Effects of environment parameters on sol-gel transition and dry-spinnability of regenerated silk fibroin aqueous solution

Protein concentration, pH, the types and concentrations of metallic ions, and extensional flow are thought to be important environment parameters affecting the natural spinning process. In this study, we investigate the effects of the types and concentrations of metallic ions (Ca²⁺, Mg²⁺, and K⁺ ions), pH, and silk fibroin concentration on the sol-gel transition and the rheological behavior of a regenerated silk fibroin (RSF) aqueous solution. The results show that with an increase in the silk fibroin concentration, the weak acidic RSF aqueous solutions containing Mg²⁺ or Ca²⁺ ions undergo a phase transition to a weak gel state. Moreover, the rheological characterization of RSF aqueous solutions shows a dramatic change, and their apparent viscosities increase by almost three orders of magnitude and approach the apparent viscosity of the native dope in the silkworm gland. By using conventional pressure equipment, we investigate the dry-spinnability of weak gels. Further, we observe that the as-spun fibers exhibit a smooth surface and have inferior mechanical properties. The structure of the as-spun fibers is predominantly in a random coil or Silk I conformation.     

Radical Polymerization and Kinetics of N,N-diallyl-N,N-dimethylammonium Chloride and Vinyl Ether of Monoethanolamine

N,N-diallyl-N,N-dimethylammonium chloride (DADMAC) and vinyl ether of monoethanolamine copolymer (VEMEA) was synthesized by radical polymerization in aqueous media using ammonium persulfate as initiator. Copolymers synthesis was carried out by varying monomer composition at low conversion level. The viscosity of high molecular weight products was measured in aqueous 1 M NaCl solution and it was increased with increasing DADMAC amounts in the copolymer due to increasing positive charge. The structure of the product was identified by FTIR, ¹H, ¹³C-NMR spectroscopies and conductometric titration methods. We calculated monomer reactivity ratios with help of Finemann-Ross, Kelen-Tudos, and inverted Finemann-Ross methods. It was found that DADMAC is more reactive than VEMEA, therefore the amount of DADMAC in the copolymers always dominated regardless of the initial monomer ratio in solution and it was shown that the monomers are connected randomly in the polymer chain. The effect of various parameters such as monomer [M], initiator [I] concentrations, ratio of comonomers, etc. on polymerization was investigated systematically. So, the polymerization rate (R_p) equation was found to be R_p=k[M]^2.6[I]^0.6 where molar fractions of DADMAC and VEMEA was 90:10 and the temperature was 65 °C. Degree of polymerization was examined by using various monomers and initiator concentrations via the dilatometeric method. It was found that the polymerization rate increased directly with total monomer concentration and initiator content.     

Cacao pod husks (Theobroma cacao L.): Composition and hot-water-soluble pectins

The composition of cacao pod husks (CPHs), the main waste product of cocoa production, and some of the characteristics of their water-soluble pectins were investigated. Milled and dried CPHs were submitted to hot aqueous extractions (50 and 100 ?C, 90 min, 1:25, w/v). The obtained fractions (labeled 50W and BW, respectively) yielded 7.5 and 12.6% pectins, respectively. The monosaccharide composition revealed the predominance of uronic acid, followed by galactose, rhamnose and arabinose, characteristic of pectins. Chemical and spectroscopic analyses (FT-IR and ¹³C NMR) showed that both fractions contained high acetyl contents (DA 29.0 and 19.2%, respectively) and are composed of low methoxyl homogalacturonans (DE 37.0 and 42.3%, respectively) with rhamnogalacturonan insertions carrying side chains containing mainly galactose. Rheological analyses were carried out with 50W and BW. Solutions of both fractions at 5% (w/v) had a non-Newtonian shear-thinning behavior, however that of 50W showed higher apparent viscosity than that of BW. Dynamic oscillatory analyses showed that 5% (w/w) 50W pectin had weak gel behavior whereas at the same concentration, BW pectin behaved as a concentrated solution. Although further investigations are required, CPH seems be a potential source of both pectins and other natural agents such as fibers and phenolics, and its use is particularly justified by growing environmental awareness.     

