Innovative technology for defluorination of secondary aluminum dross by alkali leaching

•An innovative technology for defluorination of SAD was developed, extracting all the soluble sodium fluoride and active cryolite, stabilizing the harmful fluorides towards deep detoxification.•The defluorination process gave a novel idea for the comprehensive wet processing treatment of SAD. The kinetic analysis showed that the fluoride leaching occurred according to the hybrid control model of solid product layer in-diffusion and interfacial chemical reaction.•The harmful fluoride ions in the alkali solution could be stabilized by CaO, and the solution could be recycled, which provided a new idea for the wet recovery of SAD.•The technology has been already used in a pilot plant that processes 10000 tons of SAD per year. The technology is economic and the pilot plant runs well, towards a good treatment of hazardous waste and protection of environment.