The doctoral dissertation in the field of Technical Physics will be examined at the Faculty of Science, Forestry and Technology, Kuopio campus and online.
What is the topic of your doctoral research? Why is it important to study the topic?
This doctoral research investigates bisphosphonate-functionalized silicon-based adsorbents for the recovery of scandium and uranium from multi-metal solutions relevant to mining and mineral processing, and for on-site determination of dissolved trace metals in natural waters. Scandium is strategically important for high-performance alloys and fuel cells, but it occurs at low concentrations in ores together with high concentrations of other metals, which makes its separation challenging. Uranium in polymetallic deposits and tailings poses long-term environmental and health risks. More selective and sustainable separation methods are therefore needed for both resource recovery and risk mitigation.
What are the key findings or observations of your doctoral research?
Two adsorbents were developed: bisphosphonate-functionalized thermally carbonized porous silicon, and nanostructured silicon carbide synthesized from barley husk-derived silica and then bisphosphonate-functionalized, which demonstrates that functional adsorbents can be produced from an agricultural by-product. Scandium was recovered from a leach solution of Kiviniemi ore (Rautalampi), where it was present at only 2.9 mg/L together with a large excess of competing metals. After removal of interfering metals by oxidative precipitation, scandium was adsorbed and desorbed, and its purity increased from 0.06% to 16.4%. Uranium was preferentially adsorbed from a mineral processing wastewater, with 98% adsorption efficiency and about 14-fold enrichment, and the barley husk-derived adsorbent remained functional over 20 adsorption cycles. In addition, a field-compatible method was developed for dissolved metals in natural waters, combining solid-phase preconcentration on adsorbent filters with portable X-ray fluorescence (pXRF), with detection limits of 12–30 µg/L. The results for drill hole and groundwater samples were compared with ICP-MS, and the method is presented as a semi-quantitative screening tool.
How can the results of your doctoral research be utilised in practice?
The adsorbents can be applied to the recovery and purification of scandium and to the concentration of uranium from process solutions and mining wastewaters, which facilitates their handling and disposal. The filter-based pXRF method enables rapid multi-element screening of drill hole waters and groundwater directly in the field, supporting mineral exploration and environmental monitoring, while laboratory analysis remains necessary for confirmation.
What are the key research methods and materials used in your doctoral research?
The adsorbents were prepared by thermal carbonization of mesoporous silicon, or by magnesiothermic reduction of barley husk-derived silica, followed by bisphosphonate functionalization. Their adsorption and desorption performance was evaluated in flow-through setup, including adsorption efficiency, selectivity and reusability, using a sulfuric acid leach solution and a uranium-bearing wastewater from a bench-scale mineral processing experiment. For on-site analysis, adsorbent filters were used for preconcentration of metals from water samples, followed by pXRF measurement, and the results were compared with ICP-MS analysis.
Is there something else about your doctoral dissertation you would like to share in the press release?
The thesis is based on four open access articles (Papers I–IV) and was carried out at the Department of Technical Physics, University of Eastern Finland.
The doctoral dissertation of Arezoo Rahmani, MSc, entitled Utilization of mesoporous silicon and silicon carbide for adsorption of dissolved trace metals will be examined at the Faculty of Science, Forestry and Technology, Kuopio campus and online. The opponent will be Adjunct Professor, Docent Risto Koivula, University of Helsinki, and the custos will be Dr Joakim Riikonen, 3AWater Oy. Language of the public defence is English.
For further information, please contact:
Arezoo Rahmani, [email protected], tel. +358 457 834 2466