Preparation of regenerated cellulose fiber via carbonation (II)

Sodium cellulose carbonate (CC-Na) dissolved in 8.5 wt% NaOH/ZnO (100/2–3, w/w) aqueous solution was spun into some acidic coagulant systems. Diameter of regenerated cellulose fibers obtained was in the range of 15–50μm. Serrated or circular cross sectional views were obtained by controlling salt concentration or acidity in the acid/salt/water coagulant systems. Velocity ratio of take-up to spinning was controlled up to 4/1 with increasing spinning velocity from 5 to 40 m/min. Skin structure of was developed at lower acidity or higher concentration of coagulants. Fineness, tenacity and elongation of the regenerated cellulose fibers were in the range of 1.5–27 denier, 1.2–2.2 g/d, and 8–11.3%, respectively. All of CC-Na and cellulose fibers spun from CC-Na exhibited cellulose II crystalline structure. Crystallinity index was increased with increasing take-up speed.     

Preparation of regenerated cellulose fiber via carbonation. I. Carbonation and dissolution in an aqueous NaOH solution

Cellulose carbonate was prepared by the reaction of cellulose pulp and CO₂ with treatment reagents, such as aqueous ZnCl₂ (20–40 wt%) solution, acetone or ethyl acetate, at −5–0°C and 30–40 bar (CO₂) for 2 hr. Among the treatment reagents, ethyl acetate was the most effective. Cellulose carbonate was dissolved in 10% sodium hydroxide solution containing zinc oxide up to 3 wt% at −5–0°C. Intrinsic viscosities of raw cellulose and cellulose carbonate were measured with an Ubbelohde viscometer using 0.5 M cupriethylenediamine hydroxide (cuen) as a solvent at 20°C according to ASTM D1795 method. The molecular weight of cellulose was rarely changed by carbonation. Solubility of cellulose carbonate was tested by optical microscopic observation, UV absorbance and viscosity measurement. Phase diagram of cellulose carbonate was obtained by combining the results of solubility evaluation. Maximum concentration of cellulose carbonate for soluble zone was increased with increasing zinc oxide content. Cellulose carbonate solution in good soluble zone was transparent and showed the lowest absorbance and the highest viscosity. The cellulose carbonate and its solution were stable in refrigerator (−5°C and atmospheric pressure).     

The novel use of sodium borohydride as a protective agent for the chemical treatment of vegetable fibers

The vegetable fibers used as reinforcement for polymer matrix composites are usually treated to improve their adhesion with the matrix. The chemical treatment with sodium hydroxide (NaOH) is widely employed, but it may damage the fiber surface structure, reducing its strength. This novel study is related to the use of hydride ions (H^?) as protective agent for vegetable fibers, under alkaline treatment, as a way to promote their use in polymeric composites. Sisal fibers were modified by immersion in a NaOH aqueous solution (2, 5, and 10 % wt/vol) with or without the addition of sodium borohydride (NaBH₄) (1 % wt/vol) under different treatment conditions. The treated fibers were characterized via density and moisture content analyses and also using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effectiveness of NaBH₄ to protect the sisal fiber was more pronounced in moderate NaOH concentrations (5 %) at room temperature or higher for shorter alkaline treatment times.     

Preparation and properties of fibers produced from a cellulose/complex PA solvent system precipitating in diverse coagulants

Ethanol, as the first coagulation bath, and several common organic solvents, as well as aqueous solutions of NH₄Cl, NaHCO₃ and NaOH were explored and demonstrated to be adopted as the second coagulation bath for cellulose/phosphoric acid/tetraphosphoric acid (cellulose/complex PA solvent) solution to produce novel cellulose fibers by two-stage dry-wet spinning in a laboratory scale, and effect of coagulants, cellulose concentration, solvent concentration (P₂O₅ concentration) and coagulation temperature on crystal structure and properties of corresponding fibers were investigated. Surface morphology of regenerated fibers as-spun from different coagulants was observed by scanning electronic microscope (SEM), indicating that methanol and 8 wt% NaOH aqueous solution all rendered cellulose fibers relatively dense and smooth surface. X-ray diffraction (XRD) analysis showed that cellulose fiber precipitated from 8 wt% NaOH aqueous solution had pronounced characteristic peak of cellulose II than those of fibers precipitated from other coagulants, and highest crystallinity and orientation. Meanwhile, those two coagulants referred above also gave cellulose fibers relatively higher tensile strength under the same prerequisite. TGA curves exhibited that fibers were thermally stable produced from two salt aqueous solutions (8 wt% NH₄Cl and NaHCO₃) since they had the relatively higher onset decomposition temperatures. By evaluating the effect of cellulose concentration, P₂O₅ concentration and coagulation temperature on the structure and properties of asprepared fibers, it was preferable to produce cellulose fiber from a solution at 20 wt% cellulose concentration, 73 % P₂O₅ concentration, and coagulating in methanol at coagulation temperature of 60 °C at the second-stage.     

