CHARACTERIZATION OF LIGNIN FROM EFB SODA BLACK LIQUOR AND AN EVALUATION OF ITS POTENTIALS IN THE DRILLING INDUSTRY
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Date
2006-06
Authors
CHUAH, SENG BAN
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Abstract
The enormous amount of palm oil empty fruit bunch (EFB) generated from palm
oil mills potentially recycled in the pulping industry will produce the black liquor.
The EFB soda lignin was successfully precipitated from the black liquor using
hydrochloric acid. The highest yield obtained was precipitated at pH 2 followed by pH 4
and finally pH 6. The alkaline nitrobenzene analysis indicated that EFB soda lignin
contains the guaiacyl and syringyl unit with low composition of p-hydroxyphenyl unit
which are in the same category as the cereal or grass type lignin. The ultra-violet
spectroscopy analysis showed higher absorbance of soda lignin precipitated at pH 6 as
compared to pH 4 and pH 2 which was suspected that lower pH value may have coprecipitated
the non-lignin materials. Through gel permeation chromatography (GPC)
analysis, the weight-average of sod~ lignin precipitated at pH 2 was determined as Mw
::::: 7083. On the other hand, the weight-average of soda lignin precipitated at pH 4 and
pH 6 were not measured due to the solubility problem.
This study revealed that the mineral acid had an effect on the yield recovery at
pH 2 only, where the phosphoric acid precipitated the highest yield of 1.06 g compared
to other mineral acids which were in between 0.88-0.96 g. The Alkaline nitrobenzene
oxidation analysis indicated that the soda lignin precipitated by hydrochloric acid
contained a higher composition of gauaicyl units which was dissimilated to other
mineral acids. Nevertheless, the infrared spectroscopy analysis indicated that the soda
lignin precipitated by sulfuric acid and nitric acid demonstrated an additional strong
band at 620 cm·1 (C-S stretching) and 1385 cm·1 (N03' stretching) respectively. The
ultra-violet spectroscopy analysis showed that the lignin precipitated by four types of
mineral acids had different absorbencies intensity implying that mineral acid had an
effect on the purity of lignin. The GPC analysis indicated that the weight-average of
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soda lignin precipitated by phosphoric acid (Mw == 14658) and nitric acid (Mw =::: 11180)
were relatively higher compared to soda lignin precipitated by sulfuric acid (Mw == 6421)
and hydrochloric acid (Mw == 7083). It was suspected to be due to the interaction of the
anion from mineral acid with the lignin compound.
This study also revealed that only trace amount of lignin precipitated at fraction
pH 6 from the black liquor stored after 60 days and 90 days at room temperature were
suspected to be due to the lignin compound undergone mechanism changes in the
black liquor which need more protons (lower pH value) to be precipitated. However, no
significant trend was found for the progressive changes of soda lignin properties with
respect to the storage periods and storage temperature through the alkaline
nitrobenzene analysis, GPC analysis as well as the ultra-violet visible spectroscopy
analysis.
Soda lignin can be used as a deflocculant for water based mud drilling. The
optimal dosage of soda lignin was in between 0.3 to 0.5 % w/w. Alkalinity evaluation
indicated that soda lignin had better' thinning ability at the higher pH of 12. From the
salinity evaluation, it was found that soda lignin and commercial lignosulfonate were
not suitable to be used in the presence of sodium chloride (0.7 and 1.2 % w/w) at 150
°C. However, soda lignin demonstrated better salinity tolerance if compared to
commercial lignosulfonate. Finally, the thinning ability of soda lignin could potentially
withstand higher temperature of 190°C but it showed poorer thinning ability compared
to commercial lignosulfonate. Thus, the thinning ability of soda lignin needs to be
improved via further reactions with other chemicals in order to become a novel
environment~lIy friendly thinner.
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Keywords
BLACK LIQUOR , DRILLING INDUSTRY