|Posted: 22 July 2011 at 1:36pm | IP Logged
AAQTIC PUBLISHED REPORT ON CYANIDE IN EFFLUENTS
AAQTIC, Argentine Leather Industry Chemists and Technicians Association, has published a new report on Cyanide in effluents on its website. This report is available in both English and Spanish.
CYANIDE IN EFFLUENTS
Round Table: SOME ASPECTS OF THE CURRENT PROBLEM OF TANNING EFFLUENTS
Held at the 3rd National Technical Symposium of the Tanning Industry - November 26, 2010. Paseo La Plaza, Buenos Aires.
· Lic. Patricia Casey (Quality Manager at Curtiembres Fonseca and Vice President of AAQTIC’s Board)
· Eng. Maria Inés Iribarne (Environment Manager at Curtiembre Hispano Argentina)
· Dr. Carlos Gotelli (Member of the National Academy of Pharmacy and Biochemistry -Academia Nacional de Farmacia y Bioquímica-; Member of the New York Academy of Sciences; Director of the National Center for Toxicological Research; and Consultant at the World Health Organization regarding heavy metals)
· Lic Horacio González (Business Manager at Buckman)
· Eng. Jorge Garda (Environment Manager at Curtiembres Fonseca)
· Eng. Martín Gelaf (Technical Director at Curtiembre Hispano Argentina)
Main speaker: Eng. Martín Gelaf
The main purpose of the presentation is to show the findings made on an issue that worried the tanning industry in Argentina throughout 2010: the detection of cyanide in effluents from several tanneries.
Cyanide concentration values in tanning effluents have been measured and they turned out to be higher than the permitted 1 mg/l (1 ppm) according to the Standard Method (20th Edition) for total cyanide or 0.1mg/l of cyanide destructible by chlorination according to the Standard Method CN 4500 (paragraphs C and E). As a result, penalties such as closures have been applied.
This situation has no precedents in the national and international tanning industry and, to confirm it, some local authorities have been consulted and the opinion of foreign consultants has also been considered.
In view of such reality and knowing that tanners do not use cyanide in products for their processes, it has been decided that different alternatives should be researched on. These alternatives will be shared in this presentation.
It has been established that it is a complex issue, that conclusions are partial, and that further studies must be carried out. The purposes were:
· To understand the definition of cyanide pursuant to standards.
· To know how to prepare and preserve the samples to be analyzed.
· To understand the different laboratory methods to measure cyanide levels and challenge the values obtained and potential interferences that may appear.
· To analyze which chemical products may generate cyanide under certain special pH and temperature conditions, and presence of oxidants, among others.
There are a lot of doubts with respect to the foregoing issues since the different detection methods produced different cyanide values for the same effluent sample.
The most controversial chemical product which should be studied further is the use of the TCMTB fungicide (C9H6N2S3) which is the 2-(thiocyanomethyl) benzothiazole.
One of the manufacturers, Buckman, has informed that the TCMTB molecule does not generate detectable levels of cyanide under regular conditions of application and treatment of tanning effluents, if the analytical methods are appropriate. The TCMTB chemical formula does not contain a labile cyanide group under industrial use conditions.
TCMTB is a product that decomposes at pH > 10 and temperatures > 120 °C; that is, the cyanide found was generated by the taking and preparation of the sample and the measurement method used.
Despite the remarks based on the need to treat TCMTB as interference in the analyses, many tanneries had to stop using TCMTB in their processes.
Another important issue is that work should be performed jointly with the Government Instrumentalities to know the adequate detection methods to be used, and to make sure that they are applied by qualified people, in contact with the tanneries’ technical departments.
According to the information gathered in the inspected companies, the method used by the controlling authority is not the one stated by law, and the tests performed show that different methods lead to different results.
Sodium hypochlorite oxidation is the customary method for the elimination of cyanide from industrial effluents where cyanide salts are used (e.g. Electroplating). It has been confirmed that in the case of an effluent treated in the retanning process with limit values of 700 mg/l of DQO and 200mg/l of DBO the addition of sodium hypochlorite has caused an increase in the concentration of cyanide destructible by chlorination detected by laboratory method.
For a complete version of the report in Spanish, please click here:
In English, click here
The report will be published in “Tecnología del Cuero” magazine.
AAQTIC, Argentine Leather Industry Chemists and Technicians Association, is a non-for-profit association founded in 1959 formed by technicians of the tanning industry.
After 50 years, their institutional goals keep being: making Conferences and Courses, as well as other activities in its head office. It has published its magazine, Tecnología del Cuero, since 1960 and organizes Symposia every two years. Besides, it launched its own website, www.aaqtic.org.ar, in 2000.