Water soluble carboxymethylcellulose fibers derived from alkalization-etherification of viscose fibers

Carboxymethylcellulose (CMC) fibers have been successfully prepared from viscose fibers through the process of alkalization-etherification. Parameters including reaction temperature, mass ratio of NaOH to the viscose fibers, and mass ratio of the viscose fibers to ethanol are studied. The degree of substitution (DS) and the inherent viscosity of the CMC fibers are determined. The CMC fibers are characterized by using Fourier transform infrared spectroscopy (FT-IR), ¹H-nuclear magnetic resonance spectroscopy (¹H-NMR), scanning electron microscopy (SEM), and the X-ray diffraction (XRD). The analysis demonstrates that under the experimental conditions where the reaction temperature is 40 °C, mass ratio of NaOH to the viscose fibers is 2.0, and mass ratio of the viscose fibers to ethanol is 1:15, the obtained CMC fibers possess an appropriate DS, better water-solubility, and lower degree of etching, thus they can be used as absorbable hemostatic fibers.     

Surface modified ployacrylonitrile nanofibers and application for metal ions chelation

Ployacrylonitrile (PAN) nanofibers were formed by electrospinning. Amidoxime ployacrylonitrile (AOPAN) nanofibers were prepared by reaction with hydroxylamine hydrochloride, which were used as the matrix for metal ions chelation. FTIR spectra of the PAN nanofibers and AOPAN nanofibers were recorded for analysis of the surface chemical structures. The AOPAN conventional fibers were also prepared for comparison, and surface morphologies of the modified PAN conventional fibers and PAN nanofibers were observed by FESEM. Metal ions concentrations were calculated by AAS. The chelated isothermal process and kinetics parameters of the modified PAN nanofibers and PAN conventional fibers were studied in this work. Results indicated that the saturated coordinate capacity of AOPAN nanofibers to Cu²⁺, Cd²⁺ was 3.4482 and 4.5408 mmol/g (dry fiber) respectively, nearly two times higher than that of AOPAN conventional fibers. Besides, the desorption rate of Cu²⁺ and Cd²⁺ from metal chelated AOPAN nanofibers was 87 and 92 % respectively in 1 mol/l nitric acid solution for 60 min. The isothermal processes were found to be in conformity with Langmuir model.     

TEMPO-mediated oxidation of MCC at high temperature: Synthesis and characterization of high-hydrophilic polymer

Microcrystalline cellulose was reacted with catalytic amounts of 2, 2, 6, 6-tetramethyl-1-piperidine oxoammonium salt (TEMPO), sodium hypochlorite and sodium bromide in Na₂CO₃/NaHCO₃ buffer solution at different temperatures (30 °C, 40 °C, 50 °C). The oxidation procedures included first oxidation and second oxidation. The yield of cellouronic acid produced in the second oxidation was higher than the yield of cellouronic acid produced in the first oxidation at the same oxidation temperature. Moreover, an interesting “high-hydrophilic” phenomenon appeared at higher temperature during microcrystalline cellulose second oxidation (30 °C, 40 °C, 50 °C). Properties associated with the chemical characteristics are discussed by XRD, FTIR, ¹³C-NMR and Laser Particle Analyzer in view of its interesting high-hydrophilic effects.     

Removal of benzidine-based azo dye from aqueous solution using amide and amine-functionalized poly(ethylene terephthalate) fibers

In this study, amide and amine groups bound to poly(ethylene terephthalate) fibers are used to remove the colored toxic Congo red dye from aqueous solution. The effects of process variables like pH, contact time, graft yield, and initial dye concentration on the adsorption were investigated. The maximum adsorption of Congo red to amide and amine groups was observed at pH 3 and 5 respectively. Equilibrium was attained at approximately 60 min for the amine group. The adsorption capacity of amine group on the poly(ethylene terephthalate) fiber was 46.5 mg g⁻¹ at 25 °C, which was higher than that of the amide group on the poly(ethylene terephthalate) fiber. Desorption was done using 0.1 M NH₃, and recovery was measured at 58.2 %. The used adsorbent was regenerated and recycled six times. The results showed that the amine-functionalized fiber could be considered as potential adsorbents for removal of Congo red from aqueous solution.     

