Preparation of chitosan derivative and its application in papermaking.

To improve the paper strength, a number of resins and polymeric materials are being used, which is not environmental friendly and sustainable. Therefore, bio-based paper additives for the papermaking industry are essential. In this investigation, a water soluble biopolymer like carboxymethyl chitosan (CMCh) was prepared. The degree of substitution of the prepared CMCh was 2.49. The solubility of the prepared CMCh was 2.0 (w/v) % at 50 °C, and the conductivity increased with the increase of CMCh concentration in water. The prepared CMCh was applied as dry and wet strength agent of unrefined and refined softwood pulps. Both pulp increased dry and wet strength with increasing CMCh dose. An addition of 2.0 % CMCh increased dry strength by 125 % and wet strength by 293 % of unrefined pulp. On the other hand, the dry and wet tensile index of refined pulp increased from 59.48 N·m/g to 66.11 N·m/g and 2.48 N·m/g to 3.47 N·m/g, respectively, with the addition of 1.0 % CMCh. The CMCh was also used in filler modification. The precipitated calcium carbonate (PCC) modified with CMCh increased the ash content in paper with improved strength properties. The CMCh can be used in papermaking both for improving paper strength and filler retention.

Dissolution of cellulose in imidazolium-based double salt ionic liquids.

The dissolution of cellulose in double salt ionic liquids (DSILs) was studied in detail and compared with the dissolution in individual constituent ionic liquids (ILs). The DSILs, [C4mim](CH3CO2)xCl1-x (x is the mole fraction of the single component ILs), were synthesized using acetate and chloride salts of 1-butyl-3-methylimidazolium. These DSILs were then used for the investigation of the solubility of cellulose in the whole mole fraction range. Commercial cellulose (CC) powder, kraft pulp (KP), and prehydrolysis kraft pulp (PHKP) of jute were chosen as cellulose sources. The solubility of cellulose increased with an increasing temperature for [C4mim](CH3CO2)0.6Cl0.4 and with increasing amount of [C4mim]Cl in DSILs. The maximum solubility of CC powder was 32.8 wt% in [C4mim](CH3CO2)0.6Cl0.4 at 100 °C, while for KP and PHKP, solubilities were 30.1 and 30.5 wt%, respectively under the identical condition. Cellulose could be regenerated from the DSILs using water as an antisolvent. Structure, morphology, and thermal stability of the regenerated cellulosic materials were analyzed. DSILs could be recycled >99 % without a discernible change in structure. This work demonstrates that DSILs display enhanced solubility over ILs system and have potential as a chemical processing methodology.

Alcohol-based Hand Sanitizers amid COVID-19: Chemical Formulation, Analysis, Safety.

Alcohol-based hand sanitizers (ABHSs) containing ethanol (EtOH) or isopropyl alcohol (IPA) to inactivate microorganisms help prevent the spread of respiratory diseases. These products have become very popular during the COVID-19 pandemic. Apart from vaccines or other preventative antiseptic measures, the majority of consumers have relied on different types of ABHSs to disinfect their hands. As a result, there has been a global rush in the demand for these ABHSs and other antiseptic hygiene products. This has resulted in the formation of many new commercial sanitizer producers. There are around fifty companies of varying sizes that have been marketing their ABHSs in Bangladesh, most of which have only been manufacturing their products for the first time since the COVID-19 pandemic. To monitor the quality and components of these products, the Bangladesh Council of Scientific and Industrial Research (BCSIR) analyzed approximately 200 different hand sanitizer samples using GC-FID method. All samples were alcohol-based except for 3 which were alcohol-free aqueous hand sanitizers. Of the supplied formulated ABHSs, 80 samples were found to contain only IPA and 54 contained only EtOH. However, 28 samples were found to be contaminated with methanol (MeOH), 7 samples contained only MeOH and 18 samples contained both EtOH and IPA. This is the first study to explore the analysis of alcohol content in formulated ABHSs and their marketing status in Bangladesh, but the findings could be of use in other jurisdictions as similar issues have been raised in many parts of the world.

Characterization of lignin isolated from some nonwood available in Bangladesh.

