Extraction and Characterization of Fibers from Water Hyacinth Stem Using a Custom-Made Decorticator

ABSTRACT

In the reported work, the fibers were extracted from water hyacinth plant using a custom-made fiber decorticating machine. The extracted fibers were subjected to aerobic and anaerobic retting, followed by alkali treatment. The fiber yield and the physico-mechanical properties of the extracted fibers were determined and compared with other lignocellulosic fibers. The extracted fibers were also subjected to chemical composition analysis, Fourier Transform Infrared spectroscopy, X-Ray diffraction analysis, and Scanning Electron Microscopic analysis. From the results, it is inferred that the fibers can be easily extracted after 5 days of retting. The anaerobic retting condition slightly favors yield and fiber strength. Alkali treatment significantly enhanced the tensile strength of the fiber and also resulted in a clean fiber surface. The extracted water hyacinth was found to have 67% cellulose content. The SEM analysis shows individual fiber strands, rather a meshy structure. The alkali treatment resulted in enhancement of crystallinity of the retted fibers up to 80.45%.

摘要

在报道的工作中，使用定制的纤维脱胶机从水葫芦植物中提取纤维. 对提取的纤维进行好氧和厌氧脱胶，然后进行碱处理. 测定了提取纤维的纤维产率和物理力学性能，并与其他木质纤维素纤维进行了比较. 还对提取的纤维进行化学成分分析、傅立叶变换红外光谱、X射线衍射分析和扫描电子显微镜分析. 从结果可以推断，经过5天的脱胶后，纤维可以很容易地提取出来. 厌氧脱胶条件略微有利于产量和纤维强度. 碱处理显著提高了纤维的抗拉强度，也使纤维表面清洁. 提取的水葫芦中纤维素含量为67%. 扫描电镜分析显示，单个纤维股，而不是网状结构. 碱处理使脱胶纤维的结晶度提高了80.45%.

KEYWORDS:

• Aquatic plant
• degummin
• fiber extraction
• natural fiber
• retting
• water hyacinth

关键词:

• 水生植物
• 脱胶
• 纤维提取
• 天然纤维
• 脱胶
• 水葫芦

Introduction

Water hyacinth (Eichhorinia crassipes) is a widely distributed aquatic weed throughout the globe. Water hyacinth is highly resistant to extremes of nutrient supply, pH, and temperature and has a high reproductive capacity that it becomes double in 10–15 days. The growth and spread of this perennial plant are rapid in freshwater but it can even grow in toxic water, immobile water is best for its growth. Due to its high reproduction and complex structure, it forms dense mats (Gamage and Yapa 2001; Gupta, Roy, and Mahindrakar 2012).

A large variety of weeds are present in water as well as in wetlands, which will harm agriculture and can also act as a medium for other insects and pests to grow. The complete eradication of weeds is impossible in the practical sense. So, it is high time we must think of other methods to convert this weed to some value-added products which are beneficial to society. A large number of scientific researchers are currently going on the utilization of aquatic weed plants. For instance, the pressed fibrous residues generated as a by-product during the large-scale manufacture of leaf protein from four different aquatic weeds (Chanda, Bhaduri, and Sardar 1991), production of feed and fertilizer from water hyacinth plants (Polprasert, Kongsricharoern, and Kanjanaprapin 1994), preparation of bioethanol and biomethane from aquatic weeds like Eichhornia crassipes, Lemna minor and Azolla microphylla (Kaur et al. 2019).

Since the water hyacinth causes a global threat to the waterbodies, many countries have taken efficient measures to remove these from rivers and canals. These are not completely successful, due to the adaptability of water hyacinth to grow in extreme conditions and the high rate of propagation. Knowing the practical difficulties for the complete eradication of water hyacinth from the waterbodies, the researchers attempted to exploit water hyacinth plant/stem for various applications like the production of thermo-chemical fuels (Wauton and William-Ebi 2019), green synthesis of silver nanoparticles (Mochochoko et al. 2013), removal of crystal violet dye (Kulkarni et al. 2017) organic manure (Lata and Veenapani 2011), particleboard (Salas-Ruiz, Del Mar Barbero-Barrera, and Ruiz-Téllez 2019), and carbon fiber (Soenjaya et al. 2015). Similarly, laboratory experiments show that it absorbs nutrients such as nitrates, phosphates, and other pollutants (Sooknah 2000).

