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Cellulose tosylates with different degree of substitution (DS) were prepared by reacting cellulose in DMAc/LiCl with p‐tosyl chloride at 8 °C in the presence of triethylamine. The effects of number of mole of tosyl chloride (A), number of mole of base (triethylamine) (B) and reaction time (C) on DS were studied by Response Surface Methodology (RSM)...
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The main purpose of this paper is to synthesize a novel esterified starch with an alicyclic structure. Herein, methyltetrahydrophthalic anhydride (MeTHPA), an alicyclic anhydride, was used to synthesize esterified corn starch (CS) with different degrees of substitution (DS) by a wet method. Compared with CS, the crystallinity and thermal degradatio...
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... This indicates lower thermal stability of the modified cellulose particles. The revealed reduced thermal stability of CNC-Ts is characteristic of cellulose materials containing fragments of sulfonic acids and sulfate groups (El Hamdaoui et al., 2020;Roman et al., 2004). In both cases, acid esters S(VI) associated with a cellulose matrix were split off upon heating and reduced the activation energy of the onset of thermolysis, i. e., catalyzed thermal degradation process. ...
SH-containing polymers and nanoparticles are a significant direction in the creation of novel materials. The aim of this work is the synthesis of cellulose nanocrystals (CNC) with a surface modified by tosyl functions (CNC-Ts) and their further modification into SH-containing nanocrystals (CNC-SH). CNC-Ts were synthesized in an aqueous-organic emulsion from never-dried particles, while maintaining the size and supramolecular structure of CNC; the content of Ts-functions is up to 2.5 mmol·g-1. Structure of the derivatives was analyzed by TEM, XRD, CP/MAS 13C NMR and FTIR spectroscopies. Nucleophilic substitution and hydrolysis of the obtained thioisouronium salts leads to the production of CNC-SH. To quantify SH-groups we used elemental analysis, potentiometric titration and Folin-Ciocalteu and Ellman's reagents. It is shown that SH-groups on the surface are partially oxidized and are involved in a dense network of hydrogen bonds. Rheological properties of CNC-SH hydrosols are close to those of CNC, addition of H2O2 at acidic pH leads to an increase in viscosity of the system; H2O2 added at neutral pH causes opposite effect - viscosity decreases. CNC-SH have a high capacity for sorption of Cr(VI) in acidic environments and exhibit photoreductive properties under UV irradiation.
... COs with milling temperature of 80 and 100 • C exhibited loose and porous structures [37]. Besides, their surface displayed homogenous appearance if compared to pristine MCC and COs with milling temperature of 50 • C. Interruption of the cellulose backbone can explain this observation as a result of the reaction of hydroxy group (-OH) of MCC with OA. ...
Mechanochemical reaction, a green synthetic esterification route was utilized to prepare long-chain cellulose esters from microcrystalline cellulose. The influence of reaction conditions such as reaction temperature and time were elucidated. Only low dosage of oleic acid, 1-butyl-3-metylimidazolium acetate, and p-toluenesulfonyl chloride were required. The success of modification reaction was confirmed by Fourier transforms infrared spectroscopy as a new absorbance peak at 1731 cm−1 was observed, which indicated the formation of carbonyl group (C=O). Solid-state nuclear magnetic resonance was also performed to determine the structural property and degree of substitution (DS) of the cellulose oleate. Based on the results, increasing reaction temperature and reaction time promoted the esterification reaction and DS. DS values of cellulose oleates slightly decreased after 12 h reaction time. Besides, X-ray diffraction analysis showed the broadening of the diffraction peaks and thermal stability decreased after esterification. Hence, the findings suggested that grafting of oleic acid’s aliphatic chain onto the cellulose backbone lowered the crystallinity and thermal stability.
... determines that 87.657% of the variation on Cd(II) adsorption data can be described by the mathematic model, where only 12.343% of the total variations are not explained by the mathematic model. In general, the statistical results validate the accuracy and prediction capacity of the second-order models, guaranteeing the reliability of the models [44]. Figure 7 shows the normalised residuals of the regression models. ...
