Abstract
The paper is focused on the recovery of zinc and manganese from alkaline and zinc-carbon spent batteries. Metals are extracted by sulphuric acid leaching in the presence of citric acid as reducing agent. Leaching tests are carried out according to a24full factorial design, and empirical equations for Mn and Zn extraction yields are determined from experimental data as a function of pulp density, sulphuric acid concentration, temperature, and citric acid concentration. The highest values experimentally observed for extraction yields were 97% of manganese and 100% of zinc, under the following operating conditions: temperature40∘C, pulp density 20%, sulphuric acid concentration 1.8 M, and citric acid 40 gL-1. A second series of leaching tests is also performed to derive other empirical models to predict zinc and manganese extraction. Precipitation tests, aimed both at investigating precipitation of zinc during leaching and at evaluating recovery options of zinc and manganese, show that a quantitative precipitation of zinc can be reached but a coprecipitation of nearly 30% of manganese also takes place. The achieved results allow to propose a battery recycling process based on a countercurrent reducing leaching by citric acid in sulphuric solution.
Highlights
The battery market is steadily increasing worldwide: this behaviour requires a new approach in the management of these devices once they are exhausted [1]
The powder obtained was washed with distilled water in a 1liter jacketed stirred reactor tank at 60◦C for 1 h with 20% pulp density; that temperature was chosen to increase the solubility of KOH and NH4Cl, which are the electrolytes of alkaline and Zn-C batteries, respectively
It can be inferred from analysis of variance (ANOVA) that the main factors and interactions which mainly influence the final extraction of zinc are citric acid concentration, pulp density and temperature, sulphuric acid concentration-temperature, and pulp density-temperature
Summary
The battery market is steadily increasing worldwide: this behaviour requires a new approach in the management of these devices once they are exhausted [1]. Several European Countries have autonomously developed national collection systems and infrastructures to collect and recycle all kinds of portable batteries, despite the old Directive 91/157/EEC EEC (and subsequent amending acts of Directives 93/86/EEC and 98/101/EC) that covered only batteries and accumulators containing more than 0.0005% mercury, more than 0.025% cadmium, and more than 0.4% lead (percentages by weight) [2]. These Countries have arranged a financing system that is able to cover all costs related to the recycling activities by applying a surcharge on battery selling price [1]. Recycling processes shall achieve the following minimum efficiencies [2]:
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