One of the critical challenges in the extraction of unconventional textile grade fibers such as banana pseudostem fiber, pineapple leaf fiber, water hyacinth fiber, etc. is the lack of standard or advanced fiber extraction machineries. This is because the first two fibers are byproducts, whereas the plant is cultivated for fruit only. Many research attempts have been performed for the development of machines for unconventional textile fibers; however, very few are commercially available. Many people still adopting manual extraction. This makes difficulties for bulk production of these fiber, in spite of their abundance. The poor fiber yield 2–3% is the another constrain (Badanayak, Jose, and Bose 2023).

A very recent work compared the properties of water hyacinth fiber, extracted through different methods (Chonsakorn, Srivorradatpaisan, and Mongkholrattanasit 2019). A couple of studies on the preparation of biocomposites using water hyacinth fibers with low-density polyethylene and polyester resin were reported (Ramirez et al. 2015; Supri and Lim 2009). In all cases, the fibers were manually extracted. An extensive and systematic study based on the characterization and physico-mechanical properties of water hyacinth fibers extracted using a customized decorticator for water hyacinth fiber has not been reported yet. Thus, this work aims to develop a decorticator for water hyacinth fiber extraction. The extracted fibers were subjected to aerobic (open) conditions, anaerobic (closed) retting, followed by alkali treatment (degumming). The variation in chemical composition, surface morphology, physico-mechanical properties of the fiber and yield with respect to the retting duration (5 and 7 days), and conditions (aerobic and anaerobic) are covered in this work.

Materials and methods

Materials

The water hyacinth stem used for the study was collected from the backwaters of Alleppey, Kerala, South India. After collecting the water hyacinth, the roots and leaves were removed using a knife, and the stem was cleaned with water. The chemicals used in the study, such as sodium hydroxide (assay-97%) and acetic acid (assay-99%) were purchased from Merck India.

Fiber extraction

A custom-made fiber extraction decorticator was fabricated and is shown in Figure 1. The machine is having three scrapping roller drums. Each drum has a diameter of 30 cm and 8 blades arranged in the horizontal direction. The water hyacinth stems were inserted through the feeding inlet. Due to the high-speed rotating action of the scrapping roller drum, the stem was subjected to scrapping action. As a result, the fibers are separated. Three operators can operate the machine simultaneously and it could process 18–20 kg of water hyacinth stem per hour. The fiber extracted using the developed machine is shown in Figure 1b. About 10 seconds are required to extract a single stem. After fiber extraction, a mild combing was performed on the fibers to remove the leftover stem portion if present any. The total weight of the machine is 90 kg. The height of the feeding inlet may be adjusted according to the requirement. By making necessary adjustments in the height of the feeding inlet, this machine is also found suitable for the extraction of banana pseudo-stem fiber and pineapple leaf fiber.

Figure 1. (a) Water hyacinth fiber extraction machine, (b) Water hyacinth fiber.

The length and weight of the water hyacinth stems were measured using a measuring scale and a weighing balance. For aerobic retting, 30 stems weighing 400 g were taken and processed through the extraction machine. The fibers then obtained were washed and kept in an open container while water was poured on them by keeping a material to liquor ratio of 1:5. The retting was carried out for the duration of 5 and 7 days in separate containers. Similarly, for anaerobic retting, the above-said conditions were applied; however, the container was closed with a lid. The water hyacinth stems, along with water were gently stirred once in a day. From 4 days onward, the progress of the retting was monitored regularly by checking the easiness of fiber removal from the stem by hand pulling. After 5 and 7 days, the fiber was separated from the rotten stem by repeated combing using a hair comb. The extracted fibers were initially washed in cold water and then in warm water. The washed fibers were then dried at ambient temperature and the yield was calculated based on the stem weight using the formula given as follows.

Fiber yield (%) = weight of extracted fiber after drying/weight of water hyacinth stem × 100 (1)

A schematic representation of the fiber extraction process is shown in Figure 2.

