**5. Conclusions**

Our studies showed that the incorporation of curcumin into a Zn3Al-LDH structure can be achieved by co-precipitation only if the curcumin is utilized as an ethanolic solution. However, since the co-precipitation is performed with NaOH for pH adjustment, the partial degradation of curcumin could not be avoided. Hence the curcumin release capacity of this sample (PZn3Al-Cr(ET)) under acid pH conditions was by 20% lower than that of the sample prepared by reconstruction RZn3Al-CR(Et) even if the CR-concentration in the fresh samples was not significantly di fferent (9.3 and 11.5 wt. %, respectively). The utilization of alkaline CR-aqueous solution either in the co-precipitation or in the reconstruction method leads to the obtaining of a Zn3Al-LDH structure impurified by ZnO phase where amorphous curcumin and mostly its degradation products were spread flatly on the surface of the inorganic matrix and at the edges of the layers. Taking into account both the results of the characterizations and those of CR-release tests, the preferable method to obtain CR-loaded Zn3Al solids from LDH precursors is the so-called "reconstruction" (since it does not restore the layered LDH structure) with CR-ethanolic solution which does not allow curcumin degradation and ensures also the highest curcumin release from the solid. Therefore, the sample RZn3Al-CR(Et) was the one selected for future antimicrobial activity tests.

**Author Contributions:** Conceptualization, R.Z.; formal analysis, E.B. and R.B.; investigation, O.D.P., A. ¸S. and R.Z.; methodology, O.D.P. and R.Z.; project administration, O.D.P.; visualization, O.D.P.; writing—original draft, A. ¸S. and R.Z.; writing—review and editing, R.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Romanian Ministry of Research and Innovation, CCCDI–UEFISCDI, gran<sup>t</sup> number PN-III-P1-1.2-PCCDI-2017-0387/80PCCDI, within PNCDI III program.

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