j m a t e r r e s t e c h n o l . 2 0 1 5;4(3):254–261
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Original Article
Chemical pulping of waste pineapple leaves fiberfor kraft paper production
Waham Ashaier Laftaha,∗, Wan Aizan Wan Abdul Rahamanb
a Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, Johor, Malaysiab Center for Composites, Universiti Teknologi Malaysia, Johor, Malaysia
a r t i c l e i n f o
Article history:
Received 29 August 2014
Accepted 15 December 2014
Available online 15 January 2015
Keywords:
Natural fiber
Renewable resources
Pineapple leaves
Pineapple fiber
a b s t r a c t
The main objective of this study is to evaluate the implementation of acetone as a pulping
agent for pineapple leaves. Mixtures of water and acetone with concentration of 1%, 3%,
5%, 7%, and 10% were used. The effects of soaking and delignification time on the paper
properties were investigated. Thermal and physical properties of paper sheet were studied
using thermogravimetric analysis (TGA) and tearing resistance test respectively. The mor-
phological properties were observed using microscope at 200× magnification. The paper
sheet produced from pulping with 3% acetone concentration shows the highest mechan-
ical properties. Papers strength was improved by increasing the delignification time. The
delignification time was reduced by cooking the pineapple leaves at a temperature of 118 ◦C
under applied pressure of 80 kPa which has remarkable effect on paper strength.
Chemical pulping
Kraft paper
© 2014 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier
Editora Ltda. All rights reserved.
insufficient to sustain papermaking, and an alternative source
1. Introduction
Pulp and paper industries have been considered the main con-sumers of natural resources (wood) and energy (electricity),including water, and significant contributors of pollutant dis-charges to the environment. The demand for paper and theunacceptable large ecological footprint of current paper pro-duction requires the need for alternatives. It was reported in2004 that the annual paper consumption is 52.45 kg per per-son and was 16.32% greater than in 1991. The use of printing
and writing paper grew by more than 10% from 1980 to 2000[1]. In many parts of the world, local supplies of wood can-not support the demand for pulp. As a result, the search for∗ Corresponding author.E-mail: [email protected] (W.A. Laftah).
http://dx.doi.org/10.1016/j.jmrt.2014.12.0062238-7854/© 2014 Brazilian Metallurgical, Materials and Mining Associa
non-wood raw materials in papermaking industry has beengiven more attention due to the rising consumption of woodresource for the paper production. From 1970 to present time,the non-wood plant fiber pulping capacity has increased ona global basis two to three times as fast as the wood pulpingcapacity. It was also forecasted that during the next decade,the non-wood pulp production will annually grow at an aver-age of 6%, which is three times as fast as the production of pulpon wood basis [2]. Initially, non-wood fiber pulping occurredin regions where wood supply had been reduced to levels
of fiber feedstock was mandatory. Non-wood fiber resourceshave the potential to complement conventional wood sup-plies. This is because, they are abundant, have short cycles
tion. Published by Elsevier Editora Ltda. All rights reserved.
