Acryloyl-modified cellulose nanocrystals: effects of substitution on crystallinity and copolymerization with acrylic monomers

Cellulose nanocrystals (CNCs) are crystalline nano-rods that have high specific strength with hydroxyl surface chemistry. A wide range of chemical modifications have been performed on the surface of CNCs to increase their potential to be used in applications where compatibilization with other materials is required. Understanding the surface chemistry of CNCs and critically examining the functionalization technique are crucial to enable control over the extent of modification and the properties of CNCs. This work aims to optimize the surface modification of wood-derived CNCs with isocyanatoethyl methacrylate (IEM), a bifunctional molecule carrying both isocyanate and vinyl functional groups. We studied the effect of modification reaction time and temperature on the degree of substitution, crystallinity, and morphology of the CNCs. We found that the degree of modification is a strong and increasing function of reaction temperature over the range studied. However, the highest temperature (65 °C) and the longest time of reaction (6 h) resulted in shorter, thinner, and less crystalline CNCs. We obtained surface hydroxyl conversion of 60.1?±?6% and percent crystallinity of 84% by keeping the reaction shorter (30 min) at 65 ºC. Also, the copolymerization ability of modified CNCs was verified by polymerizing attached IEM groups with acrylic monomers via solution polymerization. The polymer-grafted CNCs (6% w/w) dispersed better in an acrylic polymer matrix compared to unmodified CNCs (umCNCs), resulting in approximately 100% improvement in the tensile strength and about 53% enhancement in the hardness of the acrylic, whereas addition of 6% w/w umCNCs did not influence the strength and hardness.

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Pretreatment of Rice Straw Using a Butanone or an Acetaldehyde Dilute Solution Explosion for Producing Ethanol

Ethanol conversion from rice straw using butanone and acetaldehyde dilute solution explosions was evaluated based on the optimization of pure water explosion. To decrease residual inhibitor content, the exploded slurry was dried and investigated at different temperature. Using a 0.9-mol/L butanone solution explosion, with the explosion pressure set at 3.1 MPa, the residence time at 7 min, the dried rice straw-to-water ratio at 1:3 (w/w), and the exploded slurry drying temperuture at 90 °C for 8 h, the yields of total sugar, glucose, and xylose were 85%, 88%, 82% (w/w), respectively, and the ethanol productivity was 26.0 g/100 g rice straw dry matter. Moreover, 0.5-mol/L acetaldehyde dilute solution explosion improved the efficiency of enzymatic hydrolysis (EH) and simultaneous saccharification and co-fermentation (SSCF), and the residual inhibitors had negligible effects on EH and SSCF after detoxification by drying. The results suggested that compared with pure water explosions, the use of butanone and of acetaldehyde dilute solution explosions lowered the explosive temperature and improved the sugar yield, although relative crystallinity of the rice straw dry matter was increased after the explosion.     

Inhibition of LaNi5 electrode decay in alkaline medium by electroless encapsulation of active powder particles

Surface of powdered LaNi₅ intermetallic compound has been modified by active particle coverage with electroless nickel (Ni-P). The electrode degradation process in 6 M KOH solution has been tested across 70 charge/discharge cycles at −0.5 C/+0.5 C rates. It has been established that after approx. 25–35 initial cycles, the electrode degradation process fulfills first order chemical reaction kinetics law: logarithm of discharge capacity linearly decreases with cycle number. The rate constant for the Ni-P protected material is over 20 % lower than that of as received one. The surface modification also improves the alloy hydrogenation kinetics: exchange current densities of H₂O/H₂ system are generally greater for modified material and, contrary to uncovered material, do not practically decrease with long-lasting cycling.

