A mini review on lignin: Structures, preparations, and applications
L.V. Thuan, T.T.K. Ngan, T.N. Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 81-86
81
02(45) (2021) 81-86
A mini review on lignin: Structures, preparations, and applications
Tổng quan về lignin: Cấu trúc, phương pháp tổng hợp và ứng dụng
Le Van Thuana,b, Tran Thi Kieu Nganb, Tran Nguyen Tiena,b*
Lê Văn Thuậna,b, Trần Thị Kiều Ngânb, Trần Nguyên Tiếna,b*
aCenter for Advanced Chemistry, Institute of Research and Development, Duy Tan University, Da Nang City, 550000,
Vietnam
aTrung tâm Hóa học Tiên tiến, Viện Nghiên cứu và Phát triển Công nghệ Cao, Đại học Duy Tân, Đà Nẵng, Việt Nam
bThe Faculty of Environmental and Chemical Engineering, Duy Tan University, Da Nang City, 550000, Vietnam
bKhoa Môi trường và Công nghệ Hóa, Đại học Duy Tân, Đà Nẵng, Việt Nam
(Ngày nhận bài: 03/03/2021, ngày phản biện xong: 09/03/2021, ngày chấp nhận đăng: 05/03/2021)
Abstract
Lignin is the second most abundant natural renewable biopolymer after cellulose on the earth. It is commonly generated
as a by-product from the paper and ethanol industry. The complexity and richness of its functional groups make lignin
attractive for converting into a variety of high-value products such as syngas, carbon fiber, phenolic resin, various
oxidized products, and multifunctional hydro-carbons. This work intends to provide a comprehensive overview of
structures and different types of lignin, as well as the recent progress in its preparation techniques. Besides, the
extensive range of applications and opportunities of lignin were also discussed in detail.
Keywords: Lignin, lignocellulosic biomass, extraction methods; lignin applications.
Tóm tắt
Lignin là polymer tự nhiên phong phú thứ hai trên thế giới, sau cellulose. Nó thường được tạo ra từ sản phẩm phụ của
các ngành công nghiệp sản xuất giấy và ethanol. Với sự phức tạp và đa dạng của các nhóm chức trong cấu trúc, lignin
trở nên hấp dẫn để được chuyển đổi thành nhiều loại sản phẩm có giá trị cao như khí tổng hợp, sợi carbon, nhựa
phenolic, các sản phẩm oxy hóa và hydro-cacbon đa chức năng. Mục đích của nghiên cứu này là cung cấp một cái nhìn
tổng quan toàn diện về cấu trúc và các loại lignin khác nhau, cũng như những tiến bộ gần đây trong kỹ thuật thu nhận
lignin. Bên cạnh đó, những ứng dụng tiềm năng, định hướng phát triển trong tương lai của lignin cũng được thảo luận
chi tiết.
Từ khóa: Lignin, sinh khối lignocellulose, phương pháp tách chiết, ứng dụng của lignin
1. Introduction
most abundant natural polymer on earth, which
plays an important role in plants, including
providing mechanical supports, transporting
water and minerals, and protecting plants or
The lignin (lignum) is a component of
lignocellulose which consists also of cellulose
and hemicellulose. This material is the second
* Corresponding Author: Tran Nguyen Tien; Center for Advanced Chemistry, Institute of Research and Development,
Duy Tan University, Da Nang City, 550000, Vietnam; The Faculty of Environmental and Chemical Engineering, Duy
Tan University, Da Nang City, 550000, Vietnam
Email: trannguyentien@duytan.edu.vn
L.V. Thuan, T.T.K. Ngan, T.N. Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 81-86
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wood from chemical or microbial attacks [1]..
serious environmental pollution and resource
waste. Only approximately 2% of the produced
lignin is isolated and effectively used for various
products such as dispersants, adhesives,
surfactants, and fuel [1]. Finding new and high
value-added applications of lignin recovered from
pulping waste liquor is imperative, which has both
economic and environmental benefit. Currently,
increasing research focuses on developing
different approaches to lignin extraction and
converting it into value-added products.
