Assessment of Board-Making Parameters of Pulps Prepared by Soda Cooking, Fungal Delignification, or Enzymatic Treatment of Wheat-Straw

The comparative assessment of boardmaking parameters has been carried out with soda and biological refined pulps prepared from wheat straw. When compared with non-treated straw, biological pretreatments (solid-state fermentation with Pleurotus eryngii and Phlebia radiata, or enzyme treatments) save energy during mechanical refining. Nevertheless, except for mild cooking conditions (0.1 M NaOH, 40 °C) energy consumption is higher in biomechanical than in semichemical pulps. The factorial assessment of factors related to the quality of soda pulps, revealed similar effects of NaOH concentration (C) and temperature (T) which were much higher than the effect of reaction time (t). The most significant interaction was CxT and, in some cases, Cxt. Simple and multiple linear regression models suggested that the intensity of the 1720 cm-1 infrared band may be used in discriminating between chemical and biological pulps. Standard soda pulps still contain about 25% wt alkali-soluble material, suggesting that additional washing at room temperature could substantially improve the delignification performance. The extent of the exothermic peak ca. 360 °C (thermogravimetric analyses) paralleled pulp quality whereas that at about 325 °C (breakdown of loosely attached O-containing groups) decreased with the intensity of soda cooking. The extent of the high temperature peaks (up to 500 °C) seems to be related to lignin, which had a reduced value as an indicator of pulp quality.