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.     

Green and Efficient Synthesis of an Adsorbent Fiber by Plasma-induced Grafting of Glycidyl Methacrylate and Its Cd(II) Adsorption Performance

A new chelating adsorbent for the removal of Cd(II) from aqueous solution, PP-g-GMA-DETA fibers, is prepared by plasma induced grafting of glycidyl methacrylate (GMA) onto the surface of polypropylene (PP) fibers, followed by modification with diethylenetriamine (DETA). The effects of grafting parameters on the grafting degree are investigated. Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy prove the successful grafting of GMA onto the surfaces of PP fibers and the subsequent conversion of epoxy groups of grafted GMA to amine groups, on reaction with DETA. The adsorption performances of Cd(II) by the chelating fibers are evaluated in detail. Kinetic and isothermal parameters are also evaluated. The data fit well with the pseudo-second order and Langmuir isotherm model, respectively. The maximum adsorption capacity of Cd(II) is 46.47 mg g^-1 and the prepared fibers show selective adsorbability towards target Cd(II) in presence of competing Mg(II) ions.     

Biosorption of copper, nickel and manganese using non-living biomass of marine alga, Ulva lactuca

The adsorption of Cu2+, Ni2+ and Mn2+ onto the marine algal biomass of Ulva lactuca was investigated in single and multimetal solutions. This study was intended to determine the role of different pH values (2-8) on the biosorption of metals at different concentrations (10, 20 and 30 mg L(-1)). The biosorption capacity of Cu2+, Ni2+ and Mn2+ for 10 mg L(-1) was the same as 20 and 30 mg L(-1), increase with increasing pH up to pH 5.0 and then decreased, in single and multimetal solutions. The optimum pH value was observed in the pH range 4-5 for Cu2+ and pH 5-6 for Ni2+ and Mn2+. The maximum biosorption capacities of tested alga for Cu2+, Ni2+ and Mn2+ were 92, 80 and 75%, respectively in single metal solution at 10 mg L(-1) and pH 5.0. At a further increase of pH (8.0) the biosorption process for Cu2+, Ni2+ and Mn2+ (75, 69 and 63%, respectively at 10 mg L(-1)) was decreased. The minimum biosorptions were 60, 49 and 44% for Cu2+, Ni2+ and Mn2+, respectively in single metal solution at 10 mg L(-1) and pH 2.0. In the multimetal solution, algal biomass exhibited the maximum and the minimum biosorption capacity at different pH values the same as in single metal solution. The inhibitory role of other ions on sorption process can be well observed in multimetal mixture, where biosorption capacity of Cu2+, Ni2+ and Mn2+ were significantly decreased in the multimetal solutions. The maximum biosorption was recorded for Cu2+ (83%) in solution of Cu2+ + Mn2+, Mn2+ (67%) in solution of Ni2 + Mn2+ and for Ni2+ (74%) in solution of Ni2+ + Mn2+ at the concentration 10 mg L(-1) and pH 5.0. The observed reduction in the biosorption of Cu2+, Ni2+ and Mn2+ (65, 57 and 52%, respectively at 10 mg L(-1) and pH 5.0) was more pronounced in the multimetal solution of Cu2 + Ni2+ + Mn2+ as compared with single metal solution. The results demonstrated that the affinity of the tested alga for sorption of the investigated metal ions in single and multimetal solutions runs in the order Cu2+ > Ni2+ > Mn2+. Biosorption equilibrium was established by the Langmuir and Freundlich isotherm models. According to the analyses conducted, the biosorption of Cu2+, Ni2+ and Mn2+ to Ulva lactuca was more consistent with Freundlich isotherm.     

