The role of absorbed hemicelluloses on final paper properties and printability

Hemicelluloses isolated from eucalyptus wood were adsorbed onto both bleached eucalyptus kraft pulp and pine kraft pulp as part of a general strategy to investigate their role on final sheet mechanics and physical properties. The tensile indices increased upon hemicelluloses addition and respectively reached a maximum at 9 mg/g and 10 mg/g hemicelluloses adsorption for bleached eucalyptus kraft pulp and pine kraft pulp, whereas the tear index increased depending on the pulp type. The air permeability and surface roughness of the bleached eucalyptus kraft pulp slightly decreased, however, brightness and opacity did not changed. SEM analysis shows that hemicelluloses adsorption increases bleached eucalyptus kraft pulp fibers interaction, whereas the effect of hemicelluloses addition on the beaten pine kraft pulp is unclear. The hemicelluloses adsorption also affected printability. It was found that print through for the bleached eucalyptus kraft pulp hand sheet slightly decreased, but for the bleached pine kraft pulp hand sheet it was unaffected. Print densities were not influenced.     

Characteristics of lignocellulosic fibers from hardwood pulp by laccase-catalyzed TEMPO oxidation

There is a challenge to find an effective and eco-friendly method to achieve the modification of fibers. The effect of laccase-TEMPO system on the properties of the bleached eucalyptus kraft pulp was investigated in this work. The results were demonstrated by the decreases in curl values and kink index. In addition, carboxyl and aldehyde groups were introduced in this reaction system. Compared with initial pulp, the contents of aldehyde and carboxyl groups of the treated pulp were increased from 42.6 μmol/g, 8.4 μmol/g to 125.4 μmol/g, 26.3 μmol/g respectively. However, the treatment had a detrimental effect on the thermal stability of pulp fibers. Moreover, the crystallinity index was slightly increased (from 82.1 % to 83.8 %) after the TEMPO-mediated oxidation, but the native crystalline structure was nearly unchanged. Furthermore, after the oxidation treatment, the relatively smooth film surface became textured, the carbon and oxygen bonds were changed, which were investigated by scanning electron microscope and X-ray photoelectron spectroscopy.     

Carbohydrate analysis of plant materials with uronic acid-containing polysaccharides–A comparison between different hydrolysis and subsequent chromatographic analytical techniques

Acid hydrolysis, acid methanolysis, and enzymatic hydrolysis were compared for depolymerization of five different plant materials containing uronic acids. The analyzed plant materials were oat spelt, wheat straw, spruce thermomechanical pulp, aspen stemwood, and totally chlorine-free (TCF) bleached hardwood kraft pulp. Furthermore, GC (using both HP-1 and HP-5 capillary columns and FID and MSD detectors), HPAEC-PAD, and HPAEC-Borate techniques were compared for subsequent analysis of the released monosaccharides. It was shown that acid methanolysis combined with GC analysis is a convenient method for obtaining the sugar unit composition and amount of non-crystalline polysaccharides in different plant materials. The methanolysis method was generally superior to the hydrolysis method for xylan- and uronic acid-containing samples. However, acid and enzymatic hydrolysis showed the highest recoveries for bleached chemical pulp samples. Acid hydrolysis is also required for crystalline polysaccharides, but the strong acid conditions evidently lead to degradation of labile sugars. The plant methanolysates were not suitable as such for analysis on an HPAEC-PAD system. For analysis of the total amount of sugar units, hence including cellulose, other non-crystalline hemicelluloses, and pectins, a combination of the methanolysis and hydrolysis methods is recommended.     

Comparison of various pulping processes for producing pulp from vine shoots

The results of characterization for four different vine shoot varieties, grown using two different methods, revealed no significant differences in composition among vine varieties or between growing methods. The holocellulose content of vine shoots (67.14%) is lower than those of other non-wood raw materials (e.g. wheat straw, sunflower stalks, cotton stalks, etc.), but similar to those of pine and higher to those of olive trimmings. On the other hand, their lignin content (20.27%) is similar to those of eucalyptus and the non-wood raw materials. Also, their contents in cold-water, hot-water and 1% soda solubles, and ethanol–benzene extractables, are higher than for pine and eucalyptus.Soda, kraft, ethanol and ethylene–glycol pulping processes have low yields (29–47%) relative to the pulping processes applied to olive trimmings and wheat straw. Kraft pulp is that exhibiting the best properties, including a higher α-cellulose content (73.74%) than pulp from wheat straw or olive trimmings, but a higher lignin content (17.18%). Also, kraft pulp provides paper with the highest breaking length, burst index and tear index (viz. 1316 m, 1.63 kN/g and 1.59 mN m²/g, respectively); these values, which are intermediate among those for olive trimmings, wheat straw and sunflower seeds, are low and can be substantially improved by appropriate refining of the pulp.     