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nd rapid regeneration, and are of comparatively low price.herefore, non-wood fiber will play important roles in paper-aking as substitutes or complements to wood. Examples of
on-wood fiber resources available for paper production areheat-straw [3–5], rice-straw [6,7], sugarcane straw [8], reeds
9], bamboo [10], bagasse [11,12], kenaf [13], palm oil [14], andute [15]. Non-wood material, particularly wheat straw, wasuccessfully exploited as the main raw material for papermak-ng in China because of the limited wood resource with forestoverage of only 13.94% [16]. By a wide margin, the leadingon-wood plant fiber presently in use is straw, followed byagasse and bamboo. However, pineapple leaf fiber (PALF) isnother alternative non-wood fiber that can be used for paperroduction. There have been numerous studies carried out byesearchers on various aspects of PALF. PALF obtained fromlants bearing edible fruits were examined for textile pur-oses, and blends of PALF with silk and polyester fibers weretudied [17]. PALF have also been incorporated into thermo-lastic materials such as polypropylene and polyethylene toroduce biocomposite materials. The use of non-wood rawaterials provides several interesting advantages; specifically,
t allows wood raw materials to be saved for other more decentses and hence deforestation and replanting to be alleviated. Itan also reduce wood and cellulose fiber imports in countriesith a shortage of wood raw materials. Besides, users are
ncreasingly demanding papers that are obtained by usinglean technologies or made from recycled or non-wood fiber.he current challenges of the pulp and paper industry are thechievement of affordable quality pulp while preserving thenvironment by using increasingly smaller amounts of waternd energy and gradually fewer raw materials [4]. It is alsomportant to minimize pollution from residual effluents thatesults from cooking and bleaching of the raw materials. Thencreasing concern with the environment and its preserva-ion have exposed the need to replace the classical pulpingrocess such as kraft and sulfite pulping which use sulfur con-aining reagents. This is due to the fact that the release ofulfur to the environment can cause serious pollution problem6]. The new pulping processes using less polluting chemicalsnown as the “organosolv” processes have been developed byhe researchers to resolve the problem. During the last years,his large progress of process technology has been reported toeduce the sulfur emissions by the pulp mills. Even though thebility to obtain pulp by using the organic solvents has beennown for some time, pilot plants and small-scale industriallants exploiting them have only recently come into opera-ion. This has been the result of the shortage of alternativeso traditional procedures, which leads to the expenditure ofubstantial efforts in new processes. In fact, some processeshat use organic solvents are being reconsidered in responseo the new economic and environmental order.
. Methodology
.1. Raw material
ineapple leaves were obtained from the plantation ofalaysian Pineapple Industry Board (MPIB), Johor, Malaysia.
0 1 5;4(3):254–261 255
Industrial grade acetone with 65% purity was purchased fromKrass Instrument and Services.
2.2. Sample preparation
Dried pineapple leaves were immersed in mixtures of ace-tone/water of 1%, 3%, 5%, 7%, and 10% (v/v) for 3 days tostudy the effect of acetone concentration on paper qualityand to optimize the best mixture content for farther prepara-tion. The effect of soaking time was studied at interval timesof 3, 7, 21 and 28 days. Mixture of 3% acetone was used toinvestigate the effect of cooking time on paper properties at118 ◦C under applied pressure of 80 kPa. The pineapple leafpulp was washed with water and disintegrated in a laboratoryblender. The pulp was molded using mold and deckle. Thepaper was dried in the oven at 60 ◦C until the pulp was fullydried. Finally, the paper was pressed using the compressionmolding machine at 100 ◦C and pressure of 10 MPa to get eventhickness of paper sheet.
2.3. Testing
The turbidity of spent liquor from puling process wasdetermined using HACH Ratio/XR Turbidimeter. Thermogravi-metric analysis (TGA) was performed by using Mettler ToledoTGA/STDA851 at heating rate 10 ◦C/min with the temperaturerange between 30 ◦C and 800 ◦C. TGA was used to determinethe thermal stability of cellulose and lignin in pineapple leavesand the paper sheet. The tearing resistance test or Elmendorftear test was used to measure the internal tearing resistance ofthe paper rather than the edge-tear strength of paper. The testwas carried out according to ASTM D1922 using the HT-8181Elmendorf Tearing Strength Tester. The tearing resistance(expressed in grams-force, gf) of the paper was determinedfrom the average tearing force and the number of sheets com-prising the test piece using following equation:
Tearing resistance, gf
= 16 ∗ 9.81 ∗ average scale reading ∗ gf capacityn ∗ 1600 gf
where gf capacity = 3200 g and number of plies, n = 1.Inverted Microscope LEICA DMIRM equipped with a digital
camera was used to study the morphology of the paper at 200×magnification. Morphological study was used to observe thefibers structure and their coarseness in the paper.
