Recovery of Lead-Loaded Zeolite Particles by Flotation
Résumé
The solid/liquid separation of zeolite particles from aqueous suspensions by froth flotation was investigated as a function of various experimental parameters and discussed with respect to the selective recovery of lead-loaded zeolites. Two kinds of collectors were studied: two long-chain positively charged nitrogen-containing surfactants and the negatively charged amyl xanthate. Efficient but nonselective recovery was achieved with using stearylammonium or cetylpyridinium because these surfactants were able to bind the surface of both the lead-loaded zeolites and the sodium-containing raw materials. Amyl xanthate (AMX) did not interact with the sodium form of zeolites, preventing recovery by flotation, but it was found to react with the lead-loaded zeolites leading to the formation of an insoluble complex, Pb(AMX)2, out of the zeolite particle. Adjusting pH at an appropriate value, enabling the formation of lead hydroxide on the zeolite surface, led to the autoassembling of a Pb(OH)2/Pb(AMX)2 overlayer onto the zeolite surface. This resulted in the aggregation of the zeolite particles and their subsequent recovery by flotation. This way to recover zeolite particles loaded with heavy metal species looks promising for exploiting pure synthetic zeolite powders in wastewater treatments.