Investigation of the Photocatalytic Activity of Electrospun and Surface-Modified PAN/α-FeOOH Nanofibers for the Degradation of Hazardous Azo Dyes

Decoration of α-FeOOH nanorods over PAN nanofibers was performed using the electrospinning technique. The as-designed decorated nanofibers were characterized using various techniques such as wide-angle powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectrophotometry (UV-vis), thermogravimetry analysis (TGA), N2 adsorption-desorption isotherm (BET), and X-ray photoelectron spectrometry (XPS). α-FeOOH NRs were decorated uniformly over PAN fibers, as observed from its morphological investigation, which shows novelty. 1D α-FeOOH nanorods with PAN nanofibers have not been studied for photocatalytic characteristics. No literature mentions that α-FeOOH nanorods coated in PAN NFs act as photocatalysts to degrade hazardous azo dyes. α-FeOOH nanorods on PAN NFs inhibit aggregation and increase dye binding, boosting photocatalytic performance. PAN/α-FeOOH NFs have a maximal specific surface area with a reduced bandgap than α-FeOOH NRs. PAN/α-FeOOH nanofibers showed excellent photocatalytic activity for the degradation of Trypan blue (TB) (120 min, 99.7%) and Eriochrome black T (EBT) dyes (160 min, 97.6%), respectively, under solar light irradiation. PAN/α-FeOOH NFs have the potential to be used in the degradation of azo dyes and the treatment of wastewater due to their low energy requirements and versatility.

Preparation and characterization of magnetic nanohydrogel based on chitosan for 5-fluorouracil drug delivery and kinetic study

Chemotherapy is currently used for most cancer treatments, but one of the significant problems of this treatment is that it affects the healthy tissues of the body. Therefore, designing new systems for the intelligent and controlled release of these drugs in cancer tissues is one of the major challenges in the world. Hence, today, huge costs are spent designing appropriate new drug delivery systems (DDS) with controlled drug release. In this study, chitosan-polyacrylic acid encapsulated Fe₃O₄ magnetic nanogelic core-shell (Fe₃O₄@CS-PAA) was synthesized in the presence of glutaraldehyde used for loaded anticancer 5-fluorouracil (5-FU) drug. Also, the prepared Fe₃O₄@CS-PAA was characterized by using FT-IR, SEM, XRD, and VSM analysis. Then, drug delivery tests were carried out in the in-vitro conditions that are the simulated physiological environment and tumor tissue conditions. The drug release tests indicated that the Fe₃O₄@CS-PAA upgraded the rate of 5-FU release from nanogelic core-shell under tumor tissue conditions (pH 4.5) than physiological environments (pH 7.4). In addition, various models were used to investigate the drug release mechanism. Results of modeling studies of drug release showed the mechanism of 5-FU release from Fe₃O₄@CS-PAA controlled by Fickian diffusion.

Challenges and opportunities of solvent-based additive extraction methods for plastic recycling

Additives are ubiquitously used in plastics to improve their functionality. However, they are not always desirable in their 'second life' and are a major bottleneck for chemical recycling. Although research on extraction techniques for efficient removal of additives is increasing, it resembles much like uncharted territory due to the broad variety of additives, plastics and removal techniques. Today solvent-based additive extraction techniques, solid-liquid extraction and dissolution-precipitation, are considered to be the most promising techniques to remove additives. This review focuses on the assessment of these techniques by making a link between literature and physicochemical principles such as diffusion and Hansen solubility theory. From a technical point of view, dissolution-precipitation is preferred to remove a broad spectrum of additives because diffusion limitations affect the solid-liquid extraction recoveries. Novel techniques such as accelerated solvent extraction (ASE) are promising for finding the balance between these two processes. Because of limited studies on the economic and environmental feasibility of extraction methods, this review also includes a basic economic and environmental assessment of two extreme cases for the extraction of additives. According to this assessment, the feasibility of additives removal depends strongly on the type of additive and plastic and also on the extraction conditions. In the best-case scenario at least 70% of solvent recovery is required to extract plasticizers from polyvinyl chloride (PVC) via dissolution-precipitation with tetrahydrofuran (THF), while solid-liquid extraction of phenolic antioxidants and a fatty acid amide slip agents from polypropylene (PP) with dichloromethane (DCM) can be economically viable even without intensive solvent recovery.

