Dechlorination Kinetics Research Articles

Residual sulfite after dechlorination of water

The kinetics of dechlorination show that chlorinated organic amines are not completely dechlorinated during typical contact times. Analytical techniques for measuring residual sulfite must maintain pH neutrality in order to represent the actual extent of dechlorination and must allow for rapid and convenient operation near the sampling site in order to minimize errors due to air oxidation during the procedure. A portable, analog circuitry-based instrument using constant current coulometry with amperometric end point detection was developed and evaluated. laboratory and field operation of the instrument showed an analytical range of 0.015-to-25.0 mg sulfite/l. Relative standard deviation was typically 1–2%.

REACTION ENGINEERING OF CHEMICAL PCBs DECHLORINATION: AN EXPERIMENTAL APPROACH

Abstract This paper deals with the application of some chemical reaction engineering principles in order to develop a supported liquid phase reagent (SLPR) able to dechlorinate PCBs contained in highly viscous media. The reagent consists of polyethyleneglycols containing a dissolved base and a radical initiator. Recently this mixture was proposed as CDP(R) (Chemical Dechlorination Process) for PCBs detoxification. In this paper are reported several experimental tests designed to optimise configuration of reagents on inert support to dechlorinate the PCBs contained in the transformer oil. The main results are: the evaluation of optimum reagent load on support, the set up of dechlorination kinetics of commercial PCBs as AROCLOR 1260 in transformer oil tested in the 50-2500 ppm range. SLPR was tested in a “fixed-bed” as well as in “slurry” reactor configurations. The above results were used to design two mobile plants for on-site treatments.

Pressure and pH dependence of the kinetics of decarboxylative dechlorination of N-chloro-l-alanine

Pressure and pH dependence of the kinetics of decarboxylative dechlorination of N-chloro-l-alanine

Kinetics of the sequential dechlorination of 2,4,6-trichlorophenol by an anaerobic microbial population

A mathematical model was developed to describe the sequential dechlorination of 2,4,6-trichlorophenol to 2,4-dichlorophenol, 4-chlorophenol and phenol. Each compound was assumed to be degraded according a Michaelis-Menten expression. Experimental data were used to obtain the model kinetic constants and to test its validity. Good agreement between the model predictions and the experimental data was obtained.

The effect of chlorine position of chlorinated phenols on their dechlorination kinetics by Fenton's reagent

Chlorine position of chlorophenol isomers has a significant effect on the dechlorination kinetics of monochlorophenols, dichlorophenols, and trichlorophenols during Fenton oxidation. The effects have been evaluated by the rate constants of the dechlorination kinetic model developed in this study. It is found that the dechlorination rate of 3-CP is faster than that of 4-CP, which is faster than that of 2-CP. Since OH and Cl groups on the aromatic ring are ortho and para directors, the directory effect of OH and Cl groups enhances the dechlorination kinetics of 2-CP due to acceleration of the hydroxylation of 2-CP. Therefore, the dechlorination kinetics increases accordingly. For trichlorophenols (TCP), steric hindrance plays an important role during their dechlorination process. Specifically, the closer the chlorine atoms locate with each other on the aromatic ring, the more difficult the dechlorination processes will be. The dechlorination kinetics of dichlorophenols seems to be affected by both directory effect of OH and Cl groups and the effect of steric hindrance of chlorine atoms. The directory effect of OH and Cl groups on trichlorophenols decreases since the chlorine atom occupied the positions which are the most favorable for hydroxyl radical attack.

Toward Elucidating Mechanism And Kinetics Of Ozone Decolorization And Dechlorination Of Pulp Mill Effluents

Abstract This study elucidated the mechanism and kinetics of ozone decolorization and dechlorination of composite wastewaters obtained from various pulp mill effluents by means of ultrafiltration and freeze drying. These raw samples had similar initial true color but varied color intensity (C.I.) and biodegradability. Both raw and ozone-treated samples were separated into four components to assess the effects of ozonation on individual components. Analytical HPSEC was employed to determine the changes induced by ozonation in molecular weight distribution of lignins and their derivatives.

Microsomal dechlorination of chloroethanes: structure-reactivity relationships.

1. The dechlorination rates of six haloethanes were investigated in vitro, using liver microsomes derived from rats treated with Aroclor 1254. 2. The compounds studied were 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, 1,1,1-trifluoro-2-chloroethane and hexachloroethane. 3. Dechlorination kinetics (Km and Vmax) were measured at various substrate concentrations. 4. Electron densities in the molecules for which dechlorination data are available were calculated by the MINDO/3 method. 5. A previously reported correlation between electronic parameters and dechlorination rate was not confirmed, but rather a separate relationship between these parameters for each of three structural classes (RCH2Cl, RCHCl2 and RCCl3) was observed. 6. On the basis of these observations, possible reaction mechanisms and their toxicological implications are discussed.

Cinétique de la Déchloration du Barbane en Milieu Alcalin

4-Chloro-2-butynyl N-(3-chlorophenyl) carbamate (Barban) is an herbicide whose alkaline hydrolysis leads to the release of the chlorine atom of the ester group. The dechlorination kinetics were investigated in alkaline media at 25°C and followed spectrophotometrically or colorimetrically. The rate law of this reaction is complex and shows that the substrate as well as its anion are the reactive species. The pKa value determined spectrophotometrically was 13.50.

The Kinetics of the Radiation-induced Chain Dechlorination of Hexachloroethane in Alcohols

Abstract The kinetics of the radiation-induced dechlorination of hexachloroethane was investigated in deoxygenated alcohol solutions. The major products were hydrogen chloride, pentachloroethane, 1,1,2,2-tetrachloroethane, tetrachloroethylene, and aldehydes or acetone. No 1,1,1,2-tetrachloroethane was observed. The radiationchemical yields of these products and the disappearance of hexachloroethane were quite high; these facts indicate that a chain reaction is involved in these processes. After the hexachloroethane had effectively dechlorinated down to tetrachloro compounds, there were no marked changes in the lower chlorinated compound upon continuous irradiation. Tetrachloroethane was formed via pentachloroethane, but tetrachloroethylene was produced by means of C2Cl5→C2Cl4+Cl reaction and the yield was paticularly high in methanol compared with the other alcohols. The chain length of the dechlorination from hexachloroethane to pentachloroethane and from pentachloroethane to tetrachloroethane increased in the order of 2-propanol>ethanol>methanol. The G(−C2Cl6) and G(products) were proportional to (dose rate)−1⁄2, and the ratio of G(C2HCl5) to G(C2Cl4) was a constant in each alcohol solution, regardless of the dose rate. The α-hydroxy alkyl radical is the chain carrier for the dechlorination reaction of hexachloroethane in alcohol solutions. The relative rates of the dechlorination were found to be 1, 3, and 14 for \dotCH2OH, CH3\dotCHOH, and (CH3)2\dotCOH, respectively. The order in the rate is in agreement with that of the redox potential of these radicals. The effect of the irradiation temperature on the products yields was also examined.