Enhancement of high xylan recovery from black liquor of alkaline pretreated oil palm frond and its physicochemical properties

Abstract

The xylan recovered from alkaline black liquor (ABL) of oil palm frond (OPF) has the potential to be converted into value-added products that hold promise, especially for the pharmaceutical industry. This research highlights the maximum xylan relative recovery extracted from ABL by varying the extraction parameters such as the concentration of sodium hydroxide (NaOH) (2 to 10%) (w/v), reaction temperature (60 to 140 °C), and extraction time (30 to 150 min), followed by a 2-stage precipitation method. 6 M of hydrochloric acid (HCl) was used in the first stage to separate the lignin sub-fraction (LF) from the ABL, and 95% ethanol was used in the second stage to obtain xylan sub-fraction (XF). The optimal condition of 6% NaOH (w/v), 100 °C, and 60 min was able to recover 84% of xylan, with low contamination of lignin (7.7%) and glucan (0.3%) in XF, while higher contamination of lignin (19.3%) and glucan (10.9%) with lower amount of xylan (8.8%) were found in LF. The amount of lignin and glucan in LF through the first precipitation was higher than in XF from the second precipitation, leaving remaining fraction of XF mainly composed of xylan. In sum, the developed process reduced the alkali consumption while retaining a high xylan recovery under mild process conditions.