Graphene oxide–polysulfone filters for tap water purification, obtained by fast microwave oven treatment

The availability of clean, pure water is a major challenge for the future of our society. 2-Dimensional nanosheets of GO seem promising as nanoporous adsorbent or filters for water purification; however, their processing in macroscopic filters is challenging, and their cost\ua0vs.\ua0standard polymer filters is too high. Here, we describe a novel approach to combine graphene oxide (GO) sheets with commercial polysulfone (PSU) membranes for improved removal of organic contaminants from water. The adsorption physics of contaminants on the PSU-GO composite follows Langmuir and Brunauer–Emmett–Teller (BET) models, with partial swelling and intercalation of molecules in between the GO layers. Such a mechanism, well-known in layered clays, has not been reported previously for graphene or GO. Our approach requires minimal amounts of GO, deposited directly on the surface of the polymer, followed by stabilization using microwaves or heat. The purification efficiency of the PSU-GO composites is significantly improved\ua0vs.\ua0benchmark commercial PSU, as demonstrated by the removal of two model contaminants, rhodamine B and ofloxacin. The excellent stability of the composite is confirmed by extensive (100 hours) filtration tests in commercial water cartridges

Graphene oxide doped polysulfone membrane adsorbers for the removal of organic contaminants from water

This work explored polysulfone (PS) – graphene oxide (GO) based porous membranes (PS-GO) as adsorber of seven selected organic contaminants of emerging concern (EOCs) including pharmaceuticals, personal care products, a dye and a surfactant from water. PS-GO was prepared by phase inversion method starting from a PS and GO mixture (5% w/w of GO). The porous PS-GO membranes showed asymmetric and highly porous micrometer sized pores on membrane top (diameter ≈20 μm) and bottom (diameter ≈2–5 μm) surfaces and tens of microns length finger like pores in the section. Nanomechanical mapping reveals patches of a stiffer material with Young modules comprised in the range 15–25 GPa, not present in PS pure membranes that are compatible with the presence of GO flakes on the membrane surfaces. PS-GO was immersed in EOCs spiked tap water and the adsorbance efficiency at different contact times and pH evaluated by HPLC analysis. Ofloxacin (OFLOX), benzophenone-3 (BP-3), rhodamine b (Rh), diclofenac (DCF) and triton X-100 (TRX) were removed with efficiency higher than 90% after 4 h treatments. Regeneration of PS-GO and reuse possibilities were demonstrated by washing with ethanol. The adsorption efficiencies toward OFLOX, Rh, DCF and carbamazepine (CBZ) were significantly higher than those of pure PS membrane. Moreover, PS-GO outperformed a commercial granular activated carbon (GAC) at low contact times and compared well at longer contact time for OFLOX, Rh, BP-3 and TRX suggesting the suitability of the newly introduced material for drinking water treatment

electrochemical sensing of glucose by chitosan modified graphene oxide

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Core-shell graphene oxide-polymer hollow fibers as water filters with enhanced performance and selectivity

Commercial hollow fiber filters for micro- and ultrafiltration are based on size exclusion and do not allow the removal of small molecules such as antibiotics. Here, we demonstrate that a graphene oxide (GO) layer can be firmly immobilized either inside or outside polyethersulfone-polyvinylpyrrolidone hollow fiber (Versatile PES (R), hereafter PES) modules and that the resulting core-shell fibers inherits the microfiltration ability of the pristine PES fibers and the adsorption selectivity of GO. GO nanosheets were deposited on the fiber surface by filtration of a GO suspension through a PES cartridge (cut-off 0.1-0.2 mu m), then fixed by thermal annealing at 80 degrees C, rendering the GO coating stably fixed and unsoluble. The filtration cut-off, retention selectivity and efficiency of the resulting inner and outer modified hollow fibers (HF-GO) were tested by performing filtration on water and bovine plasma spiked with bovine serum albumin (BSA, 66 kDa, approximate to 15 nm size), monodisperse polystyrene nanoparticles (52 nm and 303 nm sizes), with two quinolonic antibiotics (ciprofloxacin and ofloxacin) and rhodamine B (RhB). These tests showed that the microfiltration capability of PES was retained by HF-GO, and in addition the GO coating can capture the molecular contaminants while letting through BSA and smaller polystyrene nanoparticles. Combined XRD, molecular modelling and adsorption experiments show that the separation mechanism does not rely only on physical size exclusion, but involves intercalation of solute molecules between the GO layers

Core–shell graphene oxide–polymer hollow fibers as water filters with enhanced performance and selectivity

