Analyzing TEMPO-Oxidized Cellulose Fiber Morphology: New Insights into Optimization of the Oxidation Process and Nanocellulose Dispersion Quality

Levanič, Jaka; Šenk, Vladimira Petrovič; Nadrah, Peter; Poljanšek, Ida; Oven, Primož; Haapala, Antti

doi:10.1021/acssuschemeng.0c05989

Cited by 82 publications

(47 citation statements)

References 47 publications

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“…The main benefit of pretreatment is to reduce the energy demand and to avoid clogging in the subsequent treatments, but pretreatments can have a notable effect on CNF characteristics and behavior. Severe pretreatment affects the integrity of the fibers and generates a large amount of fines, which is a potential problem for the subsequent processing stages (Levanič et al 2020). Several researchers have demonstrated that CNFs of very high aspect ratio, which demand a high energy consumption, have only marginal increased mechanical strength compared to less fibrillated products (Ang et al 2019;Balea et al 2016c).…”

Section: Introductionmentioning

confidence: 99%

Influence of pretreatment and mechanical nanofibrillation energy on properties of nanofibers from Aspen cellulose

et al. 2021

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The characteristics of cellulose nanofibers (CNFs) depend on many factors such as the raw material, type and intensity of the pre-treatment, and type and severity of the mechanical defibrillation process. The relationship among factors is complex but crucial in determining the final, fit-for-use CNF properties. This study aims to find the relationship between the CNF properties morphology, aspect ratio, nanofibrillation yield, transmittance and cationic demand, and the production process using bleached Aspen thermomechanical pulp as the raw material. Five different types of pretreatments were carried out and five different defibrillation intensities of high-pressure homogenization were evaluated. Pretreatments were: PFI refining at 20,000 revolutions, enzymatic hydrolysis with 80 and 240 g of enzyme per ton of dry pulp and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)–mediated oxidation with 5 and 15 mmol of NaClO per gram of dry pulp. From the twenty-five different procedures evaluated, results show that both the pretreatment and the severity of the high-pressure homogenization determined both the fibrillation yield and the CNF morphology. Moreover, the main properties of CNFs (cationic demand, yield, transmittance and aspect ratio) can be estimated from the carboxylic content of the pretreated pulp, which would facilitate the control of the CNF production and their tuning according to the production needs.

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Section: Introductionmentioning

confidence: 99%

Influence of pretreatment and mechanical nanofibrillation energy on properties of nanofibers from Aspen cellulose

et al. 2021

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“…Moreover, the presence of hemicellulose in this pulp could suppose that this loss of material could also be affected by the loss of oxidized hemicellulose. [ 28 ] This high number of effects could be responsible for the fluctuations found in the recovery rate of eucalyptus CNF, which varied in a high proportion from one cycle to the other.…”

Section: Resultsmentioning

confidence: 99%

Increasing the Possibilities of TEMPO‐Mediated Oxidation in the Production of Cellulose Nanofibers by Reducing the Reaction Time and Reusing the Reaction Medium

Sánchez-Salvador

Campano

Negro

et al. 2021

Advanced Sustainable Systems

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2,2,6,6‐Tetramethylpiperidine‐1‐oxyl (TEMPO)‐mediated oxidation of cellulose is the most effective pretreatment to obtain highly fibrillated cellulose nanofibers (CNFs). However, the associated environmental impact and the high operational costs have limited its implementation at large scale. This study aims to improve the effectiveness of this pretreatment by reducing the oxidation time and reusing the reaction medium, with the ultimate objective of upscaling a more viable sustainable process. The results show the possibility of reducing the reaction time by 85% and 60% in the case of cotton and eucalyptus pulps, respectively, without altering the properties of the obtained CNFs (carboxyl groups, nanofibrillation yield, cationic demand, and morphology). The reuse of 75% of the reaction medium for ten cycles, do not alter the properties of the CNFs either. With this approach, the consumption of TEMPO and NaBr is reduced by 67%, while that of NaClO is decreased by 42% and 22% in the oxidation of cotton and eucalyptus cellulose, respectively. At the same time, the environmental concerns derived from the disposal of the catalysts are considerably reduced.

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“…The oxidation process, using various chemicals, including metaperiodate, hypochlorite, dichromate, nitrogen dioxide, or TEMPO (2,2,6,6-tetramethylpiperidn-1-yl)oxyl) [ 239 , 240 , 241 , 242 , 243 ], makes cellulose materials more vulnerable to hydrolysis and therefore potentially degradable by the human body. The only impediment of this process is that it can significantly alter the structure of cellulose, disturbing the unique, medically desirable properties of cellulose, such as its high tensile strength and conformability.…”

Section: Toxicological Evaluation and Potential Limitations Of Ncs-based Materialsmentioning

confidence: 99%

Advanced Functional Materials Based on Nanocellulose for Pharmaceutical/Medical Applications

Nicu¹,

Ciolacu

Ciolacu³

2021

Pharmaceutics

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Nanocelluloses (NCs), with their remarkable characteristics, have proven to be one of the most promising “green” materials of our times and have received special attention from researchers in nanomaterials. A diversity of new functional materials with a wide range of biomedical applications has been designed based on the most desirable properties of NCs, such as biocompatibility, biodegradability, and their special physicochemical properties. In this context and under the pressure of rapid development of this field, it is imperative to synthesize the successes and the new requirements in a comprehensive review. The first part of this work provides a brief review of the characteristics of the NCs (cellulose nanocrystals—CNC, cellulose nanofibrils—CNF, and bacterial nanocellulose—BNC), as well as of the main functional materials based on NCs (hydrogels, nanogels, and nanocomposites). The second part presents an extensive review of research over the past five years on promising pharmaceutical and medical applications of nanocellulose-based materials, which have been discussed in three important areas: drug-delivery systems, materials for wound-healing applications, as well as tissue engineering. Finally, an in-depth assessment of the in vitro and in vivo cytotoxicity of NCs-based materials, as well as the challenges related to their biodegradability, is performed.

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Analyzing TEMPO-Oxidized Cellulose Fiber Morphology: New Insights into Optimization of the Oxidation Process and Nanocellulose Dispersion Quality

Cited by 82 publications

References 47 publications

Influence of pretreatment and mechanical nanofibrillation energy on properties of nanofibers from Aspen cellulose

Influence of pretreatment and mechanical nanofibrillation energy on properties of nanofibers from Aspen cellulose

Increasing the Possibilities of TEMPO‐Mediated Oxidation in the Production of Cellulose Nanofibers by Reducing the Reaction Time and Reusing the Reaction Medium

Advanced Functional Materials Based on Nanocellulose for Pharmaceutical/Medical Applications

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