Extraction and characterisation of cellulose from Merbau (Intsia bijuga)

Extractions of natural cellulosic material from Merbau (Intsia bijuga) were prepared at atmospheric pressure. The samples of celluloses produced were named as untreated material (RAW), post delignification cellulose (PDC), acid-bleached cellulose (ACBC), alkali-bleached cellulose (ALBC) and alkali-treated cellulose (ATC). Untreated material (RAW) is a sample which did not undergoes any chemical treatment. Dried wood samples were delignified in acetic acid/hydrogen peroxide media with addition of 5% sulfuric acid (H2SO4). The product produced of this stage was named as post delignification cellulose (PDC). The delignified cellulose was divided into two parts. It was then bleached separately in acid and alkali media. The produced samples were assigned as acid-bleached cellulose (ACBC) and alkali-bleached cellulose (ALBC) respectively. Finally, the alkali bleached cellulose was treated with 17.5% sodium hydroxide (NaOH), this produced cellulose was named as alkali-treated cellulose (ATC). The spectroscopic characterizations of celluloses samples show that untreated material (RAW), post delignification cellulose (PDC), acid-bleached cellulose (ACBC), alkali-bleached cellulose (ALBC) have native cellulose (cellulose I) structure dominated by monoclinic (Iβ) phase with z < 1. However, the alkali-treated cellulose (ATC) has totally changed the cellulose structure I to cellulose structure II. In XRD studies, in was found that crystallinity index was higher in acid-bleached cellulose (ACBC) (82.4%) followed by alkali-bleached cellulose (ALBC) (78.8%), alkali-treated cellulose (ATC) (77.9%), post delignification cellulose (PDC) (76.1%) and untreated material (RAW) (57.2%). The highest crystallinity (ACBC) give the smaller average of crystallite size (1.5368 nm) followed by ALBC = 2.0491 nm, ATC = 3.7755 nm, PDC = 8.1934 nm, and RAW = 9.6052 nm. In FTIR analysis also supported the results from the XRD analysis which indicated that RAW, PDC, ACBC and ALBC samples are cellulose I with the visible peak appeared in all sample at 1317 cm-1 and ATC is cellulose II with the existence of peak at 1315 cm-1. The unique sets of characteristic of cellulose will accelerate fundamental and applied research and development of cellulose material for a number of industrial applications.