Raw Kenaf Research Articles

Extraction of Cellulose and Microcrystalline Cellulose from Kenaf

Bast and core of kenaf which categorized as agriculture residues were used in the extraction of cellulose due to its lignocellulosic nature. In this study, cellulose was extracted from the raw kenaf by using 10% alkaline peroxide pre-treatment followed by extraction process at 85 °C using the combination of 20% (v/v) formic acid and 10% (v/v) hydrogen peroxide that formed peroxy acid. The extracted cellulose was further hydrolyzed by 1.5 M of hydrochloric acid at 80 °C to yield microcrystalline cellulose (MCC). Relatively high yield of 71.81% (w/w) and 94.8% (w/w) were achieved for extracted cellulose and MCC, respectively. Based on FESEM, the average diameter of kenaf cellulose and MCC were 12.43 μm and 11.64 μm, respectively with the separated fibrils and rod-like structural. FT-IR spectral peaks observed in the cellulose and MCC revealed that most hemicellulose and lignin were eliminated during the chemical treatments. XRD analysis results exhibited that kenaf MCC gives the sharpest and highest peak s compared to others. The results also showed that the crystallinity index of extracted cellulose and MCC were increased to 60.5% and 62.3%, respectively.

Impact of chemical treatment on the physiochemical and mechanical properties of kenaf fibers

In order to improve the impact of kenaf fibers on crack resistance, durability and mechanical properties in concrete applications, kenaf fibers were treated by different inorganic chemicals (sodium hydroxide NaOH, potassium permanganate KMnO4, potassium dichromate K2Cr2O7, hydrogen peroxide H2O2, and sodium chlorite NaClO2). The characteristics of raw and chemically treated kenaf fibers were investigated through chemical composition analysis, moisture sorption test, scanning electron microscopy test, Fourier transform infrared spectroscopy test, thermogravimetric test, X-ray diffraction test, and single fiber tensile test. Compared to raw kenaf fibers, the hydrogen peroxide treatment increased the cellulose content in the fibers by about 40%; while their crystallinity increased by 26.8%. Correspondingly, the tensile strength of the fibers increased by 18.9%. The alkaline, potassium permanganate, and potassium dichromate treatments showed only a slight increase in these properties; whereas the increases were moderate with sodium chlorite treatment.

Hydrogen adsorption capacity using modified nickel-kenaf core at different concentrations

In this study, surface chemistry modification of kenaf adsorbent in adsorptive hydrogen storage system was computationally investigated using Brunauer-Emmett-Teller (BET) surface area, thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and elemental dispersion X-ray (EDX) analysis, in which the suitability of the adsorbent was determined with detailed physicochemical characterisation analysis. The method used for surface modification was metal deposition method using Ni(NO3)2 with various concentrations at different levels of pressure (up to 6 bars). Based on this research, modified kenaf with 0.4 M Ni(NO3)2 and 2.559 m2 g-1 adsorbed up to 1.013 mmol g-1 of hydrogen compared to the raw kenaf with only 0.396 mmol g-1 of hydrogen adsorbed in 5 h. Two consecutive cycles of adsorption were carried out to show the delivery performance of hydrogen adsorptive storage. Thus, different adsorption ability between the modified kenaf and raw kenaf shows that Ni-metal on kenaf surface assists in hydrogen adsorption process.

A novel process of nanocellulose extraction from kenaf bast

Kenaf is a plant which grows fast and has good environment adaptability. It is one of the most traditional natural cellulosic fiber plants in the word. However, the high lignin content and small fiber size block its application on textile fiber production and bioenergy refinery. Nanocellulose turns out a promising way to take advantage of the kenaf resource. Herein, combined microwave and chemical treatment was employed to extract nanocellulose from kenaf bast directly. The fiber size and chemical components during the extraction processes were analyzed. Then the kenaf nanocellulose is characterized by transmission electron microscopy, x-ray diffraction and thermogravimetric analysis. The results suggest that: most of the non-cellulosic materials such as lignin and hemicellulose was removed from kenaf bast after microwave and bleaching progress, producing micron size fibers; the kenaf nanocellulose extracted by the combined microwave and chemical treatment showed an acicular morphology with nano-size fiber; it has a higher cristallinity but a bit lower thermal stability compared with raw kenaf bast. In a word, this combined treatment is significantly effectual for preparing kenaf nanocellulose. It is expected that the results can serve theoretical basis for subsequent utilization of kenaf nanocellulose.