Optimizing nanocarbon shell in zero-valent iron nanoparticles for improved electron utilization in Cr(VI) reduction

A core-shell structured zero-valent iron@carbon (ZVI@C) nanocompoiste was designed to improve the electron utilization of ZVI in the Cr(VI) reduction. The porosity of carbon layer in ZVI@C was optimized for improving the efficiency of electron utilization of ZVI in the Cr(VI) reduction process. The porous structure of carbon layer was controllably synthesized by adjusting the carbon source and the ratio of C/Fe in the precursor. The glucose was suggested as the optimal carbon source, and a high specific surface area (37.067 m²/g) was reached for the prepared ZVI@C when the ratio of C/Fe was controlled at 20. These ZVI@C performed well on Cr(VI) reduction, e.g. a complete reduction of Cr(VI) (2 mg/L) to Cr(III) within 10 min. The removal capacity (800 mg/g) exceeded previously recorded ZVI based adsorbents. The pH and initial Cr(VI) concentration were demonstrated as the key factors for the efficient electron utilization of ZVI. Furthermore, the efficiency of electron utilization of the ZVI increased up to 80% when the concentration of Cr(VI) was 2000 mg/L and the pH was controlled at 3, which was much higher than 8% of the naked ZVI.

Advances in Template Prepared Nano-Oxides and their Applications: Polluted Water Treatment, Energy, Sensing and Biomedical Drug Delivery

The nano-oxide materials with special structures prepared by template methods have a good dispersion, regular structures and high specific surface areas. Therefore, in some areas, improved properties are observed than conventional bulk oxide materials. For example, in the treatment of dye wastewater, the treatment efficiency of adsorbents and catalytic materials prepared by template method was about 30 % or even higher than that of conventional samples. This review mainly focuses on the progress of inorganic, organic and biological templates in the preparation of micro- and nano- oxide materials with special morphologies, and the roles of the prepared materials as adsorbents and photocatalysts in dye wastewater treatment. The characteristics and advantages of inorganic, organic and biological template are also summarized. In addition, the applications of template method prepared oxides in the field of sensors, drug carrier, energy materials and other fields are briefly discussed with detailed examples.

Magnetic nanocellulose-magnetite aerogel for easy oil adsorption

HYPOTHESIS

Cellulose aerogels are a new category of high-efficiency adsorbents for treating oil spills and water pollution. However, the hydrophilic properties and recyclability of aerogels after adsorption hamper developments and applications. Combining both hydrophobic and magnetic properties are expected to improve their adsorption capacity and functionality.

EXPERIMENTS

In this study, the effect of oleic acid (OA) and nanomagnetite on the preparation of magnetic nanocellulose aerogels (called as NCA/OA/Fe₃O₄) by a mechanical mixing combined with freeze-drying method have been investigated.

FINDINGS

It has been found that the optimal condition for fabricating this NCA/OA/Fe₃O₄ aerogel is 0.4 wt% nanocellulose, 3 mg mL^-1 OA and 0.5 wt% Fe₃O₄ in the aqueous solution. This aerogel has a very low density of 9.2 mg cm^-3 and demonstrates a high adsorption capacity of 68.06 g g^-1 for cyclohexane. In addition, this aerogel adsorbent demonstrates an excellent magnetic responsivity and can be easily recycled by a permanent magnet after adsorption. As a consequence, this hydrophobic magnetic NCA/OA/Fe₃O₄ aerogel is promising not only for easy oil and organic solvent adsorption but also potentially for other magnetic related applications.

Reversibly switching water droplets wettability on hierarchical structured Cu2S mesh for efficient oil/water separation

Surfaces with reversible wettability have broad applications but remain challenging since the switching process is usually energy intensive and complex. In this paper, a pyramid shaped Cu2S film with hierarchical micro/nanostructures is formed on a commercial copper mesh. This film is formed by a spontaneous redox sulfuration reaction and results in a roughened surface, which enables reversible wetting transition between superhydrophilicity to superhydrophobicity. This switching occurs by simple processes such as alternately storing in air or using an ethanol solution treatment and yields cyclic wettability switching for many cycles. This convenient wetting transition behavior, as well as strong stability and efficient oil/water separation with efficiency exceeding 98%, renders it as a potentially useful mesh material for switchable surfaces.

Mechanical properties and long-term durability of recycled polysulfone plastic

In view of the recycling of PSU plastics has a good energy saving and environmental protection significance. This paper is concerned with the mechanical properties, and long-term durability of virgin and recycled polysulfone plastics (PSU) collected from wasted PSU nonwovens, the mechanical experiment of tensile test and Izod impact test are carried out to investigate the effect of cycle processing on the performance of PSU. The long-term durability of virgin and recycled PSU is studied base on time-temperature superposition by using a dynamic mechanical analysis (DMA). The thermal stability is evaluated by pyrolytic activation energy calculated by Iso-conversional kinetics method using a Thermogravimetric analysis (TGA). The results show that the recycled PSU exhibits the similar tensile property while lower impact strength than virgin PSU. The long-term durability and thermal stability of virgin PSU are better than recycled PSU and decreased with increasing the times of cycle processing, which is attributed to the mixing of impurities and degradation of the molecular structure in the recycling process.