3. Results and discussion
3.1. Turbidity
Pulp quality is identified by the good strength, bleach abil-ity, high cellulose and hemicellulose content and low lignincontent. Therefore, it is desirable to have a pulp process thatgave the highest delignification efficiency and good quality of
cellulose and hemicellulose [18]. The effect of acetone con-centration on the pineapple leaves pulping was first observedby the turbidity of the spent liquor after the pulping pro-cess. In organic solvent pulping process, the removal of lignin256 j m a t e r r e s t e c h n o l
Acetone (1,3,5,7,9) %Soaking time (3,7,21,28,35) daysCooking time (90,180,270,360,450) mins
400
350
300
250
200
Turb
idity
(N
TU
)
150
100
50
0
Fig. 1 – The turbidity of spent liquor for various acetoneconcentrations at specified soaking time. The turbidity ofsoaking liquor for 3% acetone concentration at varioussoaking times. The turbidity of cooking liquor for 3%acetone concentration at various cooking times, attemperature of 118 ◦C.
230 C and most of it already decomposed at a temperature of
depends not only on the cleavage of ether bonds in ligninmacromolecules, but also on the ability of the aqueous solventsolution to dissolve lignin fragments [19]. The result in Fig. 1indicated that when the acetone concentration is increasedfrom 1% to 3% (v/v), the turbidity also increases dramatically,which means a large amount of lignin was precipitated at 3%
acetone concentration. Below 3% acetone concentration, theturbidity was low, which is an indication of low content oflignin dissolved [19]. On the other hand, the turbidity of the50%
10 15 20 25 30 35
0 5 10
50 10010
20
30
40
50
60
70
80
90
100
150 200 250 300 350 400
15 20 25
Lab: METTLER
30 35
Fig. 2 – TG analysis for paper produced from pulping with va
. 2 0 1 5;4(3):254–261
solution decreases with the increase of the acetone concentra-tion in the solution. Higher amount of acetone concentrationthat is above 3% is not effective for delignification due to highlyevaporated and low boiling point of acetone, which is 56.2 ◦C.
Fig. 1 illustrates the effect of soaking time on the turbid-ity of spent liquor. It can be seen that when the pineappleleaves were soaked for a longer period of time, the turbid-ity increases dramatically, which indicates that a significantamount of lignin dissolves in the solvent. The effect of cookingtime at high temperature of 118 ◦C under applied pressure onturbidity of spent liquor also shows the same trend as illus-trated in Fig. 1. From the results, delignification without anyapplied pressure and temperature requires much longer time.Fig. 1 indicates that the turbidity for cooking liquor at highertemperature is higher than the soaking liquor. This is becauseof the precipitation of lignin on the surface of the fibers dueto the presence of most of spent liquor between the fibers andthe fiber walls [19].
3.2. Thermogravimetric analysis (TGA)
Fig. 2 shows the thermogravimetric (TG) curve for pineap-ple leaves paper produced from pulping with various acetoneconcentrations. Thermal decomposition of the samples takesplace in a programmed temperature range of 30–800 ◦C. Dehy-dration as well as degradation of lignin for pineapple leavesoccurs in the temperature range 90–230 ◦C. The cellulosecomponent starts to decompose at the temperature above
◦
350 ◦C. The paper being produced shifts toward higher valuescompared to pineapple leaves indicating their increasing ther-mal stability. Thermal stability increased corresponds to the
40 46 50 55 60 65
PALF
2
**3
450 500 550 600 650
STA Re SW 9.00
700 750 ºC
40 45 50 55 60 65 70 min
3%
5%1%
7%10%
70 min
rious acetone concentrations at specified soaking time.
j m a t e r r e s t e c h n o l . 2 0 1 5;4(3):254–261 257
50%
10 15 20 25 30 35 40 46 50 55 60 65
3 days
2
**3
0 5 10
50 10030
40
50
60
70
80
90
100
150 200 250 300 350 400 450 500 550 600 650
STA Re SW 9.00
700 750 ºC
15 20 25
Lab: METTLER
30 35 40 45 50 55 60 65 70 min
21 days28 days
7 days
70 min
Fig. 3 – TG analysis for paper produced from pulping with 3% acetone concentration at various soaking times.
