Fabrication of Composite Nanofibre PEO/Lignin for Exhaust Gas

Emissions by Electrospinning

Grace Nainggolan

, Saharman Gea

, Marpongahtun

, Mahyuni Harahap

and Dellyansyah

Postgraduate Chemistry Program, Faculty of Mathematics and Natural Sciences, Universitas Sumatera Utara,

Medan, Indonesia

Cellulosic and Functional Material Research Center, Universitas Sumatera Utara, Medan, Indonesia

Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Sumatera Utara,

Medan, Indonesia

Keywords: Adsorbent, Electrospinning, Emission Gas, Lignin, Polyethylene Oxide

Abstract: Air pollution from the combustion of exhaust gas emissions increases with the rise in motorized vehicles

use which affects human health. Therefore, it is important to control gas emissions from motorized vehicles.

In this study, electrospinning was used to fabricate composite nanofibre lignin/PEO as a filter for gas

emission. The nanofibers obtained were analyzed by using SEM before and after gas emission test. The

morphological analysis showed that the presence of lignin in the PEO decreased the diameter of the

nanofibre from 800 nm to 100 nm, hence improved the gas adsorption efficiency. After gas emission test,

the filtration power was 61% for hydrocarbon gas, 81% for CO gas, and 33% for CO

gas.

1 INTRODUCTION

Dreadful air pollution is often accompanied by rapid

industrialization. In the history, millions of

premature deaths were related to extreme air

pollution. World Health Organization (WHO) study

reported that more than 80% of the world's

population have been exposed to air pollution with

levels that have surpassed 2018 WHO limits (World

Health Organization, 2016). The presence of

harmful pollutants, mixture of particles, toxic gases,

and microorganisms have greatly endangered public

health. In particular, fine particles in complex

mixtures with diameters less than 2.5 μm have been

identified as the main threat because they can easily

penetrate into human lungs and bronchi, resulting in

increased risks of asthma, lung cancer, stroke, and

heart disease (Li et al., 2019). There are 4 gas

emissions produced by motorized vehicles, such as

hydrocarbons (HC), carbon monoxide (CO),

nitrogen oxides (NOx), and other particles that come

out as exhaust gases. The main source of pollution

comes from transportation of fuel oil, which

produces 60% CO gas and 15% hydrocarbons

(Ortega et al., 2019).

Materials for air filtration are highly desired to

protect human health from extreme particle

emissions. They have been intensively studied for

the past few years. The ideal air filtrations must be

capable of efficiently trapping aerosol particles,

while still allowing air to easily pass through at the

same time. Various materials have been studied to

achieve high efficiency air filtration, including

foams, carbons, and fibers (Zhang et al., 2019).

Lignin, a plant-based biopolymer, is available

abundantly as the by-product of pulp/paper and

cellulosic ethanol industries. It is a three-

dimensional polyphenolic polymer and naturally

available in the cell wall of plants (Poursorkhabi et

al., 2015). Different lignocellulosic materials have

different lignin concentration, which can be about

15–30% of the materials. Cellulose processing

industries must separate lignin from the raw

materials. Given the high production and demand for

both paper and cellulosic ethanol, there is a

substantial amount of lignin produced annually.

Current applications of lignin are limited to low-

value products, such as dispersing agent, stabilizer,

rheology control materials, and low-cost fuel to

produce energy. However, lignin has the potential to

be utilized as higher value products, hence improve

the economics of the relevant industries

Electrospinning was commonly employed in the

manufacturing of nanofiber sheets for applications in

Nainggolan, G., Gea, S., Marpongahtun, ., Harahap, M. and Dellyansyah, .

Fabrication of Composite Nanoﬁbre PEO/Lignin for Exhaust Gas Emissions by Electrospinning.

DOI: 10.5220/0010614100002775

In Proceedings of the 1st International MIPAnet Conference on Science and Mathematics (IMC-SciMath 2019), pages 587-591

ISBN: 978-989-758-556-2

587

various fields such as nano sensors, ultrafiltration

membranes and nanocomposites (Chen et al., 2014;

Ko et al., 2015; Akgul et al., 2018; Choi et al., 2019;

Zhang et al., 2019). Pure lignin solution usually does

not have enough viscoelasticity for spinning.