A novel degumming process of kenaf

The high content of lignin is the major disadvantage for kenaf fiber separation. In order to remove lignin effectively as well as to improve the dispersion of kenaf fibers, a novel degumming process with steam explosion followed by Fenton treatment was applied in the present study. Fibers prepared by traditional chemical degumming process and raw kenaf samples were employed as control. The fiber microstructure, chemical composition, and physical and mechanical properties were characterized and analyzed in this paper. The results revealed that steam explosion coupled with Fenton treatment could effectively remove the gum materials from kenaf bast, which performed noticeably effectively in lignin removal. The refined dry fibers showed a clean and smooth surface. The average fineness of the refined dry fibers degummed by the novel process was measured to be higher than 70 dtex, which is much better than fibers prepared by the traditional chemical degumming process. It can be concluded that the novel degumming process of combined steam explosion and Fenton treatment is feasible and effective for kenaf degumming.

CO2 removal using amine-functionalized kenaf in pressure swing adsorption system

An agro-based adsorbent from kenaf (Hibiscus cannabinus L.) for CO2 removal was prepared by functionalizing it with amine. Amine functionalization improves the adsorbates–adsorbent interaction through the presence of basic active sites on the adsorbent surfaces. Several amines (MEA, DEA, MDEA, AMP, PEI, DETA, TETA, TEPA, DIPA, PEHA, TEA, and DGA) have been selected for the amine-screening process. The result revealed that adsorption capacity of raw kenaf is only 0.624 mmol/g, whereas TEPA attained the highest CO2 capture capacity (0.914 mmol/g). Further study on the effect of amine loadings was conducted using two types of amine (MEA and TEPA) and it was found that the highest CO2 adsorption capacity for is 2.070 mmol/g for MEA to kenaf ratio of 1:1 and 2.086 mmol/g for TEPA to kenaf ratio of 2:1. The regeneration study also showed that kenaf sorbent can be used for repeated cycle operations. Due to the presence of amine on kenaf, the regeneration values of MEA–kenaf (82.15%) and TEPA–kenaf (75.62%) were lower than the raw kenaf (99.07%).

Equilibrium, kinetics and thermodynamic adsorption studies of acid dyes on adsorbent developed from kenaf core fiber

Quaternized kenaf core fiber (QKCF) was used as an adsorbent for adsorption of anionic Acid Blue-25 (AB) and anionic Acid Green-25 (AG) dyes. Chemical treatment with (3-chloro-2-hydroxypropyl) trimethylammonium chloride under basic condition was applied in order to alter the surface properties of the raw kenaf core fiber. Adsorption studies were carried out to delineate the effect of initial dye concentration, temperature and pH on removal of dyes. The results show that the percentage removal of Acid Blue-25 and Acid Green-25 dyes were increased by increasing the concentrations of dyes. In addition, the maximum percentage removal was 99.8% and 99.65% for Acid Blue-25 and Acid Green-25, respectively. Langmuir, Freundlich and Temkin isotherm models were applied to analyze the data for dye adsorption at 15℃, 25℃, 35℃, and 45℃. The experimental data were best represented by the Langmuir model with maximum adsorption capacity of 303.03 mg/g and 344.83 mg/g for Acid Blue-25 and Acid Green-25 dyes, respectively, at 15℃, and the kinetic data for both dyes were best represented by the pseudo-second-order kinetic model. Thermodynamic studies indicated that the reactions of Acid Blue-25 and Acid Green-25 dyes were endothermic. It was concluded that QKCF adsorbent can be utilized as an efficient low-cost adsorbent for removal of anionic dyes.

