Sulfite-Formaldehyde Pulping and Oxygen Delignification of Wheat Straw

In this study,wheat straw pulp was prepared by sulfiteformaldehyde(SF) pulping combined with oxygen delignification to develop a sustainable methodology for chemical pulping of straw materials.The bleachability of oxygen-delignified SF pulp was also evaluated by hypochlorite bleaching.The results indicated that the Na_2SO_3 charge played an important role in lignin removal during SF pulping as well as oxygen delignification.The efficiency of oxygen delignification of wheat straw SF pulp was markedly high.After the oxygenation stage,the Kappa number decreased by over 50%(the original Kappa number of SF pulp was lower than 30) when the Na OH charge was in the range of 3%~5%.The optimal conditions for preparing bleached pulp via combined SF pulping and oxygen delignification involved the use of 12% of Na_2SO_3 and 3% of Na OH,respectively.Pulp with relatively high brightness,a low Kappa number,as well as an acceptable viscosity could be obtained when oxygen-delignified SF pulp was bleached with hypochlorite under a low active chlorine dosage.

Regulation of Superoxide Anion Radical During the Oxygen Delignification Process

In this study, the superoxide anion radicals were generated by the auto-oxidation of 1,2,3-trihydroxybenzene and determined by UV spectrophotometry, and the reaction was found to be facilitated by anthraquinone-2-sulfonic acid sodium salt. The bamboo kraft pulps were treated by the 1,2,3-trihydroxybenzene auto-oxidation method or the 1,2,3-trihydroxybenzene auto-oxidation combined with anthraquinone-2-sulfonic acid sodium salt to show the ef-fect of the superoxide anion radicals during the oxygen delignification of bamboo kraft pulp and the enhancing af-fect of anthraquinone compounds as an additive on delignification. The results indicated that the superoxide anion radicals could react with lignin and remove it from pulp with negligible damage on cellulose, and the an-thraquinone-2-sulfonic acid sodium salt could facilitate the generation of superoxide anion radical to enhance delig-nification of pulps. The oxygen delignification selectivity could be improved using the 1,2,3-trihydroxybenzene auto-oxidation system combined with anthraquinone-2-sulfonic acid sodium salt.

Acetosolv delignification of marabou (Dichrostachys cinerea) wood with and without acid prehydrolysis

The chemical composition of marabou（Dichrostachys cinerea） wood and its treatment with acetic acid were investigated.Two different treatment approaches,direct acetosolv and combined acid prehydrolysis/acetosolv,were evaluated.The effects of acetic acid concentration（50%,70% and 90%） and temperature（normal boiling temperature and 121°C） on yield of solids,solubilization of lignin and hemicelluloses and recovery of cellulose were evaluated for both treatments.High solubilization of marabou components was observed in the direct acetosolv treatment at 121°C,especially at the highest acetic acid concentration,where around 84.8% of lignin and 78% of hemicelluloses were removed.When the material was subjected to acid prehydrolysis prior to acetosolv treatment,lignin solubilization was improved,especially at low acetic acid concentrations.Above 80% of the solubilized lignin was recovered from the liquors in the direct acetosolv treatment,but the recovery was lower in the combined treatment.Cellulose was well preserved in all the treatment schemes.

Effect of Glycerol Concentration and Heating Treatment on Delignification and Bioethanol Production of Sago Dregs

The purpose of this paper was to find the suitable condition between glycerol concentration and heating time treatment in the process of delignification and bioethanol production. The production of bioethanol consisted of 3 main stages： hydrolysis, fermentation, and distillation. The best result was obtained by a glycerol concentration of 90% and 15 minutes of heating time. It was used to delignify the lignocellulose biomass waste of the sago dregs originally containing 36.56% of lignin, 37.6% of or-cellulose and 39.51% of holocellulose. Then after being delignificated by 90% of glycerol concentration with 15 minutes heating time, the lignin content decreased to 19.3%, while a-cellulose increased to 39.64% and holocellulose also increased to 62.18%. After the delignification was successful, it was followed by the bioethanol production to produce 25% of bioethanol. This research is expected to overcome the problem of the energy crisis, food crisis, and environmental pollution by the sago dregs.

