Chemical Engineering and Processing 41 (2002) 17 – 21 Removal of cyanide from aqueous solution using impregnated activated carbon Nafaaˆ Adhoum, Lotfi Monser * Institut National des Sciences Applique´es et de Technologie, De´partement de Chimie, Centre Urbain Nord B.P. 676, 1080 Tunis Cedex, Tunisia Received 27 August 2000; received in revised form 23 November 2000; accepted 24 November 2000 Abstract Impregnated activated carbons are carbonaceous adsorbents which have silver and nickel distributed on their surface. The impregnation optimises the existing properties of the activated carbon giving greater cyanide removal capacity to the carbon. This facilitates the cost-effective removal of cyanide impurities from aqueous effluent. The adsorption isotherms of the impregnating elements (Ag and Ni) from aqueous solutions on plain activated carbon was measured. The amount of adsorbed silver on plain carbon reached 45.7 mg g −1 carbon and for nickel was 4.3 mg g −1 carbon. These impregnated materials were packed in fixed bed columns and used for cyanide removal from aqueous solutions. The adsorbed capacity was monitored from the breakthrough, which indicates that the carbon is not longer adsorbing effectively. The results indicates that carbon – Ag impregnation was shown to have a cyanide removal capacity of nearly two times that of carbon–Ni impregnation and of four times that of plain activated carbon. These suggest that cyanide was probably eliminated in the forms Ag(CN) 2 − and Ni(CN) 4 complexes. However, calcination of impregnated activated carbon under nitrogen at 300°C showed similar results to impregnated non-calcinated ones. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Activated carbon; Impregnated activated carbon; Fixed bed columns; Cyanide www.elsevier.com/locate/cep 1. Introduction Cyanides are present in effluent waters of several industries. They are used in a number of chemical synthesis (nylon, fibres, resins, herbicides) and metallur- gical processes (plating and surface fishing) and there- fore, it is present in their effluent waters. As a class cyanides are highly toxic, for short-term exposure it can cause the following health effects: rapid breading, tremors and other neurological effects; for long term exposure it can cause weight loss, thyroid effects and nerve damage. Therefore, cyanide must be destroyed or removed from wastewater prior to discharge. The stricter environmental regulations to the discharge cyanides make it necessary to develop processes for their removal from wastewater. The most common method for treating free or simple cyanide is alkaline chlorination [1]. However, chlorination of cyanides re- sults in highly toxic intermediates (e.g. cyanogen chlo- ride). These compounds, together with the residual chlorine, create additional environmental problems. Consequently, there is a growing need for alternative, non-chlorine methods for the elimination of cyanides. Activated carbon was especially known for the effec- tiveness in removing organic chemicals from wastewa- ter, it is also surprisingly effective in removing inorganic pollutants [2–4]. Chen and Wang found ef- fective results using fixed bed activated carbon for the removal of copper, zinc and lead from synthetic wastewater [5]. They demonstrated that the removal of these metal ions followed the descending order: Cu  Pb Zn. Zarrouk et al. [6] studied the mechanism of adsorp- tion of gold from a cyanide solution on activated carbon. They found that the adsorption of gold com- plexes depends on initial gold concentration, tempera- * Corresponding author. Tel.: +216-1-703627; fax: +216-1- 704329. E-mail address: lotfi.monser@insat.rnu.tn (L. Monser). 0255-2701/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0255-2701(00)00156-2