Leaching of arsenic from flue gas desulphurisation gypsum using ultrasound-enhanced sulfuric acid

Abstract

The flue gas desulphurisation gypsum (FGDG) produced in nonferrous metal metallurgy industry is defined as hazardous waste because of its arsenic content. In this study, a new process for arsenic removal by ultrasound-enhanced sulfuric acid leaching was developed. The leaching characteristics of arsenic under ultrasound-enhanced leaching and conventional leaching conditions were compared. Furthermore, the results indicated that under the optimal experimental conditions, the leaching efficiency of arsenic in ultrasound-enhanced leaching was 97.07%, while that in conventional leaching was only 79.67%. The leaching kinetic data further proved that the leaching rate of arsenic is controlled by the diffusion process in the ultrasound-enhanced sulfuric acid leaching system, and the activation energy of the reaction is 13.38 kJ mol−1. On the basis of optimization of leaching process parameters, the reaction mechanism of the leaching process was studied by X-ray diffraction, X-ray photoelectron spectroscopy, Electron probe X-ray microanalyser, and scanning electron microscopy. The results of the toxicity assessment indicated that FGDG treated with ultrasound-enhanced sulfuric acid was no longer a solid hazardous waste, which is of great significance for its efficient utilization.