     

High mechanical performance based on the alignment of cellulose nanocrystal/chitosan composite filaments through continuous coaxial wet spinning

Cellulose nanocrystals (CNCs) with high crystallinity exhibit high mechanical stiffness and strength. However, the high dispersibility of CNCs results in limited spinnability and orientation. In this study, oxidized nanocellulose was selected to obtain regionally oxidized CNCs (RO-CNC) with carboxyl groups appended. For the formation of orientable and extensible RO-CNC filaments, chitosan was introduced as the sheath solution to induce orientation by electrostatic action. The chemical structures were analyzed by Fourier transform infrared spectroscopy. The morphology of the oriented CNCs filaments was characterized by scanning electron microscopy and wide-angle X-ray scattering. Analysis of the relationship between the mechanical strength and the CNCs directional arrangement revealed that the mechanical strength of the composite fibers increased with the injection speed ratio as a result of the orientation of the RO-CNC. The mechanical strength of the oriented reinforced composite filaments reached as high as 104 MPa with an orientation index of 0.73. The tensile strength and elastic modulus of the filaments increased by 33% and 20%, respectively, compared to the unmodified CNCs spun fiber.

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Effect of various environmental factors on the adsorption of U(VI) onto biochar derived from rice straw

Herein, we used biochar pyrolyzed from rice straw to adsorb uranium (U) from aqueous solutions. The adsorption of U(VI) on biochar was strongly dependent on pH but independent on ionic strength. HA/FA enhanced the sorption at pH <6.8 while inhibited the sorption at pH >6.8. The sorption reached equilibrium within 3 h, which was not mediated by pH. The adsorption process was spontaneous and endothermic, and enhanced at higher temperature. However, the influence of temperature was negligible at low initial U(VI) concentrations. Therefore, biochar derived from rice straw may be a promising adsorbent for the removal of U(VI).

     

Chemical modification of cellulose nanocrystals and their application in thermoplastic starch (TPS) and poly(3‐hydroxybutyrate) (P3HB) nanocomposites

The effect of sulfated (original), carboxylated (oxidized), and Jeffamines M2005‐grafted cellulose nanocrystals (CNCs) on the barrier and mechanical properties of thermoplastic starch (TPS) and poly(3‐hydroxybutyrate) (P(3HB)) matrices was investigated. CNCs were first oxidized via a catalytic reaction using NaClO as an oxidant and then grafted with an amine‐terminated ethylene oxide (EO)/propylene oxide (PO) copolymer (Jeffamine) by an amine‐acid coupling reaction. A degree of oxidation (DO) of 0.108 (mol/mol of anhydroglucose) was attempted for the carboxylated CNCs, whereas a degree of substitution (DS) of 0.04 (mol/mol of anhydroglucose) was determined for the M2005‐grafted CNCs. These values indicated satisfactory reactive process, with yields of 68% and 47.3% for the carboxylation and peptide coupling reactions, respectively. Fourier‐transform infrared spectroscopy (FTIR) analysis showed bands at 1643 cm^?1 and 1550 cm^?1 in the spectrum of M2005‐grafted CNCs, which qualitatively indicated the amide bond formation. In addition, the morphology and the zeta potential of modified CNCs ensured their homogeneity, stability, and surface degree of charge. In spite of a decrease in the solubility in water of the modified crystals, the procedure of chemical modification used avoided any variation in their crystalline structure and thermal stability. Then, the incorporation of sulfated, oxidized, or M2005‐grafted CNCs in matrices of TPS and P(3HB) allowed to produce reinforced nanocomposite films, with excellent barrier properties. Therefore, the chemical compatibility between CNCs and the polymer matrices is essential to produce attractive nanocomposites with improved mechanical properties for industrial applications.     

Enhanced Crude Oil Sorption by Modified Plant Materials in Oilfield Wastewater Treatment

The treatment of oilfield wastewater with high crude oil content and complex composition is a problem requiring considerable attention. In order to effectively remove crude oil contained in wastewater, in this work, rice straw, as an oil-absorbing material, was modified and used as a sorbent for crude oil. Rice straw was modified with alkali and cetyltrimethylammonium chloride (CTAC) by simple substitution reaction. The adsorption capacity of modified rice straw for oil was evaluated. The results illustrate that the adsorption rate of rice straw for crude oil was increased from 0.83 to 8.49 g/g, with the optimal conditions of 18% NaOH reacted for 90 min at 50 °C and 2% CTAC reacted for 60 min at 20 °C. The proposed modification method could be used for different materials to enhance the adsorption rate. The results of the contact angle test show that the modified straw changed from hydrophilic to hydrophobic, which may be the main reason for the improvement in the oil absorption rate. Finally, the surface structure of rice straw was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and N₂ adsorption–desorption isotherms, which further confirmed the hydrophobicity of the modified rice straw.     