Ethyl Levulinate Obtained from Lignocellulosic Waste Material with Previous Delignification by Ultrasonic-Assisted Technique

Ultrasound-assisted pretreatment under mild operating conditions has been investigated for intensification of delignification to facilitate the obtaining of ethyl levulinate from biomass. The effect of pH (2 - 12), temperature (30°C - 70°C) and pretreatment time (0 - 120 minutes) has been studied for different biomass samples. The most favorable conditions were basic pH, temperature of 70°C and pretreatment time of 2 h, obtaining values of delignification near 80 percent. The ethyl levulinate is obtained in microwave directly via from samples before and after delignification and analyzed for GC-MS. The results evidenced better yields for the delignified samples.

Structure and mechanical properties of windmill palm fiber with different delignification treatments

The removal of lignin from natural cellulose fibers is a crucial step in preparing high-performance materials,such as compressed high-toughness composites.This process can eliminate non-cellulosic impurities,create abundant compressible pores,and expose a greater number of active functional groups.In this study,biomass waste windmill palm fiber was used as the raw mate-rial to prepare holocellulose fibers through various chemical treatments.The structure,chemical composition,Fourier transform infrared spectroscopy analysis,X-ray diffraction analysis,ther-mal properties,and mechanical properties,particularly fatigue performance,were studied.The sodium chlorite treated fiber had the highest crystallinity index(61.3%)and the most complete appearance structure.The sodium sulfite treated fiber had the highest tensile strength(227.34±52.27)MPa.Hydroxide peroxide treatment removed most of the lignin and hemicellulose,increas-ing the cellulose content to 68.83%±0.65%.However,all the chemical treatments decreased the thermal property of the fibers.

Flame Retardant Material Based on Cellulose Scaffold Mineralized by Calcium Carbonate

Wood-based functional materials have developed rapidly.But the flammability significantly limits its further application.To improve the flame retardancy,the balsa wood was delignified by NaClO2 solution to create a cellulose scaffold,and then alternately immersed in CaCl_(2) ethanol solution and NaHCO3 aqueous solution under vacuum.The high porosity and wettability resulting from delignification benefited the following mineralization process,changing the thermal properties of balsa wood significantly.The organic-inorganic wood composite showed abundant CaCO_(3) spherical particles under scanning electron microscopy.The peak of the heat release rate of delignified balsa-CaCO_(3) was reduced by 33%compared to the native balsa,according to the cone calorimetric characterization.The flame test demonstrated that the mineralized wood was flame retardant and selfextinguish.Additionally,the mineralized wood also displayed lower thermal conductivity.This study developed a feasible way to fabricate a lightweight,fire-retardant,self-extinguishing,and heat-insulating wood composite,providing a promising route for the valuable application of cellulosic biomass.

Isolation and Characterization of Cellulose Nanofiber(CNF)from Kenaf(Hibiscus cannabinus)Bast through the Chemo-Mechanical Process

The present work emphasizes the isolation of cellulose nanofiber(CNF)from the kenaf(Hibiscus cannabinus)bast through a chemo-mechanical process.In order to develop high CNF yield with superior properties of CNF for improving compatibility in varied applications this method is proposed.The fiber purification involved pulping and bleaching treatments,whereas mechanical treatment was performed by grinding and high-pressure treatments.The kraft pulping as a delignification method followed by bleaching has successfully removed almost 99%lignin in the fiber with high pulp yield and delignification selectivity.The morphology of the fibers was characterized by scanning electron microscopy,which showed a smooth surface,fiber bundles,gel-shaped nanofiber,and an average size of 94.05 nm with 69%of CNF in 34–100 nm size.The chemo-mechanical process exhibited a more crystalline nature in CNF than pulp kenaf.The low zeta potential values exhibit the distribution of fibrils and colloidal suspension stability without any further agglomeration.A lower concentration of CNF is less stable exhibiting the product agglomeration.Therefore,the chemo-mechanical process for the isolation of CNF(Hibiscus cannabinus)from kenaf involves sustainable,low-cost,non-toxic,and cheap alternatives than other traditional methods.

