1. Chemical &
Biological
Engineering.
Extraction of lignin from waste paper using green solvents.
Student Name
Bethany Lilly
Supervisor
Dr Annette Taylor
Results
The key results and findings were that both solvents could
extract lignin by dissolving it from waste paper. Fig. 4 and 5
illustrate that magazine gives the highest maximum
absorbance and therefore estimated concentration for both
solvents. The error bars with standard deviation show the
range of the data.
From fig. 5 and 6 it can be predicted that for a given amount
of paper LC1.25:1 is able to dissolve a greater amount of
lignin that UC2:1.
It was observed that cellulose did not dissolve in the solvents
and there was no absorption when the concentration of
cellulose was increased.
The maximum amount of lignin that can be dissolved in both
solvents is given in table 1.
Discussion and Conclusions
• This study shows that the DESs can selectively extract lignin [11] from
lignocellulosic feedstocks of waste paper, fig 5 and 6. Conclusions can be
drawn from the comparisons between the different types of waste paper, such
as magazine giving the greatest absorbance.
• Further investigation in the future would be needed to calculate the actual
amounts of lignin dissolved as it was not possible to quantify the specific
amount of potential lignin present and therefore the concentrations in fig. 6
were an estimate using the trend line equation in fig. 4. Lignin has many
fractions [12] and only one type was investigated here, alkali lignin. Therefore a
better understanding of the other types of lignin that are present in paper is
required as well as detailed analysis of the compositions of paper as other
substances or impurities may have been responsible for part of the absorption
given [4].
• In situ processing and dissolving lignin was able to be carried out but currently
preliminary experiments to recover the solvent were not possible.
• In these experiments the amounts of lignin extracted were small and additional
investigations would be required to make DESs an efficient pretreatment
method. However, it is clear that DESs can dissolve lignin and therefore, waste
paper should be considered as a potential feedstock but further research and
development is required for it to become economical.
Introduction
Second generation biofuels, made from lignocellulosic biomass, are one of the most promising
options available as an alternative source of energy for transport [1,2]. Waste paper was chosen as a
potential feedstock as there has been less research into this type of material [3]; it can be
economically competitive and has the potential for high conversion of common products to
bioethanol [4]. The types of waste paper examined and their lignin contents were plain paper (6%),
lined paper, newspaper (17%), cardboard (15%) and magazine (14%) [4]. The amount of cellulose
generally found in waste paper ranges from 40-60% [5].
The one major issue with the utilisation of lignocellulosic biomass on a commercial scale is the
high energy and expensive pretreatment stage [6]. This is essential for delignification of
lignocellulosic biomass as the lignin component reduces the availability of cellulose for effective
downstream processes to produce high yields of bioethanol [7].
Recently, a more sustainable technique using deep eutectic solvents (DESs) has been developed,
which consists of two materials, a salt + a hydrogen bond donor (HBD), that, when mixed together
at a specific ratio as illustrated in fig. 1, form a liquid solvent at a much lower melting point than
that of the two materials individually [8,9]. They can be described as a green solvent, as they
selectively dissolve lignin from lignocellulosic feedstocks [10] and are sustainable, biodegradable,
non-toxic, cheap and require low energy conditions [8].
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 100 200 300 400 500 600 700 800 900 1000
Absorbance
Wavelength (nm)
Figure 3: Absorption spectrum for lignin in LC1.25:1 (above)
and UC2:1 (below).
0
1
2
3
4
5
0 100 200 300 400 500 600 700 800 900 1000
Absorbance
Wavelength (nm)
Figure 1: Diagram illustrating freezing point
depression of a DES at a given ration [9].
Figure 2: Appearance of the two solvents,
UC2:1 (left) and LC1.25:1 (right).
0
0.2
0.4
0.6
0.8
1
1.2
PP LP N C M
Absorbance(O.D)
Paper type
LC1.25:1
UC2:1
Figure 5: Summary graph of the maximum absorbance from all the
paper types for both solvents.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
PP LP N C M
Concentration(mg/ml)
Paper type
LC1.25:1
UC2:1
Figure 6: Summary graph of the maximum estimated concentration
from all the paper types for both solvents.