Scalable one-pot synthesis of bismuth sulfide nanorods as an electrode active material for energy storage applications

The quest for developing the scalable methods of synthesis of materials with potential electrochemical energy storage applications remains a great challenge. Herein, we propose a facile, one-step chemical precipitation method for the synthesis of Bi₂S₃ with the nanorods morphology. Influence of different synthesis temperatures on the physical, chemical, and electrochemical performance was investigated. Relatively low BET surface area and mesopore volume of Bi₂S₃ increased with the higher reaction temperature. Bismuth sulfides synthesized at various temperatures were used as an electrode active material in supercapacitor. The semiconductive properties of Bi₂S₃ resulted in exceptional capacitive behavior. Bismuth sulfide synthesized at 75 °C exhibited a specific capacitance of 457 F g⁻¹ at 1 A g⁻¹ in 6 mol L⁻¹ KOH solution as an electrolyte. Moreover, material prepared at 75 °C maintained the best capacitance value at a large current density of 20 A g⁻¹, compared with bismuth sulfides synthesized at the temperatures of 0 °C and 25 °C.

     

The Optimization of Dilute Acid Hydrolysis of Cotton Stalk in Xylose Production

Cotton stalk, a lignocellulosic waste material, is composed of xylose that can be used as a raw material for production of xylitol, a high-value product. There is a growing interest in the use of lignocellulosic wastes for conversion into various chemicals because of their low cost and the fact that they are renewable and abundant. The objective of the study was to determine the effects of H₂SO₄ concentration, temperature, and reaction time on the production of sugars (xylose, glucose, and arabinose) and on the reaction by-products (furfural and acetic acid). Response surface methodology was used to optimize the hydrolysis process in order to obtain high xylose yield and selectivity. The optimum reaction temperature, reaction time, and acid concentration were 140 °C, 15 min, and 6%, respectively. Under these conditions, xylose yield and selectivity were found to be 47.88% and 2.26 g g⁻¹, respectively.     

Kinetics of Ag/TiO2-photocatalyzed iodide ion oxidation

Abstract  

Ag-doped TiO₂ (anatase) samples (mass fraction w _Ag = 0.01 and w _Ag = 0.02) of 15.9 and 14.5 nm mean particle size and 11.46 and 10.14 m² g⁻¹ BET surface area were prepared by photodeposition. Doping results in surface plasmon resonance of the metallic silver nanoclusters at around 500 nm, but the absorption edge remains unaltered at 365 nm. Ag-doping remarkably enhances the photooxidation of iodide ion under UV light; iodine formation with Ag/TiO₂ with w _Ag = 0.01 is 16 times greater than with bare TiO₂. The reaction conforms to Langmuir–Hinshelwood kinetics with regard to both I⁻ and O₂. Increase of pH slows down iodine formation and sacrificial electron donors arrest the reaction. Pre-sonication of the catalyst slurry hinders the photocatalysis. Generation of iodine is much greater in acetonitrile than in water. Under the experimental conditions, Ag/TiO₂ with w _Ag = 0.01 is more efficient than Ag/TiO₂ with w _Ag = 0.02, and the enhanced photocatalysis is likely to be because of suppression of electron–hole pair recombination. Kinetic analysis reveals that increasing the Ag mass fraction from 0.01 to 0.02 enhances the surface pseudo-first-order rate constant but inhibits the adsorption of iodide ion and the oxygen molecule on the illuminated oxide surface.     

