吸附时间与SA-CMC-GO复合气凝胶对Pb²⁺的吸附量的关系

Figure 7. Relationship between adsorption time and the adsorption capacity of Pb²⁺ adsorbed by SA-CMC-GO composite aerogel

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图 8 温度与SA-CMC-GO复合气凝胶对Pb²⁺的吸附量的关系

Figure 8. Relationship between temperature and the adsorption capacity of Pb²⁺ adsorbed by SA-CMC-GO composite aerogel

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图 9 SA-CMC-GO复合气凝胶吸附Pb²⁺：(a) 准一级动力学模型；(b) 准二级动力学模型；(c) 粒子内扩散模型

Figure 9. Pb²⁺ adsorption by SA-CMC-GO composite aerogel: (a) Pseudo-first-order kinetic model; (b) Pseudo-second-order kinetic model; (c) Intra-particle diffusion model

q_t—Adsorption capacity at time t

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图 10 SA-CMC-GO复合气凝胶吸附Pb²⁺：(a) Langmuir模型；(b) Freundlich模型

Figure 10. SA-CMC-GO composite aerogel on Pb²⁺: (a) Langmuir model; (b) Freundlich model

c_e—Concentration at adsorption equilibrium

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图 11 循环次数与SA-CMC-GO复合气凝胶对Pb²⁺去除率的关系

Figure 11. Relationship between cycle times and the Pb²⁺ removal rate of SA-CMC-GO composite aerogel

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图 12 SA-CMC-GO复合气凝胶对Pb²⁺的吸附原理图

Figure 12. Mechanism of the adsorption of Pb²⁺ by SA-CMC-GO composite aerogel

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表 1 元素的原子分数

Table 1 Atomic fraction of the element

Atomic fraction/at%
C		O			Na
C—C	C—O	C=O	C—O	COO⁻	—
65.55	10.63	4.88	19.23	1.83	1.87

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表 2 不同吸附剂对Pb²⁺的平衡吸附时间

Table 2 Equilibrium adsorption time of Pb²⁺ by different adsorbents

Adsorbent	Time/min	Ref.
DGO/CMC	550	[3]
GO/CMC	600	[21]
NSC	150	[25]
Cell@PEI	240	[26]
NPCS-PEI	120	[27]
SA-CMC-GO	60	This study
Notes: DGO—Functionalized graphene oxide; NSC—Nano-cellulose/sodium alginate/carboxymethyl chitosan aerogel; Cell@PEI—Amino-modified cellulose aerogel; NPCS-PEI—N-methylene phosphonic acid chitosan.

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表 3 SA-CMC-GO复合气凝胶对Pb²⁺的吸附热力学相关参数

Table 3 Thermodynamically relevant parameters for the adsorption of Pb²⁺ by SA-CMC-GO composite aerogel

T/K	ΔG/(kJ·mol⁻¹)	ΔS/(kJ·mol⁻¹·K⁻¹)	ΔH/(kJ·mol⁻¹)
303	−8.297	−0.08298	−33.44
308	−7.882
313	−7.467
Notes: T—Temperature; ΔH—Enthalpy change; ΔS—Entropy change; ΔG—Gibbs free energy change.

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表 4 SA-CMC-GO复合气凝胶对Pb²⁺的吸附动力学拟合参数

Table 4 Fitting parameters for the kinetics of Pb²⁺ adsorption by SA-CMC-GO composite aerogel

Pseudo-first-order kinetic model			Pseudo-second-order kinetic model
q_e/(mg·g⁻¹)	k₁/min⁻¹	R²	q_e/(mg·g⁻¹)	k₂/(g·mg⁻¹·min⁻¹)	R²
71.71	0.02374	0.7546	230.9	3.576×10⁻⁴	0.9942
Notes: R²—Linear correlation coefficient; k₁—Pseudo-first-order kinetic constant; k₂—Pseudo-second-order kinetic constant.

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表 5 SA-CMC-GO复合气凝胶吸附Pb²⁺的粒子内扩散模型拟合参数

Table 5 Fitting parameters for the intra-particle diffusion model for Pb²⁺ adsorption by SA-CMC-GO composite aerogel

k₁/ (mg·g⁻¹·min^0.5)	R₁²	k₂/ (mg·g⁻¹·min^0.5)	R₂²	k₃/ (mg·g⁻¹·min^0.5)	R₃²
37.70	0.9920	11.13	0.9917	0.5009	0.9923
Note: k_i—Intra-particle diffusion rate constant, i=1, 2, 3.

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表 6 SA-CMC-GO复合气凝胶吸附Pb²⁺的等温线吸附Langmuir模型和Freundlich模型参数

Table 6 Isothermal adsorption parameters of SA-CMC-GO composite aerogel for Pb²⁺ adsorption by Langmuir model and Freundlich model

Langmuir model			Freundlich model
q_e/ (mg·g⁻¹)	K_L	R²	K_F	n	R²
272.5	0.4809	0.9974	155.1	7.125	0.6719
Notes: K_L—Langmuir adsorption coefficient; K_F—Freundlich adsorption coefficient; n—Adsorption strength constant.

