Comparison of Soda, Kraft, and DES Pulp Properties of European Black Poplar

Kraft pulping as the dominant pulping method contributes to several environmental problems. To overcome these problems, environmentally friendly pulping methods have been investigated. In the last years, deep eutectic solvents (DESs) have been identified as up-and-coming reagents in the lignocellulosic material processing and they are characterized as environmentally friendly. This study investigated the use of DES in pulp production from European black poplar chips. The DES mixture was prepared from choline chloride (ChCl) and ethylene glycol (EG). In addition, traditional soda and kraft pulping methods were carried out with poplar chips for comparison with the DES pulps. It was found that pulp production from poplar chips using DES was comparable to the soda and kraft pulps in terms of pulp yield, pulp viscosity, and opacity. The DES pulps easily reached target pulp freeness levels. However, the strength properties and brightness of the DES pulps were lower than those of the soda and kraft pulps. The strength properties of DES pulps can be improved with paper strength enhancers such as starch and micro or nanofibrillated cellulose. Also, the utilization of DES in pulp production may have an important role in cleaner production and it represents a greener alternative to traditional pulp production methods. Celuloza se najčešće proizvodi kraft postupkom koji je povezan s nekoliko ekoloških problema. Kako bi se ti problemi prevladali, istražene su ekološki prihvatljive metode proizvodnje celuloze. Posljednjih su godina duboka eutektička otapala (DES) prepoznata kao ekološki prihvatljivi reagensi za preradu lignoceluloznih materijala u budućnosti. U ovom je radu istraživana uporaba DES-a u proizvodnji celuloze od sječke drva europske crne topole. DES smjesa pripremljena je od kolin-klorida (ChCl) i etilen-glikola (EG). Osim toga, tradicionalnim je natronskim i kraft postupkom proizvedena celuloza od sječke drva topole radi usporedbe s celulozom proizvedenom s dodatkom DES smjese. Utvrđeno je da je celuloza proizvedena od sječke drva topole uz upotrebu DES-a u smislu prinosa, viskoznosti i neprozirnosti usporediva s celulozom dobivenom natronskim i kraft postupkom. Celuloza proizvedena uz dodatak DES-a lako je dosegnula ciljani stupanj slobode celuloze. Međutim, svojstva čvrstoće i svjetlina celuloze proizvedene uz dodatak DES-a bili su lošiji od tih svojstava natronske i kraft celuloze. Svojstva čvrstoće DES celuloze mogu se poboljšati pojačivačima čvrstoće