Therefore, it is blended with another polymer, called

as a binder. Blended solutions such as lignin and

poly(ethylene oxide) (PEO), poly(vinyl alcohol)

(PVA), or poly acrylonitrile (PAN) have been

electrospun. Most of electrospun lignin fibers were

produced from solutions prepared in N,N-

dimethylformamide. Therefore, electrospinning of

aqueous solutions is more preferred. Among water

soluble polymers, electrospinning of aqueous

solutions between lignin, PVA and cellulose nano-

crystals has been reported. Schreiber et al reported

electrospinning of aqueous solutions, such as sodium

carbonate lignin and PEO, with maximum lignin to

PEO ratio of 50/50. When PEO and lignin were

mixed together in the presence of salts and water,

the chain entanglements of PEO trapped lignin

molecules. Eventually, the bridging of PEO chains

created an association of induced complex.

Electrospinning has been the pioneer of

nanostructure 1D fiber membrane production from a

variety of materials, including polymers, composites,

and ceramics. From the electrospinning fabrication

process, the diversity of materials and their unique

association with fibers can be used for various

applications, such as biomedical, drug delivery,

tissue engineering, wound dressing, filter, membrane,

energy, and electronic applications (Bellan, 2008).

Ideal structures of carbon monoxide filters

should be characterized from small fiber diameters

and pore sizes, which are important to capture

particles effectively. High porosity is responsible to

allow air stream to pass through the gas easily.

Small fiber diameters are beneficial to provide high

filtration efficiency according to Kuwabara model.

Moreover, small pores, by relying on sieving effect,

can completely remove particles larger than they are.

Therefore, EAFMs possessing ultrafine fibers and

extra small pores are highly desired for efficient

removal of fine particles (Li et al., 2019).

2 EXPERIMENTAL

2.1 Materials

Lignin alkali (partially soluble 13.4 wt,% loss on

heating at 316ºC, pH: 6.5 (25ºC), 5% aqueous

solution, density: 1.3 g/mL at 25

C), fully

hydrolyzed PEO (Mw approx. 600000, with

viscosity 20ºC, 4% water, ≥98.0% degree of

hydrolysis) purchased from Sigma Aldrich, USA.

The lignin and PEO were used as they were. The

aqueous solutions were prepared by using distilled

water. Triton X-100 as a surfactant from Fisons

2.2 Solution Preparation

Preliminary experiments on solubility of lignin

alkali in aqueous sodium hydroxide solution with

different pH showed that solution with 0.5 mol

concentration (pH>13) was completely dissolved.

This concentration was used to prepare the blend of

lignin/PEO solution.

To prepare PEO/Lignin solution blend, lignin

and PEO were first dissolved separately to ensure

complete solubility of these materials. Alkaline

water and distilled water were warmed to about

C, before lignin and PEO were added. Stirring

was necessary when PEO was added to the solvent

to avoid agglomeration of particles. Next, each of

the solution was stirred at 70

C and 600 rpm for 2 h

to completely dissolve the polymers. An equivalent

volume of each solution was taken and mixed

together for 15 min.

2.3 Electrospinning Process

The electrospinning process of PEO/lignin solution

was prepared and carried out in a horizontal

electrospinning machine (syringe SP20, high voltage

power supply PS-35PV, and speed controller with

drum collector ESD-30S, NLI, Malaysia) on a

substrate material. The electrospinning machine had

a horizontal configuration with distance between the

needle and collector was 10 cm. Voltage applied and

feed rate were kept constant at 20 kV and 0.4 mL h

-1

respectively. After mixing, PEO/lignin mixtures

were stored for at least 1 hour before spinning

process to provide enough time to remove the effects

of applied shear stress during stirring.

2.4 Characterization

2.4.1 Scanning Electron Microscopy

The surface morphology of electrospun nanofibers

was observed by scanning electron microscopy

(SEM) at an accelerating voltage EHT of 20.00 kV,

probe = 101 Pa and signal A = SE1. The samples

were placed on an adhesive-backed carbon tape and

secured to the specimen. Next, the sample was

sputter-coated by a thin layer of gold alloy (SC 500

emscope) to reduce charges during analysis.

IMC-SciMath 2019 - The International MIPAnet Conference on Science and Mathematics (IMC-SciMath)

588

2.4.2 Emission Analyzer Test

The electrospun PEO/Lignin nanofibers were tested

by Automotive Emission Analyzer Machine from

Nanhua Instrument. The nanofiber sheets were

inserted into the engine analysis channel, and

connected to the exhaust of motorcycles. The

exhaust emission data was observed with and

without the nanofibers.

