Papermaking potential of Citrus sinensis trimmings using organosolv pulping, chlorine-free bleaching and refining

Abstract

One of the most popular ways to carry out the re-use of wastes from agriculture is the pulping, refining and bleaching of those residues for papermaking. Spain annually produces more than 300 thousand tonnes of Citrus sinensis (orange tree) trimmings, crops being concentrated in the East and the South of the country. Their chemical composition is similar to that of common hardwoods.This work aims to show the suitability of ethanolamine cooking when applied to orange tree trimmings, and to study the effect of peroxide bleaching and refining on some key properties. As for bleaching, we used a design of experiments to discuss the influence of peroxide concentration, time and temperature on the yield, brightness, viscosity, kappa number of pulps and mechanical properties of paper sheets. Refining was studied by analysing the diminishment in freeness and the mechanical properties of paper sheets formed. Results showed that even a mild bleaching process gives out a high relative brightness gain, but a multiple-step process is necessary to achieve enough brightness for printing paper. Mechanical properties of non-refined pulps were found to be too low for paper of any grade, but they were greatly improved by refining.