Characterisation of agricultural residues used as a source of fibres for fibre-cement production

Nowadays, certain components of non-wood annual plants such as corn stalk and industrial hemp core are considered waste materials or used in low value applications; both by-products have a very low cost. On the other hand, given the large quantities of these materials generated worldwide and their renewable character, it is reasonable to explore new routes for their exploitation. The aim of this paper is to study the potential of both corn stalk (Zea Mays L.) and industrial hemp core (Cannabis Sativa L.) fibres as a renewable source of cellulose fibres in the production of fibre-cement. For each source of fibres, a number of chemical cooking treatments were studied. The morphological properties of the fibres were determined using a scanning electron microscope and a fibre and pulp morphological analyser. Pulp refining was carried out in a PFI mill to improve the characteristics of the fibres. In the case of corn fibres, different degrees of refining were applied. The fibre flocculation process was investigated using several polyacrylamides. The process was studied by monitoring the chord size distribution in real time by means of a focused beam reflectance measurement probe.The results indicated that both pulps can be used for the production of fibre-cement, having the two types of pulp morphological similarities with the pine fibres currently used.Through the flocculation process it was concluded the floc size depends on the length of the fibres.     

Upgrading of hemp core for papermaking purposes by means of organosolv process

Non-wood raw materials for paper production have been maintained constant during last decade. In Europe, fibres from non-wood resources proceed mainly from flax and hemp crops. Hemp core is considered a by-product of the process, mainly used in equestrian sector. The application of these fibres for papermaking process gives a significant added value to the sector.New technologies in cooking processes like organosolv pulping gives advantages compared with traditional Kraft cooking. Hemp fibres obtained by means of organosolv process have been compared with eucalyptus Kraft pulp to determine if physical and mechanical properties of final pulps are similar.Efficiency of the organosolv cooking experiments was evaluated by means of yield, percentage of uncooked sample, kappa number and viscosity.To analyze the suitability of pulp samples for papermaking applications, different evaluation of mechanical properties as morphological characterization were done. Controlling cooking conditions of hemp core, similar properties of eucalyptus Kraft fibres are obtained.     

Study of liquids absorption and retention capacities of new cellulosic materials and sodium cellulose carboxylmethylate prepared from Posidonia

The Posidonia is a sea plant which is abundant on the Tunisian coasts. Important quantities of Posidonia oceanica fragments are accumulated every year on the beaches which must be cleaned every summer. This plant contains an important ratio of cellulosic materials. On other hand, local sanitary articles industry use important quantities of absorbing materials. The aim of this work is to take advantage of this available biomass by using it as a raw material for the preparation of some of these absorbing materials. In this aim three cellulose qualities of various purities are prepared starting from Posidonia wastes and from these three cellulosic materials six qualities of sodium carboxymethylcellulose (CMCNa) are synthesised, these qualities differ by there substitution degree. The performances of all these materials are evaluated in term of absorption and retention capacities. With this end in view, three kinds of liquids are used: the deionized water, the synthetic urine and the salt solution. Then the evaluated performances are compared with those of some commercial absorbent materials used in local industries (industrial cellulosic pulp and superabsorbant). This comparison shows that the different prepared CMCNa have a retention capacity largely higher than those of the commercial cellulosic pulp. The difference can reaches 405 %. The evaluated absorption capacities of all the prepared CMCNa are generally similar to those of the commercial cellulosic pulp. However the tested superabsorbant presents, in all cases, the best performances in term of liquid absorption and retention.     