Lignins isolated from cotton stalks, jute stick and dhaincha by acidolytic dioxane were characterized using alkaline nitrobenzene oxidation, elemental analysis, methoxyl analysis and molecular weight analysis and UV, IR (1)H NMR spectroscopy. The C(9) formulas for cotton stalks, jute stick and dhaincha (Sesbania aculeata) lignin were C(9)H(9.36)O(4.50)(OCH(3))(1.23), C(9)H(9.02)O(4.57)(OCH(3))(1.35) and C(9)H(8.88)O(4.65)(OCH(3))(1.50), respectively. All three lignins were of the guaiacyl-syringyl type. Cotton stalks lignin contained more p-hydroxy phenyl unit than dhaincha and jute stick lignins as observed by alkaline nitrobenzene oxidation products. The beta-O-4 units in these nonwood lignins had predominately erythro stereochemistry type.

Characterization and evaluation of golpata fronds as pulping raw materials.

The chemical, morphological and anatomical studies of golpata fronds have been discussed. The lignin, pentosan and alpha-cellulose in golpata fronds were comparable to some common nonwood and hardwood raw materials. The alkali, water and dichloromethane solubility were higher than wood and common nonwood. The fiber length 1.73 mm was observed, which is little bit shorter than softwood and longer than hardwood but fiber diameter was very short. The pulpability of golpata fronds has also been studied. The pulp yield was very low and Kappa number was high. The strength properties were better than that of some common nonwood pulps. FT-IR spectrum and alkaline nitrobenzene oxidation products showed that golpata fronds lignin mainly consist of syringyl (S) and guaiacyl units (V).

Potassium hydroxide pulping of rice straw in biorefinery initiatives.

Rice straw is supposed to be one of the most important lignocellulosic raw materials for pulp mill in Asian countries. The major problem in rice straw pulping is silica. The present research is focused on the separation of silica from the black liquor of rice straw pulping by potassium hydroxide (KOH) and pulp evaluation. Optimum KOH pulping conditions of rice straw were alkali charge 12% as NaOH, cooking temperature 150°C for 2h and material to liquor ratio, 1:6. At this condition pulp yield was 42.4% with kappa number 10.3. KOH pulp bleached to 85% brightness by D0EpD1 bleaching sequences with ClO2 consumption of 25kg/ton of pulp. Silica and lignin were separated from the black liquor of KOH pulping. The amount of recovered silica, lignin and hemicelluloses were 10.4%, 8.4% and 13.0%. The papermaking properties of KOH pulp from rice straw were slightly better than those of corresponding NaOH pulp.

Dissolving pulp from jute stick.

Jute stick is woody portion of jute plant, which remain as leftover after extracting bast fibre. Presently, it is being used for fencing in the rural area. In this investigation, biorefinery concept was initiated in producing dissolving pulp from jute stick by pre-hydrolysis kraft process. At 170°C for 1h of pre-hydrolysis, 70% of hemicelluloses was dissolved with negligible loss of α-cellulose. At this condition, 75% of dissolved sugars in the pre-hydrolysis liquor were in the oligomeric form. The pre-hydrolysed jute stick was subsequently pulped by kraft process with the variation of active alkali. The pulp yield was 36.2% with kappa number 18.5 at the conditions of 16% active alkali for 2h of cooking at 170°C. Final pulp was produced with 92% α-cellulose and 89% brightness after D0EpD1EpD1 bleaching. The produced dissolving pulp can be used in rayon production.

Recovering/concentrating of hemicellulosic sugars and acetic acid by nanofiltration and reverse osmosis from prehydrolysis liquor of kraft based hardwood dissolving pulp process.

This work investigated the feasibility of recovering and concentrating sugars and acetic acid (HAc) from prehydrolysis liquor (PHL) of the kraft-based dissolving pulp process prior to fermentation of hemicellulosic sugars, by the combination of activated carbon adsorption, nanofiltration (NF) and reverse osmosis (RO) processes. To reduce the fouling PHL was subjected to adsorption on activated carbon, then the treated PHL (TPHL) passed through a nanofiltration (NF DK) membrane to retain the sugars, and the permeate of acetic acid rich solution was passed through a reverse osmosis membrane (RO SG). It was found that for NF process sugars were concentrated from 48 to 227g/L at a volume reduction factor (VRF) of 5 while 80 to 90% of acetic acid was permeated. For the reverse osmosis process, 68% of acetic acid retention was achieved at pH 4.3 and 500 psi pressure and the HAc concentration increased from 10 to 50g/L.

Lignin removal enhancement from prehydrolysis liquor of kraft-based dissolving pulp production by laccase-induced polymerization.

