**3. Conclusions and Outlook**

Different interesting research subjects focusing on metal production process development and identification are published in the present Special Issue of *Metals*, with endeavors of demonstrating new insights towards future advancement of the field. Although most articles focused on hydrometallurgical operational units and processes, mineral processing procedures were also taken into account by some of them. The articles had specific views regarding waste recycling and valorization, indicating the importance of such topics between decision makers in the mining and metal sectors from economic and environmental point of views.

**Citation:** Azizi, D. Recovery and Recycling of Valuable Metals. *Metals* **2022**, *12*, 91. https://doi.org/ 10.3390/met12010091

Received: 20 December 2021 Accepted: 22 December 2021 Published: 4 January 2022

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**Copyright:** © 2022 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

As Guest Editor of this Special Issue, I am so proud of the outcome, and I have high confidence that such effort can help to make future advancement of the field. I deeply appreciate all the authors for their great efforts and contributions to this Special Issue, especially during the difficult situation caused by the COVID-19 pandemic. Their commitment and fantastic results have resulted in the publication of this Special Issue with great success. Likewise, I would like to take this opportunity to warmly thank the many anonymous reviewers who assisted me in the reviewing process. Without their help, this Special Issue could not have been finalized. Sincere thanks also goes to the Editors of *Metals* for their continuous help, and to the *Metals* Editorial Assistants for their valuable support during the preparation of this Special Issue. In particular, my sincere thanks goes to Mr. Toliver Guo for his great help and support from the beginning until the end of the project.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The author declares no conflict of interest.

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