Traditionally, lignin is considered as low-value
waste product. However, it has been studied
that lignin can be used to make high-value
products such as syngas, carbon fiber, phenolic
compounds, and multifunctional hydro-carbons
[2]. In addition, due to its diverse reaction sites,
high carbon content and low content of oxygen,
lignin can become a potential sustainable
alternative source of energy and chemicals [3].
The molecular structure of lignin is highly
dependent on the resources and extraction
processes. Different types of lignin contain
different functional groups and show different
molecular weight and elemental composition.
Therefore, the structure of lignin is extremely
complicated and difficult to determine.
However, it is generally accepted that lignin is
three- dimensional macromolecule formed by
the coupling of three phenylpropane units
(empirical formula of C31H34O11): guaiacyl,
syringyl, and p-hydroxyphenyl alcohol, which
are formed through Shikimate and Cinnamate
pathways [4].
In this review, we provide a comprehensive
overview of the structures, preparation methods
of lignin, and their applications in different
commercial fields. In addition, the challenges,
and opportunities of lignin applications were
discussed in this study.
2. Structures of lignin
Lignin is a complex, amorphous, branched
polyphenolic macromolecule with aromatic
polymeric structure [5]. The structure of lignin
varies based on the extraction process, and the
presence of various functional groups. Lignin
exhibits a high recalcitrance to chemical and
biochemical depolymerization due to the
existence of phenylpropanoid polymers, ether
linkages (β–O–4) and a range of functional
groups namely methoxy, aliphatic and aromatic
hydroxy, benzyl alcohol, ether and non–cyclic
benzyl ether and carbonyls [6]. Lignin has
different functional groups such as: hydroxyl,
methoxyl, carbonyl, and carboxyl, etc. Lignin
has three basic types of monomers; coniferyl
alcohol, sinapyl alcohol, and p-coumaryl
alcohol, also known as monolignols (Figure 1).
Peroxidase and laccase enzymes in the plant
can cause the dehydrogenation of phenolic OH
groups and generate intermediate free radicals
from these lignin precursors [7]. The exact
structure of lignin in its native form in plants is
still unclear, as studies have concluded that the
structure is modified during its isolation and
Lignin can be obtained from a variety of
natural sources, including woody biomass,
agricultural residues, and energy crops.
Lignocellulosic biomass is primarily comprised
of cellulose (38–50%), hemicellulose (23–32%)
and lignin (12–25%) components. The biomass
reserves on the earth have been estimated to be
approximately 1.85–2.4×1012 tons and about
20% of this amount of biomass is lignin.
Besides the natural abundance, lignin is also
present as a major byproduct of the pulp and
paper industry. About 50–70 million tons of
lignin is produced annually at pulp and paper
facilities world-wide. It is estimated by 2030,
this number will increase by 225 million tons
per year as the annual production of lignin [2].
However, the majority is discarded as waste or
burnt to recover heat and electricity, causing
L.V. Thuan, T.T.K. Ngan, T.N. Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 81-86
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differs from that of native lignin. Composition
and amount of lignin varies from species to
species, tree to tree, and even in woods from
different parts of the same tree [5].
Figure 1. Three phenylpropanoid units of lignin structure [8]
3. Preparation methods and types of lignin
inter and intrapolymer bonds of cellulose,
lignin, and hemicellulose. These chemical and
physical processes could be utilized separately.
However, the combination of physical and
chemical methods could remarkably increase
the biomass digestibility, leading to an increase
in the yield of the desired products [9].
Biological pretreatment, like use of fungi,
offers the benefit of low chemical and energy
use, but time taking process. Part of lignin
could be removed from other biomass by
producing digestible cellulose via passing hot
water. But, the process is energy intensive and
not suitable in sustainability aspects [10].
Lignin can be extracted from the
lignocellulosic feedstock by a variety of
methods
involving
chemical,
physical,
physicochemical, and biological treatments
(Figure 2). Depending on the process
employed, the properties of the resulting
isolated lignin differ. The physical pretreatment
involves increments in temperature or pressure
leading to a change in the structure of
lignocellulosic material and facilitating biomass
destruction. Meanwhile, the chemical treatment
involves using organic or inorganic substrates
that cause the structure disruption in the
lignocellulosic materials by interacting with
Figure 2. Different approaches to isolate lignin from lignocellulosic biomass [9]
L.V. Thuan, T.T.K. Ngan, T.N. Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 81-86
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Two major processes popular in the pulp and
emerging cellulosic ethanol sectors, which
offers significant opportunities for lignin
valorization.
paper industries to separate cellulose from
lignin, commonly known as kraft (generating
kraft lignin, sometimes also called alkali lignin)
and sulfite pulping (generating lignosulfonate).