Biomass-derived nitrogen-doped carbon quantum dots: highly selective fluorescent probe for detecting Fe3+ ions and tetracyclines

Nitrogen-doped carbon quantum dots (N-CQDs) were successfully synthesized using rice residue and glycine as carbon and nitrogen sources by one-step hydrothermal method. High quantum yield (23.48%) originated from the effective combination of nitrogen with various functional groups (CO, NH, CN, COOH and COC). The N-CQDs showed a fluorescence with the wavelength varied from 420 to 500 nm and the maximum emission wavelength being at 440 nm. N-CQDs have been importantly applied as probe to detect Fe³⁺ and tetracycline (TCs) antibiotics with remarkable performance. Using the linear relationship between fluorescence intensity and Fe³⁺ concentration, the N-CQDs could be employed as a simple, efficient sensor for ultrasensitive Fe³⁺ detection ranging from 3.32 to 32.26 µM, with a limit of detection (LOD) of 0.7462 µM. The N-CQDs showed the applicability to detect TCs. The detection limits of tetracycline, terramycin and chlortetracycline were 0.2367, 0.3739 and 0.2791 µM, respectively. The results of TC by fluorescence method in real water samples were in good agreement with standard Ultraviolet-visible (UV-vis) method. The N-CQDs have various potential applications including sensitive and selective detection of Fe³⁺ and TCs, and cellular imaging with low cytotoxicity, good biocompatibility and high permeability.

Production of electrospun nanofibers based on graphene oxide/gum Arabic

Over the last few years, the electrospinning technique has attracted significant attention for the production of novel nanofibrous materials. At the same time, the use of graphene oxide and the natural products extracted from plants and/or trees have become very popular in various fields of science. In this work, a new method for the production of nanofibers based on a combination of Gum Arabic (GA), as a natural tree gum exudate, PVA, as an environmentally-friendly stabilizer, and graphene oxide (GO) has been developed and characterized. SEM analysis showed fundamental differences on the surface of bare nanofibers with and without GO, and also significantly smaller fiber diameters in the case of the presence of GO (fibers <100 nm present). Raman spectroscopy confirmed and TGA analysis approximated the content of GO in the nanofibers. Adsorption of methylene blue on the produced nanofibrous membrane was about 50% higher in the presence of GO, which opens the possibility to use GO/GA/PVA fibers in several applications, for example for the removal of dyes.

Controllable Synthesis of Monolayer Poly(acrylic acid) on the Channel Surface of Mesoporous Alumina for Pb(II) Adsorption

Polymer/inorganic nanocomposites exhibit special properties due to highly intimate interactions between organic and inorganic phases and thus have been deployed for various applications. Among them, nanocomposites with monolayer polymer coverage on the inorganic surface demonstrate the highest efficiency for applications. However, the controllable synthesis of the polymer monolayer in mesopores of inorganic substrates remains a challenge. In this study, poly(acrylic acid)/γ-alumina nanocomposites (PAA/alumina) were synthesized via the in situ polymerization of acrylic acid impregnated in mesopores of alumina. By applying the preneutralization of monomers, the polymerization was found to be highly controllable in generating monolayer PAA coverage. The formation of monolayers was verified by thermogravimetry, semiquantitative Fourier transform infrared spectroscopy, N₂ adsorption-desorption, and Pb(II) adsorption. Alternatively, the organic loadings of PAA/alumina composite samples could be controlled in the range of 0.2 to 1.0 equiv of monolayer, together with the linearly correlated metal ion adsorption capacity. As calculated by the complexation model, one Pb(II) is combined with two carboxylate groups of PAA. The formation of the monolayer polymer inside mesoporous oxide channels represents a method for the development of highly promising functional nanocomposites.

Sandwich-like Nanosystem for Simultaneous Removal of Cr(VI) and Cd(II) from Water and Soil

In this work, a novel nanosystem with a sandwich-like structure was synthesized via face-to-face combination of two pieces of waste cotton fabrics (CFs) carrying ferrous sulfide (FeS) and carboxyl-functionalized ferroferric oxide microsphere (CFFM), respectively, and the obtained nanosystem was named as FeS/CFFM/CF. Therein, FeS has high reduction and adsorption capabilities for hexavalent chromium (Cr(VI)), CFFM possesses a high adsorption ability on cadmium ion (Cd(II)) through electrostatic attraction and chelation, and CF displays high immobilization ability for FeS and CFFM and adsorption performance on Cd(II). FeS/CFFM/CF could simultaneously remove Cr(VI) and Cd(II) from water and inhibit the uptake of Cr and Cd by fish and water spinach, ensuring the food safety. Besides, this technology could efficiently control the migration of Cr(VI) and Cd(II) in the sand-soil mixture, which was favorable to prevent their wide diffusion. Importantly, FeS/CFFM/CF possessed a high flexibility and could be conveniently produced with needed scale and shape and easily separated from water and soil, displaying a promising approach to remediate Cr(VI)-/Cd(II)-contaminated water and soil and a huge application potential.