Oxalic Acid Hydrolysis Research Articles

Controlled reaction dynamics of cellulose: Revealing the dual morphology nanocrystals

Cellulose nanocrystals exhibit diverse morphology with embedded crystallinity derived from the ordered crystalline regimes of cellulose fibers. Acid hydrolysis parameters controls the morphology of nanocrystals and is the primary efficient route for the synthesis of cellulose nanocrystals. In this study, we explored the impact of temperature on the morphology engineering of cellulose nanocrystals derived from banana pseudostem by oxalic acid hydrolysis, an underexplored method. Confirmation of successful cellulose extraction was achieved through fibrous morphology observed in FESEM and TEM analyses. X-ray diffraction and Raman spectroscopy affirmed the presence of type II cellulose. Notably, for the first time, we report the derivation of toroidal and spherulitic sheet-like morphologies in cellulose nanocrystals synthesized by hydrothermal method from banana psuedostem. Our investigation revealed that cellulose hydrolysis at 120 °C yields nanocrystals characterized by toroidal and spherulitic sheet-like morphologies with excellent crystallinity, as confirmed by FESEM and TEM analyses, with average thicknesses of 13.70 nm and 18.05 nm, respectively. Interestingly, elevating the hydrolysis temperature to 180 °C led to the collapse of these structures into carbon dots, exhibiting notable cyan emission.

Facile fabrication of arecanut palm sheath based robust hydrophobic cellulose nanopapers via self-assembly of ZnO nanoflakes and its shelf-life prediction for sustainable packaging applications

Cellulose nanofibers have been extracted from arecanut palm sheath fibers via mild oxalic acid hydrolysis coupled with steam explosion technique. Cellulose nanofibers with diameter of 20.23 nm were obtained from arecanut palm sheath fibers. A series of robust hydrophobic cellulose nanopapers were fabricated by combining the synergistic effect of surface roughness induced by the successful deposition of zinc oxide (ZnO) nanoflakes and stearic acid modification via a simple and cost-effective method. In this work, agro-waste arecanut palm sheath was employed as a novel source for the extraction of cellulose nanofibers. 2 wt% of ZnO nanoflakes and 1 M concentration of stearic acid were used to fabricate mechanically robust hydrophobic cellulose nanopapers with a water contact angle (WCA) of 134°. During the deposition of zinc oxide nanoflakes on the CNP for inducing surface roughness, a hydrogen bonding interaction is formed between the hydroxyl groups of cellulose nanofibers and the zinc oxide nanoflakes. When this surface roughened CNP was dipped in stearic acid solution. The hydroxyl groups in zinc oxide nanoflakes undergoes esterification reaction with carboxyl groups in stearic acid solution forming an insoluble stearate layer and thus inducing hydrophobicity on CNP. The fabricated hydrophobic cellulose nanopaper displayed a tensile strength of 22.4 MPa and better UV blocking ability which is highly desirable for the sustainable packaging material in the current scenario. Furthermore, the service life of the pristine and modified cellulose nanopapers was predicted using the Arrhenius equation based on the tensile properties obtained during the accelerated ageing studies. The outcome of this study would be broadening the potential applications of hydrophobic and mechanically robust cellulose nanopapers in sustainable packaging applications.

High-Performance Methylsilsesquioxane Aerogels: Hydrolysis Mechanisms and Maximizing Compression Properties.

Synthesis of methylsilsesquioxane aerogels by ambient pressure drying instead of supercritical drying has recently emerged as a major trend, but the issues of low mechanical strength and unstable performance still need to be resolved. This work reveals the microscopic formation mechanisms of gel skeleton based on the kinetic characteristics of methyltrimethoxysilane (MTMS) precursor hydrolysis and the associated sol-gel reactions. The effects of oxalic acid concentration (cOA) and hydrolysis time of MTMS solution (th) on the gelation time, morphologies, microstructures, chemical structure, and compression properties of the as-synthesized methylsilsesquioxane aerogels are investigated. The optimal cOA and th are 38.4 mmol/L and 120 min, respectively, endowing the methylsilsesquioxane aerogels with a compression strength of 0.170 MPa and a maximum compression strain of 61.2%. Precise control of the hydrolysis conditions ensures the formation of branched particle-to-particle networks, which is crucial for maximizing the compression properties of methylsilsesquioxane aerogels synthesized under industry-relevant conditions.

