Facile fabrication of PVAc-g-PVDF coating on surface modified cotton fabric for applications in oil/water separation and heavy metal ions removal

Selective separation is an effective method for the removal of heavy metal ions and waste oil from wastewater. Polyvinylidene fluoride (PVDF) was functionalized with polyvinyl acetate (PVAc) by in-situ polymerization, and novel PVAc-g-PVDF coating on surface modified cotton fabric were prepared. The contact angle (CA), pure water flux (PWF) and self-cleaning ability of coated cotton fabric were investigated in detail. In addition, the separation performance of coated cotton fabric was reflected by the removal of heavy metal ions in simulated wastewater. The results revealed that the PVAc-g-PVDF-coated cotton fabric was free of waste oil adhesion and was self-cleaning from waste oil in aqueous environment. Meanwhile, this coated cotton fabric can effectively separate oil/water mixtures with a high flux and high oil rejection, and was easily recycled for long-term use. More importantly, the heavy metal ions rejection ratio and adsorption capacity of cotton fabric were also improved with the addition of PVAc-g-PVDF coating. PVAc-g-PVDF-coated cotton fabric exhibited excellent rejection stability and reuse performances after several times fouling and washing tests. It can be expected that the present work will provide insight into a scaled-up fabrication process of PVAc-g-PVDF coating for purifying wastewater.     

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.     

Ternary carboxymethyl chitosan-hemicellulose-nanosized TiO<Subscript>2</Subscript> composite as effective adsorbent for removal of heavy metal contaminants from water

A ternary composite consisting of carboxymethyl chitosan, hemicellulose, and nanosized TiO₂ (CHNT) was prepared by incorporating TiO₂ nanoparticles into the pre-synthesized carboxymethyl chitosan-hemicellulose polysaccharide network. The microstructure and chemical composition of the obtained CHNT was characterized by TEM, SEM, FTIR, and TGA. The adsorption of some toxic heavy metals including Ni(II), Cd(II), Cu(II), Hg(II), Mn(VII), and Cr(VI), onto the as-prepared CHNT composite was investigated. The effects of pH, temperature and contacting time on the adsorption process were studied. Results revealed that the CHNT composite exhibited efficient adsorption capacity of the above metal ions from aqueous solution due to its favorable chelating groups in structure. The adsorption process was best described by the pseudo-second-order kinetic model, while isotherm modeling revealed that the Langmuir equation better described the adsorption on CHNT as compared to Freundlich model. Moreover, the CHNT loaded metal ions can be easily regenerated with EDTA and reused repeatedly up to five cycles. The environmental friendly hybrids were expected to be a promising candidate for future practical application in heavy metal contaminated water treatment.     

花生壳及其提取有价物质后的残渣在环境保护领域的应用

花生壳及其提取有价物质后的残渣在环境保护领域有大量的应用,将其制成纤维素膜或改性修饰,可用于纯水制备、膜生物反应器、海水淡化等;残渣可用于重金属离子吸附、偶氮染料吸附处理;也可热解制备富氢可燃气或发电,提供绿色能源。     

Preparation and characterization of cellulose nanofiber reinforced thermoplastic starch composites

In the present study, cellulose nanofibers composite films were manufactured based on thermoplastic starch. Nanofibers were extracted from rice straw employing a developed chemo-mechanical method. In the chemical step, almost all of non-cellulosic components were removed and a white pulp of cellulose microfibers was obtained. Then, a diluted suspension of fibers was ultrasonicated to destruct intermolecular hydrogen bonds achieving nanofibers networks. Afterward, bio-nanocomposites were prepared by film casting. In order to study the effect of nanofibers content on the composite properties, the mechanical and dynamic mechanical properties, morphology, humidity absorption, and transparency of films were investigated. The yield strength and Young modulus of nanocomposites were satisfactorily enhanced compared to the pure thermoplastic starch film. The glass transition temperature of films was shifted to higher temperatures by increasing nanofibers contents. The uniform dispersion of the nanofibers was investigated using SEM images. The humidity absorption resistance of films was significantly enhanced by using 10 wt% cellulose nanofibers. The transparency of the nanocomposites was reduced compared to the pure starch films.     

Novel nanocomposites based on hydroxyethyl cellulose and graphene oxide

In the present study, nanocomposites films formed by hydroxyethyl cellulose (HEC) and graphene oxide (GO) were synthesized and characterized. Compared with pure hydroxyethyl cellulose film, the thermal stability and mechanical properties of the composite materials were significantly improved. When the graphene loading was only 1.0 wt%, the maximum weight loss temperature increased 11.14 °C. The tensile strength and Young’s modulus of HEC/GO nanocomposites films were increased by 30.28 and 75.63 % compared to the pure HEC films, with only 1.0 wt% GO. The X-ray diffraction and Fouriertransform infrared spectroscop showed that GO sheets were completely exfoliated in the HEC matrix and suggested the presence of the weak interaction between HEC and GO sheets because of large number of oxygen-containing hydrophilic functional groups on the surface and edge of GO sheets. Furthermore, the well-dispersed GO nanosheets in the films can be inferred from the SEM and Halpin-Tsai model analysis. On the other hand, the composite films showed improved barrier properties against oxygen. This simple process for preparation of HEC/GO films is attractive for potential development of high-performance films for packing applications.     

