Cyanide removal by combined adsorption and biodegradation process
Cyanide is present in environmental matrices and waste streams as simple and complex cyanides, cyanates and nitriles (Ebbs, 2004). Cyanide compounds are extensively used in industry and their effluents are the major source of these toxic pollutants in our environment (Desai and Ramakrishna, 1998). The release of cyanide from industries worldwide has been estimated to be more than 14 million kg/yr (Ebbs, 2004). The major industries which use cyanide are electroplating and mining (extraction of gold, silver, etc.) (Akcil, 2003; Desai and Ramakrishna, 1998; Patil and Paknikar, 2000). Due to their toxic effects, cyanide- containing effluents cannot be discharged without detoxification to the environment. US-health service cites 0.Olmg/L as guideline and 0.2 mg/L as permissible limit for cyanide in effluent. Adsorption and biodegradation are two significant methods for treatment of wastewater bearing cyanide compounds. Adsorption and biological treatment either operated separately or simultaneously in one-unit results in a better removal and process performance. Microbial mass can, in some extent, adsorb the substances, but at the same time it also degrades them.