Non-cytotoxic, highly functionalized cellulose nanocrystals with high crystallinity and thermal stability derived from a novel agromass of Elettaria cardamomum, using a soft and benign mild oxalic acid hydrolysis

Non-cytotoxic, highly crystalline, and functionalized, thermally stable cellulose nanocrystals are extracted from the stems of Elettaria cardamom, a novel underutilised agromass, by employing a neat green, mild oxalic acid hydrolysis. The protocol involves a chemo-mechanical strategy of coupling hydrolysis with steam explosion and homogenization. The obtained CNC showed a crystallinity index of 81.51 %, an aspect ratio of 17.80 ± 1.03 and a high degradation temperature of about 339.07 °C. The extraction procedure imparted a high negative surface functionalization with a zeta potential value of −34.244 ± 0.496 mV and a polydispersity of 16.5 %. The CNC had no antibacterial activity, according to non-cytotoxic experiments conducted on four bacterial strains. This supports the notion of “One Health” in the context of AMR by demonstrating the safety of antibiotic resistance due to consistent exposure upon environmental disposal. The as-extracted nanocellulose crystals can be a potential candidate for commercial application in wide and diversified disciplines like food packaging, anti-infective surfaces for medical devices, biosensors, bioelectronics etc.

Optimization of microfibrillated cellulose isolation from cocoa pod husk via mild oxalic acid hydrolysis: A response surface methodology approach

Theobroma cacao L. species, cultivated worldwide for its valuable beans, generates up to 72% weight of the fruit as waste. The lack of reutilization technologies in the cocoa agroindustry has hindered the exploitation of valuable bio-components applicable to the generation of high value added bioproducts. One such bioproduct is microfibrillated cellulose (MFC), a biopolymer that stands out for its desirable mechanical properties and biocompatibility in biomedical, packing, 3D printing, and construction applications. In this study, we isolated microfibrillated cellulose (MFC) from cocoa pod husk (CPH) via oxalic acid hydrolysis combined with a steam explosion. MFC isolation started with the Solid/Liquid extraction via Soxhlet, followed by mild citric acid hydrolysis, diluted alkaline hydrolysis, and bleaching pre-treatments. A Response Surface Methodology (RSM) was used to optimize the hydrolysis reaction at levels between 110 and 125 °C, 30–90 min at 5–10% (w/v) oxalic acid concentration. The cellulose-rich fraction was characterized by Fourier-Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) analyses. Characterization analyses revealed a cellulose-rich polymer with fibers ranging from 6 to 10 μm, a maximum thermal degradation temperature of 350 °C, and a crystallinity index of 63.4% (peak height method) and 29.0% (amorphous subtraction method). The optimized hydrolysis conditions were 125 °C, 30 min, at 5% w/v oxalic acid: with a 75.7% yield. These results compare with MFC obtained through highly concentrated inorganic acid hydrolysis from different biomass sources. Thus, we show a reliable and greener alternative chemical treatment for the obtention of MFC.

Chiral Self-Assembly Behavior of Carboxylated Cellulose Nanocrystals Isolated by Recyclable Oxalic Acid from Degreasing Cotton

Carboxylated cellulose nanocrystals (OA-CNCs) isolated by aqueous recyclable oxalic acid hydrolysis from degreasing cotton were used to observe its self-assembly behavior and chiral nematic properties. The oxalic acid here served as the sole catalyst to esterify and hydrolyze the degreasing cotton. The results indicated that the obtained OA-CNC suspensions were spontaneously phase-separated into a chiral nematic mesophase above a critical concentration, and the occurrence of chiral self-assembly is highly dependent on the aspect ratio and the surface charge of the OA-CNC suspension. Scanning electron microscopy images of the cross section of OA-CNC solid films revealed a periodic ordered multilayer structure. The residual OA was easily recovered through simple re-crystallization method after reactions with a high recovery rate of at least 90%. The recycled OA (ROA) had excellent performance in terms of ROA-CNC yield even after reusing for five cycles. Moreover, the resultant ROA-CNCs from recycled OA could also form chiral nematic ordered phases with little change in the critical concentration and pitch, suggesting excellent suitability for sustainable OA-CNC production for photonics and other specialty applications.