Characterization of castor oil/polycaprolactone polyurethane biocomposites reinforced with hemp fibers

Abstact  The thermal and mechanical properties of castor oil/polycaprolactone-based polyurethane (CPU) films and polyurethane biocomposites reinforced with hemp fibers (HCPU) were investigated. Although similar films can be synthesized from petroleum, the main interest in studying these biomass-based composites is based on the fact that both fiber and matrix are derived from renewable resources. In this study, castor oil was used as a polyol for polyurethane films and hemp fiber was used to reinforce the biocomposites. To control the mechanical properties of CPU and HCPU, polycaprolactone diol (PCL) was added to the polyol mixture. Varying the mixing ratio of castor oil and PCL, the thermal and mechanical properties of the CPU and HCPU samples were investigated by using FT-IR, DSC, DMTA, Minimat, and SEM. In an attempt to improve interfacial adhesion between the fiber and matrix biocomposites, hemp fiber was reacted with MDI. FE-SEM micrographs showed that the surface of the hemp fiber became smoother after reaction with MDI. Urethane bonding formation was confirmed by FT-IR.     

茶叶纤维对Cu2+的吸附性能研究

对茶叶纤维吸附Cu²⁺的性能进行了研究。结果表明,茶叶纤维对Cu²⁺有明显的吸附作用。pH值为4.55左右,温度在30℃左右时,对Cu²⁺的吸附较为有利;当Cu²⁺的质量浓度为200 mg/L时,随着茶叶纤维添加量增加,吸附量先升后降,茶叶纤维添加量为90 mg左右时吸附量最大。茶叶纤维对Cu²⁺的吸附过程符合拟二级动力学方程。Langmuir等温吸附方程比Freundlich方程能更好地描述茶叶纤维对Cu²⁺的平衡吸附行为,最大吸附量达到16.78 mg/g。     

Experimental study on structure and mechanical properties of hemp/PBTG composites with fiber contents and thermal exposures

Most materials used in daily life are polymeric materials based on petrochemistry. The used polymeric materials can cause land pollution and air pollution after landfill or incineration. In contrast, natural fiber reinforced (NFR) composites are more suitable for the environment, however the reliability in terms of the durability and weatherability of NFR composites is still lacking. Thus, NFR composites require the reliability involved with durability and weatherability. In this work, poly(butylene terephthalate-co-glutarate) (PBTG), with a chemical structure similar to biodegradable PBAT, was used as the matrix in the composites, and hemp fibers were used as the reinforcement. Hemp/PBTG composites were fabricated by stacking hemp-fiberwebs and PBTG films with various fiber contents and thermal exposure times. Characteristics of the composites, such as the morphological structure, chemical structure, tensile properties, compressive properties, flexural properties, and impact strength, were analyzed to obtain the effects of fiber volume fraction and thermal exposure. As a result, hemp/PBTG composites were hardened in proportion to fiber volume fractions, and the hardening behavior of the composites increased tensile strength and flexural strength. However, the hardened structure of the composites decreased the impact strength and compressive strength of the composites. On the other hand, the mechanical properties of hemp/PBTG composites with thermal exposure times, were governed significantly by the brittleness behavior of the resin and the increased crystallinity of hemp fibers. Thus, the hemp fibers contributed to the improvements on structural stability, tensile strength and flexural strength of the hemp/PBTG composites, and increased the thermal durability of the composites with various thermal exposures.     

汉(大)麻与其它纤维素纤维染色性能研究

本文在汉麻纤维化学组分分析的基础上,利用中温活性染料,对多种纤维素纤维的染色性能进行了测定。研究了不同组成成分对汉麻纤维染色性能的影响,比较了汉麻纤维与其它纤维素纤维的上染百分率和上染速率的差异。结果表明,果胶和木质素的含量对汉麻纤维的染色性能均有不同程度的影响,但果胶的影响较木质素更为明显,汉麻纤维的染色性能与苎麻接近,但比棉纤维要差,更低于再生纤维素纤维。     

Selective removal of Pb(II) ions from aqueous solutions by acrylic acid/acrylamide comonomer grafted polypropylene fibers

Polypropylene-based chelating fibers grafted with acrylic acid and acrylamide side chains were simply synthesized, and subsequently employed as adsorbents for Pb(II) removal selectively from aqueous solutions. The assynthesized fibers were characterized by elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscope, and water contact angle. The adsorption results revealed that kinetics data were fitted by a pseudo-second order model (semi-saturation time 6.2 min), thereby suggesting chelating interaction to be the main mechanism during the adsorption process. The adsorption isotherm data fitted well with a Langmuir model. The thermodynamic study revealed the adsorption of Pb(II) as an exothermic spontaneous chemisorptive process. Coexisting Na(I), Mg(II), and Al(III) in solution showed negligible effects in the adsorption process. As confirmed by carboxyl amination, the carboxylate oxygen preferentially chelates coexisting Ca(II) over Pb(II), thereby leading to lower extents of Pb(II)-O chelate interaction. The spent fibers were effectively and repetitively (five cycles) regenerated while maintaining high performance upon treatment with 1 M hydrochloric acid solutions.     

