Cyanides total cyanide

J9etection of Location — Cyanide without Iron Cyanides (Short-term Stable Cyanides) Total Cyanide Total Cyanide... 

Results from Cyanide without iron cyanide Total cyanide ... 

Four procedures are available for the determination of cyanide in environmental media. These are free cyanide, total cyanide, weak acid dissociable (WAD) cyanide and amenable to chlorination (ATC) cyanide. Free cyanide is that portion of the cyanide which exists as hydrogen cyanide or as the CN- ion. Total cyanide is the cyanide released from a sample by digestion with strong mineral acid at elevated temperature. The cyanide released is distilled and... 

In the regulatory analysis of water samples, cyanide content is usually expressed in various forms as free cyanide, total cyanide, weak-acid dissociable cyanide, available cyanide, and cyanide amenable to chlorination. In wastewater, cyanide usually exists as CN and HCN, or in the form of a complex ion. Simple cyanides can be subdivided into soluble and insoluble complexes. Cyanide forms complexes with a number of metals, including cobalt, nickel, gold, iron, copper, silver, cadmium, and zinc, which are frequently found, along with cyanide, in industrial wastewater. The cyanide complexes usually have high-thermod5mamic stability constants as indicated by log /3 values in Table 9.1. 

Cyanide solutions are used almost exclusively. One typical solution contains copper cyanide 26 g/1, zinc cyanide 11 g/1, sodium cyanide (total) 45 g/1 and sodium cyanide ( free ) 7 g/l This bath is operated at pH 10.3-11.0, 110 A/m and 27-35 C, with 75 Cu-25 Zn alloy anodes. Many other solutions are used including a special rubber-bonding bath and a high-speed bath which is capable of being used at up to 16 A/dm . ... 

Total cyanide concentrations in ground water samples ranged from over 300 parts per million (ppm) at the plant site to about 1 5 ppm at a spring located along the banks of the Little Spokane River Wells used for drinking water, irrigation, and livestock purposes contained total cyanide concentrations as high as 23 ppm ... 

There is a discrepancy between the cyanide criteria for both aquatic and drinking water standards and the current analytical technology. The criteria are stated for free cyanide (which Includes hydrocyanic acid and the cyanide ion), but the EPA approved analytical methodology for total cyanide measures the free and combined forms (11). This test probably overestimates the potential toxicity. An alternative method (cyanides amenable to chlorination) measures those cyanide complexes which are readily dissociated, but does not measure the iron cyanide complexes which dissociate in sunlight. This method probably tends to underestimate the potential toxicity. Other methods have been proposed, but similar problems exist (12). The Department of Ecology used the EPA-approved APHA procedure which includes a distillation step for the quantification of total cyanide (13,14). A modification of the procedure which omits the distillation step was used for estimation of free cyanide. Later in the study, the Company used a microdiffusion method for free cyanide (15). 

Another potential problem with cyanide analysis is the recommended preservation method. The APHA standard method recommends preservation by adjusting to a pH of 12 using sodium hydroxide. The Department s laboratory has been using this method which is effective for total cyanide but unsatisfactory for free cyanide since the pH adjustment can change the cyanide species present, and thus the final result. There is no adequate preservation method for free cyanide. 

Federal drinking water standards for cyanide have been withdrawn and are not included in the latest publication. The Public Health Service limit for drinking water had been 200 ppb. Whether the limit was expressed as free or total cyanide was in question at the time. The fresh water aquatic cyanide criterion is 3.5 ppb as a 24-hour average, not to exceed 52 ppb at any time. 

Except as specifically provided in the U.S. CFR, any existing point source subject to this subpart must achieve the effluent limitations shown in Table 9.19 which represents the degree of effluent reduction attainable by applying the BAT. Alternatively, for the metal finishing industrial facilities with cyanide treatment, and upon agreement between a source subject to those limits and the pollution control authority, the amenable cyanide limit shown in Table 9.20 may apply in place of the total cyanide limit specified in Table 9.19. No user subject to the provisions of these regulations shall augment the use of process wastewater or otherwise dilute the wastewater as a partial or total substitute for adequate treatment to achieve compliance with this limitation. 

PSNS, shown in Table 9.25. Alternatively, for industrial facilities with cyanide treatment, and upon agreement between a source subject to these limits and the pollution control authority, the amenable cyanide limit shown in Table 9.26 may apply in place of the total cyanide limit specified in Table 9.25. 

The chemical speciation of cyanides varies according to their source. Specific terms used to describe cyanide include free cyanide, cyanide ion, simple cyanides, complex cyanides, nitriles, cyanogens, and total cyanide. The most common forms of cyanide in the environment are free cyanide, metallocyanide complexes, and synthetic nitriles. A brief description of each cyanide species follows (Smith et al. 1978, 1979 Towill et al. 1978 Egekeze and Oehme 1980 USEPA 1980, 1989 Davis 1981 Leduc 1981, 1984 Leduc etal. 1982 Simovic and Snodgrass 1985 Ballantyne 1987a Homan 1987 Marrs and Ballantyne 1987). 

Resources and Nonbiological Materials (Values are in mg total cyanide/kg fresh weight, or mg/L.)... 

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