In this paper we describe the results of a research performed on pen alkaline-manganese batteries with the aim of checking the possibility of minimizing the release of metals from them when, exhausted, are disposed. This goal was tempted on inserting in the batteries a certain amount of chitin able to bind the metal ions formed by the natural oxidation of the metals contained in the batteries and by the acid rain dissolving action.
The obtained results show that 1.2 g of chitin added to the common models for each middle size pen alkaline-manganese battery can lower the metal release, without relevant change of the discharge curve of the battery. The effect of the addition is particularly advantageous if the additive is contained in a PVC membrane. The way seems opened to look for more efficient still cheap additives.
The increase of the industrial activities beside some benefits to our society has produced the release of great amounts of harmful and toxic wastes into the environment. In this context a marked interest is going to be assumed by the studies concerning soil, plant and food chain pollution. A meaning example is represented by the environmental impact due to the disposal of the exhausted batteries. 1 Due to the toxicity of the contained metals the germination of some plants can be totally inhibited. 2 Furtherly it must be taken into account that the mobility of these metals into the soil, increased by the falling rain, can result in a pollution of the food chain. The batteries provided by the great manufacturers are practically free of ecologically noxious elements (green batteries) but the increasingly rigid environmental rules, adopted by CEE, suggest in any case to prevent any metal release, also with the aim of recycle them from the wastes.
Facing these problems it was hypothised to adopt an opportune additive to pen alkalinemanganese batteries with the aim of limiting the release of metals from them without any damage to their regular functioning and characteristics. 3 The choice of the additive fell on the biopolymers well diffuse both in animal and vegetal world. Among these compounds we selected chitin (polymer of 2-acetamide-2-deoxy-D-glucose) due to its cheapness (see tab. 1), resistance to high basicity conditions (as we want to apply the additive to alkaline batteries), ability to act as a strong adsorbent with chemical binding properties to metals. (see tab. 2) TABLE 1 -Comparison of the costs of different natural polymers Polymer Cost (Euro/Kg) Carrageenan 120 Cellulose 35 Agar 125 Chitosan 460 Chitin 26