*2.2. Preparation of Treated OPEFB Cellulose from Raw OPEFB*

The chemical isolation processes of the OPEFB were in accordance with the one reported by Zailuddin et al. [15]. The OPEFB was treated with 4% of NaOH solution at a temperature of 80 ◦C with constant stirring for one hour. The treated filler was washed with distilled water and filtered several times to ensure the removal of alkaline. This process was repeated four times to totally remove the hemicellulose. After that, the treated OPEFB fiber underwent bleaching treatment using dilute sodium chlorite (NaClO2) solution at a temperature of 80 ◦C under stirring conditions for 1 h. The treated fiber was washed with distilled water and filtered for several times to ensure the removal of NaClO2. These bleaching and washing procedures were repeated three times to ensure the removal of lignin and hemicellulose. The resultant cellulose is called treated OPEFB cellulose.
