Dyeing of Chemical Pulp with Natural Dyes - fibrafp7.netfibrafp7.net/Portals/0/2nd/27/9-Papadakis.pdf · Dyeing of Chemical Pulp with Natural Dyes Sofia G. Papadaki*, Emmanuel G

Dyeing of Chemical Pulp with

Natural Dyes Sofia G. Papadaki*, Emmanuel G. Koukios

National Technical University of Athens

School of Chemical Engineering,Laboratory of Organic Chemistry and Technology

Bioresource Technology Unit

Multi-product/service biomass processing systems, consisting of sequences

including

Feedstock handling & storage

Pretreatment (physical, chemical, biological)

Fractionation to main and co-products

Product & co-product upgrading

Product & co-product marketing

Integrated material/energy/economic flows

Defining Biorefineries – some theory!

28/7/2014 FIBRA 2nd Summer School, 26-31 July 2014, Lisbon

Biorefineries are one of the pillars of sustainability.

Bioremediation of degraded land and poor crop production use

of agro-industrial wastes

Zero waste holistic use of renewable resources, green

chemistry principles

Profitability value added products, create employment, support

by national and European funds, etc.

Biorefineries and Sustainability


Motivation

Nowadays, there is a worldwide resurgence of interest in natural dyes,

in the frame of the overall return to the natural resources.

This trend is based firstly on the fossil fuel depletion and secondly on

the increasing public awareness of the environmental and health

hazards related to chemical product.

Strict EU legislation Directives 2002/61/ΕU, 2004/92/ EU, EU

Regulataions Nob1907/2006, 1129/2011, 1333/2008.

Moreover, the natural dyes which are derived from wastes of

agricultural and forestry activity or the food and beverage industry,

such as vegetable and fruits peels or timber residues, and not edible

plants, such as weeds, show vital importance referring to

sustainability.


The natural colorants could be classified in five groups:

◦ Polyphenolic compounds (flavonoids and tannins),

◦ Isoprenoids (carotenoids),

◦ Tetrapyrroles (phycobilins),

◦ Quinones and

◦ N-heterocyclic compounds.

Natural Dyes

All these compounds show an important multifunctionality as

long as they perform high antioxidant, anti-inflammatory, anti-

bacterial activity.

Fibrous products coloring


The process of coloring fibrous products is significantly

complicated, but it is based on the simple mechanism of binding

to the surface of the fiber or being trapped within them a

chromophore, chemical compound that brings color.

One characteristic property of natural dyes is their limited

resistance against leaching, which is the case of paper

recycling. For this reason, their application in paper industry

shows great importance.

The different drying, extraction and dyeing methods affect

drastically the dyeing capacity of various plants.

The scope of this work is the evaluation of dyestuff plant material

drying, extraction and pulp dyeing techniques effect on the

dyeing capacity of Eucalyptus globulus L. bark on chemical pulp.


Scope

Why chemical pulp?

The study of dyeability of chemical pulp is very important as it consists almost

the 70% of the worldwide produced pulp from wood annually, because of the

improved properties paper that produces. Moreover, studies have shown that the

absence of lignin in chemical pulp leads to the need of using larger amounts of

dye in order to obtain the required colour comparing with mechanical pulp.

Why Eucalyptus globulus L. bark?

The bark of E. globulus L. is a great source of natural dyes as it contains numerous

dyestaff components such as tannins and flavonoids, with most important the

eriodictyol, naringenin, quercetin, rhamnazin, rhamnatin and taxifolin.

Moreover, it is a forest and pulp and paper industry residue, which means zero

supply cost and zero environmental impact. Paper industries in Europe produce

annually ≈ 0,5 million tones of Eucalyptus bark indicating their potential to

compile with biorefinery concept.

Drying of dyestuff plant material

Dyestuff plant material treatment

Extraction of natural colorants

Chemical pulp preparation

Dyeing of chemical pulp

Handsheet formation

Color determination


EXPERIMENTAL PROCEDURE

Drying of Dyestuff Plant Material

9

Natural drying

The natural drying took place in a dark place at room temperature (25 oC)

and relative humidity (RH) 50% approximately, for one week.

