Applicability of paper deinking process for silver separation and concentration from a paper-based printed electronics prototype.

Paper-based printed electronics (PE), such as printed radio frequency identification (RFID) antennas, are promoted as a sustainable alternative to plastic-based counterparts. However, the end-of-life of PE is not well studied yet. Composed namely of paper (<95%), if not sorted and collected properly, these objects could finish within waste paper streams and be treated by printed paper recycling lines. Within this work, the end-of-life of a silver-based RFID antenna prototype was investigated within a simplified conventional paper recycling deinking line. The objective was to verify whether traditional paper recycling unit operations are suitable to face this new contamination and separate efficiently silver together with other contaminants from the cellulosic fibers. After the PE disintegration within the pulping, efficiency of silver separation by screening, centrifugal cleaning and flotation unit operations was investigated. The influence of paper substrate nature and the applied experimental conditions was assessed. It was namely proved that if correctly optimized the pulping operation can succeed in efficient detachment of silver particles from the fibers. It was then observed that the efficiency of silver separation was impacted by the unit operation applied and followed the order: screening < flotation < centrifugal cleaning. While screening was revealed to be fairly inefficient, flotation efficiency was quite poor (20-40%) and centrifugal cleaning yielded efficiencies ranging from 70 to 99.9% in terms of silver separation. It was thus proved that the current recycling lines might be suitable for PE recycling providing the operation conditions have been optimized for this new kind of waste.