Resumen

MARTINEZ, Miguel; FERRO, Esteban  y  DE PABLOS, Fernando. Evaluation of free cyanide in superficial waters of river paraguay nearby a steel industry. Rev. Bol. Quim [online]. 2016, vol.33, n.2, pp.88-94. ISSN 0250-5460.

Siderurgical wastewater from steel industrial waste is considered as a high power pollutant due to its toxic and corrosive qualities. Toxicity in wastewaters from coke is due to high concentration of cyanides and heavy metals; the high acidity or basicity, given its corrosive features, is also a strong polluting factor. The aim of this study is determining the free cyanide concentration in samples from superficial water of the Paraguay River nearby a siderurgical plant. The colorimetric method pyridine and barbiturical acid was employed. Two samplings were made, in winter and spring (August and November 2011). The results were compared with the maximal permitted limits according to the US Environmental Protection Agengy (USEPA), as well as the limits defined by the Secretaría del Medio Ambiente de Paraguay (SEAM, resolution N° 222/02) which establishes the quality indexes of water in the Republic of Paraguay. The latter establishes a concentration of 0.20 mg CN^-. L^-1 as the top allowed value. We've found that stations E₄ and E₄' corresponding to the second sampling showed 0.81 y 2.0 mg CN^-. L^-1 as concentration values respectively, exceeding thus the accepted standard values as defined by the two organisms. However, the rest of the stations from both samplings showed values complying with the national and international norm.

Palabras clave : Free cyanide; Analysis; Water; Paraguay; River; Steel; Industry.

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