Effect of Steam Pressure on Chemical and Structural Properties of Kenaf Fibers during Steam Explosion Process

The chemical and structural properties of kenaf fibers that were treated at different steam pressures during the steam explosion process were investigated. With increased steam pressure, a higher percentage of cellulose and acid-insoluble lignin and a lower content of hemicellulose and pectin were obtained. This result was further confirmed by Fourier transform infrared (FTIR) spectroscopy. X-ray diffraction (XRD) studies revealed that the steam-exploded kenaf fibers were more crystalline than the raw kenaf fibers, and that excessive steam pressure above 3 MPa damaged the cellulose crystalline structure. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology of the treated kenaf fibers. The lower content of gums and the effective defibrillation of steam-exploded kenaf fibers demonstrated the potential of steam explosion treatment in applications of kenaf fibers.

A synthesis of results on wastes as potting media substitutes for the production of native plant species

The three major functions of a potting medium for plant production is to provide support, to retain water and nutrients, and to allow oxygen diffusion to the roots. A potting medium should meet the requirements of practical plant production such as: to be available and ready at all times, easy to handle, lightweight and to produce uniform plant growth. Constituents such as natural soil, peat, sand, perlite and vermiculite are commonly used as substrates for container plant production. Nevertheless, these materials might be fully or partially replaced by various organic or inorganic wastes, thus achieving environmental and economic benefits. This study presents a synthesis of results extracted from many trials on waste materials as potting media substitutes for the seedlings production of the following native plant species: Pinus halepensis, Quercus ilex, Quercus macropleis and Ceratonia siliqua. The studied waste materials were either organic or inorganic components including: spoils of peridotite, raw rice hulls, coconut fiber and kenaf (the ground stem of the plant H. cannabinus L). The experimental potting media tested were: peat:perlite (3:1), a common medium used for seedling production, peat:spoils of peridotite (3:1), peat:rice hulls (3:1), peat:rice hulls (1:1), peat:coconut fiber (1:1), kenaf (100%) and kenaf:peat:rice hulls (3:1:1). The main physical (water retention characteristics, bulk density, particle density, total porosity) and chemical (N, K, Ca, Mg, soluble P, exchangeable cations, pH and loss on ignition) properties of each potting medium were measured. For each plant species the following seedling quality parameters were assessed: morphological characteristics (shoot height, root collar diameter), shoot and root biomass, Dickson’s quality index and shoot and root nutrient concentrations. Then seedlings were planted in the field and their survival and growth was monitored. The feasibility of replacing peat or perlite with various waste materials as well as their effect on seedling quality and field performance are discussed.

An Investigation of Carbon Dioxide Sequestration on Amine–Modified Kenaf: Adsorption Isotherm Study

The increase concentration of CO2 in the atmosphere is linked with global climate change. Among the technology options used for CO2 capture, there is a growing interest in using adsorption method for separation process. Inspired by the most applicable technology of amine–based chemical absorption for capturing CO2, the development of amine–functionalized kenaf based adsorbent has been proposed in this study. The incorporation of amine functional group (MEA and TEPA) on kenaf was conducted via wet impregnation method. The characterization was carried out by using FESEM and FTIR. The CO2 adsorption equilibrium study have been conducted and further described by Langmuir and Freundlich isotherm equation models at temperature of 0, 25 and 50oC. Result presented shows that Freundlich isotherm model fits the experimental data for raw kenaf and amine–modified kenaf. It was indicated by the values of R2. Additionally, results for each sample show the adsorption favourability since the values of KL is less than 1 and the magnitude of Freundlich (n) is greater than 1. Finally, this study revealed that the amine–modified kenaf could become another potential adsorbent for CO2 separation.

