Hydrothermal Oxidation of Organic Compounds by Nitrate and Nitrite

Dell`Orco, P.C.; Foy, Bernard R.; Wilmanns, E.; Le, Linh-Thy; Ely, J.; Patterson, Kristine Y.; Buelow, S.J.

doi:10.1021/bk-1995-0608.ch012

Cited by 21 publications

(14 citation statements)

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“…The high level of HCl produced in the reaction demands either that the reactor be capable of handling strongly acidic solutions or that the solution is neutralized. We have also demonstrated that nitrate and nitrite salts serve as effective oxidizers for organics and ammonia at 400-550°C (13,14). Also, most chlorinated organics of concern are immiscible with water at room temperature.…”

Section: Introductionmentioning

confidence: 76%

Hydrothermal Processing of Chlorinated Hydrocarbons in a Titanium Reactor

Foy

Waldthausen

Sedillo

et al. 1996

Environ. Sci. Technol.

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Experiments are reported on the oxidative hydrothermal destruction of chlorinated organics in a corrosion-resistant titanium reactor. Oxidation reaction conditions were 250-500°C near 650 bar and reaction times of 30-100 s in a continuous-flow reactor. Trichloroacetic acid, trichloroethylene, and 1,1,1trichloroethane behaved similarly. The organic concentration was ∼1.5 wt %; hydrogen peroxide was the oxidizer; sodium bicarbonate was added to achieve neutral pH. Hydrolysis occurs at low temperature, producing chloride ion and secondary organics. Carbon dioxide is the sole carbon product at 500°C. Sodium nitrate and sodium nitrite were also found to be effective oxidizers. Corrosion of the titanium was found to be slight (<0.038 mm/yr). The reaction mixture is likely not a single phase at these conditions. The destruction efficiency for trichloroethylene was estimated as 99.96% at 450°C and 60 s, with <0.02% conversion to volatile chlorinated organic byproducts.

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Section: Introductionmentioning

confidence: 76%

Hydrothermal Processing of Chlorinated Hydrocarbons in a Titanium Reactor

Foy

Waldthausen

Sedillo

et al. 1996

Environ. Sci. Technol.

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“…Previous experiments at Los Alamos have shown that hydrothermal processing could dissolve chromium, reformulate solids, oxidize metals, and destroy organic complexants [23][24][25][26] in HLW simulants. Unlike traditional sludge treatments that require the use of organic reagents, strong acids, or strong bases, hydrothermal processing uses oxidizers present in the wastes, such as nitrates or air, and does not require additional reagents [24,26].…”

Section: Methods and Resultsmentioning

confidence: 99%

“…Unlike traditional sludge treatments that require the use of organic reagents, strong acids, or strong bases, hydrothermal processing uses oxidizers present in the wastes, such as nitrates or air, and does not require additional reagents [24,26]. A schematic of a hydrothermal unit for the treatment of HLW is shown in Figure 1.…”

Section: Methods and Resultsmentioning

confidence: 99%

Enhanced Sludge Processing of HLW: Hydrothermal Oxidation of Chromium, Technetium, and Complexants by Nitrate

Buelow¹,

Robinson²

1999

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Executive SummaryThe Office of Economic Management has identified treatment of High Level Waste (HLW) as the second most costly environmental problem facing the DOE. In order to minimize costs of disposal, the volume of High Level Waste (HLW) requiring vitrification and long term storage must be reduced. Methods for efficient separation of chromium from waste sludges, such as the Hanford Tank Wastes (HTW), are key to achieving this goal since the allowed levels of chromium in the high level glass control waste loading. At concentrations above 0.5 to 1.0 wt.% chromium prevents proper vitrification of the waste. Chromium in sludges most likely exists as the extremely insoluble oxides and minerals, with chromium in the +3 oxidation state. In order to solubilize and separate it from other sludge components, Cr(III) must be oxidized to the more soluble Cr(VI) state. Efficient separation of chromium from HLW could produce significant savings.This project sought to lay the foundation for the application of hydrothermal processing for enhanced chromium separation from HLW sludges. Experiments were conducted which examined four areas:a. Oxidation of insoluble Cr(III) solids to soluble Cr(VI) using oxygen, b. Oxidation of insoluble Cr(III) solids to soluble Cr(VI) using nitrates, c. Transport properties and speciation of reducing and oxidizing agents under hydrothermal conditions, d. Reactions of plutonium and americium under oxidizing hydrothermal conditions. From the results of our experiments in these areas, we have developed a fundamental understanding of chromium speciation, oxidation/reduction and dissolution kinetics, reaction mechanisms, and transport properties under hydrothermal conditions in both simple and complex salt solutions.Experimental results show that at moderate temperatures (125-200°C), insoluble Cr(III) hydroxide can rapidly be oxidized to soluble Cr(VI). The rate of reaction increases with increasing oxygen and hydroxide concentration and increasing temperature. Experiments also show that sludge components such as aluminate can slow the oxidation/dissolution rate, and that at higher temperatures, organic components in the waste can consume the oxygen before it reacts with the chromium. Reactions of chromium with nitrate only become important at temperatures above 350°C. At lower temperatures the rates of dissolution are not controlled by transport properties. At higher temperatures, particularly near phase transition points, reagent transport could begin to slow and effect dissolution rates. A global rate expression was developed for the reactions involving oxygen and nitrates. The expression agrees well with the experimental results.Future experiments should examine the reactions of HLW sludges with oxygen at temperatures between 100°C and 200°C at hydroxide concentrations between 1M and 6M. This work should be performed at the Hanford site. Work at Los Alamos will continue, supported by the Nuclear Weapons Program. It will focus on high temperature hydrothermal processes including the oxidation o...

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“…At Los Alamos National Laboratory, for instance, ethylenediamine tetra acetic acid (EDTA) decomposition using nitrite and nitrate in supercritical water was studied. 3) Moreover, at the Commissariat à l'énergie atomique (CEA), a mixture of dodecane and tributyl phosphate (TBP) was decomposed in supercritical water. 4) We studied two types of radioactive wastes treatment systems using supercritical water.…”

Section: Introductionmentioning

confidence: 99%

Liquid Scintillation Counter Cocktail Decomposition in Supercritical Water

Akai

Oomura

Yamada

et al. 2007

Journal of Nuclear Science and Technology

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Using supercritical water oxidation, a liquid scintillation counter cocktail used for the analysis of radionuclides was decomposed quickly and completely to water and carbon dioxide. The decomposition yield of the liquid scintillation counter cocktail increased with the reaction time, temperature, and pressure. More than 99.96% of the liquid scintillation counter cocktail decomposed with hydrogen peroxide at 773 K and 30 MPa for 3.8 min of reaction time. The liquid scintillation counter cocktail decomposed through two main reaction pathways: One had a rate-controlling intermediate whose decomposition rate was very slow and the other did not have stable intermediates. The decomposition of the rate-controlling intermediate was a significant factor in the complete decomposition of the cocktail although it did not dominate the entire decomposition process. A simple kinetic model that estimates the decomposition yield of the liquid scintillation counter cocktail was developed.

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Hydrothermal Oxidation of Organic Compounds by Nitrate and Nitrite

Cited by 21 publications

References 0 publications

Hydrothermal Processing of Chlorinated Hydrocarbons in a Titanium Reactor

Hydrothermal Processing of Chlorinated Hydrocarbons in a Titanium Reactor

Enhanced Sludge Processing of HLW: Hydrothermal Oxidation of Chromium, Technetium, and Complexants by Nitrate

Liquid Scintillation Counter Cocktail Decomposition in Supercritical Water

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