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Kraft lignin is produced in great quantities in many countries, but is mainly used as an energy source. To valorize its potential end-use applications, softwood kraft lignin was modified via sulfuric acid and sodium sulfite treatments in this study. The modification of kraft lignin through a sulfuric acid treatment resulted in a modified lignin (SA-lignin) with a charge density of 0.8 meq/g but with a limited water solubility. The sulfonation of the kraft lignin through a sodium sulfite treatment induced a soluble sulfonated lignin (SS-lignin) with a charge density of 1.4 meq/g, which was obtained under the conditions of 90 °C, 4 h, and 0.67 Na2SO3/lignin molar ratio. The elemental compositions, molecular weights, and thermal and rheological properties of modified lignin samples were characterized. [ABSTRACT FROM AUTHOR]

Alkaline peroxide mechanical pulp (APMP) is a newly emerging high yield pulp (HYP) with numerous advantages. However, the drawback of the alkaline peroxide mechanical pulp from untreated plant biomass is its poor network strength. In this work, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) modification was proposed to enhance pulp network strength by fiber surface modification that could enhance fiber bonding. Three factors were analyzed by response surface methodology (RSM) to optimize treatment conditions based on factorial designs. The results showed that the optimal conditions were CHPTAC dosage of 0.8% (oven-dry pulp), NaOH dosage of 0.1% (oven-dry pulp), and pulp concentration of 8%. The modified pulp fibers were characterized by elemental analysis, charge density analysis, Fourier transform infrared spectroscopy (FTIR), thermal gravity analysis (TGA), and internal bond strength analysis, as well as zero span tensile analysis. The physical strength of the modified APMP pulp was increased in terms of tensile index, tear index, and burst index. After modification, the tensile index, tear index, and burst index increased by 35.3%, 29.2%, and 16.7% respectively. The internal bonding strength increased by 144.4%; however, the increase of zero span tensile index of modified pulp fibers was insignificant. [ABSTRACT FROM AUTHOR]

Dilute sulfuric acid hydrolysis of Pennisetum (sp.) hemicellulose was investigated in this work. The hemicellulose was obtained by ethanol precipitation of hydrolysate produced via the microwave-assisted H2O2- NaOH extraction from the Pennisetum (sp.). Acid hydrolysis was performed by varying the process parameters, including the sulfuric acid concentration, hydrolysis temperature, solid to liquor ratio, and the reaction time. The xylose yield was selected as the target of process optimization and the orthogonal experiment of L9 (34) was designed to optimize the process conditions. The highest xylose yield of 86.5% could be obtained under the conditions of an acid concentration of 1%, the hydrolysis temperature of 105 °C, a solid to liquor ratio of 1:15, and a reaction time of 4 h. Fourier transform infrared spectroscopy (FTIR) analysis confirmed that most of the hemicellulose had been depolymerized into xylose. [ABSTRACT FROM AUTHOR]

With currently practiced technology, lignin is either incinerated in the recovery cycle of pulping or wasted in wastewater treatment systems, resulting in its underutilization. However, lignin can be converted to valueadded products. In this work, the copolymerization of soda lignin (SL) and acrylamide (AM) was carried out using potassium persulphate (K2S2O8) as an initiator in an aqueous solution to prepare water-soluble ligninacrylamide (SL-AM) copolymer as a dry strength additive. The results showed that the optimal copolymerization conditions were 7.5 AM/SL molar ratio, 3.0 wt.% (based on lignin) of K2S2O8, 90 °C, and 4 h of reaction time, which resulted in a SL-AM copolymer with 100% solubility at 10 g/L concentration at pH 7 in water, a grafting ratio of 398%, and a molecular weight of 1.94×105 g/mol. The prepared SL-AM copolymer was characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance (H-NMR) spectroscopy, and thermogravimetric analysis (TGA). By adding 1.0 wt.% of SL-AM copolymer to the pulp, the tensile, tear, and burst strengths were increased by 23.1%, 22.7%, and 15.2%, respectively, which implies that the resultant copolymer was an effective strength additive for papermaking. [ABSTRACT FROM AUTHOR]

Canola straw can be used as a raw material for the production of chemimechanical pulp (CMP). In this work, chemimechanical pulp was first produced from canola straw, and then the bleaching performance of the produced chemimechanical pulp was investigated under different conditions (dosages of NaOH and Na2SO3, time, and temperature). The results showed that the yield of chemical pretreatment in the CMP process varied between 57.6% and 64.9%, while the total yield of the process was between 54.1% and 61.9%. Subsequently, the CMP pulp produced via applying 4% NaOH and 8% Na2SO3 at 145 °C for 15 min was bleached with H2O2. The results showed that pulps bleached via applying one stage of 3% H2O2, 3% NaOH, 6% sodium silicate, 0.5% MgSO4, and 0.3% DTPA for 150 min possessed the highest brightness of 60.8% ISO, which is suitable for container board production. [ABSTRACT FROM AUTHOR]

Hemicelluloses dissolved in the pre-hydrolysis liquor (PHL) of kraft-based dissolving pulping processes can potentially be used to produce high value-added products such as fuel ethanol and xylitol. However, the isolation of lignin in PHL is a problem that remains unsolved and obstructs the utilization of those parts of hemicelluloses. Based on the principle of lignin isolation by acidification, the feasibility of using polyethylene oxide (PEO) to enhance the removal of lignin from PHL was tested in this work. The formation of lignin/PEO complexes was confirmed by means of turbidity, particle size, Fourier transform infrared spectroscopy (FTIR), and thermo-gravimetric analysis (TGA). The removal rate is affected by lignin content, chemical oxygen demand (COD), and decolorizing, and the results show that sulfuric acid acidification or PEO flocculation alone do not have an obvious effect on lignin removal from PHL. However, a much higher removal rate, compared to 2.81% (only acidification at pH 2) and 1.2% (only PEO on original PHL), of 22.75% is obtained by the sequential process of acidification and addition of PEO (pH 2 and PEO 350 mg/L in PHL). [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the bleaching performance of a Mg(OH)2-based hydrogen peroxide process at a high consistency. In this work, an industrially produced chemimechanical pulp (CMP) was bleached via Mg(OH)2- or NaOH-based hydrogen peroxide processes at 10% and 25% consistencies. The results showed that the pulp bleached under the conditions of 1.5% Mg(OH)2 and 3% H2O2 at 25% consistency had a similar brightness to, a lower yellowness index, and a higher opacity than the pulp produced under the conditions of 2.1% NaOH, 3% Na2SiO3, and 3% H2O2 at the same consistency. The temperature (70 °C) and time (150 min) of the bleaching were the same for both processes. Under the conditions stated above, the Mg(OH)2-based process had a higher yield than the NaOH-based process did. The bleaching effluent of the Mg(OH)2-based process had a higher residual H2O2, but a lower Chemical Oxygen Demand (COD) load and turbidity, compared with that of the NaOH-based process. However, the strength properties and water retention value (WRV) of the pulp bleached via the Mg(OH)2-based process were lower, while its bulk was higher than those of the pulp bleached via the NaOH-based process. [ABSTRACT FROM AUTHOR]