Hydrogen Storage in Modified Kenaf

Kenaf fiber has been recognised as a new material for adsorption based on its porous structure. However, previous studies have proved that modified kenaf could give better interaction towards adsorbates than the raw kenaf during the adsorption. In this study, kenaf core fiber has been modified using Nickel metal (Ni-metal). Different concentration of Nickel nitrate, Ni(NO3)2(0.01 M and 1 M) have been used to observe the effect of Ni-metal for hydrogen adsorption. Initially, raw kenaf sample has been grinded and sieved into 500 µm in size. Then, the sample was heated to remove the moisture and Ni(NO3)2has been added into the dried kenaf. Based on this study, modified kenaf with 0.1 M Ni(NO3)2and 1 M Ni(NO3)2has adsorbed more hydrogen compared to the raw kenaf. The result has provided a fundamental knowledge of kenaf as hydrogen storage material.

Kenaf bast cellulosic fibers hierarchy: A comprehensive approach from micro to nano

Cellulosic fibers from kenaf bast were isolated in three distinct stages. Initially raw kenaf bast fibers were subjected to an alkali pulping process. Then pulped fibers undergone a bleaching process and finally both pulped and bleached fibers were separated into their constituent nanoscale cellulosic fibers by mechanical shearing. The influence of each treatment on the chemical composition of fibers was investigated. Moreover morphology, functional groups, crystallinity, and thermal behavior of fiber hierarchy at different stages of purification were studied using scanning and transmission electron microscopies, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Microscopy studies revealed that applied procedures successfully isolated nanoscale cellulosic fibers from both unbleached and bleached pulps. Chemical composition analysis and FTIR spectroscopy showed that lignin and hemicellulose were almost entirely removed by the applied treatments. XRD and TGA analyses demonstrated progressive enhancement of properties in fibers, hierarchically, in going from micro to nano scale. Interestingly no significant evolution was observed between obtained data of characterized ubnleached and bleached nanofibers.

Characterization of Laccase-Treated Kenaf Fibre Reinforced Recycled Polypropylene Composites

Raw and laccase-treated kenaf fibre (KF) were used individually to reinforce recycled polypropylene (RPP) using extrusion and injection moulding. Laccase was used to modify the surface of the fibre to improve the compatibility between fibre and matrix. Enzyme concentration and soaking time were considered as the treatment parameters. Maleic anhydride grafted polypropylene (MAPP) was used with a ratio of 1:10 as coupling agent to fibre. Fibres were characterized by density, energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), whereas composites were characterized by density, melt flow index (MFI), mechanical tests (tensile, flexural, and impact), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), field emission electron microscopy (FE-SEM), and water uptake analysis. Density, O/C ratio, and crystallinity of the treated fibre were increased. An optimum fibre loading of 40% gave the highest tensile properties. Tensile strength improved due to coupling agent by 37%, whereas treatment of fibre did the same by 40%. Flexural, impact, and thermal properties of the composites and crystallinity of the matrix were improved due to treatment. Morphological images of the composites showed better adhesion, and moisture absorption was reduced by 37% due to treatment and use of coupling agent.

Isolation and Characterization of Cellulose Whiskers from Kenaf (<i>Hibiscus cannabinus</i> L.) Bast Fibers

Cellulose whiskers were isolated from kenaf (Hibiscus cannabinus L.) bast fibers via sulfuric acid and hydrochloric acid hydrolysis. Raw kenaf bast, NaOH treated, bleached fibers, sulfuric acid whiskers (SAW) and hydrochloric acid whiskers (HClW) morphology, functional groups, crystallinity, and thermal stability were characterized. The TEM images showed that the sulfuric acid and HCl whiskers have average diameters and length range of 3 nm and 100 - 500 nm, respectively. The FTIR study indicated that during the conversion process, most of the hemicellulose and almost all the lignin were removed by the NaOH and subsequent bleaching treatments. The crystallinity of HCl whiskers was found to be higher (84%) than that of sulfuric acid whiskers (72%). Thermogravimetric analysis indicated that HCl whiskers had better thermal stability than the sulfuric acid ones. In addition, a two-stage decomposition behavior was revealed by TGA in the sulfuric acid whiskers because of incorporation of the sulfate group with the cellulose crystals.