Preparation,Characterization and Properties of High-salt-tolerance Sodium Alginate/Krill Protein Composite Fibers

Sodium alginate (SA) and krill protein (AKP) were blended to obtain composite solution, and functional SA/AKP composite fibers were prepared via wet spinning. To further improve the salt tolerance, SA/AKP composite fibers were modified with copper sulfate aqueous solution as secondary coagulation bath because of the strong adsorption to copper ions. The CSA/AKP composite fibers with high salt tolerance have been successfully prepared. The intermolecular interaction of SA/AKP composite system and the two-order structure of protein in the composite system were characterized by Fourier transform infrared spectroscopy (FT-IR). Besides, the crystallinity, morphology, mechanical properties, salt tolerance and water resistance and thermal stability of SA/AKP composites were investigated respectively. The results showed that the adsorption rate and the adsorption capacity of the composite solution to copper ion were significantly higher than those to calcium ion. Under the effect of secondary solidification by copper sulfate, the β-sheet chain of the composite fibers increased from 41.48 % to 49.21 %, the intramolecular hydrogen bond increased from 38.18 % to 44.26 %, the intermolecular hydrogen bond decreased from 59.84 % to 54.70 % and free hydroxyl slightly decreased. The water resistance of the modified composite fibers was improved by about 22 %; when the swelling time was 25 min, the salt resistance increased by about 150 %; the number of grooves on the surface of the composite fibers obviously increased, and the grooves on the surface of CSA/AKP composite fibers and the fiber section structure were much denser; Meanwhile, copper sulfate had some influence on the crystallization, thermal stability and mechanical properties of the composite fibers.     

Bleaching of Hemp (<Emphasis Type="Italic">Cannabis Sativa</Emphasis> L.) Fibers with Peracetic Acid for Textiles Industry Purposes

Hemp plant exhibits various eco-friendly properties and hemp fiber processing does not cause environmental damage, however, it is known that most chemical operations have a risk to interrupt a sustainable production. As stated in several studies, peracetic acid is an important environmental friendly bleaching agent when compared to its conventional competitors. In this study, hemp fabric was bleached with peracetic acid with exhaustion and padding methods. The effects of temperature, pH, process time, concentration on whiteness values were determined. The influences of bleaching processes were investigated via instrumental and imaging methods. Physical properties of the treated fibers were also tested. Besides peracetic acid, hydrogen peroxide bleaching was carried out for comparison. COD values of bleaching effluents were analyzed for selected samples. Higher whiteness values were obtained with exhaustion bleachings than pad-batch bleachings. Quite high whiteness values (up to 68.13 Stensby whiteness index) attained in peracetic acid without significant fiber damage.     

Kinetics and pseudo-isotherm studies of 4-nitrophenol adsorption onto mansonia wood sawdust

Kinetic models alone are usually applied to describe adsorption onto porous materials, but little attention is given to the fact that diffusion of pollutants especially large organic pollutant molecules may also control the reaction rates. In this investigation, the kinetics and pseudo-isotherm studies of an organic pollutant, 4-nitrophenol from aqueous solution on mansonia sawdust was examined. The intraparticle diffusion particle plots revealed three distinct sections representing sorption into external diffusion, intraparticle diffusion and diffusion to a biosorption site within the particles. The fractional removal of pollutant versus square root of time plots further revealed three sectional straight lines whose slope may represent the rates of pollutant sorption into macro-, meso- and micropores.The equilibrium capacities determined using four forms of the Ho's pseudo-second order model and the Type-1 pseudo second-order expression was also used to evaluate equilibrium concentrations and pseudo-isotherms were obtained by changing initial concentration, C₀.     