Commercial hollow fiber filters for micro- and ultrafiltration are based on size exclusion and do not allow the removal of small molecules such as antibiotics. Here, we demonstrate that a graphene oxide (GO) layer can be firmly immobilized either inside or outside polyethersulfone–polyvinylpyrrolidone hollow fiber (Versatile PES®, hereafter PES) modules and that the resulting core–shell fibers inherits the microfiltration ability of the pristine PES fibers and the adsorption selectivity of GO. GO nanosheets were deposited on the fiber surface by filtration of a GO suspension through a PES cartridge (cut-off 0.1–0.2 μm), then fixed by thermal annealing at 80 °C, rendering the GO coating stably fixed and unsoluble. The filtration cut-off, retention selectivity and efficiency of the resulting inner and outer modified hollow fibers (HF-GO) were tested by performing filtration on water and bovine plasma spiked with bovine serum albumin (BSA, 66 kDa, ≈15 nm size), monodisperse polystyrene nanoparticles (52 nm and 303 nm sizes), with two quinolonic antibiotics (ciprofloxacin and ofloxacin) and rhodamine B (RhB). These tests showed that the microfiltration capability of PES was retained by HF-GO, and in addition the GO coating can capture the molecular contaminants while letting through BSA and smaller polystyrene nanoparticles. Combined XRD, molecular modelling and adsorption experiments show that the separation mechanism does not rely only on physical size exclusion, but involves intercalation of solute molecules between the GO layers

Influence of Experimental Parameters on the Determination of Tetragonal Distortion in Heterostructures by LACBED

The LACBED technique has been applied to the determination of the tetragonal distortion in $\rm Si_{1-x}Ge_xSi$ heterostructures, which are of great interest in the device technology. The strain determination has been performed on plan sections in an analytical electron microscope. The agreement between this strain value and the tetragonal distortion is influenced mainly by the local sample flatness and the acceleration voltage

Methylene Blue Doped Films of Wool Keratin with Antimicrobial Photodynamic Activity

In this work, keratin films doped with different amounts of methylene blue (MB) were developed in order to prepare new biodegradable and biocompatible materials for tissue engineering and wound healing, able to exert antimicrobial photodynamic activity upon irradiation with visible light. Preliminary results indicated that the swelling ratio, as well as the MB release, increases by increasing the pH. Moreover, the generation of reactive oxygen species (ROS) and singlet oxygen can be easily triggered and controlled by a fine-tuning of the irradiation time and MB concentration in the films. As concerns the photodynamic effects on keratin, the ROS attack does not induce any significant photodegradation on the protein, even if a slight photo-oxidation of sulfonated amino acids occurs. Finally, the film with the highest MB concentration (400 \u3bcg per gram of keratin) displays a significant photobactericidal activity against Staphylococcus aureus with a bacterial reduction that increases by increasing the irradiation time. In particular, the irradiation of KFMB400 film incubated with S. aureus at a concentration of 108 cfu mL^ 121 determined the 99.9% killing rate and the killing effect increased proportionally with irradiation time

Polysulfone Hollow Porous Granules Prepared from Wastes of Ultrafiltration Membranes as Sustainable Adsorbent for Water and Air Remediation

Polysulfone hollow fibers (PS-HF) are widely used in ultrafiltration modules for hemodialysis and drinking water purification for the removal of large colloids, microbes, and viruses. The preparation of commercial PS-HF standard modules leads to the generation of PS-HF scraps in amount higher than 5% of the total production (tons scale) that cannot be used for filtration purposes and represent large volume plastic wastes. Here, a simple approach to convert such high value waste into a new granular material with excellent adsorption properties toward organic compounds is introduced. Polysulfone hollow porous granules (PS-HPG) are prepared by a mechanical grinding process and then exploited for the removal of selected organic compounds from water under flow and batch conditions. Volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons, and also selected emerging organic contaminants (EOCs), including two common drugs (carbamazepine and diclofenac), a plastic additive (bisphenol A), and a textile dye (Rhodamine B), are successfully adsorbed. Regeneration and reuse possibility of PS-HPG are also demonstrated. Additionally, air remediation from VOCs and from airborne nanoparticles is successfully achieved by flowing an air stream through a filtration cartridge filled by PS-HP

Organic solvent-free preparation of keratin nanoparticles as doxorubicin carriers for antitumour activity

Doxorubicin is one of the most effective chemotherapeutic agents for the treatment of several neoplastic conditions, such as leukemia, neuroblastoma, soft tissue and bone sarcomas, breast cancer, ovarian cancer and others. However, its clinical application is limited by cardiotoxicity, such as cardiomyopathy, that once developed carries a poor prognosis and is frequently fatal. The controlled release of doxorubicin by means of a smart carrier is a strategy to overcome the aforementioned drawback. Herein, doxorubicin/keratin nanoparticles were prepared by loading the drug through ionic gelation and aggregation methods, without using cross linkers, organic solvents neither surfactants. Both methodologies afford nanoparticles with yields up to 100 wt%, depending on the loading amount of doxorubicin. Although aggregation yield smaller nanoparticles (100 nm), ionic gelation allows a higher drug loading (up to 30 wt%,). More importantly, nanoparticles obtained through this procedure display a pH-responsive release of the drug: indeed Peppas-Salhin model suggests that, the doxorubicin release mechanism is predominantly controlled by diffusion at pH 7.4 and by protein swelling at pH 5. Moreover, nanoparticles prepared by ionic gelation resulted in more efficient cell killing of MDA-MB-231 and MCF-7 breast cancer cells than those prepared by aggregation. Based on the herein presented preliminary results, ionic gelation emerges as a promising approach for the preparation of keratin-based doxorubicin nanocarriers for cancer therapy, that is worth to further investigate