Heavy metal ions adsorption from mine waters by sawdust

Abstract

In this work the results on the batch and column adsorption of copper and some associated ions by employing linden and poplar sawdust as a low-cost adsorbent are presented. The mine water from a local abandoned copper mine, as well as synthetic solutions of those ions which are the main constituents of the mine water were both used as a model-system in this study. The adsorption ability of the chosen sawdust to adsorb heavy metal ions is considered as a function of the initial pH of the solution and kind of metal ions. At lower pH of solutions the adsorption percentage (AD %) decreases leading to a zero AD % at pH < 1.1. Maximum AD % is achieved at 3.5 < pH < 5. It was found that poplar and linden sawdust have both almost equal adsorption capacities against copper ions. The highest AD % ( ≈80%) was achieved for Cu 2+ , while for Fe 2+ it was slightly above 10%. The other considered ions (Zn 2+ and Mn 2+ ) were within this interval. The results obtained in the batch mode were verified through the column test by using the real mine water originating from an acid mine drainage (AMD) of the copper mine "Cerovo", RTB Bor. The breakthrough curves are presented as a function of the aqueous phase volume passed through the column allowing having an insight into the column adsorption features. Breakthrough points were determined for copper, manganese and zinc ions. A very high adsorption degree -higher than 99% was achieved in these experiments for all mentioned ions. After completing the adsorption, instead of desorption, the loaded sawdust was drained, dried and burned; the copper bearing ash was then leached with a controlled volume of sulphuric acid solution to concentrate copper therein. The obtained leach solution had the concentration of copper higher than 15 g dm -3 and the amount of H 2 SO 4 high enough to serve as a supporting electrolyte suitable to be treated by the electrowinning for recovery of copper. The technology process based on the column adsorption is proposed and discussed.There are many different industrial effluents containing heavy metal ions that at present significantly contribute to environmental pollution heavily polluting the surface -and underground waters [1-6]. The metal working industry, particularly electroplating and surface finishing plants, is an important sector producing enormous amounts of wastewaters containing mainly heavy metal ions but also, in some particular cases, noble metals that must be removed and recovered Corresponding author: V. Stanković,

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