Addressing Adhesive-Induced Agglomeration: Metal Detachment and Flow Behavior in Recycled Paper Fibres/Cellulose

This study investigates the presence and potential removal of metal particles that exist in fibers obtained from recycled coated and printed paper, which must be removed through deinking and washing to ensure material safety and optimize pulp formulation for use in food and pharmaceutical packaging applications. For the production of modern packaging material, virgin cellulose fibers are combined with recycled fibers. In such a pulp mixture, recycled fibers introduce sticky particles that contain binders, metals, and ink particles. Those sticky particles that induce aggregation of residues and fibers alter pulp rheology and hinder product formation; therefore, their removal during the deinking process is essential to ensure pulp quality, process efficiency, and product viability. Recycled coated paper was pulped and deinked using a conventional washing process, and the metal content in cellulose pulp was evaluated with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Rheological measurements were used to reveal its effect on the flow behavior of pulp. The results indicate that the amount of coating with the presence of adhesives and the electronegativity of metals affects metal separation upon washing and deinking. Metals with lower electronegativity, such as Ag, Ti, Cr, V, and Zn, are easily removed from pulp after washing, improving the rheological behaviour of pulp. This research provides novel insights into optimizing the composition and processing of recycled pulp to enhance sustainability, safety, and quality in sustainable packaging production.