Preparation and use of amine-functionalized glycidyl methacrylate-g-poly(ethylene terephthalate) fibers for removal of chromium(VI) from aqueous solution

Poly(ethylene terephthalate) (PET) fibers were grafted with glycidyl methacrylate (GMA) using benzoyl peroxide as initiator. 1,6-diaminohexane (HMDA) was then covalently attached to this GMA grafted PET fibers. Variations of time, temperature, initiator and monomer concentrations were investigated. HMDA-GMA-g-PET fibers were used as a new sorbent for removal of Cr(VI) ions from aqueous solutions through batch adsorption method. Effects of various parameters such as pH, treatment time, and initial ions concentration on the adsorption amount of ions onto reactive fibers were investigated. The adsorption rates of Cr(VI) ions were much higher on the HMDA-GMA-g-PET fiber than on GMA-g-PET and ungrafted PET fiber. Within 60 min, at pH 3, Cr(VI) was removed by 98 % while the initial concentration of ions was at 25 mg/l and by 94 % at 400 mg/l. The Cr(VI) ions adsorbed were easily desorbed by treating with 1M KOH within 10 min.     

Electrospun polyindole nanofibers as a nano-adsorbent for heavy metal ions adsorption for wastewater treatment

Polyindole nanofibers were prepared via electrospinning method using acetonitrile as solvent. The obtained electrospun polyindole nanofibers were characterized with SEM, TEM, FTIR and BET surface areas measurements. Adsorption experiments were carried out in batch sorption mode to investigate the effect of pH, contact time and diameter of polyindole nanofibers. The Cu(II) adsorption was highly pH dependent and the optimum pH was found to be 6. The maximum adsorption capacities for electrospun polyindole nanofibers and polyindole powders were 121.95 and 18.93 mg/g attained in 15 and 60 min, respectively. With the diameter of polyindole nanofibers increasing, the adsorption capacity slightly decreased. The adsorption isotherm data fitted well to the Langmuir isothermal model which indicates that the monolayer adsorption occurred. The kinetics data analysis showed that the adsorption process could be described by pseudo-second order kinetic model, suggesting a chemisorption process as the rate limiting step. Thermodynamic parameters ΔHº, ΔSº and ΔGº for the Cu(II) adsorption by polyindole nanofibers were calculated. The results showed that the Cu(II) adsorption was feasible, spontaneous and endothermic. Desorption results revealed that the adsorption capacity can remain up to 75 % after 10 times usage. The electrospun polyindole nanofibers would have promising application for removal of Cu(II) from wastewater treatment.     

Surface morphologies and internal fine structures of bast fibers

Fiber surface morphologies and associated internal structures are closely related to its properties. Unlike other fibers including cotton, bast fibers possess transverse nodes and fissures in cross-sectional and longitudinal directions. Their morphologies and associated internal structures were anatomically examined under the scanning electron microscope. The results showed that the morphologies of the nodes and the fissures of bast fibers varied depending on the construction of the inner fibril cellular layers. The transverse nodes and fissures were formed by the folding and spiralling of the cellular layers during plant growth. The dimensions of nodes and fissures were determined by the dislocations of the cellular layers. There were also many longitudinal fissures in bast fibers. Some deep longitudinal fissures even opened the fiber lumen for a short way along the fiber. In addition, the lumen channel of the bast fibers could be disturbed or disrupted by the nodes and the spirals of the internal cellular layers. The existence of the transverse nodes and fissures in the bast fibers could degrade the fiber mechanical properties, whereas the longitudinal fissures may contribute to the very rapid moisture absorption and desorption.     

球状壳聚糖树脂对茶多酚的吸附热力学和动力学研究

采用反相悬浮交联法制备了球状壳聚糖树脂(RCM),通过静态吸附实验,研究了RCM对茶多酚的吸附热力学和动力学特性。结果表明:吸附等温线符合Laugmiur等温曲线,且平衡常数Kb随着温度升高而升高。吸附是非自发的、吸热的、熵增加的过程。吸附过程符合二级动力学吸附模型,吸附过程主要受粒子内扩散模型控制。     

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.     

