Environmentally-Friendly Synthesis of Ag Nanoparticles by Fusarium sporotrichioides for the Production of PVA/Bentonite/Ag Composite Nanofibers

Membranes and filters made of nanofibers can have many medicines and water treatment applications. The use of silver nanoparticles (AgNPs) with antibacterial activity in these structures improve their efficiency. However, due to the toxicity of the compounds used in the chemical synthesis of AgNPs, in this study, AgNPs were obtained through a biological process using Fusarium sporotrichioides. AgNPs preparation conditions were optimized, including F. sporotrichioides medium and AgNO₃ concentration. Next, a PVA nanofiber membrane with bentonite and AgNPs (Bio-AgNPs or Chem-AgNPs) was prepared using electrospinning. The optimal conditions for the production of Bio-AgNPs were the culture of F. sporotrichioides in the MGYP culture medium and 12 M of AgNO₃. The Bio-AgNPs particle size and zeta potential were 58 nm and ??16.8 mV, respectively, with antibacterial activity. The PVA/NB/AgNPs nanofibers operation conditions included 7.5% w/w PVA, 3% w/w bentonite, and AgNPs 5% w/w at a voltage of 11 kV, feed rate of 0.5 mL/h, and 15 cm distance between the needle and the collector. The average diameter of the PVA/NB/Bio-AgNPs nanofibers was 230 nm. Also, the presence of silver in the nanofibers was confirmed through EDX and XRD methods. The antibacterial assay of the nanofibers showed that the inhibition zone of PVA/NB/Bio-AgNPs against E. coli and S. aureus was 0.62 and 0.36 mm, which is better than PVA/NB/Chem-AgNPs and comparable with chloramphenicol. The produced membrane is suitable for water treatment, food packaging, and wound dressing because of its good thermal, mechanical, and antibacterial properties.

     

Electrospun ZnO Nanoparticles Doped Core–Sheath Nanofibers: Characterization and Antimicrobial Properties

Coaxial electrospinning technique was used to fabricate the core–sheath composite nanofibers of ZnO nanoparticle (Nps) (10%, 20% w/w) doped polymethyl methacrylate (PMMA) (as sheath) and polyvinyl alcohol (PVA) (as core). Fourier transform infrared (FT-IR) spectra were confirmed the weak forces arise between ZnO Nps, PMMA and PVA matrixes. The hexagonal (wurtzite) structure of ZnO Nps with ~?30.8 nm of diameter was confirmed from the X-ray diffraction pattern. The morphology and microstructure of core–sheath composite nanofibers were confirmed from the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is clearly seen from the TEM images that the PMMA encapsulate the PVA core. Core–sheath composite nanofibers were assessed against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) bacteria through quantitative, disk diffusion and viable cell count methods. It was found that ZnO Nps doped core–sheath nanofibers were effectively inhibit the growth of gram positive bacteria, B. subtilis.     

Preparation of Porous Nanofibers from Electrospun Polyacrylonitrile/Polyvinylidene Fluoride Composite Nanofibers by Inexpensive Salt Using for Dye Adsorption

The high surface area of porous nanofibers enhances their performance for many applications. The present study investigated electrospinning and dye adsorption properties of polymeric nanofibers which were porous by various types of salts. The salt/polyacrylonitrile/polyvinylidene fluoride composite nanofibers were electrospun, and the inexpensive salts such as sodium chloride (NaCl), sodium bicarbonate (NaHCO₃), or calcium chloride (CaCl₂) was used to manufacture the porous fibers. Subsequently, the salt was removed by a selective dissolution, and salt extraction of nanofibers was performed with the solution of hydrochloric acid (10 wt%). Salt/PVDF/PAN and porous PVDF/PAN composite nanofibers have been applied to dye adsorption of solution. The characteristics of nanofibers were studied by Fourier transform infrared microscopy (FTIR) and scanning electron microscopy (SEM) analysis. FTIR showed that the salt was extracted from PVDF/PAN nanofibers successfully, and SEM indicated that many pores were aligned with the nanofibers. The adsorption capacity of salt nanofibers webs and porous nanofibers webs for Basic Blue 41 were compared with each other, and porous fibers were obtained from NaHCO₃ having the highest dye adsorption value. Adsorption of dyes follows the Langmuir isotherm and pseudo-second order kinetics.     