In the present work, model equations describing the simultaneous removal of heavy metal ions, such as Zn(II), Cu(II), and Cd(II) ions from aqueous solutions by adsorption with phosphogypsum (PG) were calculated, employing response surface methodology (RSM), concerning operating conditions such as contact time (X1), temperature (X2), and initial pH (X3). The metal ions–PG interactions were characterised by thermal analysis techniques (TGA-DTG), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and energy-dispersive X-ray spectroscopy (EDX). The results proved that the equations of the determined model agree well with the quadratic equations with R²(Adj) values that reach up to 0.876 (p < 0.05 with a 95% confidence level). It has been demonstrated that from aqueous solutions, phosphogypsum able to simultaneously remove more than 65.51% of Cd(II), 45.57% of Cu(II), and up to 45.44% of Zn(II) ions, and the optimums were obtained at the set of parameters of a contact time of 28.79 min, the temperature of 40.62 °C, and pH 9.17. Under these conditions, phosphogypsum was more selective towards cadmium (II) ions. Furthermore, the calculated models could provide appropriate data to strengthen the adsorption process.
... For example, the synthesis of tosyl cellulose derivative intermediates through the tosylation of the primary hydroxyl group at C-6 of cellulose has been reported since the tosyl group is a good electrophile and leaving group in nucleophilic displacement (S N ) reactions or as protecting group in further reactions of the remaining free hydroxyl (-OH) groups [13][14][15]. In our previous work, we were able to synthesize tosyl cellulose with different degrees of substitution (DS) by reacting microcrystalline cellulose with p-tosyl chloride, and we have studied the effects of reaction parameters on DS by response surface methodology (RSM) [16]. Ampholytic biomaterials are semisynthesized biomacromolecular carrying both the ionic and cationic groups; they offer beneficial applications in drug delivery, protein separation, surfactants, and chelation with metal ions because of their structure specificity [17][18][19][20]. ...
A novel ampholytic cellulose derivative, cellulose-L-methionine, has been synthesized by means of an esterification reaction of microcrystalline cellulose with tosyl chloride (p-TsCl) in DMAc/LiCl (8%) at 8°C that was followed by nucleophilic displacement (SN) of the tosyl group by the L-methionine amino acid. The resulting structure of cellulose-L-methionine has been characterized by elemental analysis (CHNSO), Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H-NMR), and scanning electron microscopy (SEM). The antibacterial activity of the synthesized product was screened against Gram-positive and Gram-negative microbial strains such as Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, by the agar well diffusion method, and compared with commercial antibiotics such as ampicillin and chloramphenicol. It was found that antibacterial experiment revealed excellent antibacterial activity of the cellulose-methionine with respect to a minimal inhibitory concentration (MIC) reference.
... They are not known and must be calculated from the results of the experiments performed. [46,47] Calculations of the main effects and interactions between lead adsorption levels on PG were made with, a CCD using Nemrodw software. [48] Disclosure statement No potential conflict of interest was reported by the authors. ...
In this work, we have proposed a method of phosphogypsum (PG) recovery by attempting to use it as an adsorbent of heavy metal ions from aqueous solutions, while trying to study the different quantitative and qualitative characteristics. The PG was synthesized and characterized with X-ray diffraction (XRD) and Fourier transform infrared (FTIR). The effects of the initial concentration of lead (X1), pH of the solution (X2), and temperature (X3) on the amount of Pb(II) adsorbed were investigated. Thermodynamic parameters were calculated. The modeling of the adsorption tests by the experimental design method as well as the optimization of the parameters by the response surface methodology (RSM) is given in this article. The results obtained show that amount of Pb(II) adsorbed increases with Pb concentration and decreases as pH of the solution and temperature increase. It was found that the processes conforming to second-order kinetics and the optimal adsorption capacity of lead on PG are at a lead concentration of 109.64 mg/L, 5.25 of pH, and 70 °C for temperature. The adsorption process was found to be exothermic and spontaneous. © 2020 Taylor & Francis Group, LLC.
As the most abundant natural polymer in nature, cellulose has become the promising alternative raw material to replace fossil-based polymer. Owing to the presence of innumerable hydroxyl groups, various approaches are employed to render processability of cellulose. Herein, a sustainable esterification strategy, mechanochemical-assisted esterification, was developed to produce cellulose oleate (CO) with only a small amount of solvent. The differences in reactivity between all types of cellulose were elucidated. According to thermal stability analysis, the degradation temperature decreased after modification due to the substitution of the long oleoyl group. High degree of substitution (DS) of CO also possessed glass transition temperature (Tg) based on differential scanning calorimetry (DSC) analysis. Herewith, the processability of cellulose was introduced after modification. In this study, bamboo waste cellulose nanofiber oleate (BW CNF-OA) showed the highest DS (2.28) among the COs. Its higher surface reactivity due to the high surface aspect ratio led to a higher quantity of fatty acids attached to the cellulose. For the mechanical properties, low DS of COs exhibited higher tensile strength values. In a nutshell, this greener approach is more favorable than conventional chemical esterification in terms of reduced solvent dosage and improved sustainability.
