Valorización hidrometalúrgica de pilas Ni-Cd gastadas, utilizando ácidos orgánicos como agentes lixiviantes selectivos

Abstract

In this paper, we propose a hydrometallur-gical procedure to treat spent Ni-Cd batte-ries using organic acids as leaching agents. The electrode materials of the batteries were extracted and leached using a combi-nation of acetic, citric, and sulfuric acids and their mixtures in a two-stage selective scheme. This procedure aimed to recover metal-bearing solid products. The leachates were treated by evaporation/crystallization or chemical precipitation to obtain the so-lid products. These products were charac-terized using scanning electron microsco-py, chemical analysis by atomic absorption spectroscopy, mineralogical phases by x-ray diffraction, and infrared spectroscopy. In the first leaching step, 15 % m/m citric acid was used to recover 85±5 wt.% of the cad-mium present as a carboxylate salt. In the second leaching stage (5 % m/m acetic acid mixed with 3 % m/m sulfuric acid), 50±3 wt.% of nickel was recovered, in the form of a product consisting of a mixture of hy-droxides and salts. The remaining solid from the second leaching stage was a valua-ble metal product containing nickel (96±4 wt.%). The analysis of the results allowed us to depict a conceptual process flow diagram for the selective leaching of the spent Ni-Cd batteries, and the possible industrial use of the solid products obtained.