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长摘要

目的
随着社会经济的快速发展，工业、农业和城市产生的各类废物导致水污染问题日益严重，其中，水体中重金属污染已经成为了目前最严重的环境问题之一。而作为重金属离子的典型代表，Pb是一种常见的水环境重金属有毒污染物，能够对人类的身体健康造成极大的危害。各类水处理方法中吸附法被认为是最有效和最经济的方法，但是目前吸附法处理水体中的重金属仍存在着吸附容量不高、吸附速率低、安全环保等问题。因此，研制和开发具有优异吸附性能、可持续使用和绿色环保的新型吸附材料，对于吸附处理水体中Pb具有重要的意义。
方法
选择氧化石墨烯(GO)、羧甲基纤维素(CMC)以及海藻酸钠(SA)为原料，通过简单的溶胶-凝胶法结合冷冻干燥，构建具有三维多孔网络结构的复合气凝胶(SA-CMC-GO)。利用场发射扫描电子显微镜(SEM)、傅里叶红外光谱仪(FTIR)、X射线衍射仪(XRD)和X射线光电子能谱仪(XPS)等对SA-CMC-GO复合气凝胶的微观形貌、官能团结构等进行表征分析。以水中Pb为吸附对象，考察了pH、接触时间、初始浓度、温度等因素对SA-CMC-GO吸附处理水中Pb的影响。通过两种常用的动力学方程和粒子内扩散方程对吸附控制机制进行了分析。选取了朗格缪尔(Langmuir)等温线模型和弗伦德里希(Freundlich)等温线模型这两个经典模型对Pb的吸附行为进行了研究。研究SA-CMC-GO的吸附-脱附性能，探讨其循环使用的性能。
结果
以GO、CMC和SA为原料，成功制备得到的一类生物质复合气凝胶SA-CMC-GO。通过SEM、FTIR、XRD、XPS等对其结构和组成进行了表征，结果表明SA-CMC-GO具备三维网络多孔结构，表面存在大量的羟基、羧基等官能团。分析气凝胶在去离子水中对Pb的静态吸附，结果表明，受静电作用的影响，在pH值为2-5的范围内，复合气凝胶对Pb的吸附量随着pH的升高而升高。在最优条件下，SA-CMC-GO对Pb的吸附在60 min达到平衡，且平衡吸附量为237.62 mg·g，与先前报道大多数同类型吸附剂相当，并且与SA气凝胶(172.9 mg·g)、CMC-GO(177.96 mg·g)复合气凝胶相比吸附容量明显增加。根据动力学模型和吸附等温模型拟合的结果分析，SA-CMC-GO吸附过程更符合伪二阶动力学模型和Langmuir吸附等温模型，吸附过程是一个受化学吸附控制的单分子层吸附。进一步对热力学参数进行分析，表明整个吸附过程属于自发放热过程。SA-CMC-GO经吸附-脱附循环5次后，对于Pb的吸附量仍然保持在190 mg·g 以上。
结论
采用操作简便的溶胶-凝胶法，结合冷冻干燥技术制备了SA-CMC-GO复合气凝胶。该复合气凝胶以生物质材料CMC作为载体与GO进行复合，同时引入能够与重金属发生螯合作用的SA，进一步提升吸附能力。结果表明，该复合材料对水体中Pb具有较高的吸附容量、较快的吸附速率、易分离、可以被重复利用的特点，并且制备过程中未加入其它缩合剂，环保、易降解。推测Pb主要通过静电作用、螯合作用、扩散作用和阳离子-π相互作用等吸附在复合材料上。该复合气凝胶可用于含Pb废水的吸附处理。

创新点

目前，开发具有优异吸附性能、可持续使用和绿色环保的吸附剂仍然是水污染治理领域的焦点问题。生物质气凝胶由于绿色环保、成本低、可生物降解等优点，在吸附领域引起了广泛关注，但由于吸附速率较慢、吸附容量不高等问题限制了其作为吸收剂去除水体中重金属离子的应用。因此，开发功能性生物质复合气凝胶用于吸附处理水体中重金属离子污染物具有重要意义。
本研究以海藻酸钠(SA)、羧甲基纤维素(CMC)和氧化石墨烯(GO)为原料，采取简单的溶胶-凝胶法结合冷冻干燥，通过非共价键合的方式，构建了具有三维多孔网络结构的海藻酸钠-羧甲基纤维素-氧化石墨烯复合气凝胶(SA-CMC-GO)。该复合气凝胶内部孔洞相互连通，且有明显的褶皱，增加了其比表面积，有利于对水体中重金属离子的吸附，并且复合气凝胶表面存在的大量的-OH和-COOH官能团作为吸附位点通过静电作用和螯合作用与Pb²⁺有效结合，提升吸附速率和吸附容量。此外，GO的π共轭体系也可以通过阳离子-π相互作用吸引Pb²⁺，提升吸附效果。因此，实验结果表明，所制备的复合气凝胶对Pb²⁺的吸附可在60 min内迅速达到平衡其最大吸附量为272.5 mg·g^-1，且经过5次吸附-脱附试验，复合气凝胶仍对Pb²⁺保持较高的吸附性能。
(a) Effect of adsorption time on the adsorption performance of SA-CMC-GO aerogel to Pb²⁺ and (b) the mechanism of the adsorption of Pb²⁺ by SA-CMC-GO aerogel

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海藻酸钠-羧甲基纤维素-氧化石墨烯复合气凝胶的制备及其对Pb(II)的吸附

通讯作者: 付义乐，博士，副教授，硕士生导师，研究方向为功能材料的制备及性能研究 E-mail: fuyile@xauat.edu.cn

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Preparation of sodium alginate-carboxymethyl cellulose-graphene oxide composite aerogel for adsorption of Pb(II) ion

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通讯作者:
付义乐，博士，副教授，硕士生导师，研究方向为功能材料的制备及性能研究　E-mail: fuyile@xauat.edu.cn