Preparation and Characterization of Cellulose from Bamboo Wood and Eucalyptus Sawdust, and Evaluation of the Derivative Sodium Carboxymethyl Celluloses as Suspending Agents
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Date
2024-09
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Addis Ababa University
Abstract
Cellulose has gained a great deal of interest from researchers due to its high demand in paper, food,
cosmetics, textile and pharmaceutical industries. Woody plants and cotton are the major sources
of cellulose and its derivatives such as sodium carboxymethyl cellulose, microcrystalline cellulose,
cellulose acetate and hydroxypropyl cellulose. However, overutilization of these sources has raised
huge economic and environmental concerns forcing researchers and stakeholders to look for other
potential substitutes. In Ethiopia, bamboo wood (BW) and eucalyptus sawdust (ES) are abundant
and can be exploited as potential raw materials for cellulose extraction.
The aim of this study was therefore to extract and characterize native cellulose from BW and ES,
and evaluate the derivatives BW-SCMC and ES-SCMC as suspending agents in suspension
formulations. In this study, cellulose fibers were extracted from the aforementioned sources by
steam explosion method. SCMC was obtained from the extracted cellulose fibers, following
alkalinization and etherification steps using sodium hydroxide and monochloroacetic acid (MCA)
in isopropyl alcohol. Central composite design (CCD) with three coded values was employed. The
amount of MCA, duration of etherification and temperature of etherification were selected as
independent variables; and the degree of substitution (DS) was taken as the response variable
during optimization. By comparing several statistical parameters, two quadratic models were
selected as best fit for DS of BW-SCMC and ES-SCMC. The adequacy of the models as per
ANOVA revealed that both models have significant values indicating the terms in the models have
significant effect (P < 0.0001) on the response.
The cellulose yields on dry weight basis were found to be 48.06% ± 1.02 (BWC) and 44.21% ±
1.14 (ESC). The isolated BWC and ESC have DP of 524.64±0.89 and 701.51±1.16, and molecular
weight of 84,990.87 g/mol and 113,644.62 g/mol, respectively. The crystallinity index of BWC
and ESC was found to be 74.3% and 79.2%, respectively. Furthermore, Fourier transform infrared
(FTIR) spectra’s indicated removal of non-cellulosic constituents.
An optimum DS of 1.432 was found for BW-SCMC at the level of 1.47g of MCA, 188 min of
etherification process and 48.5oC of etherification temperature with a desirability of 1.000.
Whereas optimum DS of 1.141 was found for ES-SCMC at the level of 1.17g of MCA, 166.3 min
of etherification process and 53.65oC of etherification temperature with a desirability of 0.967.
III | P a g e
Analysis of the triplicates synthesized BW-SCMC and ES-SCMC at the optimum conditions
confirmed the effectiveness of optimization. The experimental values were found to be in close
agreement with the predicted values confirming the predictability and validity of the model.
The optimized SCMC had a yield of 1.58 g/g (BW-SCMC) and 1.31g/g (ES-SCMC) of BWC and
ESC, respectively. The appearance of new bands around 1600 and 1412 cm‐1 in the FTIR spectra
of SCMC samples showed efficient attachment of carboxymethyl groups to the cellulose chains.
The XRD analyses of the SCMC samples showed a significant reduction in crystallinity with the
main diffraction signal at 2θ = 20°. From the TGA, the Tmax of the synthesized SCMC ranged
from 285‐296 °C. The BW-SCMC (DS: 1.432) exhibited better heat stability than ES-SCMC
(1.141) and C-SCMC (DS: 0.87).
The prepared BW-SCMC and ES-SCMC were evaluated as suspending agents in paracetamol
suspensions in comparison with commercial SCMC (C-SCMC) at a concentration range of 1–4%
(w/v). The resulting suspensions were evaluated for their sedimentation volume (%), degree of
flocculation, viscosity, redispersibility and dissolution rate, and real time stability studies were
performed for 3 months. The apparent viscosities of the formulations prepared with BW-SCMC
and ES-SCMC were higher than those of C-SCMC. The flowability of the suspensions, at all
concentration levels of the suspending agents were in the order of C-SCMC > ES-SCMC > BW-
SCMC. At 1% and 2 % concentrations, BW-SCMC and ES-SCMC provided higher sedimentation
volume than C-SCMC. At 3% and 4%, all exhibited comparable sedimentation volume (100%).
Potassium dihydrogen phosphate (KH2PO4) employed as a flocculating agent increased the
sedimentation volume of all suspension formulations at 1% and 2%. The redispersibility of BW-
SCMC and ES-SCMC were better than C-SCMC at lower concentration. All prepared suspensions
showed a release of greater than 85% of drug within 1 h. The results of stability studies showed
that all suspension formulations were stable. From the findings, it can be concluded that BW-
SCMC and ES-SCMC could be used as alternative suspending agents.
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Keywords
Bamboo wood, Eucalyptus sawdust, Cellulose, Sodium carboxymethyl cellulose, Suspending agent, Steam explosion