3 RESULTS AND DISCUSSION

3.1 Morphology Fiber before Emission

Gas Tested

Non-toxic PEO was chemically stable in acidic

solutions and it has a molecular weight capable of

forming electrical fibers (Nagapudi, 2014). Fibers,

however, could not be formed from pure lignin

solutions, hence the need to add a supporting

polymer, PEO for instance. High resolution of SEM

exhibited unique morphology as the function of

PEO/Lignin ratio, and has an influence on

conductivity and solution flow rate.

Figure 1. PEO/lignin fiber of various weight ratio surface

morphology before emission gas test a) (6: 0) Mag 5 Kx;

b) (6: 0) Mag 10 Kx; c) (6: 5) Mag 5 Kx; d) (6: 5) Mag 10

The morphology of PEO/lignin blend is shown in

Figure 1 displays the surface morphology of

PEO/Lignin fibers analyzed by SEM, showing the

differences in the diameters of the fibers formed.

The flow rate, viscosity, and conductivity of the

solution had an impact on the morphology of fibers

(Nagapudi, 2014).

Low viscosity of polymer solution would tend to

form bead. In addition, higher concentration of

solutions has been observed to have formed less

beads (Harahap, 2018). In this study, PEO/Lignin

with weight ratio of 6:0 produced ultrathin

nanofibers with no presence of beads, as well as

nanofibers in the addition of lignin (Poursorkhabi et

al., 2015).

Figure 2. Diameter distribution of PEO/Lignin nanofiber

a) (6:0); b) (6:5)

Figure 2 presents that the analysis of diameter

distribution in PEO/Lignin nanofibers. The diameter

data of fibers was analyzed randomly by taking 50

fiber spots as analysis points. There were significant

differences with each lignin additional variation. The

fiber of pure PEO nanofibre was in the range of 250-

700 nm, with most fibers at 350-500 nm diameter

sizes. Meanwhile, PEO/Lignin nanofibre were at the

range of 100-800 nm, with most fibers at 300 nm

diameter (Widianto et al., 2018).

3.2 Scanning Electron Microscopy

Morphology

Surface morphology of PEO/Lignin nanofibers

before and after CO emission test is shown in

Figure 3. Gas emission test from the motorcycle

without treatment was treated as control. Pure PEO

nanofibre was a fiber sample used as the control

parameter. The data shows the ability of each fiber

Fabrication of Composite Nanoﬁbre PEO/Lignin for Exhaust Gas Emissions by Electrospinning

589

to filter gas emission. The analysis of nanofiber

before and after the emission gas test had significant

differences. After the emission test, the morphology

of nanofibers had rough surfaces with many beads,

indicating that the nanofibers had maximally

adsorbed the gas.

Figure 3. Surface morphology of PEO nanofibre with

magnification of (a) 5 Kx, (b) 10 Kx, and PEO/Lignin

nanofibre with magnification of (a) 5 Kx, (b) 10 Kx.

Figure 3 shows the results of the SEM

morphological analysis, that the ability of lignin

nanofibres to absorb gas emissions.

Numerical figures from the analysis of emission

gas test are presented in the Table 1.

Table 1. Numeric results of gas emission

No Sample HC

(ppm)

(%)

1 Control 3.50 0.08 2.43 1.80

2 6:0 1.44 0.16 1.06 1.49

3 6:5 1.35 0.69 0.44 1.20

Reduction of gas may occur because the

composition of the adsorbent mass of lignin used is

greater than the others, so that the capacity to absorb

gas emissions was higher. When the mass of the

adsorbent was higher, the absorption of gas would

be higher too. This was indicated by the results of

exhaust emission measured. The contact region

between the adsorbent and emission gas was the

adsorption zone (adsorbate). If the area of the

adsorption zone was larger, the more gas had been

absorbed. This has caused the concentration of gas

emissions released to be reduced (Rina et al., 2018).

4 CONCLUSION

Lignin/PEO nanofibers fabricated by electrospinning

method can be used as a filter for exhaust gas

emissions. The analysis of SEM morphological

prove that the electrospinning fibers have a shape of

nanostructures with 1D dimensions and 100-800 nm

fiber diameters.

The absorption characteristic of lignin nanofibers

is due to porous fibers produced which can absorb

emission of gases. The successful fabrication of

nanofibers also supports by gas emission test, in

which the reduction of HC, CO, and CO

gas is up to

61%, 81%, and 33% respectively.

ACKNOWLEDGEMENT

This study received financial support from DRPM

2020 PTM scheme, with contract number of

233/UN5.3.2.1/PPM/KP-DRPM/2020.

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