Liquid sorption behavior of superabsorbent fiber based nonwoven media

Nonwovens are widely used as liquid absorbent media. Currently, superabsorbent fibers are used in nonwovens for making them less bulky yet very effective in absorbing liquids. In this work, a series of nonwovens were prepared by random mixing and layer-wise combining of superabsorbent fibers with fibers of different cross-sectional geometries. These nonwovens were studied for their liquid absorption behavior by using gravimetric testing absorption system. It was observed that in case of random mixing, the increase in weight fraction of superabsorbent fibers led to a tremendous increase in liquid sorption capacity and liquid sorption rate. When mixed randomly with superabsorbent fibers, the finer fibers exhibited better sorption characteristics than the coarser fibers, but the non-circular fibers displayed poorer sorption characteristics than the circular ones. In case of layer-wise combining, better sorption characteristics were obtained when the liquid was first challenged by the polypropylene fiber side as compared to that by superabsorbent fiber side. The superabsorbent fibers and the circular polypropylene fibers, when combined layer-wise, resulted in higher sorption capacity but lower sorption rate than those when mixed randomly.     

An Investigation on Wear and Dynamic Mechanical behavior of Jute/Hemp/Flax Reinforced Composites and Its Hybrids for Tribological Applications

Bio-materials have ignited a quest among research fraternity to be used in every possible field of applications like automobile, sports, medical, civil and textile industry. Application spectrum of natural fiber reinforced polymer composites is spreading globally in every field of engineering having structural and tribological applications. The present work investigates the tribological performance of regionally available inexpensive plant based natural fiber reinforced polymer composites. In this work, three different types of natural fibers (jute, hemp, and flax) were reinforced with epoxy matrix to fabricate natural fiber reinforced polymer composites (NFRP) and their hybrid composites (jute/hemp/Epoxy, hemp/flax/epoxy and jute/ hemp/flax/epoxy) using hand-layup technique. Tribological performance of the developed bio-composites were evaluated in terms of frictional characteristics and sliding wear under dry contact condition at different process parameters, such as applied load (10-50 N), sliding speed (1-5 m/s) and sliding distance (1000-2000 m). Experimental results of wear analysis confirmed that incorporation of natural fibers into epoxy polymer matrix significantly improved the wear behavior of the developed NFRP composites in comparison to neat epoxy polymer. Among all the developed composites, jute/epoxy composite achieved the highest coefficient of friction, frictional force and specific wear rate. Dynamic mechanical analysis (DMA) was also analyzed to evaluate the viscoelastic behavior of the developed composites. The surface morphology of samples after wear test was examined by scanning electron microscopy to investigate and propose the possible wear mechanism of the developed composites.     

“闪爆”处理对大麻脱胶及纤维性能的影响

采用“闪爆”新技术来处理大麻纤维，分析了闪爆处理前后大麻纤维脱胶、化学组分和理化性能的变化：结果表明，“闪爆”后的大麻纤维经水洗处理后，纤维素的比率显著增加，木质素等非纤维素成分明显降低，而且脱胶效果理想，大麻纤维的红外光谱闪爆处理以后在1510cm-1处吸收峰和在1736cm-1处吸收峰趋于消失，纤维的上染性能明显改善.     

Enzymatic treatment on cotton fibers: degradation kinetics of pectin and influence of shape change on adsorption

Alkaline pectinase was one of the most effective enzymes to treat cotton as alternative agent to replace the conventional alkaline method. Removal of pectin and cutin was considered the explanation for improvement of wettability as well as water adsorption on cotton fiber. However, degradation kinetics of pectin is unclear, and the influence of fiber shape on property changes after enzymatic treatment was ignored. The main objective of this work was to reveal interactions between pectinase and cotton fiber for mechanism study. A heterogeneous catalysis kinetic equation, which is associated with Langmuir adsorption model and enzyme deactivation, was used to describe the heterogeneous catalysis. The enzymatic process conditions were optimized. Raw cotton fibers, pectinase-treated and alkali-treated fibers were characterized by impurities content determination, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). Mechanism of water adsorption enhancement on treated fibers was discussed. In addition to elimination of the outer impurities, flat fibers with less twist and shape changes of lumen were also obtained to ensure better accessibility and water adsorption after enzymatic treatment.