Integrated Biobased Processes for Nanocellulose Preparation from Rice Straw Cellulose

High-potential nanomaterials were derived from rice straw using the integrated biobased processes of enzymatic hydrolysis with green organic acid hydrolysis assisted with ultrasonication pretreatment. The optimization condition of nanocellulose preparation by enzymatic hydrolysis via central composite design (CCD) achieved a maximum nanocellulose content of 32.37 ± 0.47% using a cellulase concentration of 107.06 U/mL and 0.13% (w/w) of rice straw cellulose. The ultrasonication-assisted pretreatment prior to enzymatic hydrolysis improved nanocellulose preparation to 52.28 ± 1.55%. Integration with oxalic acid hydrolysis increased the nanocellulose content to 64.99 ± 0.16%. Granular nanocellulose was obtained and consisted of a 105–825 nm nanosize with a zeta potential value of −34.5 mV, and nanocellulose suspension showed high stability without aggregation. In addition, the remaining rice straw cellulose after oxalic acid was microcrystalline nanocellulose. All prepared nanocellulose represented a functional group as original cellulose but had a low crystallinity index (CrI) of 15.68% that could be classified as amorphous nanocellulose. Based on their characteristics, all nanocellose could be further applied in food, cosmetics, and pharmaceuticals. Moreover, the results indicated that the rice straw could be an alternative non-edible cellulose source for preparing potential nanocellulose via a controlled hydrolysis process.

Carbon black and chitin nanofibers for green tyres: Preparation and property evaluation

This research highlights the synergistic use of carbon black (CB) and chitin nanofibers (CHNFs) for developing green tyres for the first time. The CHNFs (12–30 nm) were prepared from chitin powder with the help of steam explosion and mild oxalic acid hydrolysis. The CHNFs were uniformly dispersed in natural rubber (NR) latex, dried, and mixed with CB in a two-roll mill to form NR/CB/CHNF composites. The NR/CB/CHNF composite at 1 phr CHNF loading exhibited tensile and tear strengths that were about 47 and 160 % greater than the NR-Neat, respectively. The dynamic mechanical analysis showed that the loss tangent (tan δ) at 60 °C was 50 % lower for the NR/CB/CHNF 1.0 composite than for the NR/CB50 composite. The study succeeded in developing a new green tyre tread formulation that would be helpful for attaining sustainability and a circular economy.

Silver nanoparticles and cellulose microfiber micro-composite from banana (Musa acuminata) waste: green synthesis, antioxidant property and antimicrobial capacity

The green chemistry promotes the synthesis of nanomaterials from plant extracts as a new climate intelligent alternative to the use of conventional protocols based on costly and toxic chemicals. Therefore, this research was undertaken to analyses the efficiency of banana (peels and rachis) waste extracts in the production of a micro-composite composed by silver nanoparticles (AgNPs) and cellulose microfibers (CMF) respectively. Results showed the synthesis of 24 nm diameter spherical particles AgNPs, with a peak of absorbance at 410 nm, in (v/v) water:ethanol extracts of banana peels at a final dilution of 3.10-2. Concomitantly, 50-350 µm in length and 5-10 µm of diameter CMF were obtained via the oxalic acid hydrolysis of the oven-dried banana rachis. The micro-composite (AgNPs-CMF) and AgNPs displayed an active reducing capacity over 60% determined by the DPPH test, and active bacterial activity against E. Coli and S. aureus in Petri dishes. Overall results support the use of banana waste for the synthesis of AgNPs and CMF for industrial purposes.