Optimal Design of Ozone Bleaching Parameters to Approach Cellulose Nanofibers Extraction from Sugarcane Bagasse Fibers

Cellulose nanofibers (CNFs) were isolated from sugarcane bagasse (SCB) through the combination of bio-refinery, sulfur-free, and totally chlorine free (TCF) chemo-mechanical pretreatments, with a focus on the optimal design of ozone bleaching parameters based on a response surface methodology (RSM). For this purpose, the most effective parameters in ozone bleaching (temperature, time, and pulp consistency) were set between 40 and 85 °C, 60 and 360 min, and 1–5 wt%, respectively. High-performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), Kappa number, and scanning electron microscopy (SEM) were used to chemically and morphologically characterize the SCB fibers. The size distribution and morphology of CNFs were also evaluated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). HPLC analysis revealed that percentage of cellulose increased from 41.5 to 91.39% after chemical pretreatments. FTIR and Kappa number analyses also confirmed the successful isolation of cellulose fibers from the SCB fibers after chemical pretreatments. Furthermore, DLS results showed that the hydrodynamic diameter of the isolated cellulose fibers reduced to 268 nm by dint of ultrasonication. Additionally, TEM images confirmed the isolation of CNFs: the average diameter of cellulose fibers decreased to about 28 nm after mechanical steps and the yield of fibrillation was found to be around 99%. According to the obtained results, the applied chemo-mechanical treatment appears to be promising for green and facile isolation of CNFs.     

Tailoring mesoporosity of poly(furfuryl alcohol)-based activated carbons and their ability to adsorb organic compounds from water

In this work it was shown that polymers can be recycled into a promising adsorbent for organic dyes and phenols waste removal. For this, a series of activated carbons (ACs) were produced from mixture of ferrocene or titanium acetylacetonate with poly(furfuryl alcohol) (PFA) by steam activation. The introduction of ferrocene as Fe precursor was found to be an efficient catalyst in mesoporosity development during carbonization and subsequent steam activation at 850 °C, whereas the polymer based only and titanium-doped ACs are typically microporous. The porous structure parameters were determined from nitrogen adsorption isotherms measured at 77 K. Scanning electron microscopy was applied to monitor the metal distribution of metal-loaded char and the surface morphology of activated carbons. The adsorption capacity was found to be dependent mainly on pore size distribution. In the case of phenol adsorption, the adsorption was defined by volume of pore with size 0.8–1.4 nm; whereas, for Congo red best fit was observed for volume of pore with size 2–5 nm.

     

Green Synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/Cellulose/Polyvinyl Alcohol Hybride Aerogel and Its Application for Dye Removal

A novel Fe₃O₄/cellulose–polyvinyl alcohol (PVA) aerogel was successfully synthesized by an eco-friendly and facile method in this work. Cellulose/PVA matrix was prepared through an environmental friendly physical cross-linking process and further in-situ decorated with Fe₃O₄. Series of Fe₃O₄ decorated aerogels were prepared and the effects of Fe₃O₄ nanoparticles (NPs) on the aerogels were systematic investigated. As-prepared aerogels exhibited desirable properties including nanostructure, relatively high porosity, improved mechanical and superparamagnetism. The TEM results showed that Fe₃O₄ NPs were integrated in the three-dimensional matrix of cellulose/PVA with a diameter of 9–12 nm. Furthermore, the mechanical strength of the aerogels was significantly enhanced after the introduction of Fe₃O₄ NPs. Meanwhile, the obtained Fe₃O₄/cellulose/PVA aerogel exhibited excellent adsorption performance toward methyl blue dye, and can be reused through fenton-like catalysts oxidative degradation of organic dye in H₂O₂ solution. Therefore, they will have a great potential application as eco-friendly and economical adsorbents.     

Production and characterization of KOH-activated carbon derived from polychlorinated biphenyl residue generated by the sodium dispersion process

Polychlorinated biphenyl (PCB) residues from the sodium dispersion (SD) process were employed as the raw materials for the production of activated carbon using KOH activation. The pore properties, such as the specific surface area and pore size distribution, were characterized using the Barrett–Joyner–Halenda method and the Horvath–Kawazoe method based on the N₂ adsorption isotherm at 77 K. The activated carbon produced showed similar adsorption capacities and specific surface areas to the commercially available product. The effects of the activation conditions on the porosity of the activated carbon produced were studied. The most significant factor affecting the specific surface proved to be the activation temperature. The activated carbon produced from PCB residues from the high-temperature (423–443 K) SD process had a binary pore size distribution well developed in the 4 nm region and in the micropore region. The pore structure of the carbon produced from PCB residues from the low-temperature (333–393 K) SD process had a wide range of micropores and mesopores.     

