Practical trainings, student assistants and theses

Nowadays, the processing of secondary resources is becoming more and more important as there is a high demand of critical raw materials. Especially batteries have high amounts of the critical metals Lithium, Cobalt, Manganese and Nickel as oxides used for cathode materials, as well as graphite, which is typically used as anode material. After comminution, these valuable minerals enrich in the fine fraction < 1 mm, which is called black mass. Studies have shown that froth flotation is a suitable technique to separate graphite from the cathode active materials.
In the course of the thesis, the separation of the cathode active materials, i.e. nickel-manganese-cobalt oxides, and the anode material graphite by flotation is investigated, with special focus on the influence of ultrasonication. Flotation tests will be carried out in an Outotec GTK lab cell. The flotation cell is modified in a way that ultrasound (by means of ultrasonication) can be applied during flotation. Therefore, a suitable reagent regime and process parameters for the flotation of black mass have to be established, followed by the development of suitable parameters for ultrasound treatment for this novel cell. Additionally, ultrasound will be tested in a pre-processing step before flotation as an alternative to attritioning by means of intensive shearing. Black mass from real spent lithium-ion batteries that was formerly processed via electrohydraulic fragmentation will be used for the tests. Analysis of the flotation products is done using thermogravimetric analysis and elemental analysis.

• Field of study in process, mechanical or chemical engineering or similar
• Interest in experimental investigation
• Good written and oral communication skills in English
• Please upload a short letter of motivation stating the period of time and your current grade overview to the applicant portal

• Student thesis
• Start date: by arrangement
• We offer an innovative multidisciplinary international research environment with relevance to key issues in resource technology

The old smelting activities in different regions in Germany generated large quantities of metallurgical and mining residues containing significant concentrations of valuable metals. In recent days, the contaminated surface water from these residues is treated at a wastewater treatment plant by lime precipitation. During the treatment process, dissolved heavy metals such as zinc, iron, copper, nickel, and cadmium are removed by chemical precipitation using calcium hydroxide. The generated sludge has been dewatered using a chamber filter press and is currently disposed of as a landfill. Recent investigations have demonstrated that these wastewater treatment precipitates contain a considerable of valuable metals, and it represents a promising secondary raw material for the recovery of valuable metals, especially zinc.
The objective of the proposed master thesis is to develop a hydrometallurgical process for the selective recovery of zinc from the wastewater treatment precipitates. The work will investigate selective acid leaching conditions to dissolve zinc while minimizing the dissolution of calcium, magnesium and silicon. Subsequently, the pregnant leach solution will be purified through selective precipitation of metals other than zinc by pH adjustment. After purification, high-purity metallic zinc will be recovered by electrowinning. Furthermore, the calcium-rich leaching residue will be characterized thoroughly in order to evaluate its potential for industrial applications. The process wastewater generated during the metal recovery process will be treated with membrane purification studies, contributing towards a circular economy approach.

• Conduct literature research on the recovery of zinc, calcium, and other metals through Hydro metallurgic process as well as water treatment processes through membrane technologies
• Characterization and understanding of the feed materials using various techniques, XRD, FTIR, ICPOES, XRF, etc. before and after the experimental process
• Optimize experimental conditions for high recovery rates for zinc and other valuable metals
• Design and carry out laboratory experiments with selected nanofiltration membranes, focusing on variables like pressure, pH, and concentration
• Prepare a comprehensive thesis report and, if possible, present findings at relevant conferences or workshops

• Bachelor's degree in Chemistry, Chemical Engineering, Environmental Engineering or related field
• Knowledge of hydrometallurgical methods such as Leaching, precipitation, solvent extraction, and membrane technologies
• Knowledge of analytical techniques such as ICP-OES, AAS,MS or similar for metal concentration analysis
• Good oral and written communication skills in English
• Ability to work independently and systematically
• Duration: 6 months
• Start Date: Start in September 2026 is possible
• Funding: Remuneration according to HZDR internal regulations