Revisiting the condensation reaction of lignin in alkaline pulping with quantitativity part I: the simplest condensation between vanillyl alcohol and creosol under soda cooking conditions

The condensation reaction of lignin is believed to interfere with delignification in alkaline pulping processes, without any clear evidence, which has motivated us to quantitatively revisit it. This paper is the first of a series, and hence we employed the simplest model system using 4-hydroxymethyl-2-methoxyphenol (vanillyl alcohol, Va) and 2-methoxy-4-methylphenol (creosol, Cr) under soda cooking conditions. The α-5-type condensation product between these compounds [VaCr, 2-(4-hydroxy-3-methoxybenzyl)-6-methoxy-4-methylphenol] was identified and quantified as exclusive. VaCr was yielded with a mole amount of 24%, 46%, 62%, or 72% based on that of disappearing Va at a reaction time of 120 min when the ratio of the initial concentration of Cr to that of Va was 1.0, 2.5, 5.0, or 7.5, respectively. These yields and an HPLC analysis of the reaction solution obtained by a treatment of Va as the sole compound under the same soda cooking conditions suggested the formation of self-condensation products of Va even in the treatments containing Cr. The obtained results comprehensively suggested that the self-condensation of Va progresses more readily than the condensation between Va and Cr. The factors behind this will be the topic of our next paper.

Application of Alkaline Pulping to Pruned Branches of Citrus limon from Sudan

This study aims to utilize the pruned branches of Citrus limon in pulping with alkaline pulping methods and to determine the suitability of guar gum to improve the strength properties of pulps and limitations of cutting trees for environmental issues and utilization of lemon branches as horticultural residues. These branches’ physical properties exhibited high medium density and very low percentages of bark to wood ratio. The whole chemical components of these raw materials indicated the suitability to a pulp with alkaline cooking methods. In addition, alkaline sulfite anthraquinone with methanol methods gave excellent screened yield (60.1 %), negligible rejects, bleachable Kappa number 19.5, and best strength properties, especially tensile and strengths. Alkaline sulfite with anthraquinone gave excellent screened yield with a small percentage of rejects and bleachable Kappa number. On the other hand, soda cooking produced pulps with acceptable yield (41.9 %), rejects (3 %), and suitable strengths. The soda anthraquinone pulping methods produced pulp with good yields (56 - 59.7 %). Obviously, anthraquinone’s effect in preserving carbohydrates, specifically hemicelluloses, increases the yields and strengths. Guar gum improved pulps’ physical properties when added during beating with (0.25 % on oven-dry Soda-AQ pulps). It clears Citrus limon branches’ suitability with an age of 2 years in cooking with all alkaline pulping methods applied.

Recycling Waste Cotton Cloths for the Isolation of Cellulose Nanocrystals: A Sustainable Approach

There is an interest in the sustainable utilization of waste cotton cloths because of their enormous volume of generation and high cellulose content. Waste cotton cloths generated are disposed of in a landfill, which causes environmental pollution and leads to the waste of useful resources. In the present study, cellulose nanocrystals (CNCs) were isolated from waste cotton cloths collected from a landfill. The waste cotton cloths collected from the landfill were sterilized and cleaned using supercritical CO2 (scCO2) technology. The cellulose was extracted from scCO2-treated waste cotton cloths using alkaline pulping and bleaching processes. Subsequently, the CNCs were isolated using the H2SO4 hydrolysis of cellulose. The isolated CNCs were analyzed to determine the morphological, chemical, thermal, and physical properties with various analytical methods, including attenuated total reflection-Fourier transform-infrared spectroscopy (ATR-FTIR), field-emission scanning electron microscopy (FE-SEM), energy-filtered transmission electron microscopy (EF-TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results showed that the isolated CNCs had a needle-like structure with a length and diameter of 10–30 and 2–6 nm, respectively, and an aspect ratio of 5–15, respectively. Additionally, the isolated CNCs had a high crystallinity index with a good thermal stability. The findings of the present study revealed the potential of recycling waste cotton cloths to produce a value-added product.

Micro/nano-structural evolution in spruce wood during soda pulping

Alkaline delignification of wood tissue is the core of the global pulping technology and the most prominent large-scale separation of the main wood components. This work aims at improved understanding of the interplay between the topochemistry of alkaline pulping and the associated morphological changes. Morphology and chemical structure of partially soda-delignified wood chips were studied combining X-ray tomography (XRT), X-ray diffraction analysis and compositional characterization (lignin and carbohydrate content). The XRT studies of wet samples (providing 3D structural information without interfering drying effects), allowed observation of the cell wall separation as an increasing amount of lignin was removed with the increasing pulping time. Comparison between the microstructure of the surface and the central parts of the treated chips showed a more delignified microstructure at the surface, which highlights the dependence of the delignification process on the mass transport (hydroxide ions and lignin fragments) through the wood tissue. The crystallite size of cellulose increased in the <200> crystal planes during the early stage of pulping while there was little effect on the <110> plane.

Application of alkaline Pulping to Pruned Branches of Citrus limon from Sudan

The aim of this study to utilize the pruned branches of Citrus limon in pulping with alkaline pulping methods and to determine the suitability of guar gum to improve the strength properties of pulps. The physical properties of these branches exhibited high medium density and very low percentages of bark to wood ratio. The whole chemical components of these raw materials indicated the suitability to pulp with alkaline cooking methods. Alkaline sulfite anthrquinone with methanol methods gave very good screened yield (60.1%), negligible rejects and bleachable Kappa number 19.5 and best strength properties especially tensile and strengths. Alkaline sulfite with anthraquinone gave very good screened yield with small percentage of rejects and bleachable Kappa number. On the other hand soda cooking produced pulps with acceptable yield (41.9%), rejects (3%) and suitable strengths. The soda anthraquinone pulping methods produced pulp with good yields (56 -59.7%).It is obvious the effect of anthraquinone in preserving carbohydrates specifically hemicelluloses which increase the yields and strengths. Guar gum improved the physical properties of pulps when added during beating with (0.25% on oven dry Soda-AQ pulps) It clear the suitability of Citrus limon branches with age of two years in cooking with all alkaline pulping methods applied.

Atmospheric Soda Pulping of Banana Stem

Banana stem is one of the most explored non-wood lignocellulose due to its high cellulose content with small amount of lignin. The conventional pulping processes efficiently remove the lignin, but there is potential to reduce the energy and chemical consumptions due to the low lignin content of banana stem. In this work, soda pulping was carried out for 60-120 minutes using 16-20% w/v alkali charge at boiling temperature of 105°C. The efficiency of lignin removal at low temperature was evaluated using kappa number analysis. The effects of pulping time and alkali charge on pulp properties were investigated using fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Soda pulping using 18% w/v alkali charge at 10 liquid-to-solid ratio for 90 minutes under atmospheric pressure efficiently removed lignin with minimal cellulose degradation. Extended pulping time and concentrated alkali charge would induce cellulose degradation. FTIR analysis verified that alkaline pulping caused depolymerization on both lignin and cellulose. SEM images of banana stem showed ordered structure cellulose fibrils arrangement. Removal of lignin and hemicellulose was observed through smoother surface of the banana pulp. However, TGA analysis suggested that a better thermal stability could be achieved through pulping using 16% w/v alkali charge.