Highly Dispersible Cellulose Nanofibrils Produced via Mechanical Pretreatment and TEMPO-mediated Oxidation

Cellulose nanofibrils (CNFs) can prepare flexible nanomaterials with its large aspect ratio. Due to the supramolecular, cellulose fibers are difficultly dissociated to CNFs. In order to destroy this supramolecular structure and prepare high dispersible CNFs, the mechanical and chemical treatments are required. This study examined the effects of mechanical pretreatment and TEMPO-oxidation on the properties of CNFs preparing from bleached softwood kraft pulp. The total yield of TEMPO-oxidized cellulose nanofibrils (TOCNFs) reached 85 %. The morphology, carboxyl group content, crystallinity, surface charge, self-assembling properties, and optical transmittance of the corresponding TOCNFs suspension were investigated. The transmittance of TOCNFs suspension was 95.1 % at 600 nm wavelength and its corresponding ζ- potential was -61.3 mV, indicated that the strong electrostatic repulsion between TOCNFs was the most significant factor on the highly transparent TOCNFs suspension in water. Furthermore, the mostly negative charged TOCNFs obtained by freeze drying assembled into the finest and most uniform networked structure. Such highly transparent, functionalized, selfassembled cellulose nanofibrils are favorable in transparent films, flexible displays and electrochemistry materials.     

Rheology of new green lubricating grease formulations containing cellulose pulp and its methylated derivative as thickener agents

This work is focused on the development of gel-like formulations, potentially applicable as biodegradable lubricating greases obtained by dispersing eucalyptus Kraft cellulose pulp, or its methylated derivative, in an ethyl cellulose/castor oil medium. The effects that concentration and weight ratio of the different cellulosic derivatives exert on the rheological properties, thermal resistance and mechanical stability of these oleogels were studied. The evolution of linear viscoelasticity functions with frequency was very similar to that found for traditional lubricating greases. In general, linear viscoelastic functions increase with Kraft cellulose pulp or methylcellulose concentrations and ethyl cellulose/Kraft cellulose pulp weight ratio. However, the relative elasticity of gel-like dispersions based on ethyl cellulose/Kraft cellulose pulp is not affected by the composition of these thickener blends, which allows the application of an empirical superposition method to obtain generalized master curves for describing the viscoelastic response of these formulations. On the contrary, the relative elasticity of methylcellulose-based gel-like dispersions depends on the composition of methylated cellulose pulp/ethyl cellulose blends. An Arrhenius-type equation can be used to quantify the linear viscoelastic functions thermal dependence of these gel-like dispersions. Moreover, formulations prepared using Kraft cellulose pulp/ethyl cellulose blends show appropriate mechanical stabilities to be used as bio-lubricating greases.     

Biorefinery of Cannabis sativa using one- and two-step steam treatments for the production of high quality fibres

Among the sources of lignocellulosic biomass that could be considered as a feedstock for a biorefinery, hemp (Cannabis sativa) is known for the quality and relative abundance of its fibre. In this work, two variations of the Feedstock Impregnation Rapid and Sequential Steam Treatment (FIRSST) process are compared for the production of both fibres and biomolecules (including liquid fuels) as the valorization of the entire carbon content of biomass is needed to reach economical viability. In the first variation, the fibres were isolated via two specific and sequential steam treatments while in the second variation, fibres were isolated using only one steam treatment. Both processes allowed the isolation of a fibre that was comparable to kraft pulp while reducing the amounts of ashes along the process. Compositions of the residual solid fibre at different steps of the treatment were evaluated using ASTM and TAPPI standard methods. Carbohydrates were identified and quantified using HPLC with an anion exchange stationary phase. The qualities of the FIRSST and Kraft pulp produced were compared using standard ATPPC methods. Both pulps showed similar indexes. The two-steps FIRSST process has leaded to direct isolation of cellulose, hemicelluloses and lignin that could be suitable for the production of energy (biofuels) and high value chemicals, with small investments in terms of chemicals and energy.     

复合菌剂与氮源对桉树皮堆肥的理化性质与微生物学特性的影响

为能更科学合理地利用桉树皮生产植物育苗基质,从物理化学和微生物学角度研究了添加活性微生物菌剂和氮源对桉树皮堆肥过程的影响。结果表明:化学处理(氮源)和生物-化学联合处理(氮源+菌剂)的p H先下降后上升,EC持续下降;氨氮质量分数先增加后降低,而硝态氮的质量分数在试验期间总体上一直处于增加趋势;全磷和全钾的质量分数到试验结束时均有所增加;纤维素和木质素降解迅速;细菌数量在最高温出现之后迅速增殖,真菌数量呈现先增加后降低的趋势。生物处理(菌剂)对桉树皮堆肥作用有限。在化学处理基础上添加菌剂,降低了堆肥材料的电导率和硝态氮的质量分数;促进了全钾的积累;对桉树皮纤维素和木质素的降解无明显作用;促进了可培养细菌的增殖,但对可培养真菌有拮抗作用。     