Kraft pulping is the major chemical pulping
process, accounting for 85% of the total lignin
production in the world [11]. The process is
performed at a high pH, and about 90–95% of
the lignin is dissolved into the black liquor.
Kraft lignin is typically precipitated and
recovered from black liquor by the addition of
4. Applications
The efforts in using lignin derivatives in
more sophisticated applications are currently
booming. Lack of toxicity and versatility of
lignin creates several potential industrial
application routes. Stringent regulations, bulk
availability, cost efficiency and growing need
for bio-based and renewable chemicals are
high-value lignin properties [12].
acidifying
agents.
Predominantly,
the
Lignins are being used for the controlled
release of fertilizers, modified for slow-release
fertilizers and herbicides in agriculture, as a
base for different materials application in the
fields of bioplastics, (nano)composites and
nanoparticles [13]. By considering unique
attributes of lignin, such as its binding
properties, products, such as adhesive for wood,
pellets, foundry resins, and epoxy resins could
acidification is carried out by adding either
mineral acid (e.g., sulfuric acid) or carbon
dioxide, followed by filtering, washing, and
drying for the recovery of Kraft lignin. The
sulfite pulping process is conducted between a
pH of 2–12, depending on the cationic
composition of the pulping liquor. The process
uses a heated aqueous solution of a sulphite or
bisulfite salt with counter cations such as
sodium, ammonium, magnesium, or calcium.
Lignosulfonates, isolated lignins from the
sulfite process, contain significant amounts of
sulfur in the form of sulfonate groups. Since
be
produced.
Properties,
such
as
hydrophobicity, antioxidant and thermal
resistance, could also facilitate lignin use in
thermoplastics, composites, and packaging.
Furthermore, as adsorbents in solution,
protective UV-absorbents, dispersants, to
improve the saccharification of lignocelluloses
in the production of biofuels, in electro-chemical
applications and in environmentally friendly
functionalization approach to extend the role of
lignin for future biomass and biofuel
applications [14]. By con- trolling the structure
of lignin, other advanced applications could be
developed, such as nano/microcapsules,
lignosulfonates
are
widely
available,
lignosulfonates were used in a wide range of
applications, such as dispersants, flocculants,
concrete additives, and composites [9].
Organosolv process is one of the most
relevant methods, which is based on the
solubilization of lignin using a mixture of
different organic solvents and water as cooking
liquor. It is also helpful in extracting highly
homogeneous lignin, which enables its further
valorization into value-added products [7].
Since the organosolv process is conducted in
the absence of sulfur, it has recently been
utilized more so than Kraft and sulfite pulping.
Furthermore, the large-scale production of
organosolv lignin is expected from the
nano/microporous
materials,
and
lignin
nanotubes, as a smart DNA delivery without
possessing the cytotoxicity related to carbon
nanotubes [15]. Significant scope for diverse
applications (Figure 3) principally segmented as
power/energy, macromolecules and aromatics.
L.V. Thuan, T.T.K. Ngan, T.N. Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 81-86
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Figure 3. Application fields of lignin [12]
5. Conclusions
based biomaterials, the high value-added
applications of lignin still face some challenges
mainly due to its complicated and changeable
macromolecular structure. We hope that in the
future, the advancement of science and
technology will overcome these obstacles,
thereby further expanding the valuable
applications of lignin.
This review discussed the structures,
extraction methods, and applications of lignin.
Lignin is available in huge amounts as a by-
product of the pulping process, and this will
further increase as the lignocellulosic ethanol
process gets commercialized. Grand amount of
lignin is produced worldwide. However, only a
small amount is applicable for further
applications such as additives, dispersants,
binders, or surfactants. The remaining part is
burn and cause environmental problem. Many
research efforts have been done in developing
processes that could produce valuable lignin-
derived compound. Recently, there have been
more investigations conducted on using lignin
to construct medical materials, electrochemical
energy materials, and 3D printing composites.
