Preparation of CNT composites from coal pyrolysis catalyzed by different alkali metals for adsorption of Rhodamine B

doi:10.16085/j.issn.1000-6613.2024-0906

Abstract

Abstract:

In the process of preparing high specific surface area and high porosity carbon nanotubes (CNTs) composite materials from coal pyrolysis, compared to Ba(OH)₂ and NaOH, KOH has stronger alkalinity which can release a large amount of carbon sources in coal and promote the growth and formation of open structures of CNTs. In order to reduce the disintegration of CNTs structure by strong alkalinity, urea co-doping is used to improve alkalinity and pore structure, so as to increase the microporosity and the adsorption sites of nitrogen and oxygen functional groups on the surface of CNTs. This article used bituminous coal as a carbon source and different alkaline metals as catalysts to prepare carbon nanotube composite materials. The influence of alkaline metals on the growth of CNTs and the synergistic effect of alkaline metals and urea on the removal of Rhodamine B were studied, and the kinetic model, isothermal adsorption model and thermodynamic model were discussed. The adsorption process conformed to the pseudo second-order kinetic model and the Freundlich isotherm adsorption model. The calculation based on the van Hough equation indicated that the adsorption was an endothermic, spontaneous and irreversible process. The results indicated that the optimal composite material NCNT-K could achieve a maximum adsorption capacity of 598.09mg/g at 323K.

Key words: carbon nanotubes, coal, adsorption, Rhodamine B, modeling

摘要：

煤热解制备高比表面积和高微孔率碳纳米管（CNT）复合材料过程中，KOH相比于Ba(OH)₂和NaOH催化剂具有更强碱性，能够释放煤中大量碳源和促进CNT的生长和开口状结构形成。为了减少强碱性对CNT结构的崩解，以尿素协同掺杂改善碱性和孔结构，以提高微孔率和CNT表面氮氧官能团的吸附位点。本文以烟煤为碳源，利用不同碱性金属作为催化剂制备碳纳米管复合材料，研究了碱性金属对CNT生长的影响以及碱金属与尿素协同作用对罗丹明B去除的影响，探讨了动力学模型、等温吸附模型和热力学模型。吸附过程符合伪二阶动力学模型和Freundlich等温吸附模型。基于范霍夫方程计算表明该吸附是一个吸热的、自发的、不可逆的过程。最佳复合材料NCNT-K在323K时可达到最大吸附量，为598.09mg/g。

关键词: 碳纳米管, 煤, 吸附, 罗丹明B, 模型

CLC Number:

TQ610.9

WANG Ying, TANG Mengfei, WANG Ying, ZHANG Chuanfang, ZHANG Guojie, LIU Jun, ZHAO Yuqiong. Preparation of CNT composites from coal pyrolysis catalyzed by different alkali metals for adsorption of Rhodamine B[J]. Chemical Industry and Engineering Progress, 2025, 44(7): 3985-3996.

王影, 汤孟菲, 王莹, 张传芳, 张国杰, 刘俊, 赵钰琼. 碱金属催化煤热解制备CNT复合材料用于吸附罗丹明B[J]. 化工进展, 2025, 44(7): 3985-3996.

Figures/Tables 15

工业分析W_ad^①/%				元素分析W_d^②/%
灰分	水分	挥发分	固定碳^③	C	H	N	S
5.53	3.25	30.91	60.33	73.75	4.42	1.45	0.22

复合材料	比表面积/m²·g^-1	微孔比表面积/m²·g^-1	孔容/cm³·g^-1	微孔体积/cm³·g^-1	微孔含量/%	平均粒径/nm
CNT-K	1128	1090	0.580	0.443	76.38	2.082
NCNT-K	1439	1384	0.669	0.584	87.29	1.932
CNT-Na	252	198	0.259	0.104	40.15	4.745
NCNT-Na	726	700	0.370	0.292	78.92	2.077
CNT-Ba	18	11	0.037	0.008	21.62	9.294
NCNT-Ba	15	6	0.034	0.007	20.59	16.037

