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Silk as a highly valuable natural protein fiber is deeply loved by consumers in the textile and clothing industry due to its advantages of elegant wearing soft touch and good breathability. In addition its excellent biocompatibility biodegradability and mechanical strength make it have great potential in the biomedical field. In China a large amount of waste silk cocoons and waste liquid are generated during the silk reeling process every year. Meanwhile with people regularly updating their clothing home textiles and other lifestyle habits a large amount of waste silk products are quickly generated. The recycling and reuse of waste silk products cocoons silk fibers and sericin protein not only promote resource conservation and reduce pollution and carbon emissions but also play a crucial role in the supply of textile industry raw materials and alleviating resource pressure. The article summarizes the recycling and reuse methods of waste silk and their main applications in order to purify the environment reduce garbage emissions save resources and maximize the value of silk fibers. There are three common methods for recycling waste silk physical chemical and biological methods. Physical recycling is a reuse technology that uses cutting and crushing methods to classify recycle and reprocess waste materials in order to achieve effective recycling of resources. Chemical recycling method refers to the use of special environments or chemical reagents for recycling. It mainly uses a ternary solvent system lithium bromide solution formate solution ionic liquid or other solvents to degumm dissolve and extract useful substances from waste silk such as silk fibroin or sericin protein. The biological recycling method mainly converts most waste textiles including waste silk into bioenergy through direct combustion or composting. The recycling method is simple and convenient and can to some extent reduce the burden of landfill. However burning waste silk will release a large amount of carbon dioxide into the atmosphere. Therefore combustion is not an ideal solution for the recycling and reuse of waste textiles. After recycling waste silk it is first screened and cleaned preliminarily. Then a certain amount of waste silk is weighed and boiled with deionized water in a bath ratio of 1︰20 using a 1% sodium carbonate solution for 30 minutes. After repeating three times a bitter rouge solution is usually used to determine their degree of degumming and the sericin produced during the degumming process is collected. Finally the cleaned and degummed silk is dissolved using the ternary solvent system mentioned in the chemical recycling method. The obtained silk fibroin protein and silk fibroin protein solutions are collected separately and mainly used as electrode materials functionalized silk fibroin materials intelligent silk fibroin textiles recycled composite materials and filtration materials. The development of silk functional materials is an important research field. The sericin protein in silk has various forms of biological activity and pharmacological effects including anti-oxidant anti-constipation and anti-tumor effects. When it is cross-linked copolymerized and blended with other polymer materials especially artificial polymers it can be modified into functional materials. Functional composite materials not only possess the characteristics of silk but also combine functions such as bioactive factors and peptides. They play a more important role in skin wound healing making it faster and providing a better wound healing environment for full-thickness burn and diabetes wound patients. At present direct addition and genetic engineering technology are the main methods for endowing silk materials with multifunctionality. Among the recycling methods of waste silk such as physical chemical and biological methods each has its own advantages and disadvantages. Compared to other methods chemical recycling has lower costs and is more suitable for large-scale applications with comprehensive advantages. Chemical recycling methods can be used to recover waste silk fibers and silk fibroin materials are extracted and reused which can effectively reduce resource waste. Silk and its derivatives are widely used in smart textiles such as sensors electronic skins energy storage devices spontaneous devices microneedles and radiation cooling. However the functional application of silk materials often reduces some of their original properties resulting in poor overall performance of the prepared smart wearable products. Therefore in functionalizing silk materials the performance of the original silk materials should be optimized and preserved. In the future the recycling and utilization of waste silk should be developed towards high performance low cost and clean production. There are mainly six points to be further considered as follows development of low-cost and green silk fibroin extraction technology focus on the recovery and utilization of silk fibroin protein in the degumming wastewater of the cocoon silk industry preparation of functional silk fibroin fibers development of intelligent silk fibroin textiles preparation of multifunctional electrodes development and application of waste silk in filtering materials to improve its recycling rate. [ABSTRACT FROM AUTHOR]

