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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/).
The digital pictures of (a) cut-up and used paper cups (UPCs), (b) used paper cups soaked in deionized water, (c) the inner thin PE film and the cellulose paper board, and (d) used paper pulp board after shredding (p-UPCs).