Characterization of black liquors from kraft pulping of first-thinning Scots pine (Pinus sylvestris L.)

Abstract

Formation of hydroxy acids and soluble lignin fragments was investigated during conventional kraft pulping of first-thinning Scots pine (Pinus sylvestris L.) stem wood and its long-fiber outer part and short-fiber inner part. The results indicate that there are characteristic differences in the formation of hydroxy acids in these specific tissues, due to the slightly different contents of cellulose, hemicelluloses, and lignin. Notable are the differences in the formation of xylan-derived acids (2-hydroxybutanoic and xyloisosaccharinic acids) and glucomannan- and cellulose-derived acids (3,4-dideoxy-pentonic and glucoisosaccharinic acids). In contrast, no significant differences were found in the average molecular masses of the dissolved lignins in these black liquors. Finally, the black liquor from the outer part of first-thinning pine was shown to have similar properties as the black liquor from the reference mature wood material.

Development of Method to Determine the Concentration of Alkali-Soluble Lignin using Coomassie Brilliant Blue G-250

“…Quantitative preparation A lignin sample from 3 mL of black liquor from aspen kraft pulping was prepared by acid precipitation according to a previous report (Rautiainen and Alén 2010). The lignin precipitate was washed by 5 mM H2SO4 twice and then with water for three times, respectively.…”

“…Lignin concentration in black liquor was determined using the absorbance at 280 nm according to the method of Rautiainen and Alén (2010).…”

Dissolved and Colloidal Substances (Dcs) and the Charge Demand of Papermaking Process Waters and Suspensions: A Review

“…Spent liquor from the kraft pulping process also contains components that can contribute significantly to cationic demand (Alber et al 1998;Bikova et al 2000;Vu et al 2003;Lisboa et al 2005;Neto et al 1999;Sjöholm et al 2000;Rautiainen and Alén 2010;Jansson and Brännvall 2011;Magaton et al 2011). Even though kraft pulping systems invariably employ devices called brown-stock washers to remove black liquor from the pulp before it arrives at the paper machine system, the washing process is never 100% complete (Hart 2011;Pacheco et al 2006).…”

“…In the case of kraft pulps, though lignin is clearly released from the fiber (Alber et al 1998;Bikova et al 2000;Duarte et al 2003;Rautiainen and Alén 2010), the relationship of such lignin to cationic demand is not well known. Alber et al 1998 found that a totally chlorine free (TCF) bleaching cycle was particularly prone to releasing a lot of lignin into the water phase.…”

“…In addition, studies have shown that released lignin has a great tendency to deposit back onto fibers surfaces, especially if the pH is adjusted from an initial high value (> 10) to a range suitable for papermaking (Alber et al 1998;. As shown by Alén and Vikkula (1989) and Rautiainen and Alén (2010), the most prominent lignin-derived species in black liquor tend to be uncharged or have just one carboxylate group and of very low mass, thus not likely to be important contributors to cationic demand. Detailed structural analyses of dissolved pine and eucalyptus kraft lignins revealed the presence of several carboxylated species (Neto et al 1999;Silvestre et al 2000;Balakshin et al 2003), but there has been no demonstration as to whether such species contribute significantly to cationic demand.…”