Study on the mechanism of adsorption of dioxins by oxygen-containing functional groups on activated carbon surface
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摘要: 以分子结构和性质与二噁英相似的二苯并呋喃为模型化合物,椰壳炭为吸附剂,在120 ℃条件下进行了吸附实验。将硝酸改性后的样品分别在300、500、800 ℃进行热处理,比较了原始样品和改性后的椰壳炭对二苯并呋喃的吸附能力。并利用BET、TPD-MS、元素分析等手段对改性前后椰壳炭的物理化学性质进行了表征。结果表明,硝酸改性后椰壳炭表面含氧官能团增多,抑制了其对二苯并呋喃的吸附,其中,内酯基对二苯并呋喃吸附的影响最大,通过热处理,减少含氧官能团的含量,可提高椰壳炭对二苯并呋喃的吸附容量。Abstract: The adsorption behaviors of the model molecule dibenzofuran (DBF) with similar molecule structure and size to dioxins on the activated carbon was elucidated. The activated carbon adsorbent was coconut shell-based. The adsorption experiments were conducted at 120 ℃. The activated carbon samples were modified by nitric acid at 300, 500, and 800 ℃, and their DBF adsorption capacities were compared. The physico-chemical properties of samples were characterized by BET, TPD-MS, elemental analysis, and other instruments. The results demonstrated that nitric acid treatment could inhibit the adsorption of DBF on activated carbon. The DBF adsorption capacity of activated carbon was related to its surface oxygen-containing functional groups. Lactone groups on activated carbon had the biggest influence on the DBF adsorption. Heat treatment reduced the content of surface oxygen-containing functional groups, and improved the adsorption capacity of DBF.
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Key words:
- activated carbon /
- oxygen-containing functional groups /
- adsorption /
- dibenzofuran /
- dioxins
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表 1 不同样品的孔结构参数
Table 1 Textural properties of different samples
Sample SSA/
(m2·g−1)Pore volume/
(cm3·g−1)Micropore volume/
(cm3·g−1)Average pore diameter AC-950 1033.9 0.559 0.343 2.162 AC-O-12 h 1021.2 0.547 0.342 2.141 AC-O-300 1025.3 0.551 0.352 2.143 AC-O-500 1028.6 0.559 0.338 2.174 AC-O-800 1057.8 0.590 0.364 2.137 表 2 改性前后样品的元素组成
Table 2 Elemental composition of the sample before and after modification
Sample Content w/% C O N H AC-950 96.40 1.72 0.42 1.46 AC-O-12 h 85.87 11.02 1.00 2.11 AC-O-300 87.52 9.78 0.90 1.80 AC-O-500 90.20 7.50 0.78 1.52 AC-O-800 94.61 3.44 0.87 1.08 note: oxygen element is obtained by difference subtraction 表 3 不同样品表面含氧官能团的含量
Table 3 The content of oxygen-containing functional groups on the surface of different samples
Sample Adsorption capacity/(mg·g−1) Functional group types carboxyl lactone anhydride phenolic hydroxyl quinone and carbonyl AC-950 235.3 0.00 0.00 0.00 0.00 0.11 AC-O-12 h 129.2 0.71 0.57 0.22 1.53 0.67 AC-O-300 148.7 0.00 0.56 0.23 1.58 0.70 AC-O-500 185.9 0.00 0.00 0.22 1.56 0.68 AC-O-800 229.4 0.00 0.00 0.00 0.00 0.08 note: contents of various functional groups (mmol) -
[1] GUO Y, LI Y, ZHU T, WANG J, YE M. Modeling of dioxin adsorption on activated carbon[J]. Chem Eng J,2016,283:1210−1215. doi: 10.1016/j.cej.2015.08.067 [2] 周旭建. 多孔碳材料对二噁英吸附特性的机理研究[D]. 杭州: 浙江大学, 2016.ZHOU Xu-jian. Study on the adsorption mechanism of porous carbon materials to dioxins.[D]. Hangzhou: Zhejiang University, 2016. [3] 唐娜, 罗伟铿, 石运刚, 王美欢, 郑佳. 废物焚烧及工业金属冶炼烟气中二噁英的排放水平及同系物分布[J]. 