Synthesis of Novel Chelating Surfactants and Their Use in Recovery of Metals by Ion Flotation

For more than 100 years the EU mining industries have been discarding their extractive-waste residues. Estimates suggest this represents 29% of the EU-28’s current waste output. When poorly managed these residues are a significant environmental hazard. Sulfidic Cu-Zn, Zn-Pb and Cu-Zn-Pb tailings pose the largest challenge, as they are prone to acid mine drainage. However, these tailings also contain valuable metals. Remediation and reprocessing of sulfidic mining waste sites can contribute to ecological and economic progress by developing methodologies to assess the resource potential of Europe’s main tailings families and explore eco-friendly mining chemicals to be used in advanced metal-extraction/recovery set-ups. This work will target the synthesis of new eco-friendly mining chemicals that could be used in novel beneficiation/metal extraction/metal recovery flow sheets. In order to overcome the inherent environmental problems associated with traditional, petroleum-derived mining chemicals, the focus will be on the development of ion flotation chemicals derived from renewable bio-based materials that could be used in the metal-recovery step of the tailings reprocessing chain. This will be achieved through the design and preparation of new surfactants containing chelating groups using renewable starting materials or natural products with surfactant properties that are abundantly available. Besides that, research of the efficiency and selectivity of the recovery of valuable metals from aqueous leachates by ion flotation will also be conducted to corroborate the efficiency of prepared compounds in the beneficiation and metal-extraction steps in the reprocessing of Cu-Zn, Zn-Pb, Cu-Zn-Pb tailings. The overall goal can be divided into a number of focused objectives: 1) To develop a synthetic procedure for the preparation of new surface-active compounds incorporating a variety of chelating groups, using renewable starting materials or natural products. 2) To examine the surfactant properties of prepared ligands in order to gain insight into their potential for use in ion flotation. 3) To conduct research on the selective removal of metals (Cu2+, Pb2+, Zn2+, In3+, Ga3+) by ion flotation from the diluted aqueous phase and to find the conditions of recovery of the metals of interest. The surfactant properties are going to be quantified by determination of critical micelle concentration, surface tension and pC20 value of their aqueous solutions. Based on the insights obtained from the quantification of surfactant properties of specific ligands, efficiency and selectivity of the recovery of metal ions from aqueous solutions are going to be examined by laboratory scale ion flotation experiments.