With the increasing awareness of human environmental protection, the development of biodegradable bio-based materials has received more attention. As the off-cuts of silk, a natural protein fiber, waste silk still retains excellent properties such as biodegradability and biocompatibility, recycling and utilization of waste silk is currently very limited. To find a possible method to recycle low-cost waste silk and process it into high-value-added products, in this work, the waste silk from the silk spinning process was prepared into silk nonwoven (SN) with excellent air permeability, softness, water–oil amphiphilicity, biodegradability, and ultraviolet resistance by the wet laid process. The results showed that the uniform SN could be prepared when the alkali concentration was higher than 0.6%. The permeability of SN is higher than 80 mm/s, and the bending stiffness is lower than 0.085gf·cm2/cm. Notably, SN possesses entanglement at both fiber and fibril levels, enabling it to achieve a base strength of 0.58 MPa without additional reinforcement. The water contact angle and oil contact angle of SN were below 40° and 50°, respectively. The ultraviolet protection of SN-0.6 was classified as very good, with a degradation rate of 4.31% of SN-0.6 after 30 days of burial. The present research shows that silk nonwoven is a potential bio-based material with promising applications in the field of packaging and cleaning. [ABSTRACT FROM AUTHOR]

In this work, polydopamine (PDA) was used to facilitate the reduction of silver nitrate (AgNO3) to silver nanoparticles (AgNPs) and the simultaneous loading on waste silk fabrics (PDA-SF/AgNPs). The removal activity of the obtained composite PDA-SF/AgNPs on different dyes in the presence of hydrogen peroxide (H2O2) and potassium peroxymonosulfate (PMS) was compared. The effects of reaction temperature, H2O2/PMS dosage, dye concentration, composite dosage, electrolyte concentration and time in two catalyst systems on the dye removal were discussed. The results showed the dye removal of Telon Red A2R reached 81% and 95% in 30–50 min in PDA-SF/AgNPs-H2O2 and PDA-SF/AgNPs-PMS system, respectively. Quenching experiments demonstrated that ·OH, ·O2– and SO4-· were produced during the degradation process, and the possible degradation pathway of Telon Red A2R were analyzed by HPLC-MS. In addition, the kinetic study indicated that the removal of dye followed quasi-second-order adsorption kinetics. These findings suggest that fabric-based composites have great potential and applications in catalysis and treatment of wastewater.

In the context of environmental protection, the various waste textiles have caused considerable contamination and aroused extensive concern worldwide. This paper used waste silk products to fabricate the regenerated silk fibroin(RSF)/polyvinyl alcohol(PVA) blended fibers by the dry-wet spinning method. The spinning dope was the 20 wt% RSF/PVA (4/6) blended aqueous solutions, and the coagulation bath was non-toxic and harmless ethanol. We explored fibers' microstructure transformation at different spinning stages, forming mechanism, and structure and performance under different spinning parameters. The results showed that as the spinning process progressed, the β-sheet structure content and molecular chain orientation of fibers increased gradually from 30.8 % to 48.9 % and from 0.81 to 1.26, respectively. The solution experienced slight shear action in the spinning tube and then coagulated to cylindrical fibers immediately in the coagulation bath. With the extension of coagulation time, the impermeable skin structure and the stable network core structure locked the internal moisture, resulting in a gradually numerous internal pores. The increasing drawing speed ratio could reduce fibers' diameter and porosity while the growing coagulation time witnessed an improvement of microstructure. The porosity could be precisely modified. Under the optimum spinning parameters (drawing speed ratio of 1.2 and coagulation time of 60 s), the as-spun fibers had the breaking stress, initial modulus, and breaking strain of 0.29±0.04 cN/dtex, 12.22±2.55 cN/dtex, and 439±129 %, respectively. The fibers in this paper have high feasibility for subsequent secondary processing and show broad application prospects in the biomedical field. [ABSTRACT FROM AUTHOR]