A chemical process for preparing cellulosic fibers hierarchically from kenaf bast fibers

The objective of this research was to evaluate an all-chemical process to prepare nano-scale to macro-scale cellulosic fibers from kenaf bast fibers, for polymer composite reinforcement. The procedure used in this all-chemical process included alkaline retting to obtain single cellulosic retted fiber, bleaching treatment to obtain delignified bleached fiber, and acidic hydrolysis to obtain both pure-cellulose microfiber and cellulose nanowhisker (CNW). At each step of this chemical process, the resultant fibers were characterized for crystallinity using X-ray diffraction (XRD), for functional groups using the Fourier Transform Infrared spectroscopy (FTIR), and for surface morphology using both the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical components of the different scale fibers were analyzed. Based on the raw kenaf bast fibers, the yields of retted fibers and bleached fibers were 44.6% and 41.4%. The yield of the pure cellulose microfibers was 26.3%. The yield of CNWs was 10.4%, where about 22.6% α-cellulose had been converted into CNWs. The fiber crystallinity increased as the scale of the fiber decreased, from 49.9% (retted single fibers) to 83.9% (CNWs). The CNWs had fiber lengths of 100 nm to 1400 nm, diameters of 7 to 84 nm, and aspect ratios of 10 to 50. The incorporation of 9% (wt%) CNWs in polyvinyl alcohol (PVA) composites increased the tensile strength by 46%.

Chemical composition, crystallinity, and thermal degradation of bleached and unbleached kenaf bast (Hibiscus cannabinus) pulp and nanofibers

Kenaf (Hibiscus cannabinus) nanofibers were isolated from unbleached and bleached pulp by a combination of chemical and mechanical treatments. The chemical methods were based on NaOH-AQ (anthraquinone) and three-stage bleaching (DEpD) processes, whereas the mechanical techniques involved refining, cryo-crushing, and high-pressure homogenization. The size and morphology of the obtained fibers were characterized by environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM), and the studies showed that the isolated nanofibers from unbleached and bleached pulp had diameters between 10-90 nm, while their length was in the micrometer range. Fourier transform infrared (FTIR) spectroscopy demonstrated that the content of lignin and hemicellulose decreased in the pulping process and that lignin was almost completely removed during bleaching. Moreover, thermogravimetric analysis (TGA) indicated that both pulp types as well as the nanofibers displayed a superior thermal stability as compared to the raw kenaf. Finally, X-ray analyses showed that the chemo-mechanical treatments altered the crystallinity of the pulp and the nanofibers: the bleached pulp had a higher crystallinity than its unbleached counterpart, and the bleached nanofibers presented the highest crystallinity of all the investigated materials.

Carding Kenaf for Nonwovens

Kenaf is a bast fiber that offers the advantage of being biodegradable, renewable, and environmentally safe. Unfortunately, mechanically harvested (raw) kenaf fibers are coarse, brittle, and difficult to process through conventional textile and nonwoven equipment. Kenaf batts can be prepared by an air-laid process, but the batts do not have stable uniform structures. In earlier work, we attempted to card kenaf on a cotton card, since carded batts should provide better structural integrity than air-laid batts. Unfortunately, it was impossible to card raw kenaf fibers on a conventional cotton card, because the raw kenaf was discharged from the card as trash. Carding of treated ( chem ically processed) kenaf was moderately successful, although a fair proportion of kenaf was still lost during the carding process. We modified a conventional cotton card to process kenaf fibers into nonwoven structures by using different wire combinations, carding plates, card speeds, and settings. Kenaf batts (pure or blended with polypro pylene) were carded on this modified machine. Nonwoven mats were made using three methods: through-air thermal bonding, needle punching, and needle punching followed by thermal bonding. Although each of these procedures produced kenaf mats with good strength and uniformity, the combined treatment produced the strongest mats. Details of card modification as well as gathered data and properties of the mats are presented.