## 1 Introduction
The most environmentally effective techniques available for the AMD treatment are the internal neutralization methods, water-covers and biological/natural degradation processes. A number of factors dictate the level of the treatment system that is necessary to ensure that the effluent standards will be met. These include the chemical characteristics of the AMD; quantity of water in need of treatment; local climate; and sludge characteristics. The chemicals usually used for the AMD treatment include limestone, hydrated lime, soda ash, caustic soda, carbide lime, ammonia, calcium peroxide, and fly ash. Saked lime neutralization, referred to in the mining circles as the \"chemical process\", is often used to treat the AMD in the mining industry. Previous studies showed that slaked lime can treat the wastewater effectively. It had the capability to increase pH value and also can treat heavy metals for example at pH ranges 10-11 for zinc, 9.2-11.6 for lead, 4-11.8 for iron, and 7-11.8 for copper [16]. Another study showed that slaked lime can be used to treat an effluent from a dairy farm using the coagulant techniques and the results indicated that the suspended solids, organic matter, and nitrogenous and phosphate compounds were reduced [17]. The neutralization method can remove the dissolved metals from the wastewater due to the pH dependence of the metal solubility, and it is a very effective operation for wastewater purification. However, for some metal ions, such as Ni and Mn, a higher pH value over the effluent standard is required to remove them as a sludge precipitation. In this case, more operation is needed to lower the pH value below the effluent standard. If the processing in the pH region above the effluent standard needs to be avoided, other removal methods must be applied for that. adsorption is one of the effective techniques for removal the metal ions from water. Application of organic or inorganic adsorbents to wastewater treatment has been reported [18; 19; 20]. Especially, the natural materials that are available in large quantities, or certain waste products from the industrial or agricultural operations, may have a potential as the inexpensive sorbents for heavy metals from AMD. Due to their low cost, after these materials have been expended, they can be disposed of without expensive regeneration [18]. Most of structural proteins are found in the skin, tendons, cartilage, bones, and connective tissues of animals. In the papers [21; 22] are presented very useful data about the main sources, properties, and chitin application as well as properties and application of chitosan, the most important derivative of chitin. Chitosan is a cationic polymer obtained from the chitin comprising copolymers of \(\beta\) (\(1\to 4\))-glucosamine and N-acetyl-D-glucosamine [23]. Chitosan is soluble in the acidic aqueous media, and is used in many applications (food, cosmetics, biomedical, and pharmaceutical applications). Furthermore, chitosan has applications in drinking water and wastewater treatment due to its ability to remove metallic ions from solutions. The ability of chitosan to remove arsenic from natural water, and copper and zinc from mining wastewater was verified [19]. This polymer has been shown to be the biologically renewable, biodegradable, biocompatible, non-antigenic, non-toxic, and biofunctional. Metal removal caused by the adsorption is usually affected by the electrostatic interaction, chelating effect or chemical bonds. Thus, it is expected that the adsorption method can remove metals which have a higher solubility in an acidic or neutral range below the effluent standard pH value. The aim of the present investigation was to examine the possibility of purification of the AMD generated from the copper ore mining activities in southeast Serbia by combining the neutralization and adsorption methods.