Citric Acid and Vitamin C as Coupling Agents for the Surface Coating of ZrO<Subscript>2</Subscript> Nanoparticles and Their Behavior on the Optical,Mechanical, and Thermal Properties of Poly(vinyl alcohol) Nanocomposite Films

A series of bio-nanocomposites (BNC)s were fabricated through solution casting method. At first, the surfaces of ZrO₂ NPs were functionalized with citric acid and Vitamin C as green modifier agents. Then, PVA as polymer matrix was embedded with different contents (4, 8 and 12 wt%) of modified ZrO₂ (m-ZrO₂) NPs with the aim of ultrasonic irradiation process. The resulting BNCs were studied by various techniques. Thermal stability of obtained BNCs was enhanced after NPs’ addition to the PVA matrix. Optical activity of these new BNCs makes them potential candidate for UV shielding material. Lastly, the tensile strengths of the BNCs were increased in comparison to the pure PVA.     

类氧化硅气凝胶吸附材料的制备及其吸附性能

以有机硅高沸物和Na₂SiO₃·9H₂O为原料，采用溶胶-凝胶法制备出疏水性的类氧化硅气凝胶吸附材料。采用透射电子显微镜、傅里叶变换红外分析仪和比表面与空隙度分析仪对该吸附材料的结构进行表征。表征结果显示，该吸附材料呈海绵状多孔结构，比表面积为294.48 m²/g，孔径分布较宽（为2 ~140 nm），平均孔径为8.95 nm。实验结果表明：采用该吸附材料常温下静态吸附处理质量浓度为10 mg/L的罗丹明B（RhB）溶液，在类氧化硅气凝胶吸附材料加入量50 g/L、静态吸附时间5 h的最佳静态吸附工艺条件下，RhB去除率为98.8%，吸附后RhB质量浓度为0.124 mg/L;采用该吸附材料常温下动态吸附处理质量浓度为15 mg/L的RhB溶液，吸附4 h后开始穿透，吸附7 h后完全穿透。穿透时间较长，表明该吸附材料具有较大的吸附容量。     

Biodegradable Films Based on Blends of Gelatin and Poly (Vinyl Alcohol): Effect of PVA Type or Concentration on Some Physical Properties of Films

The aim of this work was to develop biodegradable films based on blends of gelatin and poly (vinyl alcohol) (PVA), without a plasticizer. Firstly, the effect of five types of PVA with different degree of hydrolysis (DH) on the physical properties of films elaborated with blends containing 23.1% PVA was studied. One PVA type was then chosen for the study of the effect of the PVA concentration on the mechanical properties, color, opacity, gloss, and water solubility of the films. The five types of PVA studied allowed for films with different characteristics, but with no direct relationship with the DH of the PVA. Therefore, the PVA Celvol^®418 with a DH = 91.8% was chosen for the second part, because they produced films with greater tensile strength. The PVA concentration affected all studied properties of films. These results could be explained by the results of the DSC and FTIR analyses, which showed that some interactions between the gelatin and the PVA occurred depending on the PVA concentration, affecting the crystallinity of the films.     

Toughening of Polyvinyl Alcohol Hydrogel Through Co-Crosslinking and its Wastewater Treatment Performance by Immobilizing with Microorganism

In order to improve the hydraulic impact resistance of the polyvinyl alcohol (PVA) hydrogel as microorganism immobilization carrier and meet the requirements of long-time aeration of sewage treatment, the toughening PVA hydrogel beads were prepared by co-crosslinking with polyoxypropylene triol (PPG) through the boric acid (H₃BO₃)-chemical crosslinking method. It was found that PPG could increase the consumption of H₃BO₃, participated and accelerated the crosslinking reaction of PVA, and the pore size of the surface layer and core layer of the hydrogel beads can be controlled. With increasing PPG content, the shear storage modulus (G’) and the effective network density (ν_e) increased first, reached maximum in presence of 2 wt% PPG, and decreased afterwards. A relatively low content of PPG could promote the formation of relatively uniform and dense network structure in PVA hydrogel, resulting in an improvement of the mechanical property and long-term hydraulic stability of the gel beads. By addition of PPG, the capillary water absorption capacity of PVA hydrogel can be enhanced and the high permeability can be kept well. When applying in waste water treatment, the value of the oxygen uptake rate (OUR) and COD removal rate of the PVA hydrogel immobilized with activated sludge had no obvious difference with addition of PPG, and a high microbial activity can be maintained.     