Microencapsulated phase change material via Pickering emulsion based on xylan nanocrystal for thermoregulating application

Phase change materials (PCM) are promising for thermal regulation and energy storage, but suffer from the deformation and leakage of capsules. Herein, inspired by cellulose nanocrystal (CNC), xylan nanocrystal (XNC) with a dimension of 25–60 nm was successfully prepared through oxalic acid hydrolysis of high-crystalline xylan as raw materials via a top-down approach. With the introduction of hydrophobic groups, compared to XNC, succinylated XNC showed more remarkable emulsifying property over 7 days of storage at room temperature. Microencapsulated PCM composite consisting of sodium alginate (SA) as “matrix” and succinylated xylan nanocrystal (XNC) stabilized paraffin-based Pickering capsule (PCM beads) as “core” was facilely fabricated. PCM composite with the latent heat of 105.59 J·g−1 showed excellent thermoregulating performance. Our work suggests a new pathway toward sustainability of hemicelluloses in the application of food emulsion and thermal energy management.

Activated Carbon Modified by Ester Hydrolysis of Ethyl Acetate for Water Vapor Adsorption Enhancement

To improve water vapor adsorption, this study employed oxalic acid–ethyl acetate acidic hydrolysis to modify honeycomb activated carbon and introduce hydrophilic functional groups. Scanning electron microscopy (SEM), Boehm titration, Fourier transform infrared spectroscopy (FT-IR), and an automatic surface area analyzer (BET) were used to characterize the microscopic morphology, surface functional groups, specific surface area, and pore size changes. The results showed that, when the concentration of oxalic acid is 0.0006 mol/cm3, the specific surface area is 179.06 m2/g. After hydrolysis with ethyl acetate, the original functional groups became more abundant, while the number of total acidic functional groups on the surface grew from 0.497 mmol/g to 1.437 mmol/g. The static water vapor adsorption experiments were conducted on modified activated carbon under constant temperature and humidity conditions. Compared with unmodified activated carbon, the activated carbon modified with 0.0006 mol/cm3 oxalic acid increased the adsorption capacity of water vapor by 15.7%. The adsorption capacity of activated carbon after being combined with 0.0006 mol/cm3 oxalic acid and ester hydrolysis modification increased by 37.1%. At the same temperature, the adsorption capacity increased with a higher relative humidity. At the same relative humidity, the adsorption capacity decreased as the temperature rose. Therefore, this modification method may provide clues for the application of enhancing the hygroscopic ability of activated carbon.

Enhanced performance of cellulose nanofibre reinforced styrene butadiene rubber nanocomposites modified with epoxidised natural rubber

The present work focuses on the potential use of Pandanus kaida proproot cellulose nanofibre as reinforcing filler for styrene butadiene rubber (S) vulcanizates in the presence of epoxidised natural rubber (E) as modifier. The incompatibility between the polar cellulose and non-polar styrene butadiene rubber can be overcome by the use of epoxidised natural rubber (E). This is a facile process compared to other strategies where cellulose nanofibers are chemically modified thus making the process expensive. Initially, cellulose nanofibre was extracted from Pandanus kaida prop root via hydrothermal assisted oxalic acid hydrolysis. FESEM image revealed that cellulose nanofibres (PN) had a diameter of around 15–30 nm. S/PN masterbatches were prepared via latex stage mixing, co-coagulated, later melt-mixed with E and other compounding ingredients followed by vulcanisation. The investigation of mechanical properties revealed that PN nanofiber at 5 phr loading (S/PN5) resulted in enhanced properties. For further improvement, epoxidised natural rubber (E) was used as modifier at various loadings in S/PN5. At 1 phr of E loading (S/PN5/E1), the tensile strength, modulus, tear strength and abrasion resistance index improved significantly by 150%, 47%, 93% and 19%, respectively, compared to S gum vulcanizates. Strain sweep studies indicated better fibre-matrix interaction in the presence of E1. DMA studies revealed a higher storage modulus, lower damping, higher cross-link density and lower adhesion factor for S/PN5/E1 composites.