Lignin removal is essential for value-added utilization of hemicelluloses and acetic acid present in the prehydrolysis liquor (PHL) of a kraft-based hardwood dissolving pulp production. In this paper, a novel process concept, consisting of laccase-induced lignin polymerization, followed by filtration/flocculation, was developed to enhance the lignin removal. The results showed that the lignin removal increased from 11% to 46-61% at laccase concentration of 1-4 U mL(-1). The GPC results showed that the molecular weight of the lignin from the laccase treated PHL was increased by 160% in comparison with the original one. The subsequent flocculation using singular Poly-DADMAC system or dual polymer system of Poly-DADMAC/CPAM can further remove 10-15% lignin. The concentrations of hemicelluloses and acetic acid were negligibly affected during the laccase treatment, while flocculation caused 12-15% of total sugar loss. Additionally, the process incorporates this new concept into the kraft-based dissolving pulp production process was proposed.

Furfural formation from the pre-hydrolysis liquor of a hardwood kraft-based dissolving pulp production process.

This study aimed to produce furfural from the PHL. Results showed best furfural yield of 32.8% and the furfural selectivity of 37.7% in the monophase system (170 °C, 100 min), while they were 60.1% and 69.8%, respectively in the biphase system. The lower furfural selectivity in the monophase system was explained by more side reactions, such as fragmentation, condensation reactions, resinification and others. Model compounds such as: xylose, furfural, syringaldehyde, were used to confirm/identify these side reactions. The addition of dilute sulfuric acid/acetic acid in the system under the same conditions decreased the recovery of furfural. The addition of syringaldehyde into the PHL also led to a decrease in the furfural yield, supporting the conclusion that lignin structures in the PHL may also be involved in the side reactions, thus decreasing the furfural yield.

Recovery of acetic acid from pre-hydrolysis liquor of hardwood kraft-based dissolving pulp production process by reactive extraction with triisooctylamine.

Acetic acid was one of the main compositions of the pre-hydrolysis liquor (PHL), which was recovered by reactive extraction with triisooctylamine (TIOA) diluted with decanol. Dilution of TIOA played an important role in extracting acetic acid from the PHL. The recovery of acetic acid from the PHL by TIOA was increased from 10.34% to 66.60% with the dilution of TIOA to 20% by decanol at the HAc to TIOA molar ratio of 1, consequently, the equilibrium distribution coefficient KD increased. The effects of time, temperature and pH on the extraction process were also studied. The extraction process was very fast. The acetic acid extraction decreased from 65.13% to 57.34% with the rise of temperature to 50°C from 20°C. A higher pH increased the dissociation of acetic acid, as a result, decreased acetic acid extraction. The hemicelluloses in the PHL were unaffected on the extraction process of acetic acid.

Separation of lignocellulosic materials by combined processes of pre-hydrolysis and ethanol extraction.

In this paper, we proposed a new modification for an ethanol-based pulping process, which would consist of the pre-hydrolysis (pre-extraction) of wood chips for removing hemicelluloses; the ethanol extraction of pre-hydrolyzed wood chips for removing lignin; and the post purification of cellulose, leading to the production of pure cellulose. We also experimentally evaluated the separation of hemicelluloses from the pre-hydrolysis liquor (PHL) obtained from a pulp mill. To remove lignin from the PHL, it was acidified to a pH of 2, which resulted in 47% lignin precipitation. The lignin separation from the acidified PHL was further improved via adding polyethylene oxide and poly aluminum chloride or adding ethyl acetate. To recover the hemicelluloses from the acidified PHL, ethanol was added to the acidified PHL with a volumetric ratio of 4 to 1. The isolated lignin and hemicelluloses were characterized by a Fourier transform infrared spectroscopy (FTIR) and a gas permeation chromatography (GPC).

Effect of different locations on the morphological, chemical, pulping and papermaking properties of Trema orientalis (Nalita).

The chemical compositions and fiber morphology of stem and branch samples from Trema orientalis at three different sites planted in Bangladesh were determined and their pulping, bleaching and the resulting pulp properties were investigated. A large difference between the stem and branch samples was observed. The stem samples have consistently higher alpha-cellulose and lower lignin content, and longer fibers than the branch samples in all sites. T. orientalis from the Dhaka and Rajbari region had higher alpha-cellulose content and longer fiber length, resulting in higher pulp yield and better papermaking properties. The T. orientalis pulp from Rajbari region also showed the best bleachability.