The influence of water jet pressure settings on the structure and absorbency of spunlace nonwoven

Nowadays, the use of nonwovens as absorbent products is increasing. One of the most important methods for the nonwoven production is spunlace. This research evaluates the effect of spunlace nonwoven structures in wicking, water retention, water vapor permeability and porosity structural parameter of nonwoven. Carded webs from polyester fibers and viscous fibers of four different basis weights (35, 40, 45, and 50 g/m²) were hydroentangled using three different water jet pressures (50, 60, and 70 bar). To study the effect of these variables on the structure of nonwovens and absorbency related properties, sample’s characteristics such as thickness and mass density were measured. An electrical resistance technique was used to study the liquid penetration into nonwovens. The results showed that with increasing water jet pressure, mass density increased and other parameters like thickness, water retention, water vapor permeability and capillary pore size decreased. Also, it was observed with increasing basis weight, the sample thickness increased. On the other hand, with increasing weight, the amount of water retention, water vapor permeability and porosity structural parameter of nonwoven were reduced. The wicking characteristic of nonwovens using the least jet pressure and weight was the best of all the samples.     

The preparation and characterization of conductive poly(ethylene terephthalate)/polyaniline composite fibers using benzoyl peroxide

Conductive polyaniline (PAn)/poly(ethylene terephthalate) (PET) composite fibers were prepared by chemical polymerization of aniline in the presence of PET fibers using benzoyl peroxide (Bz₂O₂) in organic solvent/aqueous hydrochloric acid mixtures. The effects of polymerization conditions such as organic solvent/water ratio, oxidant, aniline and hydrochloric acid concentrations and temperature were investigated on the amount of PAn deposited on PET fiber and the electrical surface resistance of composite fibers. The maximum PAn content and the lowest electrical surface resistance of composite fibers were observed at HCl concentrations of 0.5 mol L⁻¹. The properties of PAn/PET composite fibers such as density, diameter, tensile strength and breaking elongation were also investigated in comparison with those of pure PET. Characterization of conductive composite fibers was carried out by FTIR, TGA, SEM techniques, surface resistance measurements, and cross section images taken by optical microscope.     

Preparation of electrospun silk fibroin/Cellulose Acetate blend nanofibers and their applications to heavy metal ions adsorption

Silk fibroin (SF)/Cellulose Acetate (CA) blend nanofibrous membranes were prepared by electrospinning and their heavy metal absorbabilities were examined in an aqueous solution after ethanol treatment. The electrospun nanofibrous membranes were comprised of randomly oriented ultrafine fibers of 100–600 nm diameters. As a result of field emission electron microscope (FEEM), the anti-felting properties of the blend nanofibrous membranes were markedly improved after treatment with 100 % ethanol when SF was blended with CA. Metal ion adsorption test was performed with Cu²⁺ as a model heavy metal ion in a stock solution. The SF/CA blend nanofiber membranes showed higher affinity for Cu²⁺ in an aqueous solution than pure SF and pure CA nanofiber membranes. Especially, the blend nanofibrous membranes with 20 % content of CA had an exceptional performance for the adsorption of Cu²⁺, and the maximum milligrams per gram of Cu²⁺ adsorbed reached 22.8 mg/g. This indicated that SF and CA had synergetic effect. Furthermore, the parameters affecting the metal ions adsorption, such as running time and initial concentration of Cu²⁺, had been investigated. The results showed that the adsorption of the Cu²⁺ sharply increased during the first 60 min, the amount of metal ions adsorbed increased rapidly as the initial concentration increased and then slope of the increase decreased as the concentration further increased. This study provides the relatively comprehensive data for the SF/CA blend nanofibrous membranes application to the removal of heavy metal ion in wastewater.     

The effect of additives on the ensilage of forage of differing perennial ryegrass and white clover content