In order to reuse the waste fabric and develop a novel textile-based adsorbent for heavy metal removal, the waste silk fabric was modified by tannic acid (TA) and the prepared adsorbents were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analysis. The removal of Cd(II), Cu(II), and Ni(II) ions from aqueous solutions was investigated using the modified silk fabric (TA-SF) under various conditions and the adsorption behavior of heavy metal ions was compared with the original silk fabric. The results showed that the maximum metal adsorption amounts reached 100% in 10 min. The adsorption isotherm models were demonstrated using Langmuir, Freundlich, and Temkin isotherm models, and the adsorption of TA-SF to Cd(II), Cu(II), and Ni(II) were well fitted with Langmuir isotherm than Freundlich and Temkin isotherm model. Moreover, the adsorption kinetics was well fitted with to the pseudo-first-order and pseudo-second-order kinetic models, and adsorption kinetics indicated that the former model was better suited than the latter. For 60 mg/L initial concentrations of Cd(II), Cu(II), and Ni(II) at pH 9.0, the adsorbents' maximum adsorption capacity was 8.03 mg g−1, 7.42 mg g−1, and 7.47 mg g−1, respectively. Within 5 min, the absorbed metal ions on TA-SF could mostly be desorbed. Moreover, TA-SF can adsorb heavy metal ions from dyeing aqueous solution, showing its capability of simultaneous removal of heavy metal and waste dyes. The results suggest that the lower-cost TA-SF could be an effective adsorbent for removing heavy metals from industrial wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, polydopamine (PDA) was used to facilitate the reduction of silver nitrate (AgNO 3) to silver nanoparticles (AgNPs) and the simultaneous loading on waste silk fabrics (PDA-SF/AgNPs). The removal activity of the obtained composite PDA-SF/AgNPs on different dyes in the presence of hydrogen peroxide (H 2 O 2) and potassium peroxymonosulfate (PMS) was compared. The effects of reaction temperature, H 2 O 2 /PMS dosage, dye concentration, composite dosage, electrolyte concentration and time in two catalyst systems on the dye removal were discussed. The results showed the dye removal of Telon Red A2R reached 81% and 95% in 30–50 min in PDA-SF/AgNPs-H 2 O 2 and PDA-SF/AgNPs-PMS system, respectively. Quenching experiments demonstrated that ·OH, ·O 2 – and SO 4 -· were produced during the degradation process, and the possible degradation pathway of Telon Red A2R were analyzed by HPLC-MS. In addition, the kinetic study indicated that the removal of dye followed quasi-second-order adsorption kinetics. These findings suggest that fabric-based composites have great potential and applications in catalysis and treatment of wastewater. [ABSTRACT FROM AUTHOR]

Spontaneous fermentation is a traditional and ecologically friendly way to purify silk, but the knowledge of the microbial structure in this system is limited. The fermentation liquids (W1 and W2) from two waste silk refining systems were analyzed for their bacterial community and diversity. W1 had higher oil-removing and degumming efficiency than W2, and so was superior for the recovery of waste silk. The bacterial community structures of W1 and W2 were characterized by polymorphisms in the 16S rRNA gene. Two corresponding clone libraries (C1 and C2) were constructed from each system. Using amplified rDNA restriction analysis (ARDRA), 112 randomly selected clones were grouped in 24 operational taxonomic units (OTUs) from C1 and 113 clones were grouped in 20 OTUs from C2. The bacterial diversity of C1 was higher than C2 according to the Shannon-Weaver index. Sequencing and phylogenetic analysis indicated that Firmicutes were the most dominant group in both samples, followed by Bacteroidetes. Clones related to Synergistetes were only found in C1. This investigation expands substantially our knowledge of the bacterial composition and diversity in waste silk refining systems. The results also revealed that the silk-spinning system may harbor a bacterial population structure suitable for metagenomic mining for novel bacterial lipase, esterase, and protease. [ABSTRACT FROM AUTHOR]