环境安全学报,2018,(4):1496−1502.TANG Na, LUO Wei-keng, SHI Yun-gang, WANG Mei-huan, ZHENG Jia. Emission levels and homologous distribution of dioxins from waste incineration and industrial metal smelting fume[J]. J Environ Safety,2018,(4):1496−1502. [4] EVERAERT K, BAEYENS J, CREEMERS C. Adsorption of dioxins and furans from flue gases in an entrained flow or fixed/moving bed reactor[J]. J Chem Technol Biotechnol,2003,78(2/3):213−219. [5] LI H W, LEE W J, TSAI P J, MOU JL, CHANG GP, YANG KT. A novel method to enhance polychlorinated dibenzo-p-dioxins and dibenzofurans removal by adding bio-solution in EAF dust treatment plant[J]. J Hazard Mater,2008,150(1):83−91. doi: 10.1016/j.jhazmat.2007.04.077 [6] LASHAKI M J, ATKINSON J D, HASHISHO Z, PHLLIPS J H, ANDERSON J E, NIOHOLS M. The role of beaded activated carbon's surface oxygen groups on irreversible adsorption of organic vapors[J]. J Hazard Mater,2016,317:284−294. doi: 10.1016/j.jhazmat.2016.05.087 [7] ZHANG X, GAO B, CREAMER A E, CAO C, LI Y. Adsorption of VOCs onto engineered carbon materials: A review[J]. J Hazard Mater,2017,338:102−123. doi: 10.1016/j.jhazmat.2017.05.013 [8] SU W, ZHOU Y, WEI L, SUN Y, ZHOU L. Effect of microstructure and surface modification on the hydrogen adsorption capacity of active carbons[J]. New Carbon Mater,2007,22(2):135−140. doi: 10.1016/S1872-5805(07)60014-6 [9] QIAO W, KORAI Y, MOCHIDA I, HORI Y, MAEDA T. Preparation of an activated carbon artifact: Oxidative modification of coconut shell-based carbon to improve the strength[J]. Carbon,2002,40(3):351−358. doi: 10.1016/S0008-6223(01)00110-5 [10] VILLACAÑAS F, PEREIRA M F R, ÓRFÃO J J M, FIGUEIREDO J L. Adsorption of simple aromatic compounds on activated carbons[J]. J Coll Inter Sci,2006,293(1):128−136. doi: 10.1016/j.jcis.2005.06.032 [11] SHEN W, LI Z, LIU Y. Surface chemical functional groups modification of porous carbon[J]. Recent Pat Chem Eng,2008,1(1):27−40. doi: 10.2174/2211334710801010027 [12] FIGUEIREDO J L, PEREIRA M F R, FREITAS M M A, ORFAO J J M. Modification of the surface chemistry of activated carbons[J]. Carbon,1999,37(9):1379−1389. doi: 10.1016/S0008-6223(98)00333-9 [13] CHIANG H-L, HUANG C P, CHIANG P C. The surface characteristics of activated carbon as affected by ozone and alkaline treatment[J]. Chemosphere,2002,47(3):257−265. doi: 10.1016/S0045-6535(01)00215-6 [14] CHIANG H L, CHIANG P C, HUANG C P. Ozonation of activated carbon and its effects on the adsorption of VOCs exemplified by methylethylketone and benzene[J]. Chemosphere,2002,47(3):267−275. doi: 10.1016/S0045-6535(01)00216-8 [15] LI L, LIU S, LIU J. Surface modification of coconut shell based activated carbon for the improvement of hydrophobic VOC removal[J]. J Hazard Mater,2011,192(2):683−690. doi: 10.1016/j.jhazmat.2011.05.069 [16] KIM K, KANG C, YOU Y, CHUNG M. Adsorption–desorption characteristics of VOCs over impregnated activated carbons[J]. Catal Today,2006,111(3):223−228. [17] JARAMILLO J, A’LVAREZ P M, GO’MEZ-SERRANO V. Preparation and ozone-surface modification of activated carbon. Thermal stability of oxygen surface groups[J]. Appl Surf Sci,2010,256(17):5232−5236. doi: 10.1016/j.apsusc.2009.12.109 [18] LILLO-RO’DENAS M A, CAZORLA-AMORO’S D, LINARES-SOLANO A. Behaviour of activated carbons with different pore size distributions and surface oxygen groups for benzene and toluene adsorption at low concentrations[J]. Carbon,2005,43(8):1758−1767. doi: 10.1016/j.carbon.2005.02.023 [19] GUO Q, JING W, HOU Y, HUANG Z, MA G, HAN X, SUN D. On the nature of oxygen groups for NH3-SCR of NO over carbon at low temperatures[J]. Chem Eng J,2015,270:41−49. doi: 10.1016/j.cej.2015.01.086