The Effect of Plasma Pretreatment on the Flotation of Lithium Aluminate and Gehlenite Using Light-Switchable Collectors

The pyridinium phenolate punicine is a switchable molecule from Punica granatum. Depending on the pH, punicine exists as a cation, neutral molecule, anion, or dianion. In addition, punicine reacts to light, under the influence of which it forms radical species. We report on three punicine derivatives that possess an adamantyl, 2-methylnonyl, or heptadecyl substituent and on their performance in the flotation of lithium aluminate, an engineered artificial mineral (EnAM) for the recycling of lithium, e.g., from lithium-ion batteries. By optimizing the parameters: pH and light conditions (daylight, darkness), recovery rates of 92% of LiAlO2 are achieved. In all cases, the flotation of the gangue material gehlenite (Ca2Al[AlSiO7]) is suppressed. IR, the contact angle, zeta potential measurements, TG-MS, and PXRD confirm that the punicines interact with the surface of LiAlO2, which is covered by LiAl2(OH)7 after contact to water, resulting in a hydrophobization of the particle. The plasma pretreatment of the lithium aluminate has a significant influence on the flotation results and increases the recovery rates of lithium aluminate in blank tests by 58%. The oxidative plasma leads to a partial dehydratisation of the LiAl2(OH)7 and thus to a hydrophobization of the particles, while a reductive plasma causes a more hydrophilic particle surface.