Abstract:
This research aims to study the synthesis of carboxymethyl cellulose (CMC) from rice husk using high pressure homogenization (HPH) and ultrasonic as pre-treatment to reduce the particle size of cellulose from
rice husk prior to CMC synthesis. The HPH pre-treatment was studied at three pressure levels: 400, 700 and 1000 bar for three cycles. The ultrasonic pre-treatment was studied at three amplitude levels: 20%, 40% and
60% for 30 min. Results showed raw cellulose from rice husk had an average particle size of 174.57 ± 3.30 µm. The cellulose with HPH and ultrasonic as a pre-treatment caused smaller cellulose particle sizes, with values
in the range of 57.68111.03 µm. The cellulose processed by HPH at a pressure of 400 bar had the smallest particle size, in the range of 57.68 ± 0.58 µm. The synthesized CMC from rice husk cellulose showed that the
percentage yield, purity value, and degree of substitution of CMC were between 100.98 and 138.46%, 78.41 and 92.26%, and 0.367 and 0.586%, respectively. The synthesis of CMC from rice husk cellulose showed that
the percentage yield, purity, and degree of substitution were 100.98138.46%, 78.4192.26%, and 0.3670.586%, respectively. The highest percentage yield of the CMC was obtained by pre-treatment with using
ultrasonic at 40% of amplitude, which was 138.46 ± 3.81%. The SEM images revealed a slight roughness on the surface of the CMC sample, while the more uniform surface was found in the commercial CMC. In addition, the
synthesized CMC contained three main elements: carbon (C), oxygen (O), and sodium (Na) were observed by energy dispersive X-ray spectroscopy (EDS). The FTIR spectra confirmed the replacement of the hydroxyl group
by the carboxymethyl group by indicating peaks at wavenumber positions 1590 cm-1 and 1413 cm-1. The FTIR spectra clearly displayed the functional group of CMC. Therefore, rice husk has the potential to produce CMC
using HPH or ultrasonic treatment. Furthermore, this research will be an alternative strategy to add the value to rice husks and reuse it to the food system for future research.