In this study, 100% polyester and silk yarns and core-spun polyester silk yarns with two core/sheath ratios are produced. Fabrics are knitted from these yarns. Effect of core positioning on sheath coverage and core-sheath ratios and plying on various properties of yarns is analyzed. High level of unevenness is observed for core-spun yarns and plying improves many of the yarn characteristics. Z-twisted core-spun yarn produced with core filaments positioned left to the silk fibers during spinning has poor sheath coverage. Tenacity, elongation, and their CV are improved with increased percentage of core. It is observed that in a core-spun yarn sheath also contribute substantially to the yarn strength. The yarn to metal friction increases with increasing polyester content. Silk-rich core-spun yarn has less hairiness and better uniformity than the yarn with less silk content. Thermal comfort and wicking behavior of these fabrics are investigated in terms of fabric thickness, yarn structure, and fiber properties. The thermal conductivity of silk fabrics is the highest followed by silk rich and then polyester-rich fabrics. The thermal resistance of the fabrics is directly proportional to fabric thickness. The higher water vapor permeability, wicking, and transient heat flow observed for polyester and polyester rich fabrics indicate that they give an unpleasant cool effect to skin. [ABSTRACT FROM AUTHOR]

Polymer-based composite structures have advantages over many other materials. The most important advantage is the higher mechanical properties obtained from the composites when supported by fiber reinforcement. The mechanical and thermal properties of fiber-reinforced composite structures are affected by the amount of fibers in the structures, orientation of the fibers and fiber length. Silk and cotton fibers are used in many fields but especially in clothing and textiles. However, there is not enough research on their usage as reinforcement fibers in composite structures. Silk fibers as a textile material have better physical and mechanical properties than other animal fibers. The improvement of the mechanical and physical properties of the composite structures allows them to be used in many areas. From economical, technological and environmental points of view, the improvement of mechanical and physical properties of polymeric materials are receiving much attention in recent studies. In this study, different application areas were chosen to evaluate the waste silk and waste cotton rather than classic textile applications. Waste silk and cotton and recycled polycarbonate polymer were mixed and as a result composite structures were obtained. Silk and cotton waste fiber dimensions were in between 1 mm, 2.5 mm and 5 mm. The recycled PC/silk and cotton wastes were mixed in the rates of 97%/3%. Mixtures were prepared by twin-screw extruder. Tensile strength, % elongation, yield strength, elasticity modulus, Izod impact strength, melt flow index (MFI), heat deflection temperature (HDT) and Vicat softening temperature properties were determined. To determine the materials' thermal transition and microstructure properties, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used. [ABSTRACT FROM AUTHOR]

Dispersion of iron was achieved on waste silk fibers (wSF) after grafting of polydopamine (PDA). The catalytic activity of the resulting material (wSF-DA/Fe) was investigated in Fenton-like removal of toxic aromatic dyes (Methylene Blue, Cationic Violet X-5BLN, and Reactive Orange GRN) water. The dye removal yield reached 98%, 99%, and 98% in 10–40 min for Methylene Blue, Cationic Violet X-5BLN, and Reactive Orange GRN, respectively. The catalytic activity was explained in terms of the effects of temperature, dyes, and electrolytes. In addition, the kinetic study showed that the removal of dyes followed pseudo-1st order adsorption kinetics. These findings allow envisaging the preparation of fiber-based catalysts for potential uses in environmental and green chemistry. [ABSTRACT FROM AUTHOR]

With excellent biocompatibility and biodegradability, silk fibroin has been developed into many protein materials. For producing regenerated silk fibroin (RSF) fibers, the conformation transition of silk fibroin needs to be thoroughly studied during the spinning process. Since the many silk fabrics that are discarded comprise an increasing waste of resources and increase the pressure on the environment, in this paper, waste silk fiber was recycled in an attempt to prepare regenerated fibroin fiber by dry-wet spinning. Ethanol was the coagulation bath. The rheological properties of all the RSF solutions were investigated to acquire rheology curves and non-Newtonian indexes for spinnability analysis. Four stages of the spinning process were carried out to obtain RSF samples and study their conformation transitions, crystallization, and thermal properties by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, and differential scanning calorimetry. Quantitative analysis of the FTIR results was performed to obtain specific data regarding the contents of the secondary structures. The results showed that higher concentration spinning solutions had better spinnability. As the spinning process progressed, random coils were gradually converted into β-sheets and crystallization increased. Among the different influencing factors, the ethanol coagulation bath played a leading role in the conformation transitions of silk fibroin. [ABSTRACT FROM AUTHOR]