Identification and reactions of cyanide and thiocyanate in coal gasification wastewaters. Sixth quarterly report

• Main Authors: Luthy, R.G., Bruce, S.G. Jr., Walters, R.W., Nakles, D.V.
• Language: unknown
• Published: 2020
• Subjects: 01 COAL; LIGNITE; AND PEAT; COAL GASIFICATION PLANTS; WASTE WATER; CYANIDES; CHEMICAL ANALYSIS; THIOCYANATES; ABSORPTION SPECTROSCOPY; CHEMICAL REACTIONS; OXIDATION; PRESERVATION; SULFATES; SULFIDES; CARBONIC ACID DERIVATIVES; CHALCOGENIDES; HYDROGEN COMPOUNDS; INDUSTRIAL PLANTS; LIQUID WASTES; ORGANIC COMPOUNDS; ORGANIC SULFUR COMPOUNDS; OXYGEN COMPOUNDS; SPECTROSCOPY; SULFUR COMPOUNDS; WASTES; WATER; Carbonic acid
• Online Access: http://www.osti.gov/servlets/purl/6532290; https://www.osti.gov/biblio/6532290; https://doi.org/10.2172/6532290

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. Cyanide preservation procedures require the removal of sulfide and high levels of carbonate. An analytical procedure for thiocyanate determination based on a copper-pyridine colorimetric method with pre-extraction has been tested successfully on most samples. Kinetic studies on the reaction of cyanide with polysulfide-sulfur showed that the reaction was of order 1.54 +- 0.25 with a rate constant of about 0.24 (M/l) /sup -0/ /sup 54//min. Results of this work may help predict interrelationships among cyanide, sulfur and thiocyanate during oxidation of coal gasification wastewaters. Control of cyanide-polysulfide reaction requires selective control of sulfide oxidation kinetics.