Fractionation of Polyethylene-Coated Kraft Paper Cups Using a Choline Chloride/Oxalic Acid Deep Eutectic Solvent

Polyethylene-coated kraft paper cups have emerged as a more sustainable alternative to conventional plastic packaging; however, they remain difficult to recycle because the polymer barrier hinders separation of the lignocellulosic matrix.^1,2 This study investigated their fractionation into polyethylene, cellulose-rich, and lignin-rich fractions using a deep eutectic solvent (DES) composed of choline chloride and oxalic acid in a 1:1 molar ratio.³ The process comprised DES-assisted disintegration, polyethylene cleaning, and sequential alkaline and neutral washing. Polyethylene was separated from the paper matrix, whereas cellulose and lignin were only partially fractionated. Mass yields of 58.72% cellulose-rich fraction, 5.56% polyethylene, and 3.67% lignin-rich fraction were obtained. DES recovery reached 78.18% in the first cycle, and the recovered solvent was reused across five consecutive treatment cycles. DES losses occurred during handling, while part of the lignin remained dissolved in the solvent.⁴ The method shows potential for recycling and valorizing multilayer paper cups.