Enhanced mechanical properties of silk fibroin-based composite plates for fractured bone healing

We successfully fabricated bacterial cellulose/silk fibroin (BC/SF) composite plates having similar strength to that of human cortical bone (12.8–17.7 GPa). The mechanical properties of the BC/SF composite plates were investigated at various BC nanofiber contents. The BC nanofibers acted as good reinforcements for the stress transfer produced by the interactions between the BC nanofibers and the SF matrix, as confirmed by the molecular deformation of the BC nanofibers. The BC/SF composite plates have a promising potential as a replacement material for existing metal bone plate.     

Synthesis and characterization of electrically conductive composite films of polypyrrole/poly(acrylonitrile-co-styrene)

Homogeneus Polypyrrole (PPy)/poly(acrylonitrile-co-styrene) (SAN) composite thin films were prepared by chemical polymerization of pyrrole on poly(acrylonitrile-co-styrene) matrix. Ce (IV) is used as an oxidant for in-situ polymerizion of pyrrole on SAN matrix, having an advantageous over the impregnation method. The formation and incorporation of PPy in the copolymer matrix were confirmed by FTIR-ATR and UV-Visible spectrophotometric measurements. Thermal analyses showed that after polymerization of Py in copolymer matrix, thermal behavior of SAN was changed and derivative of weight loss at this temperature was increased by increasing of PPy content. XPS and FTIR-ATR analysis of composite films indicated cerium salt with nitrate ion acted as a dopant. The increase in the AC electrical conductivity of the PPy/SAN composites over pure SAN was observed. At lower frequency up to 10⁵ Hz, conductivity was shown an independent behavior from frequency; but at high frequencies (10⁵–10⁷ Hz), dependence on frequency was explained by polaron and bipolaron formations of PPy. The dispersion of PPy particles in copolymer matrix was proven by SEM, AFM and digital camera. By the increase of PPy content in the composite films, increase in AC conductivities, and decrease in dielectric constants and loss were observed.     

Formation of metal complex in a poly(hydroxamic acid) resin bead

Poly(hydroxamic acid) resin beads were prepared and complexed with various metal ions. We used IR spectroscopy to investigate the structure of metal complex. It proved that the products formed by introduction of metal ions gave stable and colored complex. It was found that the resin bead as synthesized would be a good column packing material for continuous extraction. Energy dispersive spectroscopy was used to study the distribution of metal ions in the resin matrix. It could be tentatively concluded that adsorption and diffusion of metal ions in the chelating resins mainly depended on the loading of the resin matrix which indicated interacting sites with metal ions.     

Manufacturing and analyses of wet-laid nonwoven consisting of carboxymethyl cellulose fibers

Carboxymethyl cellulose (CMC) is a cellulose derivative having water-soluble property, biodegradability, and biocompatibility. It has been used in various medical applications as forms of gel, film, membrane, or powder. In this study, composite CMC nonwovens were produced, by a wet-laid nonwoven process, to improve the wet strength of carboxymethyl cellulose nonwovens. Followed by preparing the CMC fibers from cotton fiber, the composite CMC nonwovens composed of CMC fibers and PE/PP bicomponent fibers were manufactured by using 85/15 % v/v of ethanol/water solution as a dispersion medium. Structural analyses of CMC fibers, such as XRD, TGA, FT-IR, and degree of substitution indicated that CMC fibers were successfully produced. The wet strength of CMC nonwoven was dramatically increased by blending with the PE/PP fibers without sacrificing the key properties for wound dressing materials such as liquid absorption, gel blocking and liquid retention. It is expected that the composite CMC nonwovens will be a good candidate for wound dressing materials for mild exudate condition.     

The transport of metal ions through fiber supported solid membranes in mixed solvents

The transport of metal ions has been explored of bismuth, cadmium and lead from source solution to receiving phase through the fiber supported solid membrane system. The fibers supported solid membranes were prepared by chemically modification of cellulose fibers with the introducing the ion exchanging groups. The experimental variables explored were concentration of metal ions in the source solution, mixed solvent composition in the receiving phase and stirring speed of the bulk source solution and receiving phase. The efficiency has been evaluated for the transport of metal ions from the source to receiving phase through the fiber supported solid membrane. The pre-concentration was investigated of metal ions from the dilute solutions. The fiber supported solid membrane with two-channel systems had been investigated for the transport of metal ions from the source to receiving phase. The capillary action phenomenon helps to effectively transport the metal ions through the fiber supported solid membrane.     