复合材料	C原子分数/%	N原子分数/%	N物种比例/%
复合材料	C原子分数/%	N原子分数/%	N-6		N-5		—NH₂		N-Q		N—O
CNT-K	84.41	1.47	29.17		15.38		22.33		14.25		18.88
NCNT-K	90.47	0.91	42.21		16.92		16.63		11.32		12.92
CNT-Na	80.06	1.52	29.89		30.14		27.35		9.60		3.02
NCNT-Na	87.37	1.47	14.84		26.19		24.70		24.78		9.49
CNT-Ba	87.64	1.79	25.11		27.80		13.86		26.58		6.64
NCNT-Ba	86.10	1.75	19.83		31.40		9.64		17.18		21.95
复合材料	O原子分数/%	O物种比例/%
复合材料	O原子分数/%	C $̿$ O^①		C $̿$ O^②		C—O		COOH		H₂O(ad)
CNT-K	14.12	44.25		43.16		10.82		1.32		0.46
NCNT-K	8.62	55.82		19.72		15.69		7.57		1.20
CNT-Na	18.41	22.47		40.43		30.04		5.76		1.30
NCNT-Na	11.16	13.59		32.24		42.03		8.16		3.97
CNT-Ba	10.57	32.22		34.26		19.16		11.29		3.07
NCNT-Ba	12.15	33.93		35.01		24.95		4.33		1.78

复合材料	C原子分数/%	N原子分数/%	N物种比例/%
复合材料	C原子分数/%	N原子分数/%	N-6		N-5		—NH₂		N-Q		N—O
CNT-K	84.41	1.47	29.17		15.38		22.33		14.25		18.88
NCNT-K	90.47	0.91	42.21		16.92		16.63		11.32		12.92
CNT-Na	80.06	1.52	29.89		30.14		27.35		9.60		3.02
NCNT-Na	87.37	1.47	14.84		26.19		24.70		24.78		9.49
CNT-Ba	87.64	1.79	25.11		27.80		13.86		26.58		6.64
NCNT-Ba	86.10	1.75	19.83		31.40		9.64		17.18		21.95
复合材料	O原子分数/%	O物种比例/%
复合材料	O原子分数/%	C $̿$ O^①		C $̿$ O^②		C—O		COOH		H₂O(ad)
CNT-K	14.12	44.25		43.16		10.82		1.32		0.46
NCNT-K	8.62	55.82		19.72		15.69		7.57		1.20
CNT-Na	18.41	22.47		40.43		30.04		5.76		1.30
NCNT-Na	11.16	13.59		32.24		42.03		8.16		3.97
CNT-Ba	10.57	32.22		34.26		19.16		11.29		3.07
NCNT-Ba	12.15	33.93		35.01		24.95		4.33		1.78

参数	伪一阶	伪二阶	参数	第一步	第二步	第三步
k/min^-1	0.2531	0.0002	K/mg·g^-0.5∙t^-0.5	49.63	8.04	4.76
q_e/mg·g^-1	137.60	157.81	C	0.90	82.89	103.46
R²	0.8708	0.9320	R²	0.9942	0.9567	0.9041

温度	Langmuir模型			Freundlich模型			q_e/mg·g^-1
温度	q_max/mg·g^-1	K_L/L·mg^-1	R²	n	K_F/mg·g^-1·L^1/ⁿ ·mg^-1/ⁿ	R²	q_e/mg·g^-1
298K	288.15	1.61	0.9675	1.64	17.92	0.9914	275.13
313K	490.17	0.56	0.9707	7.74	269.41	0.9897	454.43
323K	598.26	0.80	0.9723	8.31	364.81	0.9877	598.09

温度	∆G^⊖/kJ·mol^-1	∆H^⊖/kJ·mol^-1	∆S^⊖/kJ·mol^-1·K^-1
298K	-7.15	+0.11	+4.65
313K	-14.56
323K	-15.84

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