Novel Fabrication of PAA/PVA/Yeast Superabsorbent with Interpenetrating Polymer Network for pH-Dependent Selective Adsorption of Dyes

Traditional superabsorbent polymers have wide application potential as an adsorbent, but the poor physical and mechanical properties limit their further applications. To tentatively overcome this dilemma, a novel poly(acrylic acid)/poly(vinyl alcohol)/yeast superabsorbent polymers (PAA/PVA/yeast SAPs) with interpenetrating polymer networks (IPNs) were fabricated herein via solution polymerization. The mechanical stability tests showed that the resulting products could desirably resist the destruction of shear flow (<5000 rpm) and load pressure (<3 kg). The effects of yeast content, pH, contact time, initial dye concentration and temperature were systematically studied to evaluate their adsorption properties. Consecutive five cycles of adsorption–desorption indicated that their easy regeneration and reusability. More importantly, the PVA/PAA/yeast SAPs displayed brilliant pH-dependent selective adsorption for dyes in dye mixtures. It is believed hereby that the PAA/PVA/yeast SAPs can be expected to be economically and technically feasible for the scalable treatment of dyes wastewater.     

An Effect of Salt Concentration and Inoculum Size on Poly(Vinyl Alcohol) Utilization by Two <Emphasis Type="Italic">Sphingomonas</Emphasis> Strains

Due to its widespread use and water solubility, poly(vinyl alcohol) (PVA) has the potential to find its way into various water or soil ecosystems. Despite the fact that many bacterial species with the capacity of utilizing PVA have been found and described, the influences of some environmental factors on their capabilities to biodegrade PVA have not been adequately studied. Therefore, study was made of the effects of two environmental factors on PVA degradation exhibited by two Sphingomonas strains. Both strains originated from common wastewater treatment plants, and proved to be considerably sensitive to increased inorganic salt concentrations; in brief, 13.3 mmol/l either of phosphate or chloride ions significantly delayed the degradation process or inhibited it entirely. In contrast to such halosensitivity, both strains were able to rapidly utilize PVA under suitable conditions, even when low inoculum sizes were applied. Initial cell densities, ranging from 10⁰ to 10⁷ cells/ml, were used in two series of degradation trials and PVA degradation occurred in all cases; merely delays extending over several days in the degradation process were noted when inoculum sizes of 10⁰–10³ cells/ml were applied.     

Non-isothermal Crystallization Behaviors of Polyvinyl alcohol/Hydroxyethyl Cellulose Blend Films

In this work, polyvinyl alcohol/hydroxyethyl cellulose (PVA/HEC) blend films were fabricated by solution casting and the crystalline morphology as well as non-isothermal crystallization kinetics of the blends was investigated detailedly with polarized optical microscopy, X-ray diffraction and differential scanning calorimetry. With fixed cooling rate, the crystallization time for PVA/HEC was less than that for neat PVA. The crystallization peak temperature of PVA/HEC decreased first and then increased with the increase of HEC. With higher cooling rate, the crystallinity and crystallization time decreased. It worth noting that large spherocrystal with a size of 35 μm was observed by polarized optical microscopy for PVA/HEC blends for the first time.     

Ultrastructural, Morphological, and Antifungal Properties of Micro and Nanoparticles of Chitosan Crosslinked with Sodium Tripolyphosphate

Recent studies have demonstrated the antibacterial effect of micro and nanoparticles of chitosan (CS) crosslinked with sodium tripolyphosphate (TPP), and incorporating metallic ions, bringing that the size, shape, and zeta potential are related to the antimicrobial potential. However, there are few studies on the antifungal activity and the effect of TPP on the antimicrobial potential. Micro and nanoparticles were prepared from CS by ionotropic gelation with TPP, and structurally characterized by transmission and scanning electron spectroscopy, and Fourier transformed infrared spectroscopy. Depending on the concentration of CS and TPP, spherical particles were obtained from 80 nm to 20 μm. Subsequently, particles were evaluated for their antifungal potential against Aspergillus parasiticus assessing radial growth, spore germination, and morphological changes. An increase in the antifungal potential compared with CS in solution was observed, inhibiting the development of the fungus causing clear morphological changes in both, hyphae and spores. Particle size and the availability of functional groups of CS/TPP (amino group and phosphate), suggest a possible synergistic effect between CS and TPP.     

