**3. Results and Discussion**

#### *3.1. Mass Balance for Physical Pre-Treatment*

After three stages of attrition, samples were divided into the following two parts: Coarse fraction (larger than 1.7 mm) and fine fraction (smaller than 1.7 mm). The coarse fraction consisted of a ferrous fraction (22%) and non-ferrous fraction (4%), while the fine fraction contained graphite carbon with metallic powder. Water used for the initial washing contained soluble electrolytes, primarily KOH (4%). According to our results, 1924 g of metallic powder (68% of total mass) was recovered from 2833 g of battery waste with a mass balance of 98.9%. During attrition with water, the pH decreased slightly to 12.8 (stage 1), 11.4 (stage 2), and 10.3 (stage 3).

Table 3 presents the average composition of batteries after physical pre-treatment with recirculated water. This distribution corresponds to results from an investigation on the composition of spent AA alkaline batteries by Almeida et al. [26]. Findings from their study reported alkaline batteries to consist of 2.9% plastic and paper, which is equivalent to the non-ferrous fraction of our study; 21.8% metal and brass, which is equivalent to the ferrous fraction; and 75.3% anode and cathode, which is equivalent to KOH and metallic powder. Although slight differences may be attributed to the sampling method and technical separation, these results indicate the high efficacy of washing for obtaining metallic powder.

**Table 3.** Composition of the battery after separation by attrition and magnetic separation (physical pre-treatment).


The chemical composition of the resulting metallic powder from the attrition process is shown in Table 4. The quantities of zinc and manganese are 240 and 326 g per kg of metallic powder, respectively. The high concentration of potassium (25.5 g/kg) is associated with the high quantity of alkaline

batteries in comparison to Zn–C batteries in the original sample. The collected metal powder was then transferred to the acid leaching process.