Aim
To test whether different DESs can dissolve lignin from the
lignocellulosic feedstock of different varieties of waste paper.
y = 6.32x - 0.04
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.02 0.04 0.06 0.08 0.1
Absorbance(O.D)
Concentration (mg/ml)
y = 2.38x + 0.03
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
Absrobance(O.D)
concentration (mg/ml)
Figure 4: Calibration curve of absorbance as a function of
lignin concentration with a trend line equation for both
solvents LC1.25:1 (above), UC2:1 (below).
References
[1] A. Yousuf, 2012, Biodiesel from lignocellulosic biomass – prospects and challenges, Waste Management, 32:2061-2067.
[2] A. A. N. Gunny, D. Arbain, M. Z. M. Daud and P. Jamal, 2014, Synergistic action of deep eutectic solvents and cellulases for lignocellulosic biomass hydrolysis, Materials Research Innovations, 18: 1-3.
[3] P. Champagne, 2007, Feasibility of producing bioethanol from waste residues: a Canadian perspective, Resources, Conservation and Recycling, 50: 211-230.
[4] L. Wang, M. Sharifzadeh, R. Templer and R. J. Murphy, 2013, Bioethanol production from various waste papers: economic feasibility and sensitivity analysis, Applied Energy, 111: 1172-1182.
[5] M Ioelvich, 2013, Plant biomass as a renewable source of biofuels and biochemicals, Lambert Academic Publishing, Germany, 1-58.
[6] P. B. Subhedar and P. R. Gogate, 2013, Intensification of enzymatic hydrolysis of lignocellulose using ultrasound for efficient bioethanol production: a review, Industrial and Engineering Chemistry Research, 52:11816-11808.
[7] D. Gao, C. Haarmeyer, V. Balan, T. A. Whitehead, B. E. Dale and S. P. S. Chundawat, 2014, Lignin triggers irreversible cellulase loss during pretreated lignocellulosic biomass saccharification, Biotechnology for Biofuels, 7: 1-13.
[8] A. P. Abbott, D. Boothby, G. Capper, D. L. Davies and R. K. Rasheed, 2004, Deep eutectic solvents formed between choline chloride and carboxylic acids: versatile alternatives to ionic liquids, Journal of the American Chemical Society, 126: 9142-9147.
[9] G. Garcia, S Aparicio, R. Ullah and M. Atilhan, 2015, Deep eutectic solvents: physicochemical properties and gas separation applications, American Chemical Society, 29: 2616-2644.
[10] L. Zhang and H. Yu, 2013, Conversion of xylan and xylose into furfural in biorenewable deep eutectic solvent with trivalent metal chloride added, Bioresources, 8: 6014-6025.
[11] M. Francisco, A. van den Bruinhorst and M. C. Kroon, 2012, New natural and renewable low transition temperature mixture (LTTMs): screening as solvents for lignocellulosic biomass processing, Green Chemistry, 14: 2153-2157.
[12] G. Jiang, D. J. Nowakowski, A. V. Bridgwater, 2010, A systematic study of the kinetics of lignin pyrolysis, Thermochimica Acta, 498: 61-66.
0.15g of the 5 waste paper types was added to both
solvents and an absorbance reading was taken every
0.5 days until no further lignin was dissolved. A
concentration was estimated using the calibration
curves from known amounts of lignin (fig 4).
Preliminary experiments tested adding lignin (Sigma-
Aldrich) to the solvents to assess whether they
dissolved lignin (Fig.3). The absorbance of lignin was
tested on a UV-VIS Spectrophotometer. Absorbance
readings were taken at a suitable wavelength of 350nm.
Cellulose was also tested to ensure that there was no
evident absorption spectrum, therefore indicating that
the DESs were able to selectively dissolve lignin.
Lactic acid and choline chloride [11] (LC1.25:1), and
urea and choline chloride (UC2:1) [8] DESs were made
by adding the two materials together at the given mole
ratios at 60˚C and stirring until a clear liquid had
formed (Fig.2).
Methods
DES Solubility (g/ml)
LC1.25:1 0.09
UC2:1 0.03
Table 1: The solubility of the
DESs UC2:1 and LC1.25:1.