Synthesis of mesoporous silica materials from municipal solid waste incinerator bottom ash

Incinerator bottom ash contains a large amount of silica and can hence be used as a silica source for the synthesis of mesoporous silica materials. In this study, the conditions for alkaline fusion to extract silica from incinerator bottom ash were investigated, and the resulting supernatant solution was used as the silica source for synthesizing mesoporous silica materials. The physical and chemical characteristics of the mesoporous silica materials were analyzed using BET, XRD, FTIR, SEM, and solid-state NMR. The results indicated that the BET surface area and pore size distribution of the synthesized silica materials were 992 m²/g and 2–3.8 nm, respectively. The XRD patterns showed that the synthesized materials exhibited a hexagonal pore structure with a smaller order. The NMR spectra of the synthesized materials exhibited three peaks, corresponding to Q² [Si(OSi)₂(OH)₂], Q³ [Si(OSi)₃(OH)], and Q⁴ [Si(OSi)₄]. The FTIR spectra confirmed the existence of a surface hydroxyl group and the occurrence of symmetric Si–O stretching. Thus, mesoporous silica was successfully synthesized from incinerator bottom ash. Finally, the effectiveness of the synthesized silica in removing heavy metals (Pb²⁺, Cu²⁺, Cd²⁺, and Cr²⁺) from aqueous solutions was also determined. The results showed that the silica materials synthesized from incinerator bottom ash have potential for use as an adsorbent for the removal of heavy metals from aqueous solutions.     

Recycling of the hyperaccumulator Brassica juncea L.: synthesis of carbon nanotube-Cu/ZnO nanocomposites

The methods of synthesizing carbon nanotube (CNTs)-Cu/ZnO nanocomposites using a Cu hyperaccumulator (Brassica juncea L.) constitute a new insight into the recycling of hyperaccumulators and provide a new route for the further development of green nanostructure syntheses. In this paper, CNTs-Cu/ZnO nanocomposites have been synthesized using B. juncea plants as the sources of C, Cu, and Zn. The synthesized CNTs-Cu/ZnO nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectra (EDS). The synthesized CNTs were characterized further by selected area diffraction (SAD) patterns and Raman spectroscopy. The results demonstrated that the structure of individual CNTs was middle-hollow, with an outer diameter of about 80 nm. The synthesized CNTs were not at all crystalline and there were a few defects in the walls. The outer diameter of CNTs-Cu/ZnO nanocomposites was 110 nm. The diameters of Cu/ZnO nanoparticles were 29.5/32.7 nm, respectively. Cu/ZnO nanoparticles that had grown onto the CNT surface were nonuniform and agglomerated. The Cu/ZnO nanoparticles were pure.     

Facile Preparation of Chitosan Films for High Performance Removal of Reactive Blue 19 Dye from Aqueous Solution

This study aimed at finding effective strategies for high-performance removal of reactive blue 19 (RB19) dye from aqueous solution. Chitosan (CS) films had been prepared by using solvent casting with mild drying for this purpose. The CS films were characterized by X-ray diffraction, field-emission scanning electron microscopy, and Fourier transform infrared (FTIR) spectroscopy. The performance of RB19 removal using CS were evaluated by varying contact time, solution pH, initial dye concentration, and adsorbent dosage. Adsorption isotherms, kinetics, and desorption were investigated by batch experiments. Results showed that CS films exhibited the optimal adsorption performance for RB19 removal and high maximum adsorption capacities of RB19, which were 799 and 822.4 mg g^?1 at 20 and 40 °C, respectively. Adsorption kinetic data were well described by the pseudo-second-order kinetic model. FTIR analyses further indicated that interactions between RB19 and the CS film occurred during adsorption. The CS films also exhibited satisfactory desorption of RB19 at about 80 % after 30 min of desorption at pH 11. Our study demonstrated that the CS films can be easily prepared and applied for effective removal of RB19 in treatment of wastewater.     

Biosynthesis and Characterization of Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) from Bacillus cereus S10

The biodegradable and biocompatible copolymer poly-(3-hydroxybutyrate-co-5 mol% 3-hydroxyvalerate), poly-(3HB-co-5 mol% 3HV), was synthesized by Bacillus cereus S10 and the highest yield was determined as 69.91 % at pH 7 and 30 °C after 48 h of incubation using a glucose as the sole carbon source. Poly-(3HB-co-5 mol% 3HV) was purified from bacterial biomass using chloroform. FTIR analysis showed absorption bands at 1,723, 1,274, 1,373, 1,453, 2,932 cm^?1 corresponding to C=O, C–O stretching, CH₃, –CH₂ and –CH groups, respectively. ¹H-NMR and ¹³C-NMR analysis confirmed that the copolymer was composed of 95 mol% of 3-hydroxybutrate and 5 mol% of 3-HV monomeric units. Poly-(3-HB-co-5 mol% 3HV) was used for nanoparticles preparation. The diameter of nanoparticles was 202 nm.