Traditional wood adhesives have the problems of excessive dependence on fossil resources and environmental pollution. Cellulose, a renewable biomass resource with a low price and huge output, provides a basis for preparing biomass wood adhesives. In this study, a new type of polyamide resin was prepared by modifying microcrystalline cellulose and reacting with natural citric acid. Specifically, toluenesulfonyl cellulose (TS) was synthesized, and functional amino cellulose (AC) was prepared by a nucleophilic substitution reaction with hyperbranched polyamide (HP). Then cellulose-based hyperbranched polyamide resin (CHP) was prepared by polycondensation with citric acid. The structure of CHP resin was investigated by FTIR, XPS, 13C NMR and GPC, and plywood was prepared to study its mechanical properties. Due to the formation of hyperbranched cross-linked network structure inside the resin, the prepared plywood has excellent properties. The dry shear strength reaches 2.24 MPa, and the strength reaches 1.25 and 1.31 MPa after soaking in water at 63 °C and 93 °C for 3 h. The resin in this study has a simple preparation process and excellent performance, which provides a solid foundation for developing high-performance cellulose-based wood adhesives.
SH-containing polymers and nanoparticles are a significant direction in the creation of novel materials. The aim of this work is the synthesis of cellulose nanocrystals (CNC) with a surface modified by tosyl functions (CNC-Ts) and their further modification into SH-containing nanocrystals (CNC-SH). CNC-Ts were synthesized in an aqueous-organic emulsion from never-dried particles, while maintaining the size and supramolecular structure of CNC; the content of Ts-functions is up to 2.5 mmol·g-1. Structure of the derivatives was analyzed by TEM, XRD, CP/MAS 13C NMR and FTIR spectroscopies. Nucleophilic substitution and hydrolysis of the obtained thioisouronium salts leads to the production of CNC-SH. To quantify SH-groups we used elemental analysis, potentiometric titration and Folin-Ciocalteu and Ellman's reagents. It is shown that SH-groups on the surface are partially oxidized and are involved in a dense network of hydrogen bonds. Rheological properties of CNC-SH hydrosols are close to those of CNC, addition of H2O2 at acidic pH leads to an increase in viscosity of the system; H2O2 added at neutral pH causes opposite effect – viscosity decreases. CNC-SH have a high capacity for sorption of Cr(VI) in acidic environments and exhibit photoreductive properties under UV irradiation.
Tremendous potential exists to use cellulose as a support for the immobilization of enzymes. In the current study, cellulose was transformed into cellulose tosylate, and α-Amylase was immobilized using the derivatized polymer. Techniques like Fourier transform infrared, scanning electron microscopy, thermogravimetric analysis, and X-ray diffraction methods were used to characterize the support. The support is a perfect illustration of how both covalent and hydrophobic/ionic types of immobilizations can be experimentally used on support. The support was found to show max degradation at 320.2 °C with 3.2 % residual substance and crystallinity of about 56.6 %. The support presented maximum enzyme loading at the support: enzyme ratio of 1:4. The immobilized enzyme displayed two ideal pH values (about 4.6 and 7) and two ideal temperatures (approximately 60 °C & 40 °C). It was discovered that the immobilized α-amylase could be used easily eight times with 9.9 % residual activity. The findings of this study show that the immobilized cellulose tosylate enzyme has the potential for application in both acidic and neutral pH environments with the best activity for commercial use.
This study intends to synthesis chitosan‐aromatic aldehyde Schiff bases (ChSB) to investigate their thermal stability and kinetics degradation. All samples were characterized by FTIR, XRD and SEM techniques. Chitosan and chitosan derivatives were subjected to thermo‐gravimetric analysis, at four multiple heating rates 5, 10, 15 and 20 °C.min⁻¹. Calculations using two isoconversional integral methods, Flynn Wall Ozawa and Kissinger were performed. The changes in Entropy, Enthalpy, Gibbs free energy, and lifetime have been estimated. Thus, chitosan modification with aromatic aldehydes would have an accelerating effect on thermal decomposition. In addition, chitosan p‐chlorobenzaldehyde were found to have the relative highest activation energy and the highest lifetime to thermally decompose amongst the other examined biopolymers. The kinetic process for the degradation of pure chitosan, chitosan‐N,N‐dimethylaminobenzaldehyde and chitosan‐p‐chlorobenzaldehyde was most probably described by an exponential function E1.While for chitosan‐p‐methoxybenzoaldehyde the function D12 corresponding to a mechanism coupling “transfer and diffusion” seems to describe the degradation.