Figure 2. Schematic representation of the extraction and characterization of water hyacinth fiber.

Alkali treatment

After water retting, the detachment of the fibers from the stem was found to be good, but some of the stem and fleshy parts were found adhered to it. Further cleaning of the fibers was performed with alkali treatment. The fibers were treated with 10% NaOH (on the weight of the fiber) for 1 hour at 90°C for 30 minutes, with fiber-to-liquor ratio of 1:50. After the alkali treatment, the fibers were washed in running water and neutralized using a 1.0% acetic acid solution and then with cold water. The alkali-treated fiber samples were dried at an ambient temperature (Jose, Salim, and Ammayappan 2016).

Analysis of physical properties

The fiber samples were pre-conditioned at 27°C and 65% RH before testing. For measuring the length and the linear density of water hyacinth fiber, the length and weight of 100 individual fibers were taken. The fiber diameter was measured using a computerized projection microscope (RxLr-4, Radical Fiber plus). The moisture content in the fiber was measured according to the ASTM D2495–07 standards by the oven drying method. The analysis of bundle strength and elongation of the retted and the alkali-treated fiber was done through the ASTM D2524–95 method using a stelometer (Satatex Engineering Company, India). The tensile strength was calculated using the formula.

Fiber bundle strength (g/tex) = breaking load (kgf)/fiber bundle weight (mg) × length of the specimen (mm) (2)

Fourier Transformation Infrared Spectroscopy (FTIR) and XRD analysis

The degummed and retted fibers were finely chopped before analysis. Further, the FTIR analysis was performed using a double-beam FTIR spectrophotometer with ATR attachment (PerkinElmer Spectrum Two). The transmittance spectra were recorded at a wavelength from 400 to 4000 cm⁻¹. The X-ray diffraction studies were performed with the aid of a Rigaku X-ray diffractometer (MiniFlex 600) operating at 40 kV and 15 mA.

SEM analysis and chemical composition

The surface morphology of the fiber samples was analyzed using a scanning electron microscope (JEOL JSM 6390). The samples are mounted with double-sided carbon tape on aluminum stub. All specimens were sputtered with a thin layer of gold in auto fine coater JEOL JFC 1600 and the images were examined at an accelerating voltage of 20kv at 330× magnification. The chemical component analysis was performed as described by Pandey, Jose, and Sinha (2022).

Results and discussion

Physico-mechanical properties

The average length of the water hyacinth stem was found to be 30–35 cm and the weight ranged from 17 to 20 g, depending upon the length. A matured stem and the extracted fibers after 5 days of retting are shown in Figure 3. The physico-mechanical properties of the fibers extracted through water retting by keeping different retting conditions are listed in Table 1.

Figure 3. (a) Matured water hyacinth stem (b) extracted fibers after 5 days retting.

Table 1. The physico-mechanical properties of the water hyacinth fiber.

Retting duration	Sample description	Fiber yield (%)	Diameter (µm)	Bundle Strength (g/tex)	Fiber length (cm)	Liner density (tex)
7 days	Aerobic	0.83	90.50 (37.8)	7.63	17.8	0.021
	Anaerobic	0.87	73.29 (43.9)	8.67	17.20	0.017
	Degummed Anaerobic	NA	77.03 (49.9)	8.80	20.60	0.018
	Degummed Aerobic	NA	72.89 (42.5)	9.58	19.01	0.016
5 days	Aerobic	1.22	87.00 (42.9)	8.23	14.19	0.016
	Anaerobic	1.27	83.93 (46.8)	8.41	13.89	0.015
	Degummed Aerobic	NA	82.45 (43.5)	9.12	15.8	0.017
	Degummed Anaerobic	NA	74.52 (46.4)	8.86	17.8	0.021

From Table 1, it is apparent that the fiber yield is higher in 5 days retting than 7 days, irrespective of the retting conditions. The fiber diameter seems to be varied from 70 to 90 µm. In comparison with 7 days retting duration, the variation in the fiber diameter looks minimum in 5 days’ retting period. The CV% looks very high in all retted and degummed fibers. In almost all cases, significant reduction in diameter after alkali treatment was observed. This may be due to the removal of remaining fleshy portions and non-cellulosic matter from the fiber surface. In the 7 days retted fibers, the anaerobic retting resulted in higher tenacity (8.67 g/tex) than the aerobic method (7.63 g/tex). The alkali treatment significantly improved the tensile strength of both aerobic and anaerobic methods; however, here also the above said trend was noticed. After 5 days of retting, the variation in the tensile strength among anaerobic and aerobic conditions was found to be negligible (2.1%). Here also, the tensile strength of the fibers was enhanced after alkali treatment. The moisture content of the fiber as found to be nearly 8.0%.

