Hydrometallurgical recovery of critical metals from an incinerated fly ash of municipal solid waste from western India

ABSTRACT The global generation of 2.2 billion tons of municipal solid waste (MSW) as a result of population growth, rapid urbanization, and industrial development has highlighted an urgent need for MSW management. Incineration is widely accepted as one alternative to landfilling; however, the recovery of heavy metals from the incinerated fly ash (IFA) before its final disposal is highly desirable to make the process sustainable. In this study, we studied the recovery of zinc and lead from typical MSW-IFA employing hydrometallurgical techniques. Sulfuric acid leaching was performed to selectively leach out zinc over the lead at the optimal condition of H2SO4 concentration = 1.5 M, temperature = 30°C, S/L ratio = 150 g/L, time = 2 h, and stirring speed = 300 rpm. The sulfate leach liquor was treated with a 5% stoichiometric excess of oxalic acid to precipitate>99% of zinc to be recovered as ZnC2O4·2 H2O. Further, the remaining lead in leach residue was subsequently leached in 50 g/L NaCl solution for 2 h yielded>94% efficiency. The dissolved lead was crystallized to recover the crystals of PbCl2. The demonstrated process leads towards the recovery of critical metals from an alternative source of MSW-IFA.