Unified Kinetic Model for Cellulose Deconstruction via Acid Hydrolysis

Producing bacterial cellulose from industrial recycling paper waste sludge

This study aimed to produce bacterial cellulose from paper waste sludge (PWS) as a method of utilizing the cellulose source from the remaining pulp in the material. Initially, PWS was hydrolyzed by sulfuric acid to create an enriched-reducing sugar hydrolysate. One-factor experiments were conducted with a fixed amount of PWS (5 g) to investigate the influence of hydrolysis conditions, including water, sulfuric acid addition, temperature, and retention time, on the production yield of reducing sugars. Based on these results, the Box-Behnken model was designed to optimize the hydrolysis reaction. The optimal hydrolysis conditions were 10 ml/g of the sulfuric acid solution (30.9%) at 105.5 °C for 90 min of retention time 0.81 (gGE/g PWS), corresponding to a conversion yield of 40.5%). Subsequently, 100 ml of the filtered and neutralized PWS hydrolysate was used as the culture to produce the bacterial cellulose (BC) using Acetobacter xylinum, which produced 12 g/L of bacterial cellulose. The conversion yield of bacterial cellulose calculated as the ratio of the weight of produced bacterial cellulose to that of cellulose in PWS reached 33.3%. The structure of the obtained BC was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) to indicate the formation of nano-cellulose fiber networks. This research proposed a combined method to convert paper waste sludge into bacterial cellulose, demonstrating the potential for waste utilization and sustainable production of paper industries for added-value products.

New Perspectives into Cellulose Fast Pyrolysis Kinetics Using a Py-GC × GC-FID/MS System

Cellulose pyrolysis is reportedly influenced by factors such as sample size, crystallinity, or different morphologies. However, there seems to be a lack of understanding of the mechanistic details that explain the observed differences in the pyrolysis yields. This study aims to investigate the influence of particle size and crystallinity of cellulose by performing pyrolysis reactions at temperatures of 673–873 K using a micropyrolyzer apparatus coupled to a GC × GC-FID/TOF-MS and a customized GC-TCD. Over 60 product species have been identified and quantified for the first time, including water. Crystalline cellulose with an average particle size of 30–50 × 10^–6 m produced 50–60 wt % levoglucosan. Predominantly amorphous cellulose with an average particle size of 10–20 × 10^–6 m resulted in remarkably low yields (10–15 wt %) of levoglucosan complemented by higher yields of water and glycolaldehyde. A detailed kinetic model for cellulose pyrolysis was used to obtain mechanistic insights into the different pyrolysis product compositions. The kinetics of the mid-chain dehydration and fragmentation reactions strongly influence the total yields of low-molecular weight products (LMWPs) and are affected by cellulose chain arrangement. Levoglucosan yields are very sensitive to the activation of parallel cellulose decomposition reactions. This can be attributed to the mid-chain reactions forming smaller chains with the levoglucosan ends, which remain in the solid phase and react further to form LMWPs. Direct quantification of water helped to improve the description of the dehydration, giving further indications of the dominant role of mid-chain reaction pathways in amorphous cellulose pyrolysis.

Hierarchically porous poly(amidoxime)/bacterial cellulose composite aerogel for highly efficient scavenging of heavy metals

Developing cheap, green, efficient and renewable adsorbents to address the issue of heavy metal pollution is highly desired for satisfying the requirements of economy sustainability and water security. Herein, a composite aerogel composed of bacterial cellulose (BC) and poly(amidoxime) (PAO) has been fabricated via a facile and scalable self-assembly and in situ oximation transformation for heavy metals removal. Benefiting from the unique three-dimensional (3D) interconnected porous architecture and high density of amidoxime functional moieties, the developed PAO/BC composite aerogel is capable of efficiently sequestrating heavy metals with exceptional sorption capacities, e.g. 571.5 mg g^-1 for Pb²⁺, 509.2 mg g^-1 for Cu²⁺, 494 mg g^-1 for Zn²⁺, 457.2 mg g^-1 for Mn²⁺, and 382.3 mg g^-1 for Cd²⁺, outperforming most reported nano-adsorbents. Meanwhile, the sorption equilibrium for the investigated five heavy metals is achieved within 25 min with high removal efficiencies. Significantly, the developed PAO/BC composite aerogels possess superior reusability performance. Furthermore, the PAO/BC aerogels-packed column can continuously and effectively treat the simulated wastewater with multiple heavy metals coexisting to below the threshold value in the drinking water recommended by World Health Organization (WHO), highlighting its feasibility in the complex environmental water.