Optimization and Characterization of Cellulose Extraction from Grevillea robusta (Silky Oak) Leaves by Soda-Anthraquinone Pulping Using Response Surface Methodology

Response surface methodology (RSM) using the central composite design (CCD) was applied to examine the impact of soda-anthraquinone pulping conditions on Grevillea robusta fall leaves. The pulping factors studied were: NaOH charge 5% to 20% w/v, pulping time 30 to 180 minutes, and the anthraquinone charge 0.1 to 0.5% w/w based on the oven-dried leaves. The responses evaluated were the pulp yield, cellulose content, and the degree of delignification. Various regression models were used to evaluate the effects of varying the pulping conditions. The optimum conditions attained were;NaOH charge of 14.63%, 0.1% anthraquinone, and a pulping period of 154 minutes, corresponding to 20.68% pulp yield, 80.56% cellulose content, and 70.34% lignin removal. Analysis of variance (ANOVA), was used to determine the most important variables that improve the extraction process of cellulose. The experiment outcomes matched those predicted by the model (Predicted R2 = 0.9980, Adjusted R2 = 0.9994), demonstrating the adequacy of the model used. FTIR analysis confirmed the elimination of the non-cellulosic fiber constituents. The lignin and hemicellulose-related bands (around 1514 cm−1, 1604 cm−1, 1239 cm−1, and 1734 cm−1) decreased with chemical treatment, indicating effective cellulose extraction by the soda-anthraquinone method. Similar results were obtained by XRD, SEM and thermogravimetric analysis of the extracted cellulose. Therefore, Grevillea robusta fall leaves are suitable renewable, cost-effective, and environmentally friendly non-wood biomass for cellulose extraction.

Effect of hot-water extraction of sugar maple on organosolv delignification and lignin recovery

This paper reported a gradual disassembly of the chemical components of hardwood,starting with hot-water extraction(HWE)for the removal of hemicelluloses,followed by organosolv delignification to remove the lignin.Under mild acid conditions,in addition to hemicelluloses,lower molecular weight lignin fractions were removed(~15%of the total lignin)in the HWE pre-treatment;also,the cleavage of the acid-labile lignin-carbohydrate bond took place to some extent.As a result,the HWE pretreatment promoted the subsequent delignification process and facilitated the lignin recovery from the spent liquor,in terms of higher delignification efficiency and higher purity of the lignin recovered from the spent liquor.The effects of the HWE pre-treatment prior to the delignification process were investigated in this study for both the oxygen-pressurized acetone-water(AWO)and the ALCELL processes,with focuses on the delignification efficiency and the properties of the lignin recovered from the process spent liquor.

Pulping of Wheat Straw with Caustic Potash-Ammonia Aqueous Solutions and Its Kinetics

A pulping technology of wheat straw with aqueous ammonia and diluent caustic potash was investigated.Because its strong alkalinity, the addition of caustic potash not only reduced the quantity of NH3 consumed and cooking time, but also enriched the black liquor with nutrients such as potassium and nitrogen, which could be used as fertilizer for agriculture. Various pulping conditions including composition of cooking liquor, liquor-to-solid ratio,maximum cooking temperature, time to reach the maximum temperature and time at the maximum temperature were studied systematically to determine the suitable pulping conditions. Results of the cooking course showed that there were three distinct delignification phases, namely, the bulk delignification phase from the beginning of cooking to 100 ℃, the supplementary delignification phase from 100 ℃ to 155 ℃ for 45min and the third delignification phase till the end of cooking. The rate of delignification was found to be first order with respect to residual lignin and 0.34 order with respect to [OH-]. The activation energy of the delignification reaction was 29.75 kJ·mol-1 and the rate equation of delignification was also obtained.

