title: Dechlorination of hexachlorobenzene using ultrafine Ca-Fe composite oxides.
abstract: Ca-Fe composite oxides with different Ca/Fe atomic ratios were synthesized by co-precipitation method and characterized by X-ray diffraction (XRD), scanning electron microscopy with elemental X-ray analysis (SEM-EDX) and inductively coupled plasma optical emission spectrometer (ICP-OES). Their dechlorination activities were evaluated using hexachlorobenzene (HCB) as a model compound. The results indicate that the dechlorination activity is related to the composition of metal oxides. Different compositions lead to the formation of different phases of Ca-Fe composite oxides. When Ca/Fe atomic ratio was 3.4, the dechlorination activity reached 97%, which was the highest in the dechlorination of HCB at 300 degrees C for 0.5 h. This may be related to the formation of Ca(2)Fe(2)O(5) phase and small agglomerate size of oxide crystal of about 1 microm. The effect of reaction time on HCB dechlorination and the pathway of dechlorination were investigated using the Ca-Fe composite oxide with the highest activity. It was found that hydrodechlorination took place in the destruction of HCB, the dechlorination efficiency is almost 100% after 2 h reaction. After reaction, quantitative measurement of chloride ion and qualitative analysis of CaCO(3) indicate besides hydrodechlorination, other degradation routes may be present. The mechanism of synergic dechlorination using Ca-Fe composite oxides was discussed.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Ma
authors.forename: Minghui
authors.initials: M
authors.lastname: Zheng
authors.forename: Wenbin
authors.initials: W
authors.lastname: Liu
authors.forename: Yong
authors.initials: Y
authors.lastname: Qian
authors.forename: Bing
authors.initials: B
authors.lastname: Zhang
authors.forename: Wenxia
authors.initials: W
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D011232:Chemical Precipitation; D006581:Hexachlorobenzene; D007501:Iron; D010084:Oxidation-Reduction; D010087:Oxides; D010833:Phytic Acid
chemical_list: D010087:Oxides; D006581:Hexachlorobenzene; D010833:Phytic Acid; D007501:Iron