Changes in accessibility of cellulose during kraft pulping of wood in deuterium oxide

• Published in: Carbohydrate polymers Vol. 101; pp. 792 - 797
• Main Authors: Pönni, Raili, Galvis, Leonardo, Vuorinen, Tapani
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 30.01.2014; Elsevier
• Subjects: Accessibility; Applied sciences; Birch; Cellulose - chemistry; Cellulose and derivatives; Cellulose microfibril; Deuteration; Deuterium oxide; Deuterium Oxide - chemistry; Exact sciences and technology; Hydrogen-Ion Concentration; Infrared spectroscopy; Kraft pulping; Natural polymers; Paper, paperboard, non wovens; Physicochemistry of polymers; Polymer industry, paints, wood; Pulp manufacturing; Sulfates - chemistry; Water retention value; Wood - chemistry; Wood. Paper. Non wovens; Infrared spectroscopy; Birch; Accessibility; Water retention value; Kraft pulping; Cellulose microfibril; Deuteration; Deuterium oxide; Pulping; Cellulose; Paper pulp; Hardwood; Experimental study; Deuteriation; Sodium hydroxide; Medium effect; Deuterium Oxides; Water holding capacity; Sodium sulfide; Molecular accessibility
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2013.10.001

•Cellulose microfibril aggregation occurs during the heat-up period of kraft pulping.•Hemicellulose dissolution promotes cellulose microfibril aggregation.•Increase in kraft cooking alkalinity increases cellulose microfibril aggregation. Fresh birch chips were treated with different concentrations of sodium hydroxide and sodium sulfide in deuterium oxide in typical kraft pulping conditions and the extent of irreversible deuteration of the chips/pulps was followed by Fourier transform infrared (FT-IR) spectroscopy. Water retention values (WRV) of pulps were measured to evaluate accessibility of cellulose. The kraft pulping with deuterium oxide led to significant proton-deuterium exchange that was not reversed when the chips/pulps were washed with water. The deuteration followed a first order dynamics with a maximum obtained in the beginning of delignification stage. Higher dosages of effective alkali resulted in a higher degree of deuteration and lower WRV. An inverse relationship between the extent of deuteration and WRV suggests that both were induced by cellulose microfibril aggregation. Results also indicate that hemicellulose dissolution plays an important role in the induction of cellulose microfibril aggregation, while lignin dissolution has less influence.