Potential aspect of rice husk biomass in Australia for nanocrystalline cellulose production

Nanocrystalline cellulose(NCC) was produced from rice husk biomass(Oryza sativa) by a chemical extraction process to explore the potential aspect of agro-waste biomass in Australia. In this work, the delignified rice husk pulp(D-RHP) was produced by alkaline delignification of raw rice husk biomass(R-RHB) using 4 mol·L^(-1) alkali solutions(Na OH) in a jacketed glass reactor under specific experimental conditions. D-RHP was bleached using 15% sodium hypochlorite, and the bleached rice husk pulp was coded as B-RHP. Finally,raw suspension of NCC was produced by the acid hydrolysis of B-RHP using 4 mol·L^(-1) sulphuric acid. The raw suspension of NCC was neutralized by a buffer solution and analyzed by TAPPI, FT-IR, XRD, SEM, AFM, and TEM. FT-IR spectra of NCC are different to R-RHB but similar with B-RHP and D-RHP. From XRD results, the crystallinity of NCC was found to be approximately 65%. In AFM analysis particle thicknesses have been confirmed to be in the range of(25 ± 15.14) nm or(27 ± 15.14) nm which is almost the same. From TEM analysis particle dimensions have been confirmed to be in the range of(50 ± 29.38) nm width and(550 ± 302.75) nm length with the aspect ratio ~ 11:1(length/diameter) at a 500 nm scale bar. On the other hand, at a 200 nm scale bar the particle dimensions have been confirmed to be in the range of(35 ± 17) nm width and(275 ± 151.38)nm length with the aspect ratio ~ 8:1. The aspect ratio of individual crystalline domain was determined in TEM analysis which is 10:1(100/10). Therefore the aspect ratios and dimensions of nanoparticles in NCC suspension are almost the same and in nano-meter scale, as confirmed from both AFM and TEM results. The yield of NCC from B-RHP was found to be approximately 95%, and the recovery of cellulose from R-RHB is about 90%.

Pulping of Wheat Straw with Caustic Potash-Ammonia Aqueous Solutions and Its Kinetics

A pulping technology of wheat straw with aqueous ammonia and diluent caustic potash was investigated. Because its strong alkalinity, the addition of caustic potash not only reduced the quantity of NH3 consumed and cooking time, but also enriched the black liquor with nutrients such as potassium and nitrogen, which could be used as fertilizer for agriculture. Various pulping conditions including composition of cooking liquor, liquor-to-solid ratio, maximum cooking temperature, time to reach the maximum temperature and time at the maximum temperature were studied systematically to determine the suitable pulping conditions. Results of the cooking course showed that there were three distinct delignification phases, namely, the bulk delignification phase from the beginning of cook- ing to 100℃, the supplementary delignification phase from 100℃ to 155℃ for 45min and the third delignification phase till the end of cooking. The rate of delignification was found to be first order with respect to residual lignin and 0.34 order with respect to [OH - ]. The activation energy of the delignification reaction was 29.75kJ·mol-1 and the rate equation of delignification was also obtained.

Exploring hemp seed hull biomass for an integrated C-5 biorefinery:Xylose and activated carbon

Large quantities of hemp hulls can be completely utilized for creation of value-added products (cost effective biofuels and biochemicals) through a biorefinery approach. A sustainable approach in making xylose, a low calorie sweetener and high surface area activated carbons (AC) for super capacitors, attracts interest. The AC when leveraged as a co-product from biorefinery process makes it more cost effective and, in this paper, we discuss the production of xylose and AC from hemp seed hull with methane sulphonic acid (MSA) hydrolysis. Xylose recovery with MSA hydrolysis was 25.15 g/L when compared to the traditional sulphuric acid (SA) hydrolysis of 19.96 g/L at the same acid loading of 1.8 %. The scanning electron microscope (SEM) images and Fourier transform infrared (FT-IR) spectra indicate partial delignification along with hemicellulose hydrolysis responsible for high xylose recovery. Post hydrolysis fibers were KOH activated and carbonized to make AC. The MSA hydrolyzed and KOH activated fiber produced pure, fluffier and finer particle AC with a drastic increase in surface area 1 452 m2/g when compared to SA hydrolyzed of 977 m2/g. These results indicate the potential of MSA in dilute acid hydrolysis of biomass for xylose recovery and production of high surface area activated carbon. From a production standpoint this can lead to increased use of sustainable low-cost agricultural biomass for making high surface area AC as components in supercapacitors.