• Journal of Environmental Science International
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• v.5 no.5
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• pp.569-577
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• 1996

pure compound chloromethanes; methyl chloride, methylene chloride, chloroform and The carbon tetrachloride were used as a model of chlorocarbon system with Cl/H ratio to investigate thermal stability and hydrodechlorination process of carbon tetrachloride under excess hydrogen atmosphere. The parent thermal stability on basis of temperature required for 99% destruction at 1 second no was evaluated as $875^{\circ}C$ for $CH_3Cl$, $780^{\circ}C$ for $CH_2Cl_2$, $675^{\circ}C$ for $CHCl_3$ and $635^{\circ}C$ for $CCl_4$. Chloroform was thermally less stable than $CCl_4$ at fairly low temperatures $(<570^{\circ}C).$ The lion of $CCl_4$ became more sensitive to increasing temperature, and $CCl_4$ was degraded CHCl3 at above $570^{\circ}C.$ The number and quantity of chlorinated products decreases with increasing temperature for the Product distribution of $CCl_4$ decomposition reaction system. Formation of non-chlorinated hydrocarbons such as $CH_4$, $C_2H_4$ and C_2H_6$ increased as the temperature rise and particularly small amount of methyl chloride was observed above $850^{\circ}C$ in $CC1_4$/$H_2$ reaction system. The less chlorinated products are more stable, with methyl chloride the most stable chlorocarbon in this reaction system.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.430-437
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• 1997

Uranyl-peroxide compound was prepared by the reaction of excess hydrogen peroxide solution and trace uranium in filtrate from nuclear fuel conversion plant. The $CO_3{^{2-}}$ in filtrate was removed first by heating more than $98^{\circ}C$, because uranyl-peroxide compound could not be precipitated by $CO_3{^{2-}}$ remaining in filtrate. The optimum condition for uranyl-peroxide compound was ageing for 1 hr after controling the pH with $NH_3$ gas and adding the excess $H_2O_2$ of 10ml/lit.-filtrate. Uranium concentration in the filtrate was appeared to 3 ppm after the precipitation of uranyl-peroxide compound, and the chemical composition of this compound was analyzed to $UO_4{\cdot}2NH_4F$ with FT-IR, X-ray diffractometry, TG and chemical analysis. Also, this fine particle, about $1{\sim}2{\mu}m$, could be grown up to $4{\mu}m$ at pH 9.5 and $60^{\circ}C$. The separation efficiency of precipitate from mother liquor was increased with increase of pH and reaction temperature. Otherwise, the crystal form of this particle showed octahedral by SEM and XRD, and $U_3O_8$ powder was obtained by thermal decomposition at $650^{\circ}C$ in air atmosphere.