Effect of oxalic acid and sulphuric acid hydrolysis on the preparation and properties of pineapple pomace derived cellulose nanofibers and nanopapers

Nanocellulose is the “green magnet” which attracts a wide spectrum of industries towards it due to its availability, biodegradability, and possible smart applications. For the first time, pineapple pomace was being explored as an economic precursor for cellulose nanofibers. Nanofiber isolation was accomplished using a chemo-mechanical method and solution casting was adopted for the development of nanopapers. Moreover, the study examines the structural, optical, crystalline, dimensional, and thermal features of nanofibers isolated using different acid hydrolysis (oxalic acid and sulphuric acid) methods. Fourier-transform infra-red spectroscopy, 13C solid-state nuclear magnetic resonance spectroscopy, and X-ray diffraction analysis indicated the presence of type I cellulose. The transmittance, crystallinity index, and thermal stability of PPNFS (sulphuric acid treated fiber) were greater than PPNFO (oxalic acid treated fiber). The transmission electron microscopy and dynamic light scattering analysis confirmed the nanodimension of PPNFO and PPNFS. While comparing the optical and mechanical properties of nanopapers, PPNFS outperforms PPNFO. The tensile strength of the prepared nanopapers (64 MPa (PPNFO) and 68 MPa (PPNFS)) was found to be high compared to similar works reported in the literature. The prepared nanopaper is proposed to be used for food packaging applications.

Elucidation of oil-in-water emulsions stabilized with celery cellulose

Celery pomace (Rw), an agricultural residue, is a cellulose source for the separation of celery cellulose. Oxalic acid hydrolysis, followed by high pressure homogenization, was used to separate nanocellulose with aspect ratios of 63.8–171.7. Different sizes of celery cellulose were obtained, which were used as stabilizers for oil-in-water emulsions. The aspect ratio of nanocellulose significantly affected their emulsifying ability. With the change in the oil phase volume and solid content of celery nanocellulose, the surface coverage ratio of the emulsifying droplets increased from 0.2 to 8.1. In addition, the environmental factors, such as ionic strength, pH values, and temperature negligibly affected the stability of the emulsion. It shown that flexible celery cellulose played an important role in the stability of emulsion, and the higher concentration of cellulose improved the non-covalent “physical” cross-linking between molecules. The results suggest the possibility of using celery or other vegetables cellulose for stabilizing oil-in-water emulsions.

Preparation and characterization of waxy maize starch nanocrystals with a high yield via dry-heated oxalic acid hydrolysis

In this study, we prepared waxy maize starch nanocrystals (SNCs) for the first time using dry-heated oxalic acid hydrolysis with or without ultrasonic treatment. The dry-heating treatment was subjected to oxalic acid hydrolysis to produce SNCs with a high yield of 89.6%. Dynamic light scattering showed that the size of the obtained SNCs was 46.58–197.15 nm, and the polydispersion index was 0.28–0.52. Atomic force microscopy investigation found that the SNCs had a major axis of about 211.5 nm and a height of about 9.4 nm. The thermogravimetric analysis revealed that the SNCs’ thermal stability slightly improved compared with that of native starch. X-ray diffraction indicated that the produced SNCs preserved the A-type crystal form of native starch, with the relative crystallinities of 29.52%–42.44%. The newly fabricated SNCs have potential applications in agriculture, cosmetics, and advanced materials.

Hybrid films based on holistic celery nanocellulose and lignin/hemicellulose with enhanced mechanical properties and dye removal

The endeavor to isolate celery lignocellulosic components and reconstruct into nanocellulose filled and holistic biocomposite films is to demonstrate the potential of re-engineering vegetables into nanocomposite films. The structure−properties relations of these hybrid films were analyzed systematically. The work explored that celery was isolated into the cellulose-rich solid and lignin/hemicellulose (LH) solution using moderate alkali immersions. The 16.1% LH yield was obtained, and cellulose nanofibrils (CCNF) were derived from the solid, at 43.1% yield of the original celery by oxalic acid hydrolysis. Oxalic acid hydrolysis followed by microfluidization was used to separate CCNF with dimensions of 5–6 nm and 1.3–1.7 μm. The LH solution containing CCNF was cast into film structures that exhibited significantly improved mechanical and flexibility properties. Moreover, results suggested that these hybrid films showed a high MB removal efficiency, which ranged from 192.1 to 429.9 mg/g. Totally, over 67.9% celery hybrids were used and it provided an effective and value-added utilization technology for celery and other vegetables.