In spite of the increasing utilization of lignin-
References
[1] Q. Tang, Y. Qian, D. Yang, X. Qiu, Y. Qin, and M.
Zhou, “Lignin-Based Nanoparticles: A Review on
Their Preparations and Applications,” Polymers
(Basel)., vol. 12, no. 11, p. 2471, Oct. 2020, doi:
10.3390/polym12112471.
[2] D. S. Bajwa, G. Pourhashem, A. H. Ullah, and S. G.
Bajwa, “A concise review of current lignin
production, applications, products and their
environment impact,” Ind. Crops Prod., vol. 139,
no.
February,
p.
111526,
2019,
doi:
10.1016/j.indcrop.2019.111526.
L.V. Thuan, T.T.K. Ngan, T.N. Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 81-86
86
[3] I. Spiridon, “Extraction of lignin and therapeutic
applications of lignin-derived compounds.
review,” Ind. Crops Prod., vol. 154, no. May, 2020,
doi: 10.1016/j.indcrop.2020.112732.
A
review,” Environ. Chem. Lett., vol. 18, no. 3, pp.
771–785, 2020, doi: 10.1007/s10311-020-00981-3.
[10] P. Dey, P. Pal, J. D. Kevin, and D. B. Das,
“Lignocellulosic bioethanol production: prospects of
emerging membrane technologies to improve the
process – a critical review,” Rev. Chem. Eng., vol.
36, no. 3, pp. 333–367, Apr. 2020, doi:
10.1515/revce-2018-0014.
[11] H. Chen, Lignocellulose Biorefinery Engineering:
Principles and Applications. 2015.
[12] N. Mandlekar et al., “An Overview on the Use of
Lignin and Its Derivatives in Fire Retardant
[4] A. Eraghi Kazzaz, Z. Hosseinpour Feizi, and P.
Fatehi, “Grafting strategies for hydroxy groups of
lignin for producing materials,” Green Chem., vol.
21, no. 21, pp. 5714–5752, 2019, doi:
10.1039/C9GC02598G.
[5] L. D. Tolesa and M.-J. Lee, “Strategies for Lignin
Pretreatment, Decomposition and Modification: A
Review,” J. Bahan Alam Terbarukan, vol. 9, no. 1,
pp. 01–20, 2020, doi: 10.15294/jbat.v9i1.23392.
[6] V. K. Ponnusamy et al., “A review on lignin
structure, pretreatments, fermentation reactions and
biorefinery potential,” Bioresour. Technol., vol.
Polymer Systems,” in Lignin
Applications, 2018.
- Trends and
[13] M. Norgren and H. Edlund, “Lignin: Recent
advances and emerging applications,” Curr. Opin.
Colloid Interface Sci., vol. 19, no. 5, pp. 409–416,
2014, doi: 10.1016/j.cocis.2014.08.004.
271,
pp.
462–472,
2019,
doi:
10.1016/j.biortech.2018.09.070.
[7] M. P. Pandey and C. S. Kim, “Lignin
Depolymerization and Conversion: A Review of
Thermochemical Methods,” Chem. Eng. Technol.,
vol. 34, no. 1, pp. 29–41, 2011, doi:
10.1002/ceat.201000270.
[8] E. P. Feofilova and I. S. Mysyakina, “Lignin:
Chemical structure, biodegradation, and practical
application (a review),” Appl. Biochem. Microbiol.,
vol. 52, no. 6, pp. 573–581, 2016, doi:
10.1134/S0003683816060053.
[14] O. Yu and K. H. Kim, “Lignin to materials: A
focused review on recent novel lignin applications,”
Appl. Sci., vol. 10, no. 13, 2020, doi:
10.3390/app10134626.
[15] S. M. R. Wahba, A. S. Darwish, I. H. Shehata, and
S. S. Abd Elhalem, “Sugarcane bagasse lignin, and
silica gel and magneto-silica as drug vehicles for
development of innocuous methotrexate drug
against rheumatoid arthritis disease in albino rats,”
Mater.
Sci.
Eng.
C,
2015,
doi:
[9] A. Eraghi Kazzaz and P. Fatehi, “Technical lignin
and its potential modification routes: A mini-
10.1016/j.msec.2014.12.054.
6 trang
16/04/2022
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