Determination of total cyanide in thiocyanate-containing wastewaters

Abstract

1677At hlgh acidities, thiocyanate reacts wlth nitrate or other oxidants to produca free cyanlde. For thiocyanate-contalnlng wastewaters, a total cyanide procedure is reported based on use of EDTA at pH 4.0, acetate buffered, to dlsrupt the complexes of cadmlirm, chromium, copper, Iron, nlckel, and rlnc. NRrlte Interference is obvlated by adding sulfamic acid to the sample. Sulfldos are removed from the sample by lnltlal treatment with cadmium carbonate and, If necessary, from dlstliiates wlth aadmlum nitrate.

Hydrogen Cyanide Exhaust Emissions from In-Use Motor Vehicles

“…Six successive measurements of 0.04 N sodium hydroxide solution (i.e., in the absence of CN - ) produced a mean reading of −0.9 ± 1.6 μg-L -1 CN - (1 SD), affording a LOD of 5 μg-L -1 CN - (3 SD). This value compares favorably to reported LOD values for colorimetric CN - detection in wastewater, 10−20 μg-L -1 ( , ), and is 1−2 orders of magnitude lower than detection limits reported using anion chromatography ( , ). Since 4.0 × 10 -5 absorbance units correspond to 2 × 10 -3 μg-L -1 CN - , instrumental sensitivity is well below the uncertainty introduced by the multistep chemistry of the method.…”

Total cyanide determination by a segmented flow injection–on-line UV digestion–amperometric method

“…At high acidity and in the presence of strong oxidants (e.g., NO 3 2 ), the sulfur in the thiocyanate is oxidized with concomitant liberation of hydrogen cyanide. 8 Under the experimental conditions that exist during the FI-UV determination of cyanide, no production of HCN from SCN 2 in the presence of nitrate occurs. For example, cyanide recovery from the sample containing 0.200 mg L 21 CN 2 , 500 mg L 21 NO 3 2 and 100 mg L 21 SCN 2 was 102%.…”

“…1,2 Serious problems associated with the approved method have been recognized. [3][4][5][6][7][8][9] Most of them stem from the fact that the method utilizes harsh analytical conditions ( > 100 °C and pH < 0). In addition, the chromogenic reaction in the spectrophotometric quantification procedure involves the addition of the strong oxidant (chloramine-T).…”

Destruction of Iron-Complexed Cyanide by Alkaline Hydrolysis

“…The cyanide analytical procedure was compared with an EDTA-ligand displacement technique for determination of total cyanide (Csikai and Barnard, 1983). The cyanide analytical procedure was compared with an EDTA-ligand displacement technique for determination of total cyanide (Csikai and Barnard, 1983).…”