Pure perennial ryegrass or perennial ryegrass/white clover mixtures (70:30 and 40:60 on a fresh-matter basis) were ensiled in laboratory silos either untreated or alter treatment with freshly cultured Lactobacillus (Lb.) plantarun or freshly cultured Lb. plantarum plus Lactococcus (Lc.) lactis. freeze-dried Lb. plantarum or freeze-dried Lb. Plantarum plus sodium formate, sodium formate or formic acid. The effect of these additives on silage fermentation characteristics and quality of the resultant silages was examined. There were significant interactions between treatments and herbages for all silage quality parameters measured, except for acetic acid concentration. The influence of additives on the final pH of all silages was small but statistically significant. Lactic acid concentration was not directly related to herbage mixture, overall mean values ranging from 118 to 120 ± 1.5 g kg^?1 dry matter (DM), but wider variation was seen between treatments for individual herbage mixtures. Acetic acid concentrations were significantly (P<0·001) affected by herbage mixture ensiled, increasing linearly as clover content increased from zero to 60%. Untreated control and formic acid-treated silages contained significantly (p<0·001) higher acetic acid concentrations than those treated with other additives. Silage ammonia N concentrations were significantly (p<0 001) influenced by herbage mixture. Lowest ammonia N concentrations (< 50 g kg^?1 DM) were observed in silages that had been treated with formic acid, freshly cultured Lb. plantarum or Lb. plantarum plus Lc. lactis. The fraction 1 leaf protein (FILP) contents of silages were significantly (P <0·001) affected by both treatment and herbage mixture, with consistently and significantly higher values found in freshly cultured inoculant-treated silages. A poor correlation (r²= 0·12) existed between ammonia N and FILP in all silages. The inclusion of up to 60% white clover in the ensiled herbage did not adversely affect final silage quality. However, additive treatment markedly influenced the residual FILP content of silages, those treated with freshly cultured inoculants having the highest values.     

Glycoalkaloids in potato tubers grown under controlled environments

Tuber content of α-solanine, α-chaconine, and total glycoalkaloids (TGA) was determined for the potato cultivars, Norland, Russet Burbank, and Denali grown under different environmental conditions in growth chambers. The lowest TGA concentrations (0.30 to 0.35 mg g¹ dry tissue) were found in the cv. Norland with 400 μnol m^-2 s^-1 photosynthetic photon flux (PPF), 12 h day length, 16 C temperature, and 350 μmol mol^-1 carbon dioxide. The ratio of α-chaconine to α-solanine was close to 60:40 under all growing conditions, except that it was 50:50 under the low temperature of 12 C. Cultivars responded similarly to environmental conditions although TGA was about 20% greater in cv. Russet Burbank and about 30% greater in Denali compared to Norland. The largest changes in TGA occurred with changes in temperature. In comparison to 16 C, TGA were 40% greater at 12 C, 80% greater at 20 C, and 125% greater at 24 C (0.70 mgg ^-1 dry weight). The TGA concentratation increased from 10 to 25% with an increase in light from 400 to 800 μmol m^-2 s^-1 PPF for all three cultivars. TGA increased 20% with extension of the day length from 12 to 24 hr and also increased 20% when carbon dioxide was increased from 350 to 1000 umol mol^-1. TGA concentrations were not influenced by changes in relative humidity from 50 to 80%. TGA concentrations decreased only slightly in harvests made from 9 to 21 weeks after planting. Variations in TGA among the different growing conditions and cultivars were below 20 mg/100 g fresh weight (= 1.0 mg g^-1 dry weight) recognized as the upper concentration for food safety. However the results suggest that TGA should be considered when potatoes are grown at temperatures above 20 C.     

Optimization of elecrospinning process of zein using central composite design

Biodegradable edible sub-micron electrospun zein fibers were prepared using acetic acid as solvent. The solution concentration at three levels: 22, 26 and 30 w/v %, the electrospinning voltage at three levels: 10, 20 and 30 kV, the solution flow rate at three levels: 4, 8 and 12 ml/h and the distance between needle tip and collector at three levels: 10, 15 and 20 cm were studied. Central composite design (CCD) was utilized to modeling the effect of electrospinning parameters of zein solution on average fiber diameters and the data were analyzed using response surface methodology (RSM). Coefficient of determination, R², of fitted regression model was higher than 0.9 for response. The analysis of variance table showed that the lack of fit was not significant for response surface model at 95 %. Therefore, the model for response variable was highly adequate. Results also indicated that the solution concentration had significant influence (P<0.0001) on morphology and diameter of fibers. By increasing the solution concentration, uniform and bead-free fibers were obtained. As the solution concentration was increased, the average fiber diameters were also increased. Furthermore, the electrospinning voltage had significant effect (P<0.0001) on average fiber diameters. By increasing the electrospinning voltage, the average fiber diameters increased. The solution flow rate and the distance between needle tip and collector had no significant influence on the average fiber diameters. According to model optimization, the minimum average fiber diameter of electrospun zein fiber is given by following conditions: 24 w/v % zein concentration, 10 kV of the applied voltage, 10 cm of needle tip to collector distance, and 4 ml/h of solution flow rate.     