Electrospun meta-aramid/cellulose acetate and meta-aramid/cellulose composite nanofibers

Meta-aramid/cellulose acetate and meta-aramid/cellulose composite nanofibers were successfully prepared in this paper. There were some new interactions formed among composite ingredients and the beads of nanofibers decreased with increasing the weight proportion of ingredients and concentration of composite solution. The meta-aramid/cellulose acetate composite solution was more favorable for electrospinning because of its lower viscosity and surface tension than meta-aramid/cellulose composite solution, and the uniform nanofibers were obtained when the weight proportion of meta-aramid/cellulose acetate was larger than 1:2, however, it was feasible for meta-aramid/cellulose composite solution when the weight proportion of composite solution exceeded 4:1. The thermal property and mechanical property of composite nanofibers were improved after blending meta-aramid with cellulose acetate or cellulose.     

Colorimetric detection of transition metal ions with azopyridine-based probing molecule in aqueous solution and in PMMA film

We report on an azopyridine derivative for probing transition metal ions and fabrication of its films. The probe, AP, showed a sensitive absorption change toward transition metal ions, especially cobalt ion, even at the concentration of ppm range, accompanied by yellow-to-red color transition with noticeable isosbestic point. In addition, the AP-containing PMMA film with high transparency can be fabricated by spin-casting without any aggregation of AP. The film with PMMA matrix shows good sensitivity toward cobalt ion similar to the case in the solution with a feature of metallochromic transition.     

茶树黄金芽CsHIPP26.1蛋白螯合离子的筛选与鉴定

重金属相关异戊二烯化植物蛋白(HIPPs)由于其独特的重金属结合域和异戊二烯序列的结构特点,成为一类重要的金属分子伴侣.为鉴定茶树(Camellia sinensis)黄金芽CsHIPP26.1蛋白的螯合离子,将pET-32a-CsHIPP26.1重组质粒和空载体分别转入大肠杆菌BL21,在分别添加4 mol·L-1的...     

Structure,electrical and mechanical properties of polyamide 66/acid-treated MWCNT composite films prepared by solution mixing in the presence of nonionic surfactant

Two different sets of polyamide 66(PA66)-based composite films containing 2.0-10.0 wt% acid-treated multiwalled carbon nanotubes (MWCNT) were manufactured by solution mixing and casting method in the presence or absence of a nonionic surfactant. For the improved dispersion and interfacial interaction of MWCNTs in the PA66 matrix, carboxylic acid-functionalized MWCNTs were prepared by the acid-treatment of pristine MWCNTs. The uniform dispersion of the acidtreated MWCNTs in the PA66 matrix was confirmed from FE-SEM images of the fractured composite film surfaces. DSC thermograms supported that the acid-treated MWCNTs served as nucleating agents for the melt-crystallization of PA66 in both composite films prepared with/without the addition of the surfactant. The electrical and tensile mechanical properties of the composite films prepared with the surfactant were ~20 % higher than those of the composite films manufactured without the surfactant. For both composite films, sheet resistivity and tensile mechanical properties were found to be highly decreased and increased, respectively, with the increment of the acid-treated MWCNT content.     

Electrospinning of cellulose nanofibers mat for laminated epoxy composite production

In this study, a new approach consisting of chemical treatment steps followed by electrospinning process was applied to produce cellulose nanofibers from wheat straws. Wheat straws were initially pretreated by NaOH solution to open the complex structure of raw materials and remove non-cellulosic materials. Then, acid and alkali hydrolysis was separately performed to eliminate hemicellulose and soluble lignin. Also, bleaching processes were implemented to remove the insoluble lignin. Cellulose nanofibers were produced by electrospinning of various concentrations of cellulose in different solvents including sodium hydroxide/urea/thiourea, pure trifluoroacetic acid (TFA), and TFA/methylene chloride. Images obtained by Scanning Electron Microscope (SEM) showed long and uniform nanofibers produced from electrospinning of cellulose/TFA/methylene chloride solution. An epoxy based laminated composite was prepared by a lamina of cellulose microfiber and electrospun nanofiber mat using hand lay-up composite manufacturing method. The fracture surface of the epoxy nanocomposite was analyzed by SEM images. In addition, the mechanical properties of laminated epoxy composites were compared with pure epoxy by conducting tensile and impact tests. Tensile test results showed that the ultimate tensile strength, elongation, and modulus of laminated epoxy nanocomposites were significantly increased. Moreover, it was found that by adding a nanofiber lamina in the epoxy composite, the impact resistance was significantly improved as a result of crack growth prevention.     

