Citation: Klemenˇ ci´ c, M.; Bolanˇ ca Mirkovi´ c, I.; Bolf, N.; Marki´ c, M. Determination of the Mass Fractions of the Heavy Metals in the Recycled Cellulose Pulp. Polymers 2024, 16, 934. https://doi.org/10.3390/ polym16070934 Academic Editors: Marta Fernandes and Jorge Padrão Received: 1 March 2024 Revised: 21 March 2024 Accepted: 24 March 2024 Published: 29 March 2024 Copyright: © 2024 by the authors. 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/). polymers Article Determination of the Mass Fractions of the Heavy Metals in the Recycled Cellulose Pulp Mia Klemenˇ ci´ c 1, *, Ivana Bolanˇ ca Mirkovi´ c 1 , Nenad Bolf 2 and Marinko Marki´ c 2 1 Faculty of Graphic Arts, University of Zagreb, 10 000 Zagreb, Croatia; ivana.bolanca.mirkovic@grf.unizg.hr 2 Faculty of Chemical Engineering and Technology, University of Zagreb, 10 000 Zagreb, Croatia; marinko.markic@fkit.unizg.hr (M.M.) * Correspondence: klemencic.mia@gmail.com Abstract: In the process of paper recycling, certain amounts of metals can be found in the cellulose suspension, the source of which is mainly printing inks. The paper industry often uses different technologies to reduce heavy metal emissions. The recycling of laminated packaging contributes to the formation of sticky particles, which affects the concentration of heavy metals. This study aimed to determine the mass fraction of metals in the different phases of the deinking process to optimize the cellulose pulp’s quality and design healthy correct packaging products. In this research, the deinking flotation of laminated and non-laminated samples was carried out by the Ingede 11 method. As a result of the study, the mass fractions of metals in cellulose pulp were divided into four groups according to the mass fraction’s increasing value and the metals’ increasing electronegativity. The quantities of metals were analyzed using Inductively Coupled Mass Spectrometry (ICP-MS). The separation of metals from cellulose pulp is influenced by the presence of adhesives and the electronegativity of the metal. The results of the study show that the recycling process removes certain heavy metals very well, which indicates the good recycling potential of pharmaceutical cardboard samples. Keywords: recycling paper; pharmaceutical packaging; flotation deinking; heavy metals; IPC-MS 1. Introduction Cellulose is the most abundant natural polymer on Earth [1]. It is a flexible, renewable, and biodegradable raw material, making it widely used in the packaging industry [2–4]. All plant matter has, on average, a cellulose concentration of roughly 33% [5]. Cellulose is a complex carbohydrate found in plant cell walls, providing rigidity and strength to plant cells. It is made up of repeating units of β-D-glucose linked together by β-1,4-glycosidic bonds. It has a linear semicrystalline structure containing a long chain of repeated D- glucose units linked by a β-1,4 glycosidic bond between D-glucopyranosyl units. The key process of cellulose pulp production is the extraction of cellulose in its fibrous form [6,7]. Most of the paper today is prepared from the cellulose pulp of coniferous trees (spruce and pines), whose three main components are cellulose, hemicellulose, and lignin [8]. Cellulose has fiber-forming properties due to the presence of straight, long, and parallel chains. It provides strength and stability to the paper structure. Hemicelluloses are a group of polysaccharides that can influence characteristics such as paper porosity, absorbency, and printability. Lignin is a complex polymer that is a natural binding component of wood cells that helps hold cellulose chains together [9]. Paper is a flat material made of plant cellulosic fibers, usually mechanical and/or chemical wood pulp, but also recycled fibers, non-fibrous components (minerals and additives), and water [10]. Different paper products will have different compositions [11,12]. Packaging is known as a protective outside layer, which tends to protect its contents from any physical, chemical, or biological hazards. Food and drugs are subject to the same Polymers 2024, 16, 934. https://doi.org/10.3390/polym16070934 https://www.mdpi.com/journal/polymers