Valorización de escorias obtenidas tras el proceso de reciclaje de baterías automotrices mediante lixiviación del plomo residual empleando solventes eutécticos profundos (DES).

Abstract

The recycling of automotive batteries is one of the most polluting processes in the world due to the generation and accumulation of hazardous waste such as foundry slag. In the present study, a relatively cheap and safe alternative is proposed for the removal and recovery of lead from samples of said slag. Through analysis of TCLP extracts, it was found that the samples did not comply with the permissible limits of international regulations. Lead was found by XRF/XRD in concentrations up to 5.4% mainly as anglesite (PbSO4). For the hydrometallurgical processing, deep eutectic solvents (DES) were used, mainly recognized for being biodegradable and safe. Six operational variables were evaluated: type of sample, solvent, concentration, temperature, time, and pressure application. Using a solvent prepared based on choline chloride and glycerin in a 2:1 molar ratio, it was possible to dissolve 95% of the lead present in an acidic sample. This leaching efficiency was reached by applying a temperature of 90 oC, agitation of 470 rpm, pulp concentration of 5% and allowing a time of 5 hours to elapse. In addition, it was verified that applying hydrothermal pressure was not necessary in order to obtain favorable results. An optimized lead solution was placed inside of an electrowinning cell achieving 55% of lead recuperation on the cathode. The ability of DES to decontaminate slag was demonstrated so that the company complies with regulations, recovers the valuable metal, and grants the remaining material new possibilities of application.