Fate of Conductive Ink Pigments During Recycling and Landfill Deposition of Paper-Based Printed Electronics
Date of Award
Doctor of Philosophy
Chemical and Paper Engineering
Dr. Andro Mondala
Dr. Jan Pekarovic
Dr. Dan Fleming
Dr. Jorge Rodriquez
Printed electronics, end fate, conductive inks, recycled papermaking, landfill deposition, landfill deposition
Printed electronics (PE) are being developed as an alternative to traditional electronics, due to the more efficient use of materials and lower cost of production. The overall goal of this study was to understand how metallic pigments in conductive inks in PE are partitioned during landfill disposal and paper recycling conditions. The purpose is to assess the potential environmental impacts of PE landfilling in terms of metal leaching and to help develop new strategies for sequestering metallic ink components while paper-based PE are subjected to conventional paper recycling methods. The objective of this research is to study the fate of PE metallic pigments by analyzing how metals partition across different streams in the recycled papermaking system, the potential leaching characteristics of the inks, and the ink film characteristics on paper that will help to show whether or not the metallic pigments can be removed from the paper fibers. Three studies were conducted to address each of these specific objectives In the first study, three conductive inks used to create PE - nickel, silver flake and nanoparticle inks were printed on label paper substrates simulating PE materials, which were then pulped and screened in benchscale experiments. Accepts, rejects, and wastewater streams were collected and analyzed using Atomic Absorption Spectrometry (AAS) to measure the metal concentrations in each stream and create a material balance around the pulping and screening process. Results showed that for the nickel and silver flake inks the metallic pigments partitioned mostly into the “accepts” stream, while for silver nanoparticle inks, the metallic pigments were partitioned mostly to the wastewater stream. The second study involved landfill simulation experiments to evaluate the potential leaching of metal pigments from polymer and paper based PE while subjected to landfilling conditions using EPA methods 1311 (Toxicology Characteristic Leaching Procedure) and Hazardous Waste Test Method - SW 846. Results show that the nickel ink used could potentially form hazardous leachate if landfilled, because it crossed 5 parts per million in the leachate. The silver inks did not cross 5 parts per million threshold named in the Toxicology Characteristic Leaching Procedure (TCLP) test and do not pose a leaching potential in a landfill at the weight fractions tested. The third study involved a qualitative assessment of nickel and silver conductive ink penetration and adsorption/absorption characteristics in paper substrates using scanning electron microscopy (SEM). From these microscopic observations, we can substantiate the findings from the re-pulping and screening test when talking about removing and recovering these pigments from the paper fibers during recycling. Results showed that nickel and silver flake inks do not penetrate the fiber pores and are mostly concentrated in the paper substrate surface, but appear to have become attached or bonded to the fiber surface in some regions. The silver nanoparticle pigments have migrated into the void structure of the sheet, but because they do not appear to become attached or bonded to the fiber surface, re-pulping and screening may readily remove the nanoparticles. Based on these observations, it is likely that nickel and silver flake inks can be removed and recovered more easily than the silver nanoparticle ink. This research shows PE could provide papermakers with an opportunity to innovate their process and potentially create a new revenue stream by recovering metallic pigments. Landfill operators should be aware that metallic pigments could show up at their facility in order to establish the necessary measures for sequestering potentially hazardous materials from leachate streams.
Atkinson, James Edward, "Fate of Conductive Ink Pigments During Recycling and Landfill Deposition of Paper-Based Printed Electronics" (2017). Dissertations. 3144.
Materials Science and Engineering Commons, Wood Science and Pulp, Paper Technology Commons