A competitive analysis of the properties of water hyacinth fibers with other ligno cellulosic fibers is shown in Table 2. The fiber yield is very low (1.2–1.3% only) and this may be a major reason, for not performing many studies on water hyacinth fiber, in spite of its abundance. The fibers extracted from water hyacinth look very delicate with a bundle strength of 7–10 g/tex. The fiber is very fine (0.016–0.021 tex) in comparison with the listed lignocellulosic fibers. Since its stem is very short, the fiber length is also small as compared to the tabulated lignocellulosic fibers. A study conducted by Ajithram et al (2022) reported 2.41 MPa tensile strength for the fiber extracted from water hyacinth stem.

Table 2. Comparison of physico-mechanical properties of water hyacinth fiber with other lignocellulosic fibers.

Fiber	Fiber yield (%)	Diameter (µm)	Bundle strength (g/tex)	Fiber length (m)	Liner density (tex)	Moisture content (%)	Reference
Water hyacinth	1.2–1.3	75–90	7.5–10	0.25–0.30	1.6–2.1	7.8–8.5	Present study
Jute	3–4	17–20	30–35	1.5–3.7	2.3–4.5	12–13	Mishra et al. (2004) Das et al. (2014)
Roselle	4.9	50–80	21.5	0.12	3.5–4.0	8.0	Kalita et al. (2019)
PALF	2–3	45–50	23–30	1.0–1.2	3.5–4.3	5.0–7.0	Hazarika et al. (2017)
Banana	1.4	80–250	20–30	0.60–0.66	3–7	10–11	Reddy and Yang (2015)
Sisal	4–5	100–300	15–30	1.5	25–30	10–12	Naveen et al. (2019) Basu et al. (2015)
Typha	8.95		38.58	0.21–0.56	5.5–6.3	7.8–8.25	Pandey, Jose, and Sinha (2022)

FTIR analysis

Since the highest yield and tensile strength were observed after 5 days of retting, the FTIR, SEM, chemical component analysis was performed with these fibers only. The FTIR spectra of 5 days retted and alkali-treated water hyacinth fibers in aerobic and anaerobic conditions are shown in Figure 4.

Figure 4. FTIR spectra of aerobic retted, anaerobic retted, aerobic degummed, and anaerobic degummed water hyacinth fibers.

The spectrum shows all characteristic peaks corresponding to cellulose, hemicellulose, and lignin. The broad peak at 3328 cm⁻¹ corresponds to –OH stretching vibration, mainly due to the presence of moisture content. A small, peak at 2917 cm⁻¹ indicates the presence of C–H stretching in alkanes (Pandey et al. 2018). The characteristic bands of hemicelluloses and lignin were observed around 1613 cm⁻¹ due to the conjugated > C=O stretching of ester and aldehyde groups (Basu et al. 2015). The small peak at 1424 cm⁻¹ region indicates the vibration of CH₂ that is strong in crystalline cellulose and weak in amorphous cellulose. The strong peak in the region of 1022 cm⁻¹ reveals the presence of C–O stretching of cellulose, hemicellulose, or lignin (Hazarika et al. 2017; Pandey, Jose, and Sinha 2022). After alkali treatment, a marginal reduction in the intensity of the peaks at 2917 and 1022 cm⁻¹ was observed, perhaps due to the removal of hemicelluloses, pectins, and lignin (Sun et al. 2003).

