Low-temperature dechlorination of hexachlorobenzene on solid supports and the pathway hypothesis

被引:30
作者
Gao, Xingbao [1 ]
Wang, Wei [1 ]
Liu, Xiao [1 ]
机构
[1] Tsinghua Univ, Dept Environm Sci & Engn, Beijing 100084, Peoples R China
关键词
hexachlorobenzene; dechlorination; pathway; solid supports;
D O I
10.1016/j.chemosphere.2007.10.041
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
The dechlorination of HCB was carried out under low-temperature and oxygen deficient conditions on different solid supports such as SiO2, CaO, CaSiO3, cement and treated fly ash (tFA). All the tested supports except SiO2 showed a HCB dechlorination potential. The dechlorination efficiencies (D-1) of HCB by CaO, CaSiO3, tFA and cement reached 64.62%, 76.15%, 79.97% and 32.21% at 350 degrees C for 4 h, respectively. It was thought electrons in the vacancies originated from the unsaturated metallic ions and O2 - oil the crystal surfaces made the D, different between SiO2, CaO and CaSiO3. Comparing the D-1 by tFA and cement, the high dechlorination potential of tFA was due to the more free electrons from the crystal defects and the transition metals, and the more active points for the gas-solid phase reaction, which both had positive effects oil dechlorination reaction. The effect of Cu addition (0.2 - 5.0%) on HCB dechlorination might result from the Ullmann coupling which was not notable in enhancing the dechlorination reaction. From the study, we can draw the Conclusion that the dechlorination potential mainly depends oil the support characteristic rather than the transition metal content. Based oil this study and previous references, the dechlorination/polymerization induced by the electron transfer mode was thought to be the dominant pathway while the hydrogen transfer mode was minor. The electron was originated from the crystal defects or induced by transition metals, and the dissociation of a chloride ion happened forming a radical, and then the polymerization of radicals led to the formation of high-molecular-weight compounds which seemed to cause the material imbalance. (c) 2007 Elsevier Ltd. All rights reserved.
引用
收藏
页码:1093 / 1099
页数:7
相关论文
共 42 条
[1]  
[Anonymous], 2007, NAT IMPL PLAN STOCKH
[2]   Electron affinities and reductive dechlorination of toxic polychlorinated dibenzofurans: A density functional theory study [J].
Arulmozhiraja, S ;
Morita, M .
JOURNAL OF PHYSICAL CHEMISTRY A, 2004, 108 (16) :3499-3508
[3]   Global hexachlorobenzene emissions [J].
Bailey, RE .
CHEMOSPHERE, 2001, 43 (02) :167-182
[4]   Hexachlorobenzene in the global environment: Emissions, levels, distribution, trends and processes [J].
Barber, JL ;
Sweetman, AJ ;
van Wijk, D ;
Jones, KC .
SCIENCE OF THE TOTAL ENVIRONMENT, 2005, 349 (1-3) :1-44
[5]   Acetone-photosensitized reduction of carbon tetrachloride by 2-propanol in aqueous solution [J].
Betterton, EA ;
Hollan, N ;
Arnold, RG ;
Gogosha, S ;
McKim, K ;
Liu, ZJ .
ENVIRONMENTAL SCIENCE & TECHNOLOGY, 2000, 34 (07) :1229-1233
[6]   Microbial hexachlorobenzene dechlorination under three reducing conditions [J].
Chang, BV ;
Su, CJ ;
Yuan, SY .
CHEMOSPHERE, 1998, 36 (13) :2721-2730
[7]   Treating contaminated sediment with a two-stage base-catalyzed decomposition (BCD) process: bench-scale evaluation [J].
Chen, ASC ;
Gavaskar, AR ;
Alleman, BC ;
Massa, A ;
Timberlake, D ;
Drescher, EH .
JOURNAL OF HAZARDOUS MATERIALS, 1997, 56 (03) :287-306
[8]   Surface properties of carbons obtained from hexachlorobenzene and hexachloroethane by combustion synthesis [J].
Cudzilo, Stanislaw ;
Huczko, Andrzej ;
Pakula, Maciej ;
Biniak, Stanislaw ;
Swiatkowski, Andrzej ;
Szala, Mateusz .
CARBON, 2007, 45 (01) :103-109
[9]   ULLMANN SYNTHESIS OF BIARYLS [J].
FANTA, PE .
SYNTHESIS-STUTTGART, 1974, (01) :9-21
[10]   Theoretical study of the dechlorination reaction pathways of octachlorodibenzo-p-dioxin [J].
Fueno, H ;
Tanaka, K ;
Sugawa, S .
CHEMOSPHERE, 2002, 48 (08) :771-778