Synthesis and characterization of cellulose carbamate by liquid-solid phase method

An efficient and environmentally friendly method for the synthesis of cellulose carbamate from a mixture of cellulose pulp or the activated cellulose pulp and urea was presented in this paper. Cellulose carbamate with a nitrogen content of 1.21 % and 3.29 % were successfully synthesized via esterification reaction in the high-boiling aprotic and polar N-methyl-2-pyrrolidone solvents (hereinafter NMP). The structures of cellulose carbamate were characterized by Fourier transform infrared spectroscopy (FTIR), Kjeldahl analysis, thermo-gravimetric analysis, scanning electron microscopy (SEM), X-ray diffractometry (XRD), and ¹³C-solid-state NMR. The results showed that some functional groups of the alkali cellulose were substituted by amino in the high-boiling aprotic and polar solvents, then the cellulose carbamate was prepared with the reduced crystallinity and thermal decomposition temperature. In addition, the product was prepared with uniform substitution and distribution of carbamate group in the cellulose chain, which guaranteed its good solubility in aqueous alkali as well as its spinnability to produce fiber.     

Isolation and characterization of nanocrystalline cellulose from different precursor materials

Nanocrytalline cellulose (NCC) was isolated using cellulose extracted from two different precursor materials: Eucalyptus globulus and rice straw. The two ground precursor materials were autoclaved with a 10 % NaOH solution at 120 °C for 3 h. The alkali-treated precursor materials were bleached using sodium chlorite/acetic acid and sodium hypochlorite. The bleached precursor materials were acid-hydrolyzed in 65 % (w/w) sulfuric acid at 45 °C for 30-120 min. The changes in the chemical composition of the two precursor materials were studied before and after bleaching by Fourier transform infrared spectroscopy according to the NREL report and TAPPI standards. Hydrolyzates were characterized by X-ray diffractometry, thermogravimetric analysis, Zeta-potential analysis, and transmission electron microscopy. The results revealed that the physical properties of NCC were strongly dependent on the acid-hydrolysis time.     

Xylanase pre-treatment of giant reed organosolv pulps: Direct bleaching effect and bleach boosting

The effect of enzymatic pre-treatment with xylanase preparation (endo-1,4-β-xylanase activity; EC 3.2.1.8) on properties and bleachability of organic solvent-based Ethanol-Alkali, Organocell (alkali-anthraquinone-methanol) and ASAM (alkali-sulfite-anthraquinone-methanol) pulps produced from agro-fibre crop giant reed (Arundo donax L.) has been examined and compared with traditional kraft pulp. The enzyme-assisted removal of xylan-associated lignin fragments and hexenuronic acids caused direct brightening and delignification during the enzymatic stage, while somewhat affecting the pulp strength properties. The xylanase bleach boosting substantially improved subsequent chemical bleaching of organosolv pulps by hydrogen peroxide. The savings in bleaching chemicals with simultaneous increase in brightness and degree of delignification were observed. The enzymatic pre-treatment improved the intrinsic viscosity of bleached organosolv pulps.     

Isolation of cellulose with ionic liquid from steam exploded rice straw

Isolation of cellulose from straw is a bottleneck for exploiting such biomass resources. In recent years, considerable concerns have arisen over new efficient and environmentally friendly way for this purpose. A novel method for cellulose isolation has been proposed by dissolving steam exploded rice straw in 1-allyl-3-methylimidazolium chloride ionic liquid (IL), following regeneration of crude cellulose by diluting the cellulose-ionic liquid solution adequately after separation of insoluble residues. The crude cellulose was then bleached by 2% hydrogen peroxide aqueous solution with low-flux ozone blowing into. No acid-insoluble lignin and only 0.85% hemicelluloses were detected in the bleached cellulose. The isolated cellulose was analyzed by SEM, FT-IR, ¹³C CP/MAS solid state NMR, XRD spectroscopes, and the results indicated that high quality cellulose preparation could be isolated in this manner from rice straw.     