Scanning electron microscopic analysis

Figure 5 shows the surface morphology of water hyacinth fibers (5 days, anaerobic retting) under high magnification. In the case of retted fibers, the surface looks very rough with the adhesion of slight amount of fleshy materials, which remains on the fiber surface even after the combing and washing. After alkali treatment, the surface looks smooth and free from fleshy matters (Figure 5c,d). As a result, a slight reduction in the fiber diameter was also observed after degumming. The porous appearance of the fiber got transformed into a rigid structure. It is apparent from the SEM images that the degummed fiber would be much suitable for further processing such as composite preparation. Unlike other natural fibers like cotton, the surface of the water hyacinth fibers is having a channel-like structure and it is visible after the removal of gummy materials and other fleshy parts from the fiber through alkali treatment.

Figure 5. SEM images of (a) 5 days aerobic retted fiber (b) 5 days anaerobic retted fiber (c) 5 days aerobic retted fiber after alkali treatment (d) 5 days anaerobic retted fiber after alkali treatment.

Chemical composition

The chemical composition analysis of water hyacinth fiber (5 days, anaerobic retting) is shown in Table 3. It is observed from the table that, the water hyacinth fiber is rich in cellulose content (67.5%). The hemicellulose is the second major component (22.3%). Only 6.66% of lignin was present. Similar results have been reported elsewhere (Chonsakorn, Srivorradatpaisan, and Mongkholrattanasit 2019). The cellulose and lignin content of the fiber is responsible for the mechanical properties of the fiber. The cellulose content is found to be higher than other lignocellulosic fibers such as roselle (52%), jute (61%), coconut fiber (38%), but less than corn leaf fiber (69%), flax (79%), and pineapple leaf fiber (71%) (Basu et al. 2015; Hazarika et al. 2017; Kalita et al. 2019; Li, Tabil, and Panigrahi 2017; Pandey, Jose, and Sinha 2022; Singh et al. 2022).

Table 3. Chemical composition analysis of water hyacinth fiber.

Sample	Cellulose (%)	Lignin (%)	Hemi cellulose (%)	Ash content (%)
Water hyacinth fiber	67.5	6.6	22.3	7.1

XRD analysis

Figure 6 depicts the comparison of the crystallinity index of retted and degummed water hyacinth fibers (5 days, anaerobic retting). Both the fibers showed peaks at an angle of 2 theta 15–16, 22. Both the peaks resemble the XRD spectra of popular lignocellulosic fibers. However, after alkali treatment the peaks found to be sharp due to the removal of noncellulosic materials from the fiber. This caused by the increase in the crystallinity of the degummed fiber (Basu et al. 2015). Apparently, the crystallinity index of the retted fibers was enhanced from 63.73% to 80.45% after alkali treatment. This may be due to the removal of non-crystalline portions including hemicelluloses, pectins, and lignin (Basu et al. 2015)

Figure 6. XRD pattern of (a) retted and (b) degummed water hyacinth fiber after 5 days of retting.

Conclusion

Water hyacinth is one of the most popular aquatic weeds. In spite of its abundance, a meticulous study on the extraction and its fiber properties is lacking in the literature. The custom-made water hyacinth fiber extractor developed in this study can consume 18–20 kg stem per hour. Retting followed by alkali treatment enhanced the strength and smoothness of the fibers by the removal of lignin and pectins. Water hyacinth fibers have comparatively less yield and strength than other popular lignocellulosic fibers. However, they are rich in cellulosic content. FTIR and chemical composition analysis confirm the lignocellulosic characteristics of the water hyacinth fiber. The SEM images showed single fiber strands instead of bunched or meshy structures. The alkali treatment increased the crystallinity index up to 80.45%. It is concluded that the fibers extracted from water hyacinth could find potential use in the textile and related applications.

Highlights

• A custom-made decorticator was developed for the extraction of water hyacinth fiber

• The extracted fibers were retted and further degummed with alkali

• The fiber yield and the physico-mechanical properties of the fibers were determined

• The results inferred that the fibers can be easily extracted after 5 days of retting

• The anaerobic retting condition slightly favors yield and fiber strength.

Ethical Approval

We confirm that all the research meets ethical guidelines and adheres to the legal requirements of the study country. The research does not involve any human or animal welfare-related issues.

Acknowledgements

The authors would like to express their gratitude to their respective institute for providing facilities to conduct the present research.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The research work was financially funded by M/S Nova Milan, Costa Rica