A comparison of kraft and kraft-sodium borohydrate brutia pine pulps

Although the reaction of borohydrate with lignin is well-known, limited literature is available regarding the effect of borohydrate on kraft pulp yield and pulp and fiber properties. Therefore, the objective of this study was to study the effects of borohydrate on kraft pulps for Burita pine. First, the optimal cooking conditions for kraft method were determined by varying the active alkali (16% and 18%) and cooking time (60, 90, and 120 min). Then, kraft-sodium borohydrate cooks were done at optimal kraft condition by adding sodium borohydrate to the cooking liquor at the amount of 1%, 2%, and 3% (o.d. wood). The results indicated that adding sodium borohydrate in kraft cook not only increases the pulp yield but also significantly decreases the amount of rejects leading to improved selectivity of the lignin removal and delignification rate. Also, kraft-sodium-borohydrate pulps gave higher pulp viscosity and brightness; however, the strength properties were little lower compared to the kraft method.