Two characteristic cellulose nanocrystals (CNCs) obtained from oxalic acid and sulfuric acid processing

We systematically compare the different properties of cellulose nanocrystals (CNCs) obtained by oxalic acid and sulfuric acid hydrolysis methods. The variant characteristics of two kinds of CNCs were confirmed by XRD, DLS, Zeta, TGA, and SEM techniques. When CNCs were mixed with PEG, and the chiral nematic tissue of CNCs was retained in the solid film to observe the liquid crystal phase by evaporation-induced self-assembly. The brilliant snowflake-like pattern of CNC film was observed through oxalic acid instead of sulfuric acid. More importantly, carboxylated CNCs prepared by oxalic acid was easily formed a liquid crystal phase by adding cationic solutions into 1.27% CNC solution. The extra properties of CNCs obtained by oxalate dihydrate contribute to its potential application prospects in optical devices and chiral separation.

A comparative study of lignocellulosic nanofibrils isolated from celery using oxalic acid hydrolysis followed by sonication and mechanical fibrillation

Two lignocellulosic nanofibrils (LCNF) were produced from celery using oxalic acid hydrolysis and sonication (OS) or refining by a SuperMassColloider grinder treatment (MT). Physicochemical properties, such as morphological properties, crystallinity, thermal stability, zeta potential and transmittance for the obtained nanofibrils were evaluated. Compared to refining in SuperMassColloider grinder, OS treatment contributed greater separation of nanofibril bundles by introducing negative carboxyl groups. In detail, mechanical fibrillation resulted in the LCNF with longer length and thicker diameter. OS treatment produced LCNF with smaller height of 5.5 nm and higher aspect ratio than the one obtained by MT treatment, and endowed high crystallinity and thermal stability due to its preferential degradation of amorphous carbohydrates and lignin. Furthermore, OS-LCNF with carboxyl group contributed more stable aqueous suspension with surface charge of − 32.9 mV, better than MT-LCNF sample with entangled network structure. The comparative study can gain insight into the use of celery as a potential source for nanocellulose production.

High-Yield Synthesis of Functionalized Cellulose Nanocrystals for Nano-Biocomposites

A facile versatile green one-step procedure to fabricating functionalized cellulose nanocrystals (CNCs) with high yields and thermostability was put forward via molten oxalic acid hydrolysis by aid of simultaneous microwave and sonication. The synchronized hydrolysis and esterification of cellulose took place in the one-pot solvent-free reaction, and thus we developed an environmentally benign and scalable concurrent acid hydrolysis/Fischer esterification method to produce acid-functionalized CNCs using microwave and sonication in 85.5% yield. Compared to classical methods for the functionalization of CNCs, the presented study avoided the extensive consumption of water and solvent and achieved zero waste liquid discharge. Moreover, the used solid acid could easily be recycled to make it possible for the large-scale and cleaner production of CNCs. The resultant CNCs with high thermal stability and excellent dispersion stability are excellent for nano-biocomposite applications.

From wheat straw to xylitol: bioconversion by a genetically engineered Candida guilliermondii strain

In order to produce bioethanol from olive tree pruning biomass, deacetylation was performed employing sodium hydroxide. Optimal conditions were determined using experimental design techniques. The highest acetic acid removal (3.8 g/dm3), obtained by response surface methodology, was at optimum pretreatment conditions of temperature 60 °C, 0.8% NaOH and residence time 60 min. After oxalic acid hydrolysis of pretreated biomass, the hydrolysates were directly used for ethanol production without further detoxification process.Ethanol yields ranged from 0.19 to 0.45 g/g, reaching the maximum yield value when pretreatment was carried out at 130 °C with 100 mM oxalic acid, involving a combined severity factor (CSF) of 1.05. The highest ethanol concentration obtained from pretreated biomass was 6.2 g/dm3 at 150 °C, using 75 mM of oxalic acid (CSF = 1.53).