Growth and heavy metals accumulation potential of microalgae grown in sewage wastewater and petrochemical effluents

Microalgae exhibit a number of heavy metal uptake process by different metabolism. In this study, the ability of microalgae for removal of heavy metal from wastewater was studied. Growth and biochemical contents of microalgae were determined by spectrophotometer. Heavy metal analysis of wastewater effluents were performed by atomic absorption spectrophotometer before and after treatment at laboratory scale. The growth of Scenedesmus bijuga and Oscillatoria quadripunctulata in sewage wastewater was higher than those grown in synthetic medium. Whereas, the growth of S. bijuga and O. quadripunctulata in sterilized petrochemical effluents was slightly lower than that grown in the standard synthetic medium. The chlorophyll, carotenoid and protein content of S. bijuga and O. quadripunctulata grown in sterilized sewage wastewater were higher than those grown in the standard medium. Similarly S. bijuga and O. quadripunctulata grown in sterilized petrochemical effluents showed lower contents of pigments and protein than those grown in sewage and synthetic medium. Heavy metals copper, cobalt, lead and zinc were removed by 37-50, 20.3-33.3, 34.6-100 and 32.1-100%, respectively from sewage wastewater and petrochemical effluent using Ocillatoria culture. The metal absorption by S. bijuga were (Cu, Co, Pb, Zn) 60-50, 29.6-66, 15.4-25 and 42.9-50%, respectively from sewage and petrochemical effluents. Both species showed high level of heavy metal removal efficiency and metal sorption efficiency of both microalgae depended on the type of biosorbent, the physiological status of the cells, availability of heavy metal, concentration of heavy metal and chemical composition of wastewater.     

Biosorption kinetics of Cu (II) ions removal from aqueous solution using bacteria

The present study highlights the effective removal of Cu (II) ions from synthetic solution using bacteria such as B. subtilis, P. aeruginosa and E. cloacae. Batch biosorption studies show that the biosorption of B. subtilis is effective when the concentration ranges from 25-200 mg L(-1). Biomass dosage, pH and the initial metal ion concentration have a profound effect on the biosorption process and this is reported in this study. In order to understand the nature of the biosorption process, Langmuir and Freundlich isotherm models were applied. Pseudo first and second order models were used to study the biosorption kinetics. The results show that these bacterial strains are very much suitable for the removal of Cu (II) ions. Being cost effective and efficient in toxic metal ion removal, these bacteria can be used on a large scale.     

酸性电解水结合复合膜对橘柚保鲜效果的研究

为了防止橘柚采后枯水腐烂,采用酸性电解水浸果处理,并结合海藻酸钠、羧甲基纤维素钠、茶多酚、抗坏血酸配制成的复合保鲜剂进行涂膜处理后,将橘柚果实置于温度为 (8±1)℃、湿度为75%~80%的条件下存放120 d,以好果率、失重率、细胞膜透性、可滴定酸度、可溶性固形物以及类胡萝卜素为指标进行保鲜效果的评价,通过正交试验确定最佳保鲜方法。本研究所用的复合膜是多孔网络结构的薄膜,空隙小而细腻、均匀分散,复合膜处理后的果皮表面平整光滑,断面结构致密,在果实表面形成屏障。结果表明：酸性电解水处理能有效控制橘柚果实采后病害的发生,复合膜处理可以较好地控制橘柚的腐烂和失水现象,延缓果实衰老,有效保持可滴定酸和可溶性固形物的含量,还能提高果皮色泽;正交试验优化得出最优的保鲜方法,以有效氯含量为30 mg/L的酸性电解水浸果15 min,并联合海藻酸钠0.5%、羧甲基纤维素钠0.5%、茶多酚2.0%、抗坏血酸1.0%配比组合下的复合保鲜剂涂膜20 min。因此认为,酸性电解水结合复合膜处理能提高采后橘柚的品质、延长果实保鲜期。     

Electrical Resistivity of Plasma Treated Viscose and Cotton Fabrics with Incorporated Metal Ions

Cellulose fabrics (viscose and cotton) were treated with atmospheric pressure dielectric barrier discharge (DBD) in air. After DBD treatment, samples were characterized and volume electrical resistance was measured under different relative humidity conditions (φ=40-55 %). Results have shown that DBD treatment increases wettability and polar surface functional groups content, which consequently causes a decrease of volume electrical resistivity of cellulose fabrics in measured relative humidity range (φ=40-55 %). Metal ions (silver, copper, and zinc) were incorporated in untreated and plasma treated samples through sorption from aqueous solutions and incorporation of metal ions into plasma treated cellulose samples decreased electrical resistivity even further. Resistivity of cotton and viscose fabrics with incorporated metal ions followed the order Zn²⁺ > Cu²⁺ > Ag⁺. The most pronounced decrease, for entire order of a magnitude, was obtained by modification of cotton fabric with DBD and silver ions, where value of resistivity dropped from GΩ to a several dozens of MΩ.