**5. Conclusions**

The applied analysis methods enabled the characterization of the present material structures of the investigated slag samples. Through the synergetic e ffect of the two imaging techniques (SEM-based image analysis and X-ray CT), it was possible to identify potential valuable phases and assess the recyclability of these contents. The application of these imaging techniques improves the understanding of the size, shape, and association of the present phases. The Cu-metal contents within the slag samples represent the main valuable component. For a sustainable recycling of these contents, the slag structure has to be optimized and adjusted to the requirements of following processes with the help of various process parameters (e.g., cooling rate). The detailed characterization of the slag structure by imaging processes in combination with fluid flow modeling approaches via computational fluid dynamics represents the basis for an adjusted process optimization and further improvement of recyclability. The main conclusions from the present study in short are as follows:


**Author Contributions:** M.B. conceptualized the paper. N.B. was responsible for the metallurgical tests. T.H. was responsible for sample analysis with a mineral liberation analyzer (MLA) including quality control, data processing, and data evaluation. T.L. was responsible for sample analysis with X-ray computed tomography (XCT) including quality control, data processing, and data evaluation. M.B. and T.L. were responsible for the grinding tests of the material. M.B., N.B., T.L., and T.H. analyzed, interpreted, and collated all results. M.A.R., B.F., and U.A.P. interpreted the results, supervised the work, and supported the preparation of the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors would like to thank the German Research Foundation (DFG) for funding of the X-ray microscope (Zeiss Xradia 510 Versa) INST 267/129-1.

**Conflicts of Interest:** The authors declare no conflicts of interest.