Environmental application of rice straw in energy production and potential adsorption of uranium and heavy metals

The sustainable development of agricultural waste is nowadays a main strategy in producing neutral CO₂ energy and metal removal technologies. In Egypt, large amounts of rice straw are annually burnt in the open air causing severe air pollution that could be directed to co-firing and adsorption technologies. On bench scale, rice straw was positively contributed in a clean and smokeless co-firing process with methanol due to the oxidizing effect of the alcohol. The co-firing temperature control is vital to develop the adsorptive character of the residual ash and to avoid prolonged time needed to improve the physical properties of the rice straw if applied directly as a biosorbent. The consumed methanol in the process ranges from 0.15 to 0.3 liter per each kg of straw depending on its compaction. The grossed heat value from such process may drive steam generator for electricity. The residual ash was subsequently cross-linked in uranium and heavy metals adsorption tests from solutions. The porous texture of the residual ash and the amorphous nature of the silica along with potassium content provide a suitable condition for uranium immobilization especially if phosphorus or vanadium exist. The resulted chemical precipitate is analogues in composition to meta-ankoleite (KUO₂PO₄·3H₂O) or hydrated carnotite (K₂(UO₂)₂V₂O₈)·1-3H₂O respectively. The XRD data of the latter form show an enhancement in crystallinity of the amorphous precipitate with the heated samples.     

Structure Selectivity of Alkaline Periodate Oxidation on Lignocellulose for Facile Isolation of Cellulose Nanocrystals

Reported here for the first time is the alkaline periodate oxidation of lignocelluloses for the selective isolation of cellulose nanocrystals (CNCs). With the high concentrations as a potassium salt at pH 10, periodate ions predominantly exist as dimeric orthoperiodate ions (H₂I₂O₁₀^4?). With reduced oxidizing activity in alkaline solutions, dimeric orthoperiodate ions preferentially oxidized non‐ordered cellulose regions. The alkaline surroundings promoted the degradation of these oxidized cellulose chains by β‐alkoxy fragmentation and generated CNCs. The obtained CNCs were uniform in size and generally contained carboxy groups. Furthermore, the reaction solution could be reused after regeneration of the periodate with ozone gas. This method allows direct production of CNCs from diverse sources, in particular lignocellulosic raw materials including sawdust (European beech and Scots pine), flax, and kenaf, in addition to microcrystalline cellulose and pulp.     

Lauric arginate/cellulose nanocrystal nanorods-stabilized alkenyl succinic anhydride pickering emulsion: enhancement of stabilization and paper sizing performance

Biodegradable colloidal particle materials are becoming attractive candidates as eco-friendly chemical additives in the low-carbon economy era. However, developing cheap, stable, and efficient paper-sizing agents is still a challenging issue for both the paper-making academic community and industry. Here, an easy-fabricating, stable, and high-performance alkenyl succinic anhydride (ASA) paper-sizing emulsion that is stabilized by lauric arginate (LAE)/cellulose nanocrystals (CNCs) nanorods is developed. Furthermore, the partial hydrophobization between ASA and LAE/CNCs can be adjusted due to the partial hydrophobization between ASA and LAE/CNC nanorods, resulting in improved stability of the ASA-sizing emulsion. This novel paper-sizing emulsion is shown to have a small droplet size (0.8 μm), high hydrolysis resistance, and a high paper-sizing degree (300 s) along with a remarkable hydrophobicity contact angle of 110° for long-term storage. This work enables the realization of an interfacial self-assembled Pickering-stabilizer, which leads to an environmentally friendly, pervasive and cost-effective emulsification technique for next-generation paper-sizing additives.

     

Introducing lanthanide metal–organic framework and perovskite onto pulp fibers for fluorescent anti-counterfeiting and encryption

