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Identification and reactions of cyanide and thiocyanate in coal gasification wastewaters.

Carnegie-Mellon University. Environmental Studies Institute

Identification and reactions of cyanide and thiocyanate in coal gasification wastewaters.

by Carnegie-Mellon University. Environmental Studies Institute

  • 102 Want to read
  • 26 Currently reading

Published by Dept. of Energy, for sale by the National Technical Information Service] in [Washington], [Springfield, Va .
Written in English

    Subjects:
  • Thiocyanates.,
  • Chemical reactions.,
  • Cyanides.

  • Edition Notes

    SeriesFE ; 2496-23, FE -- 2496-23.
    ContributionsLuthy, Richard G., United States. Dept. of Energy.
    The Physical Object
    Paginationiv, 41 p. :
    Number of Pages41
    ID Numbers
    Open LibraryOL17650081M

    The thiocyanate ion can be oxidized at acid pH by hydrogen peroxide to generate sulfate and cyanide. The reaction is catalyzed by hemoglobin acting as a peroxidase. Thiocyanate is analogous to the cyanate ion, [OCN]-, wherein oxygen is replaced by sulfur. [SCN]- is one of the pseudohalogens, due to the similarity of its reactions to that of.   Cyanide is usually found in compounds (substances formed by joining two or more chemicals). Cyanide can interact with metals and other organic compounds (compounds that include carbon). Sodium cyanide and potassium cyanide are examples of simple cyanide compounds. Cyanide can be produced by certain bacteria, fungi, and algae, and is found in a number of foods and plants.

    The cyanide toxic effect is due to its reaction with the trivalent iron in the cytochrome oxidase (cyt aa3) to inhibit electron transport and thus preventing the cells from consuming oxygen, leading to rapid impairment of the vital functions. Several cyanide poisonings in fire cases, which led to . Abstract. Thiocyanate ion is oxidized at acid pH by hydrogen peroxide to sulfate and cyanide. The reaction is catalyzed in the erythrocyte by hemoglobin acting as a peroxidase (donor: H 2 O 2 oxidoreductase, EC ). Kinetic studies show thiocyanate ion .

    This reaction can similarly be represented as: M** * S W S" = MS + S fM S" The required dosage of polysulf ide-sulfur to convert cyanide to thiocyanate may be greater than stoichiometric requirements which is a CN:poly-S° ratio > by weight PREVIOUS WORK The reaction between cyanide and polysulf ide-sulf ur to form thiocyanate was. Although the typical detoxifying agents used in cyanide poisoning induce thi- ocyanate formation, biochemical cyclic reactions with cyanide are possible, resulting in detectable levels of cyanide from ex- posure to thiocyanate. 18 Thiocyanate may be analyzed in samples properly preserved for determination of cyanide; however, thi- ocyanate also.


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Identification and reactions of cyanide and thiocyanate in coal gasification wastewaters by Carnegie-Mellon University. Environmental Studies Institute Download PDF EPUB FB2

Cyanide and thiocyanate in coal gasification wastewaters Richard G. Luthy, Samuel G. Bruce, Jr., Richard W. Walters, David V. Nakles Carnegie-Mellon University, Pittsburgh, Pa. The U. Department of Energy (DOE) is evaluating the technical feasibility of a number of coal gasification processes for mak ing synthetic natural gas from coal.

The. Get this from a library. Identification and reactions of cyanide and thiocyanate in coal gasification wastewaters. [Richard G Luthy; Carnegie-Mellon University. Environmental Studies Institute.; United States. Department of Energy.].

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Thiocyanate causes interference when cyanide is being determined in water and waste water. This is because it reacts as cyanide and its value is included in the total sum determined.

This procedure is not disrupted by fold amounts of cyanide based on thiocyanate. Reactions between cyanide and compounds, which contain S–S bonds, in aqueous media result in formation of thiocyanate.

In this work, we studied the kinetics of reactions of thiosulfate with free cyanide and its complexes under environmental conditions.

Rates of reactions between cyanide species and thiosulfate decrease in the following order: CN− > HCN > [Fe(CN)6]3− > Cited by: 1. Recovery of copper cyanide from waste cyanide solution by LIX Minerals Engineering22 (2), DOI: / Caliphs M.

Zvinowanda, Jonathan O. Okonkwo, Rogers C. Gurira. Improved derivatisation methods for the determination of free cyanide and cyanate in mine effluent.