Viscoelastic characterization of a new guar gum derivative containing anionic carboxymethyl and cationic 2-hydroxy-3-(trimethylammonio)propyl substituents

A new guar gum derivative (CMHTPG) containing anionic carboxymethyl and cationic 2-hydroxy-3-(trimethylammonio)propyl substituents was characterized with the help of a stress-controlled rheometer for its linear viscoelastic behavior in aqueous systems. The frequency-dependent elastic modulus (G′) and viscous modulus (G″) curves for 0.5, 1.0, 1.5 and 2.0 g/dl of aqueous CMHTPG solutions were found to cross at a given frequency. The crossover frequency value decreased with the increase of CMHTPG concentration. At 25 °C, the longest relaxation time was obtained to be 5.556 s for aqueous 2.0% CMHTPG solution while the shortest relaxation time to be 0.027 s for aqueous 0.5% CMHTPG solution, showing a strong concentration dependence on the viscoelastic properties. Moreover, the complex viscosity (η*) of aqueous CMHTPG solution was found to increase with the increase of CMHTPG concentration, and to decrease with the increase of frequency. By investigating the viscoelastic properties of aqueous CMHTPG salt solutions containing various concentrations of NaCl, it was observed that the addition of NaCl could lead to a slight increase in the G′, G″ or η* value. Temperature was confirmed to have an important influence on the viscoelastic properties of aqueous CMHTPG solution. For aqueous 1.0% CMHTPG solution, the activation energy reflecting the temperature sensitivity of the complex viscosity was determined at the frequency of 1.0 rad/s and found to be 16.94 kJ/mol.     

Comparative study of organosolv lignins from wheat straw

Dewaxed wheat straw was treated with acetic acid–H₂O (65/35, v/v), acetic acid–H₂O (80/20, v/v), acetic acid–H₂O (90/10, v/v), formic acid–acetic acid–H₂O (20/60/20, v/v/v), formic acid–acetic acid–H₂O (30/60/10, v/v/v), methanol–H₂O (60/40, v/v) and ethanol–H₂O (60/40, v/v) using 0.1% HCl as a catalyst at 85 °C for 4 h, in which 78.2, 80.0, 88.2, 89.4, 94.1, 23.5 and 37.4% of the original lignin, and 42.4, 58.7, 70.0, 65.1, 76.5, 14.2 and 22.2% of the original hemicelluloses was released, respectively. Lignins obtained were characterized by their content of hemicelluloses, composition of phenolic acids and aldehydes, molecular weight, thermal stability and by UV, Fourier transform infrared (FT-IR), ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The results showed that aqueous organic acid was more effective than aqueous organic alcohol for extensive delignification and selective fractionation of cellulose, lignin and hemicelluloses from the straw. In particular, the addition of formic acid gave a significant effect on the dissolution of lignin. All the acid-insoluble lignin fractions contained small amounts of contaminated hemicelluloses as shown by their content of neutral sugars, 0.9–4.3%, and had weight-average molecular weight between 3960 and 4340 g mol⁻¹. An increase in concentration of acetic acid or formic acid in organosolv resulted in an increment in release of guaiacyl units and in lignin condensation. However, the lignin preparations released during the treatment with aqueous organic alcohol without organic acid contained almost equal amounts of non-condensed guaiacyl and syringyl units with fewer p-hydroxyphenyl units. The β-O-4 ether bonds together with β-β, β-5 and 5-5′ carbon–carbon linkages were identified to be present in lignin substructures.     

Preparation and characterization of silver-loaded hemp fibers with antimicrobial activity

The objective of this research was to impart antimicrobial properties to hemp fibers by incorporation of silver ions in hemp fibers by chemisorption. Sorption properties of hemp fibers were improved by non-selective oxidation using hydrogen peroxide and potassium permanganate. The optimal conditions for silver ions sorption by hemp fibers were determined by changing sorption conditions: pH value and concentration of aqueous silver nitrate solution, as well as duration of sorption. The maximum sorption capacity of modified hemp fibers was 1.84 mmol of Ag⁺ ions per gram of fibers. Antimicrobial activity of silver-loaded hemp fibers against different pathogens: Staphylococcus aureus, Escherichia coli, and Candida albicans was evaluated in vitro. Obtained silver-loaded hemp fibers show antimicrobial activity against tested pathogens.