A Novel Kinetic Modeling Framework for the Polycondensation of Sugars Using Monte Carlo and the Method of Moments

The kinetics of the hydrolysis and polycondensation reactions of saccharides have made the subject of numerous studies, due to their importance in several industrial sectors. The present work, presents a novel kinetic modeling framework that is specifically well-suited to reacting systems under strict moisture control that favor the polycondensation reactions towards the formation of high-degree polysaccharides. The proposed model is based on an extended and generalized kinetic scheme, including also the presence of polyols, and is formulated using two different numerical approaches, namely a deterministic one in terms of the method of moments and a stochastic kinetic Monte Carlo approach. Accordingly, the most significant advantages and drawbacks of each technique are clearly demonstrated and the most fitted one (i.e., the Monte Carlo method) is implemented for the modeling of the system under different conditions, for which experimental data were available. Through these comparisons it is shown that the model can successfully follow the evolution of the reactions up to the formation of polysaccharides of very high degrees of polymerization.

Accurate molar masses of cellulose for the determination of degradation rates in complex paper samples

Complex cellulosic samples are often difficult to analyse with size-exclusion chromatography. The strong molecular associations of hemicelluloses and lignin with cellulose produce multimodal molar mass distributions (MMD) that are difficult to interpret. More reliable ways of calculating the molar masses of cellulose are thus necessary. This is particularly relevant when studying the kinetics of paper degradation, as the number average molar mass is the most precise indicator. In this study various data handling methods based on the deconvolution of bimodal and multimodal MMDs of complex cellulosic samples after SEC-MALS-DRI analysis are examined in order to propose more accurate paper degradation rates. Two deconvolution methods, which do or do not rely on polymer calibration curves were developed and were applied to several kraft and groundwood pulp papers unaged and hygrothermally aged. The deconvolution methods are discussed and evaluated in light of calculated cellulose activation energies, degradation rates and paper usable lifetime predictions.

Disintegration of the agricultural by-product wheat bran under subcritical conditions

BACKGROUND

The disintegration of destarched wheat bran in water and sulfuric acid (pH 3) under subcritical conditions (275-300 °C) and at short reaction times (1-4 min) was investigated. A cascade process comprising a stepwise separation of the liquid was applied to reduce the formation of undesired degradation products.

RESULTS

The highest degree of biomass disintegration (67% dry mass solubilization) was achieved by application of a cascade process at 275 °C (pH 3). Regarding the dissolution of carbohydrates (monomeric and oligomeric form), the total glucose yields remained below 60%, while the total xylose and arabinose yields were about 76% and 67%. Approximately 74% of the protein and 95% of the mineral fraction could be extracted. The application of the cascade process enabled a substantially reduced formation of degradation products.

CONCLUSION

When operating hydrothermally and subcritically in order to avoid some problematic aspects of a biorefinery, an extensive disintegration and monomerization of wheat bran and its constituents remains difficult even under the tested conditions (300 °C, pH 3). However, the applied cascade process proved to be useful to increase the yields and to substantially reduce the formation of undesired degradation products. Despite this fact, increased water consumption has to be conceded. © 2018 Society of Chemical Industry.

Investigating the DMPO-formate spin trapping method for the study of paper iron gall ink corrosion

Reactive oxygen species evidenced in acidic iron gall inks are not hydroxyl radicals and are not linked to paper degradation.

Hydrolysis of cellobiose to monosaccharide catalyzed by functional Lanthanum(iii) metallomicelle

Cellobiose could be effectively hydrolyzed to monosaccharide (glucose, fructose and 1,6-anhydroglucose) by the catalysis of metallomicelle La(DMBO)₂under mild conditions.