Selective extraction of Zn from spent batteries using alkaline leaching solutions based on glycine as complexing agent

The current high demand for raw materials requires the exploitation of new deposits and the development of recycling processes to recover valuable materials present in waste. The valorization of black mass from spent Zn/C and alkaline batteries can not only preserve raw materials (Zn, Mn or graphite), but also reduce hazardous wastes toward the environment. The main objective of the present research has been the application of an alkaline glycine leaching for the valorization of one selected black mass from spent Zn/C and alkaline batteries supplied by Envirobat (Spain). The effects of reaction time, temperature, pH, glycine concentration, solid/liquid ratio, H 2 O 2 concentration, black mass particle size, and ultrasound treatment have been studied. It can be concluded that using optimised conditions (pH = 8, 0.5 h of leaching reaction, 25 °C, 8/1 of glycine/Zn molar ratio, 1/80 w/v black mass/leaching solution ratio, and without H 2 O 2 addition) it is possible to extract more than 90 % of Zn and less than 1 % of Mn from the black mass of Zn/C and alkaline batteries. The addition of H 2 O 2 does not improve the Zn extraction probably due to H 2 O 2 decomposition by Mn compounds from the black mass.