50%
10 15 20 25 30 35 40 46 50 55 60 65
90 mins
450 mins
2
**3
0 5 10
50 100
10
40
30
20
50
60
70
80
90
100
150 200 250 300 350 400 450 500 550 600 650
STARe SW 9.00
700 750 ºC
15 20 25
Lab: METTLER
30 35 40 45 50 55 60 65 70 min
270 mins360 mins
180 mins
70 min
Fig. 4 – TG analysis for paper produced from pulping with 3% acetone concentration at 118 ◦C and various cooking times.
n o l . 2 0 1 5;4(3):254–261
Acetone (1,3,5,7,9) %Soaking time (3,7,21,28,35) daysCooking time (90,180,270,360,450) mins
10000
9000
8000
7000
6000
Tear
ing
forc
e (g
f)
5000
4000
3000
2000
1000
0
Fig. 5 – Effect of acetone concentrations, soaking time and
258 j m a t e r r e s t e c h
amount of lignin presence in the paper. The higher the ligninthe least stable the paper is thermally. Paper soaked in 10%acetone contains the highest lignin amounting to 27.7% com-pared to the pineapple leaves that consist of about 30% lignin.The paper produced from pulping with 3% acetone concentra-tion shows the highest thermal stability, with the least amountof lignin. Major decomposition of cellulose component in theresultant paper occurred at a temperature of approximately370 ◦C [17].
Thermal stability of the paper sheets pulped with 3% ace-tone is slightly increased with soaking time as shown in Fig. 3.Thermal stability increases with the decrement of lignin inthe paper. The amount of lignin has been slightly decreased inconjunction with the increase in delignification time. Reduc-tion of lignin with delignification time indicates that the timeof soaking is an important factor in determining the quality ofpaper, which means a good quality paper with good thermalstability and low lignin content is produced at long soakingtime. Twenty-eight days of delignification time at room tem-perature results in full removal of lignin; therefore, the paperhad the highest thermal stability.
Fig. 4 indicates that the time was reduced initially whentemperature and pressure increased. When the cooking timeextended to 180 min, the thermal stability was the highest
Fig. 6 – Light microscopic images at 200× magnifications of pineacetone; (b) 3% acetone; (c) 5% acetone; (d) 7% acetone; and (d) 10
cooking time on tearing force of the paper.
and the amount of lignin in the paper was reduced to the
lowest level. However, as the cooking time was further pro-longed, the thermal stability reduced at which after 450 min,the paper being produced shows the lowest thermal stabilityapple leaves acetone/water mixture pulp fibers: (a) 1%% acetone concentration, at specified soaking time.
o l . 2 0 1 5;4(3):254–261 259
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tasrrhrturioth[
Elementaryfiber
Technicalfiber
F7
j m a t e r r e s t e c h n
ith high content of lignin. However, the amount of remainingignin in the paper sheet did not show any significant changesbove 360 min, which is similar to that at 90 min. Even thoughhe turbidity of the cooking liquor has been increased withime, higher amount of lignin was observed in the paperroduced after 450 min of cooking. This is due to the facthat the dissolved lignin was precipitated back onto thebers [19].
.3. Tearing resistance
he result in Fig. 5 indicates that the strength of paper waseduced at acetone concentration above 3% (v/v). It is there-ore equivalent to the turbidity test, where less lignin has beenissolved in the solvent. As a consequence, higher amountf lignin remaining in the paper sheet causes the paper toecome brittle and hence constitutes to lower strength prop-rties.