Air drying

The air drying took place in a laboratory tunnel air dryer at different

levels of temperature (30, 50 and 70 ± 2 °C), relative humidity (50 and 95

% RH), constant air velocity (2 m/s) and atmospheric pressure for 24 h.

Freeze drying

The plant materials were initially frozen at -30 oC for 48 h and freeze

dried for 24 h using a Lyovac Gt 2 laboratory freeze dryer. The freeze

drying was performed under high vacuum conditions (0.06 mbar).

The dried bark was ground in several sizes (Fritsch Cutting

Mill Pulverisette 15) and stored in dark and dry place.

Grain size classification took place, using the Fritsch

Vibratory Sieve Shaker Analysette 3 Spartan (measuring

range: 19.1 - 0.063 mm, sieving time: 10 min, middle

amplitude).


Dyestuff Plant Material Treatment

For the production of the natural dyes, conventional, ultrasound and

microwave assisted aquatic extraction took place.


Extraction of natural colorants

In both cases, specific amounts of the ground bark were extracted with 125 ml of

deionized water. In each experiment the determination of the specific amounts of

extracted plant material resulting from the Φ/Χ ratio, which derives from the oven dry

weight of the extracted plant material divided by the oven dry weight of the pulp dyed

with the plant extract. The final extract obtained after filtration of the insoluble residues

through a copper filter fabric.

Method Temperature (oC)

Time (min)

Conventional Extraction 40, 80 15, 30, 60

Ultrasound Assisted Extraction 250 W and 20 kHz

25, 40, 80 5, 10, 15

Microwave Assisted Extraction 200 W and 400 W

40, 80 5, 10 ,15

Chemical pulp preparation

Chemical pulp originated from spruce softwood was used.

The supplied chemical pulp was torn into small pieces by

hand and added into deionized water (2 % w/w mixture

consistency).Then, vigorous mixing of the resulting

mixture took place for 6 h using a mechanical mixer at

2000 rpm. After filtration, the produced pulp had

moisture content of 92% w/w and was stored in an

airtight plastic pot at 4 oC.


All the produced extracts were used for the dyeing of chemical pulp.

Conventional and ultrasound assisted process took place.

In all cases, the dyeing was realized using a liquor ratio of 55:1 ml/g.


Dyeing of Chemical Pulp

Method Temperature (oC)

Time (min)

Conventional Dyeing 25, 40, 80 15, 30, 60

Ultrasound Assisted Dyeing 250 W and 20 kHz

25, 40, 80 5, 10, 15

Microwave Assisted Dyeing 200 W and 400 W

40, 80 5, 10,15

Isotropic handsheet derived from dyed and undyed pulp were formatted

according to SCAN-C-26:76 and SCAN-C-M5:76 methods using the

Lorentzen and Wettre standard equipment (sheet former model SCA, sheet

press and rapid dryer). The handsheets were stored in a dark and dry place for

at least 24 hrs before their color determination.

The CIE L*a*b* system was applied for the color determination of the

produced sheets by using a Dr. Lange colorimeter.

The final dyeing result derived from the total color difference ΔE*ab between

each dyed sheet and a reference sample (undyed sheet). The total color

difference is given from the following equation:

where ΔL*= L*sample - L

*reference, Δa*= a*

sample - a*

reference and Δb*= b*sample - b

*reference


Handsheet formation and color measurement

RESULTS General assumptions

Severe extraction and dyeing conditions (Te = Td = 80 oC and te = td = 60 min) give

tense dyeing result.

The “limiting saturation value”, describes the fact that beyond this limit any increase

of the Φ/Χ ratio is unable to cause any further colour change, as the pulp fibers

cannot absorb any more dye.

Even in mild conditions the limiting saturation value for E. globulus L. bark is around

Φ/Χ = 1.4. Therefore, the experiments for optimization of grain size, extraction

and dyeing method occurred with extracts produced at Φ/Χ ratio of 0.4 and 0.6

units, respectively. By avoiding the saturation limit, every colour change would be

significant.

In the frames of this study, not only the final dyeing result but also the low cost and

environmental impact were taken under consideration during the selection of the

most efficient extraction and dyeing conditions. Therefore, conditions such as short

residence time and low temperature were preferred.


