Fractionation by classification as a prerequisite to the purification of old corrugated container material for preparing dissolving grade pulp

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Abstract
The valorization of old corrugated containers (OCC) as a sustainable raw material for dissolving-grade pulp (DGP) production represents a promising avenue for advancing circular economy goals. This study evaluates flat-screening and fiber fractionation by classification as prerequisites to chemical purification for upgrading OCC into high-purity cellulose materials. Flat-screening with agitation (0.010″ slotted screen) effectively removed fines, ash, and water-soluble impurities while retaining a high yield of accepts with minimal impact on fiber morphology and composition of cellulose, hemicellulose, and lignin. Fractionation using a Bauer-McNett Fiber Classifier distinguished OCC into long and short fibers based on coarseness and length and almost entirely removed fines, resulting in compositional differences among fractions. Subsequent chemical purification involved a three-stage process comprising formic acid pulping, alkaline extraction, and alternating bleaching with chlorine dioxide and alkaline peroxide (D0EpD1EpD2). Long fiber fractions exhibited properties comparable to unbleached softwood kraft pulp, whereas short fibers resembled semichemical hardwood pulp, demonstrating the potential for tailored chemical treatments to optimize resource efficiency. Fine particles (~22%) removed during fractionation by classification were found to contain high levels of lignin (22.1%), hemicellulose (14.5%), and ash (12.4%), highlighting their removal as a key factor in tuning the chemical uniformity of the resulting pulp. Mechanical fractionation by classification facilitated a more effective chemical purification process and produced high-purity OCC approaching DGP quality, characterized by reduced impurities, increased cellulose content and brightness, while maintaining high treatment yield and preserving the degree of polymerization. This study demonstrates the potential of screened and classified OCC as a scalable feedstock for high-purity cellulose applications with further refinement. By integrating mechanical fractionation and chemical purification processes, the approach enhances the sustainability and efficiency of dissolving pulp production from pulp blends like OCC, offering a viable pathway for the valorization of recovered paper products into high-value applications.
Funding Information
  • U.S. Department of Agriculture (Accession Number: 1026690, Accession Number: 1026690, Accession Number: 1026690)

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