The research of anti-counterfeiting and encryption has always been a subject of universal concern all over the world. Herein, lanthanide metal–organic framework (Eu-MOF) and CH₃NH₃PbBr₃ (MAPbBr₃) perovskite were introduced onto pulp fibers (PFs) to prepare fluorescent anti-counterfeiting and encryption papers. Eu-MOF@PFs paper emitted red fluorescence at 254 nm UV excitation. The optimum preparation conditions of Eu-MOF@PFs were 2.5 mmol of Eu(NO₃)₃, 4 h of reaction time and room temperature. When MABr ink was written on Pb/Eu-MOF@PFs paper, the green fluorescent handwriting and red fluorescent paper were observed under 365 nm and 254 nm UV excitation, respectively. The appropriate addition amount of lead nitrate was 0.6 mmol. Pb/Eu-MOF@PFs paper was immersed in MABr solution to prepare MAPbBr₃@Pb/Eu-MOF@PFs paper. Under 254 nm and 365 nm UV irradiations, MAPbBr₃@Pb/Eu-MOF@PFs paper emitted red-green double fluorescence and the quantum yields of which were 3.11% and 2.48%, respectively. The crystal structure of MAPbBr₃ was easily destroyed by polar solution, which realized on/off switching of the luminescence signal for multistage information encryption. The above paper-based fluorescence materials were potential for advanced anti-counterfeiting and encryption applications.

     

Brown pigments based on perovskite structure of BiFeO3−δ

Light brown inorganic pigments based on BiFeO₃ doped by Sr²⁺ cations were prepared by a conventional solid-state reaction at high temperature. This study is focused on the synthesis of Bi_1?x Sr _x FeO_3?δ powders in a range of substitution (x = 0–0.35; with step size 0.05). The main role of strontium is to overcome the defects that come to exist during the evaporation of Bi over material preparation. The substitution of trivalent bismuth ions by divalent strontium ions results in oxygen deficiency in the lattice, which was proved by both thermogravimetric analysis and elemental analysis. The substitution has a positive effect on the thermal stability of samples. The thermal stability of BiFeO₃ is 1046 K, whereas the substitution of 20 mol% of Bi³⁺ by Sr²⁺ ions shifted it to 1403 K and powder with composition Bi_0.65Sr_0.35FeO_3?δ has a thermal stability that is higher than 1434 K. An increasing range of substitution is connected with the change in the pigment color from reddish-brown to orange-brown and back to reddish-brown. The Bi_0.85Sr_0.15FeO_3?δ pigment prepared by calcination at 1273 K offers the most interesting color properties (L* = 45.57; a* = 20.38; b* = 26.23).

     

Insight into the extraction and characterization of cellulose nanocrystals from date pits

This study aims to extract and characterize cellulose nanocrystals (CNCs) from date pits (DP), an agricultural solid waste. Two methods were used and optimized for the cellulose nanocrystals (CNCs) extraction, namely the mechanical stirrer method (CNCs₁) and the Soxhlet apparatus method (CNCs₂) in terms of chemical used, cost, and energy consumption. The results showed that scanning electron microscopy revealed the difference in the morphology as they exhibit rough surfaces with irregular morphologies due to the strong chemical treatments during the delignification and bleaching process. Moreover, transmission electron microscopy analysis for CNCs reveals the true modification that was made through sulfuric acid hydrolysis as it presents cellulose microfibrils with a packed structure. Fourier transform infrared proved that the CNCs were successfully extracted using the two methods since most of the lignin and hemicellulose components were removed. The crystallinity index of CNCs₁ and CNCs₂ was 69.99%, and 67.79%, respectively, and both presented a high yield of CNCs (≥10%). Ultimately, both techniques were successful at extracting CNCs. Based on their cost-effectiveness and time consumption, it was concluded that method 1 was less expensive than method 2 based on the breakdown of the cost of each step for CNCs production.     

Pretreatment of Rice Straw by a Hot-Compressed Water Process for Enzymatic Hydrolysis

Hot-compressed water (HCW) is among several cost-effective pretreatment processes of lignocellulosic biomass for enzymatic hydrolysis. The present work investigated the characteristics of HCW pretreatment of rice straw including sugar production and inhibitor formation in the liquid fraction and enzymatic hydrolysis of pretreated material. Pretreatment was carried out at a temperature ranging from 140 to 240 °C for 10 or 30 min. Soluble oligosaccharides were found to constitute almost all the components of total sugars in the liquid fraction. The maximal production of total glucose at 180 °C and below accounted for 4.4–4.9% of glucan in raw material. Total xylose production peaked at 180 °C, accounting for 43.3% of xylan in raw material for 10-min pretreatment and 29.8% for 30-min pretreatment. The production of acetic acid increased at higher temperatures and longer treatment time, indicating more significant disruption of lignocellulosic structure, and furfural production achieved the maximum (2.8 mg/ml) at 200 °C for both 10-min and 30-min processes. The glucose yield by enzymatic hydrolysis of pretreated rice straw was no less than 85% at 180 °C and above for 30-min pretreatment and at 200 °C and above for 10-min pretreatment. Considering sugar recovery, inhibitor formation, and process severity, it is recommended that a temperature of 180 °C for a time of 30 min can be the most efficient process for HCW pretreatment of rice straw.     