0

5

10

15

20

25

30

35

40

0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 2,2

ΔΕ

*

Φ/Χ (g/g)

TE = 80 oC, tE = 60min

TB = 80 oC, tB= 60min VB/X = 55:1 ml/g

Grain size effect on total color difference (ΔE*ab )

In this figure, the effect of

grain size on the ΔE*ab is

presented at severe

conventional extraction and

dyeing conditions.

The optimum grain size

ranges from 1.4 to 1.0 mm.

The decrease of ΔE*ab as the

grain size increases is

significant.

The ΔE*ab could be

tripled by using the

optimum grain size.

From this point all the

experiments occurred at the

optimum grain size.


Effect of extraction methods on total color difference in various conditions

(ΔE*ab ).


0

5

10

15

20

25

30

35

80 o

C, 6

0 m

in

80 o

C, 3

0 m

in

80 o

C, 1

5 m

in

40 o

C, 6

0 m

in

40 o

C, 3

0 m

in

40 o

C, 1

5 m

in

80 o

C, 5

min

80 o

C, 10 m

in

80 o

C, 1

5 m

in

40 o

C, 5

min

40 o

C, 1

0 m

in

40 o

C, 1

5 m

in

25 o

C, 5

min

25 o

C, 1

0 m

in

25 o

C, 1

5 m

in

80 o

C, 5

min

80 o

C, 1

0 m

in

80 o

C, 1

5 m

in

40 o

C, 5

min

40 o

C, 1

0 m

in

40 o

C, 1

5 m

in

ΔΕ*a

b

Extraction conditions (Te, te)

Microwave Assisted

Extraction

Conventional

Extraction

Ultrasound Assisted

Extraction

Td=25oC

td= 30min

Φ/Χ = 0.6

Eucalyptus globulus L. bark

L* a* b* h

(degrees)

C ΔΕ*

Conventional

Extraction

79,0 8,2 13,2 58,15 15,54 22,5

Ultrasound Assisted

Extraction

74,1 7,57 10,81 55,00 13,20 23,62

Microwave Assisted

Extraction

73,47 8,11 11,67 55,20 14,21 28,32

Effect of dyeing methods on total color difference in various conditions

(ΔE*ab ).


Eucalyptus globulus L. bark

L* a* b* h

(degrees)

C ΔΕ* ΔΕ* Φ/Χ=2,2

Conventional

Dyeing 79,0 8,2 13,2 58,2 15,5 22,5 28,6

Ultrasound

Assisted Dyeing 78,3 7,2 11,9 58,8 13,9 20,4 30,1

Microwave

Assisted Dyeing 75,9 8,2 15,7 62,4 17,7 28,1 36,5


Effect of drying methods and condition on dyeing capacity of Eucalyptus globulus

L. bark

Dyestuff plant

material Method a b k0 k R2 SSE

Eucalyptus

globulus L.

Air drying 2.5 -0.4 3.3E-07 - 0.9403 2.7 E-02

Freeze

drying - - - 1.4 E-02 0.9997 1.02E-05

A first order kinetic model describing the moisture transfer during drying is considered:

-dX/dt = k (X – Xe)

where X is the material moisture content (dry basis) during drying (kg water /kg dry solids), Xe, is

the equilibrium st moisture content of dehydrated material (kg water /kg dry solids), k is the

drying rate (min-1),and t is the time of drying (min).

Assuming that the hot air flow in the case of air drying and the layer thickness are stable, the drying

rate is related only to the air temperature (T) and humidity (Y) as it is described:

The fitness was checked with coefficients of determination (R2) and the sum of square errors

(SSE). Air drying

Color stability against ageing.

Relatively mild

conditions of conventional

extraction and dyeing were

selected in order to study

the colour stability.

Colour measurements

took place on dyed

handsheets four days and

six months after their

dyeing.

The dyeing result of E.

globulus L. bark on chemical

pulp show significant

stability against ageing.


CONCLUSIONS

The presented results prove that the E. globulus L. bark can be used sufficiently as a source of natural colourants for the chemical pulp.