When the pineapple leaves was soaked in the ace-one/water mixtures at 3% acetone concentration (v/v) for
longer period of time, the paper strength increased ashown in Fig. 5. The improvement in paper strength is aesult of low lignin content at longer soaking time. Theesults in Fig. 5 show that the temperature and pressureave positive effect on paper strength and more lignin wasemoved from pineapple leaves. Applying pressure duringhe cooking increases the boiling point of cooking solventp to higher temperature of 118 ◦C and enhances the ligninemoval. These conclude that the tearing strength of the papers dependent upon the lignin content, where the reductionf lignin increases the tearing resistance and produced bet-
er paper quality. In order to produce chemical-grade pulps,igh temperature and long cooking time are the main factors20].
ig. 8 – Light microscopic images at 200× magnification of pinea days; (c) 21 days; and (d) 28 days soaking time, at 3% acetone c
Fig. 7 – Micrograph of pineapple leaves fiber bundles.
3.4. Morphological analysis
The fibers structure and coarseness of the pineapple leavesfiber using various acetone concentrations in the ace-tone/water mixture pulping were observed by using themicroscope, as shown in Fig. 6. The results showed that therewere large fiber bundles in the paper sheets, being orientatedin various orientations. The large fiber bundles were madeof a number of technical fibers that were made of even finerelementary fibers of below 10 �m diameters [17] as shown inFig. 7. However in Fig. 6(b), larger portion of elementary fiberswas distributed throughout the paper sheets, hence introduc-ing to the paper strength. This is because, the fiber extractionfrom dried leaves proved difficult with more tissues presenton the surface and fine fibers torn from the bundles [17]. Dry-ing the leaves also made it almost impossible to remove thetechnical fibers from the bottom face of the leaves. Besides,delamination of elementary fibers in the solvent containing
more than 3% acetone concentration did not adequately occurdue to acetone evaporation or due to dilution of the acetoneconcentration in the spent liquor during washing [19].pple leaves acetone/water mixture pulp fibers: (a) 3 days; (b)oncentration.
260 j m a t e r r e s t e c h n o l . 2 0 1 5;4(3):254–261
Fig. 9 – Light microscopic images at 200× magnification of pineapple leaves acetone/water mixture pulp fibers: (a) 90 min; time
r
(b) 180 min; (c) 270 min; (d) 360 min; and (e) 450 min cooking
When the soaking time was prolonged, more elementaryfibers have been delaminated from the technical fibers asshown in Fig. 8. Fig. 9 also shows the same result whenthe pineapple leaves were cooked under pressure for up to450 min. However, the delamination of the elementary fiberswas improved when temperature and pressure were appliedduring the cooking. From the color of the fibers as observed inall Figs. 6–8, in addition to the brown color of lignin particleson the fibers, many other parts of the paper appear brownish.This indicates that some lignin, although not in particle formor not being observed by the light microscope, exists in thefiber wall [19]. For instance, the acetone is not nearly as strongas caustic, which can shorten the fiber lengths and led to poorsurface appearance of the paper sheets as can be seen fromthe micrographs in all figures.
4. Conclusions
The 3% acetone concentration shows the highest lignin sol-ubility, the best tear properties, better delamination anddistribution of technical fibers, hence producing the mostacceptable properties of paper. The pineapple leaves with 3%
, at 3% acetone concentration.
acetone concentration must be soaked for a longer periodof time to achieve the optimum delignification. Cooking thepineapple leaves at high temperature and applied pressurefor more than 450 min reduced delignification time. Ace-tone/water mixtures can be used as alternative-pulping mediadue to low polluted spent liquor as a result of low consump-tion of acetone during the pulping process. Besides, pineappleleaves constitute an effective alternative pulping raw mate-rial, where paper sheets with good properties can be producedbased on pineapple leaves fibers.
Conflicts of interest
The authors declare no conflicts of interest.
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