Recovery, characteristics and potential use as linerboard coatings material of lignin from oil palm empty fruit bunches' black liquor

This paper is a report of a project to recover and evaluate the lignin obtained from the black liquor of oil palm empty fruit bunches (OPEFBs). The potential use of the recovered lignin for the production of linerboard coating was also studied. The influence of the pHs (5, 4, 3, and 2) of the black liquor on the recovery mass and the characteristics of the lignin from the OPEFBs were studied. The recovery mass of lignin increased with the decreasing the pH of the black liquor. The results demonstrated that altering the pH did not affect the chemical components of the recovered lignin. However, the structure of the recovered lignin progressively degraded in the form of Hibbert's ketone when a lower pH was applied. Thus, to avoid the over degradation of lignin from drastic acidification, the lignin of the OPEFBs recovered at pH-5 was selected for the preparation of linerboard coating. The OPEFB's lignin-based coatings were prepared by mixing 3% oxidized starch solution at various levels of lignin (1, 3, 5, 7 and 9% w/w of the solution). The OPEFB's lignin-based coating had a viscosity approximately the same as commercial wax. The water absorption of the coated linerboards decreased (p < 0.05) when the lignin content increased from 1 to 5%. However, an inverse trend was observed when lignin content was higher than 5%. The mechanical properties of the linerboards coated with OPEFB's lignin-based coatings were similar to those with a commercial wax coating. This study suggests that lignin-based coatings obtained from OPEFBs can be used as an alternative agent for the production of linerboard coating.