Decomposition of hexachlorobenzene over Al_2O_3 supported metal oxidecatalysts

Decomposition of hexachlorobenzene(HCB)was investigated over several metal oxides(i.e.,MgO,CaO,BaO,La2O3,CeO2,MnO2, Fe2O3,and Co3O4)supported on Al2O3,which was achieved in closed system at a temperature of 300°C.Catalysts were prepared by incipient wetness impregnation with different metal oxides loading and impregnating solvents.The decomposition effciency of different catalysts for this reaction depends on the nature of the metal oxide used,and Al2O3 supported La2O3 was found to be the most active one.Pe...

Monitoring bioaccumulation and toxic effects of hexachlorobenzene using the polyurethane foam unit method in the microbial communities of the Fuhe River,Wuhan

Hexachlorobenzene （HCB） is a chlorinated aromatic hydrocarbon that was widely used for seed dressing in prevention of fungal growth on crops, and also as a component of fireworks, ammunition, and synthetic rubbers. Because of its resistance to degradation and mobility, HCB is widely distributed throughout the environment and is accumulated through food chains in different ecosystems. In this study, a preliminary investigation was carried out on the bioaccumulation and the toxic effects of HCB in the microbial （protozoan in particular） communities in the Fuhe River, Wuhan, a water body receiving industrial wastewaters containing HCB and other pollutants, using the standardized polyurethane foam units （PFU） method. Field samples were taken from eight stations established along the Fuhe River in January and August 2006. The concentration ratios of HCB in microbial communities and in water were 9.66-18.64, and the microbial communities accumulated 13.29-56.88 μg/L of HCB in January and 0.82-10.25 μg/L HCB in August. Correlation analysis showed a negative correlation between the HCB contents in the microbial assemblage, and the number of species and the diversity index of the protozoan communities. This study demonstrated the applicability of the PFU method in monitoring the effects of HCB on the level of microbial communities.

Hexachlorobenzene Episode in Turkey

During the period 1955-1959, approximately 4000 people in southeast Anatolia developed porphyria due to the ingestion of hexachlorobenzene (HCB), a fungicide added to wheat seedlings. These HCB exposures subsequently led to the development of bullae on sun-exposed areas, hyperpigmentation, hypertrichosis, and porphyrinuria. The condition was called kara yara or 'black sore.' Many of the breast-fed children under the age of 2 years whose mothers had ingested HCB-treated grain died from a disease known as pembe yara or 'pink sore.' In this follow-up study of 252 patients, 20-30 years postexposure, there were 162 males and 90 females, with an average current age of 35.7 years, an average of onset of 7.6 years, and a duration of 2.2 years. Many patients had dermatologic, neurologic, and orthopedic symptoms and signs. The observed clinical findings include scarring of the face and hands (83.7％), hyperpigmentation (65％), hypertrichosis (44.8％), pinched facies (40.1％), painless arthritis (70.2％), small hands (66.6％), sensory shading (60.6％), myotonia (37.9％), cogwheeling (41.9％), enlarged thyroid (34.9％), and enlarged liver (4.8％). Urine and stool porphyrin levels were determined in all patients, and 17 have at least one of the porphyrins elevated. A total of 56 specimens of human milk obtained from mothers with porphyria were analyzed for HCB. The average value was 0.51 ppm in HCB-exposed patients compared to 0.07 ppm in unexposed controls. Offspring of mothers with three decades of HCB-induced porphyria appear normal. 1989 Academic Press, Inc.

Synthesis of a magnetic micro/nano Fe_xO_y-CeO_2 composite and its application for degradation of hexachlorobenzene

A micrometer-sized nanostructured,magnetic,ball-like FexOy-CeO2 composite was synthesized through an ethylene-glycol mediated process.The synthesized samples were characterized by scanning electron microscopy combined with energydisperse X-ray analysis,transmission electron microscopy and X-ray powder diffraction.In the synthesis system,polyethylene glycol (PEG) and urea were found to play significant roles in the formation of the micrometer-sized spherical architecture of the precursor.The details of morphology and particle size could be changed with the initial concentration of Fe(NO3)3-9H2O and Ce(NO3)3-6H2O as the reactants.The magnetic FexOy-CeO2 composite with a similar morphology was readily obtained by calcination from the precursor.The characterization of transmission electron microscopy showed the calcined ball-like architecture was a highly porous structure consisting of many nanoparticles.Because of the micrometer-sized nanostructure and the multi-components as well as the magnetism,the as-obtained FexOy-CeO2 composite showed better activity and potentially easy recovery for the harmless degradation of hexachlorobenzene (HCB).

Rapid degradation of hexachlorobenzene by micron Ag/Fe bimetal particles

The feasibility of the rapid degradation of hexachlorobenzene （HCB） by micron-size silver （Ag）/iron （Fe） particles was investigated.Ag/Fe particles with different ratios （0,0.05%,0.09%,0.20%,and 0.45%） were prepared by electroless silver plating on 300 mesh Fe powder,and were used to degrade HCB at different pH values and temperatures.The dechlorination ability of Fe greatly increased with small Ag addition,whereas too much added Ag would cover the Fe surface and reduce the effective reaction surface,thereby decreasing the extent of dechlorination.The optimal Ag/Fe ratio was 0.09%.Tafel polarization curves showed that HCB was rapidly degraded at neutral or acidic pH,whereas low pH levels severely intensified H2 production,which consumed the reducing electrons needed for the HCB degradation.HCB degradation was more sensitive to temperature than pH.The rate constant of HCB dechlorination was 0.452 min-1 at 85℃,50 times higher than that at 31℃.HCB was degraded in a successive dechlorination pathway,yielding the main products 1,2,4,5-tetrachlorobenzene and 1,2,4-trichlorobenzene within 2 hr.

溶剂红135染料中六氯苯含量的测定

Determination of hexachlorobenzene (HCB) in the solvent red 135 by solvent extraction GC-MS with selected ion monitoring mode.The result showed that the detection limit is 0.05 mg/kg.The relative standard deviation is 3.3%.This method is suitable for the analysis of the HCB in the solvent red 135.