Optimization of boron-doping process of titania nanotubes via electrochemical method toward enhanced photoactivity

In this work, we were focused on the development of the electrochemical approach resulting in a stable boron doping of titania nanotubes. The doping procedure concerns anodic polarization of as-anodized titania in a H₃BO₃ solution acting as n boron precursor. The series of attempts were taken in order to elaborate the most beneficial doping conditions. The parameters of electrochemical doping allowing to obtain boron-doped titania characterized by the highest photoconversion efficiency are as follows: reaction voltage 1.8 V, process duration 0.5 h, and the concentration of boric acid 0.5 M. Spectroscopy techniques such as UV-vis, X-ray diffraction, photoluminescence emission, and X-ray photoelectron spectroscopy were used to characterize the absorbance capability and the crystalline phase, to confirm the presence of boron atoms and to study the nature of chemical compounds, respectively. The well-ordered structure of titania and resistance of its morphology toward electrochemical treatment in H₃BO₃ were confirmed by scanning electron microscopy images. However, cyclic voltammetry and electrochemical impedance spectroscopy studies showed the significant difference in conductivity and capacitance between doped and pristine titania. Moreover, the photocurrent densities of the B-doped sample were about seven times higher in comparison with those generated by the pure titania nanotube electrode.

     

Pyrolytic synthesis and Eu→Eu reduction process of blue-emitting perovskite-type BaLiF3:Eu thin films

Perovskite-type barium lithium fluoride (BaLiF₃) was synthesized by pyrolysis of metal trifluoroacetates. The reaction temperature necessary for producing a single-phase material was found to be 600°C, which was lower than that for a conventional solid-state reaction or a melting method. Eu-doped BaLiF₃ was also prepared and characterized to examine the suitability of trifluoroacetates for precursors in synthesizing homogeneous complex metal fluoride materials. It was demonstrated that trivalent Eu³⁺, which was used as acetate for a starting material, was reduced to divalent Eu²⁺ in the pyrolysis process of BaLiF₃, as indicated by a broad blue emission due to an allowed 4f⁶5d→4f⁷ transition at 408 nm with a ultraviolet excitation at 254 nm. The concentration quenching of the blue emission occurred at 5 at% of Eu in BaLiF₃, indicating that Eu was homogeneously dispersed in the BaLiF₃ host lattice. Mechanisms of the formation and reduction process of BaLiF₃ were discussed based on pertinent chemical reactions.     

Covering of nanometric calcite with α-cyclodextrin

In the present experiments, the monodisperse calcium carbonate nanoparticles obtained in the reactor (three-phase reaction) with rotating discs have been covered with α-cyclodextrin. Both pure CaCO₃ nanoparticle and α-cyclodextrin-coated CaCO₃ powders were deeply analysed by the use of the scanning electron microscope, the dynamic light scattering and the thermogravimetric method. The experimental data have allowed for determination of effective diameter of the obtained particles (aggregates of ca. 30 nm single crystals) and their size distribution (almost monodisperse—ca. 390 nm) as well as for distinction between α-cyclodextrin molecules present on calcite surface or free α-cyclodextrin molecules if presented in the sample. It was found that the nanometric CaCO₃ obtained in the reactor with rotating discs can be covered with a maximum of 1.15% α-cyclodextrin monolayer. The maximal coverage of the CaCO₃ calcite particles with α-cyclodextrin can be done by 24-h shaking of 50 mg nanometric calcium carbonate with 25 mg of 36.79 mM α-cyclodextrin aqueous solution.