纤维质生产燃料乙醇产业化研究进展

利用纤维素生物质资源生产燃料乙醇是纤维素类物质工业转化的一个重要方面。本文对国内外纤维燃料乙醇生产中的重要工艺,如原料预处理、纤维素水解、五碳糖与六碳糖发酵等研究情况进行了综述,并对国内外产业化情况进行了介绍。     

纤维质生产燃料乙醇产业化研究进展

利用纤维素生物质资源生产燃料乙醇是纤维素类物质工业转化的一个重要方面。本文对国内外纤维燃料乙醇生产中的重要工艺。如原料预处理、纤维素水解、五碳糖与六碳糖发酵等研究情况进行了综述。并对国内外产业化情况进行了介绍。     

Low-temperature pyrolysis on jute fibers as a thermochemical modification method

Low-temperature pyrolysis up to 200, 250, 300 °C was conducted in order to remove non-cellulosic compounds without damaging the structure of the cellulose in jute fibers. The chemical, morphological, and mechanical aspects of prepared low-temperature pyrolyzed jute fibers were investigated by Fourier transform infrared (FTIR) spectroscopy, the wettability test in water/dichloromethane system, moisture content measurement, X-ray diffraction (XRD) analysis, scanning electron microscope (SEM), and tensile test using universal testing machine (UTM). It was confirmed that hydrophilic compounds including absorbed water, low molecular weight compounds such as waxes, hemicellulose, and lignin were largely removed from the fibers. Increasing amounts of non-cellulosic compounds were removed as the maximum pyrolysis temperature was increased. The degree of hydrophilic nature of jute fibers were reduced by low-temperature pyrolysis and thus water absorptivity of pyrolyzed jute fibers was reduced as maximum pyrolysis temperature increased. Furthermore, XRD analysis and morphological studies by SEM indicated that the crystalline structure of native cellulose was rarely damaged after pyrolysis up to 300 °C. In case of mechanical properties, breaking tenacity and breaking strain of the fibers decreased with increasing maximum pyrolysis temperatures because flaws formed on the surface of pyrolyzed jute fibers acted as weak-links. In agreement with predictions made according to Weibull’s weakest-link theory, it was found that shortened pyrolyzed jute fibers could have higher breaking tenacities compared with raw jute fibers of the same length. In addition, the compatibility with hydrophobic matrix was investigated by the mechanical properties of polypropylene (PP) reinforced with jute fibers. Consequently, it was hypothesized that low-temperature pyrolysis could be used to process raw jute fibers for use as short fiber reinforcements in fiber-polymer systems or be a simple and effective pretreatment method for a wide range of further chemical treatments.     

Sodium carboxylmethylate cellulose from date palm rachis as a sizing agent for cotton yarn

The chemical composition of date palm rachis wastes, which are widely available cellulosic biomass-based agricultural crops in Tunisia, were characterized to determine if they had the potential for use as a starting raw material to prepare cellulose derivatives. To accomplish this, several sodium cellulose carboxylmethylates (NaCMCs) were prepared and tested as sizing agents for coating yarn. The synthesis of NaCMC was conducted in n-butanol containing NaOH (40 %) as a solvent mixture and monochloroacetic acid (MAC) as the etherifying reagent. The NaCMC samples were characterized based on their degrees of substitution (DS) and polymerization (DP). The prepared NaCMC samples were then tested as sizing agents for cotton yarn in textile applications. Specifically, different NaCMC samples were used to prepare a coating bath, which was then applied to size a cotton yarn textile. The quality of the coated yarns was subsequently evaluated by determining three parameters, yarn hairiness, the load at break, and the elongation at break. The sizing performances of the NaCMCs prepared from date palm rachis wastes were then compared with those of commercial NaCMC. The values of hairiness, breaking load, and breaking elongation of some of the NaCMC-treated yarns were as high as those prepared using commercial additives as sizing agents. These findings indicate that the cellulose derivatives prepared in this study are good candidates for alternatives to currently available additives.     

Environmentally friendly pulping and bleaching of bagasse

Depithed Sudanese bagasse was examined for its suitability for pulp production. Bagasse fibre dimensions, morphological and chemical characteristics are reported. The pulping trials were carried out with soda–AQ and alkaline sulphite–AQ (AS–AQ) methods and soda method as reference. The AS–AQ pulping gave the best results in yield, degree of delignification, mechanical and optical pulp properties. Blending of bagasse and bamboo alkaline sulphite–anthraquinone pulps in different ratios gave well-balanced pulp strength characteristics with good tensile and tear indices, widening the range of different end products from bagasse pulp. Totally chlorine free bleaching (Q₁O/PQ₂P) of the best unbleached bagasse pulps gave bleached pulps of 76.9% ISO brightness, suitable for use in writing and printing grades of paper.