The grain size affect drastically the dyeing capacity of the bark and the optimum grain size was determined in the range of 1.4 and 1.0 mm.

The low dyeing temperature and short extraction residence time that were achieved show great industrial interest because of their low cost and environmental impact.

The dyed handsheets showed great colour stability in ageing, a fact that presents the E. globulus L. bark as a promising dyestuff material with application mainly in packaging products.

Referring to the ultrasound and microwave assisted processes

In both cases of extraction and dyeing, strongest dyeing result was achieved in shorter time and lower temperature in comparison with the conventional ones.

“The limiting saturation value” was achieved in lower Φ/Χ ratios.

Air drying in low temperature and high RH was indicated as the optimum drying method for the dyestuff plant material.


SUGGESTIONS FOR FURTHER STUDY

The study of the dyeing capacity of the remain liquor after

the dyeing process, in order to save water, energy and raw

materials.

The alternative exploitation of the remain plant material

as absorbent, fertilizer or biofuel.

The use of mordants in order to achieve stronger and

more stable dyeing results.


PRESENTATION OF THE BTU/NTUA GROUP

BIORESOURCE TECHNOLOGY UNIT

National Technical University of Athens (NTUA), Athens, Greece (1917-)

School of Chemical Engineering (1917-)

Division IV: Process & Product Development (1983-)

◦ BTU was established in the mid-80’s

PRESENTATION OF BTU/NTUA

BTU Vision The emergence of a new generation of

technologies for the large-scale conversion of renewable raw materials of biological origin to various industrial and energy market outlets

◦ Research, development, demonstration and diffusion as “levers” for technological change


BTU Strategy & Approach

Systemic: Identifying critical questions for in-depth investigation within well-defined frames

◦ Integrated energy and material systems

Interdisciplinary: Combining various relevant scientific and technical elements

◦ Engineering; chemical; biological; socio-economic

Networking: National, European, International


BTU Research Areas

Evaluating the Resource Basis

◦ Studies of bioresource potential; physico-chemical characteristisation of crops and residues

New Resource/End-use Interfaces

◦ Biorefining; Physico-chemical fractionation and pretreatment of lignocellulosic asnd other biological raw materials


BTU Research Areas (cont’d)

Utilisation of Non-wood Fibre Sources

◦ New feedstocks for cellulose and fibre industries; environment friendly conversion processes

Bioethanol/BioH2: Steps to Solar Future

◦ Fermentation of lignocellulosics and other unconventional substrates; new bioconversion routes; sustainable biosystems


BTU Research Areas (cont’d)

Bio-Heat and Bio-Electricity Options

◦ Thermochemical densification; pre-pyrolytic treatment; upgrading lignocellulosic and other unconventional feedstocks

Integrating Local/Regional Applications

◦ Local-level bioenergy studies; technology diffusion; policy & decision-making support tools and models

A New Concept of Executive Education

This unique executive level graduate program will provide 9-

weeks of intensive study over a 3-year period.

For 3-weeks each summer over 3 consecutive years,

participants will engage in a course of study that will culminate

in an Executive Masters of Science Degree in Sustainability Policy and

Practice.

This new MSc degree will be conferred at successful

completion of the full course of study by the National Technical

University of Athens in cooperation with other Universities.


SUPER: Sustainability policy and

practice: an executive re-training

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http://super.chemeng.ntua.gr

http://super.chemeng.ntua.gr/

Acknowledgements

The research has been supported by the Senator Committee of Basic Research, Program “PEVE 2009”, R.C. No

65/1784 of the National Technical University of Athens. The authors wish to thank the Athenian Paper Mills - Softex

for the donation of the spruce softwood chemical pulp.

THANK YOU FOR YOUR

ATTENTION

Contact Info:

Dr. Sofia Papadaki

Bioresource Technology Unit, NTUA

[email protected];

[email protected]

Tel. +302107723149; +306976291715

mailto:[email protected]

mailto:[email protected]

Documents

Dyeing of Chemical Pulp with Natural Dyes - fibrafp7.netfibrafp7.net/Portals/0/2nd/27/9-Papadakis.pdf · Dyeing of Chemical Pulp with Natural Dyes Sofia G. Papadaki*, Emmanuel G