1. Introduction. Thiocyanate (SCN −) is a sulfur compound that is produced naturally as either a non-functional detoxification product of cyanide ingestion or a defence compound against microbial enzyme rhodanese, which is widely distributed among the thiobacilli catalyzes the reaction of cyanide with thiosulfate to produce sulfite and thiocyanate (Ramirez et al.,Gupta.

The waste containing high concentrations of cyanide is produced also during the underground coal gasification. The degree of contamination of soil with cyanides depends on their amount and activity. Most of cyanides are deposited in the environment as complexes of Fe(CN) 6 3− and Fe(CN) 6 4−.

Their toxicity is low, but due to the light. Free cyanide and thiosulfate (Reaction 8) are preferentially oxidised prior to the oxidation of copper cyanide and thiocyanate which occur in parallel.

The control of pH is important since at low pH, HCN forms which is not readily oxidised and the rate of cyanate oxidation increases.

2 4 4 H 2 5 S 2 3 HO →+ 5HSO (8) Hydrogen. The principal iron mineral of concern, pyrrhotite, is reported to react first via its labile sulphur atom to yield thiocyanate and ferrous sulphide: The ferrous sulphide formed oxidizes rapidly to ferrous sulphate and the ferrous iron then combines with cyanide 2+ 2-FeS + 20 2 + Fe + S04 Fe 2 + + 6 ~ + Fe(CN): These reactions will be competing.

The chapter reviews coal gasification wastewater sampling and analytical strategies, and discusses representative characterization data to highlight the effect of water chemistry on effluent composition and handling.

Water management and treatment play critical roles in the design of coal gasification facilities. This report discusses: (i) procedures for preservation and identification of cyanide and thiocyanate in coal gasification wastewaters, (ii) possible pathways for aqueous phase formation of. We have explored the simultaneous degradation of cyanides and thiocyanate present in wastewaters from a cokemaking factory using photoassisted methods under varied illumination conditions (from simulated solar light to UV light).

Overall, the photochemical degradation of cyanides was more efficient than that of thiocyanates, regardless of the illumination conditions, the effect being more. Provided is a method for regenerating cyanide from thiocyanate. The method comprises contacting the thiocyanate with an oxidizing gas containing ozone, generally a mixture of oxygen and ozone.

The pH of the contacting medium is generally less than to assure that HCN is the predominant species relative to CN. The method has important applications to processes involving cyanidation.

(reaction 8) • As for other methods, ferrocyanide is not destroyed, but only partially oxidized to ferricyanide (reaction 5). Requires an additional stage and reagent to remove iron cyanide (if precipitate (such as in reaction 9) • May leave residual chlorine in solution, thereby requiring a polishing pond or aeration stage for removal.

Book. Aug ; Derek W. Tomlinson Management of Cyanide in Industrial Process Wastewaters. Article. Dec ; coal coking, coal gasification and wood processing result in the production.

The effluent of distilled and extracted Lurgi coal gasification wastewater has been found to have low biodegradability and high toxicity, which inhibits further biodegradation. However, ozonation enhances the biodegradability and reduces the toxicity of this effluent, enabling further biological treatment and increased removal of organic materials.

Reaction mechanisms are given throughout. The methods are compared in regard to their effectiveness in treating various cyanide species: free cyanide, thiocyanate, weak-acid dissociables and strong-acid dissociables. KEY WORDS cyanide, metal-cyanide complex, thiocyanate, oxidation, separation.

cost effectiveness are needed to treat cyanide and thiocyanate in wastewater. We herein propose a novel oxidant, ferrate [Iron(VI)] for destruction of cyanide and thiocyanate in gold mill wastewaters. FERRATE (IRON(VI)) Iron is commonly exists in the +2 and +3 oxidation states; however, in a strong oxidizing environment.

This report discusses: (i) procedures for preservation and identification of cyanide and thiocyanate in coal gasification wastewaters, (ii) possible pathways for aqueous phase formation of thiocyanate in these waste-waters, and (iii) reaction of cyanide and polysulfide-sulfur to produce thiocyanate.

Thiocyanate is one of the major constituents of waste water from factories for the gasification of coal, where various by-products are formed during the production of gas for fuel, coke, and substances for chemical industries.

Cyanide is usually converted to thiocyanate by the addition reaction of sulfur.Detection of cyanide and by-products in seawater: A desk-based assessment Page viii Glossary Adduct: the product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components.

Analyte: a substance that it is of interest for identification or measurement through an.Cyanide will preferentially leach sulfide minerals and will react with sulfur to produce thiocyanate. These reactions will also enhance the oxidation of reduced sulfur species, increasing the requirement for lime addition to control the pH at a sufficient level to avoid the volatilization of hydrogen cyanide (HCN).