A Combined Theoretical and Experimental Framework for Shifting to Greener Reagents in Mineral Processing

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Mineral processing utilizes many toxic or hazardous reagents which have adverse health effects in the workplace and pollute the environment after disposal in tailing ponds. The progressive tightening of wastewater and health regulations portends a future where the industry, to preserve its social license, will be forced to replace the toxic reagents by the greener alternatives. To meet this need, it is important to develop greener renewable alternatives to the conventional surfactants (e.g. collectors and regulators in flotation). The current strategy for the development of new flotation surfactants is trial and error, which is costly and arduous, while the prediction toolbox consists of generic rules such as the soft hard acid base rule, pH control of the electrostatic interactions, and surface recognition. However, even at a generic level, predictive rules have not emerged for renewable surfactants which differ from the conventional counterparts by bulkier headgroups with multiple adsorption moieties and structural isomers. An alternative computational approach, such as density functional theory (DFT), is also very challenging given its limitations to capture the mineral-solution interface and computational cost to model different structural and compositional defects of real-world mineral particles, which entails impractical screening of thousand adsorption structures for a large set of headgroups of renewable surfactants. To accelerate the introduction of renewable surfactants to flotation practices, I propose to develop and test a descriptor-based approach that allows predicting the affinity of mineral surfaces to the renewable surfactants. The computational cost will further be reduced by employing scaling relations between the adsorption energies of adsorbates. The introduction of scaling relations in 2007 was a decisive step in evolving the computational design of catalysts. However, this advanced approach has not been used for screening flotation reagents as yet. The theoretical predictions will further be tested and corrected using spectroscopic, interfacial, and flotation techniques. The major practical outcomes are a) cleaner ore processing technologies for mineral industry with less impact on the environment, b) guidelines for employing renewable surfactants in other industries such as oil and gas recovery. The proposed interdisciplinary research will train the next generation of highly qualified personnel in the advanced research and engineering approaches required to advance sustainability not only in mineral industries but also in oil and gas, chemical, paints and pigments, and consumer care industries.