Switchable selective collectors for flotation of engineered artificial minerals

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There is growing concern about reliable and unhindered access to critical raw materials such as platinum, palladium, tantalum, rare-earth elements, but also other elements such as copper and lithium, which play important roles in modern technology. In the project pillars A and B, the priority programme SPP 2315 addresses slag formation to concentrate diluted elements as engineered artificial minerals (EnAMs). The applicant´s proposal is located in project pillar C as its goal is to develop selective composition-dependent separations by means of new and switchable collectors which are related to the natural product Punicine from Punica granatum. The charges of Punicine derivatives can be adjusted from positive to twofold negative by the pH. In addition, exposure to daylight (> 5000 lux; 3300–5300 K) reversibly gives persistent radicals in water which are redox active. Coulombic interactions, hydrogen bond formations, pi-donor, pi-acceptor and sigma-donor capabilities, important for complexation and adsorption on surfaces, can either be reversibly tuned by external parameters such as pH or light, or even switched “on” and “off”. Remarkable adjustable selectivities toward metals have been identified in model reactions. In first flotation experiments, the recovery rate of lithium aluminate, an important engineered artificial mineral (EnAM), increase at pH 6-7 by 60% simply by changing the light scenario from “daylight” to “darkness” (< 40 lux). On the basis of these promising preliminary results, the objective of this proposal is the development of switchable collectors for the flotation of EnAMs which goes in parallel with studies of effective and often problematic releases of the particles from the collectors after the flotation. We will install known flotation-active functional groups onto the Punicine core to make them switchable, i.e. selective toward target EnAMs depending on pH and light in order to allow effective separations from undesired EnAMs or gangue materials. Target EnAM particles contain lithium, copper, tantalum, rare-earth elements and those of the platinum group.