Contact Angle Analysis Research Articles

Investigation of the effect of permeation and antifouling characteristics of hybrid poly(vinylidene fluoride) membranes tailored with ZIF‐67 metal–organic frameworks

AbstractHerein the ZIF‐67, a hydrophilic cobalt‐based zeolitic imidazolate framework is synthesized and incorporated with a poly(vinylidene fluoride) (PVDF) to fabricate hybrid ultrafiltration membranes by phase inversion method. The characteristics of PVDF/ZIF‐67 membranes are examined using different analytical techniques such as Fourier‐transform infrared spectroscopy, X‐ray diffractometer, scanning electron microscope, atomic force microscope, and contact angle analysis. The membrane performance is probed using pure water flux (PWF), bovine serum albumin (BSA), and humic acid (HA) rejection. The maximum water flux of 162.5 Lm2 h−1 with BSA and HA rejection of 97% and 98.2%, respectively, exhibited by 1.5 wt% ZIF‐67. The contact angle value is reduced from 83.5 to 58.6° indicating the increase in hydrophilic nature of PVDF membranes by the addition of ZIF‐67. The presence of ZIF‐67 in the PVDF membrane matrix showed outstanding anti‐bacterial properties against Escherichia coli and Staphylococcus aureus. Overall, the PVDF/ZIF‐67 ultrafiltration membranes demonstrate the potential for water treatment applications.

Effect of graphene oxide/layered double hydroxide modified by 7‐octenyltrimethoxysilane on the mechanical and gas barrier properties of fluoroelastomers

AbstractLayered double hydroxide/graphene oxide (GLDH) composites (SGLDH) modified by 7‐octenyltrimethoxysilane (7‐OTOS) were prepared by co‐precipitation method. The structure and morphology of SGLDH were characterized using x‐ray diffraction, Fourier‐transform infrared spectroscopy (FTIR), x‐ray photoelectron spectroscopy, scanning electron microscopy (SEM), high‐resolution transmission electron microscopy, energy‐dispersive x‐ray spectroscopy, and thermogravimetric analysis. According to the obtained results, 7‐OTOS was successfully grafted onto graphene oxide (GO) and layered double hydroxide (LDH) surfaces. 7‐OTOS was grafted on both GO and LDH surfaces, which is why the amount of LDH loaded on the SGLDH surface was significantly increased compared with that on the GLDH composite. The filler‐matrix interfacial interactions of the SGLDH‐filled fluoroelastomer composites were characterized using contact angle analysis, dynamic mechanical analysis, RPA analysis, FTIR, SEM, and cross‐linking density tests. It was indicated that the interfacial interactions between the SGLDH and matrix were significantly improved, and the SGLDH was well dispersed in the fluoroelastomer composites. In addition, the gas barrier properties and mechanical properties of the fluoroelastomer composites were tested. The carbon dioxide permeability coefficients of the fluoroelastomer composites filled with 10‐phr SGLDH increased by about 32.1% and 20.3%, and the tensile strengths increased by about 47.6% and 27.7%, respectively, compared with those of the fluoroelastomer composites filled with 10‐phr LDH and GLDH.Highlights SLDH nanocomposites are based on silyl ether linkages to increase LDH loading. Elastomer nanocomposites exhibited interfacial cross‐linking mechanism. Interfacial interactions were exhibited between FKM and SGLDH. FKM/SGLDH exhibited enhanced gas barrier properties (+32%) compared to FKM. FKM/SGLDH exhibited enhanced mechanical properties (+47%) compared to FKM.

Investigating the impact of metal ion variations in terephthalate metal–organic frameworks on the organic solvent nanofiltration performance of mixed matrix membranes

Nano-fillers integrated into mixed matrix membranes (MMMs) present promising alternatives for organic solvent nanofiltration (OSN). In this work, our objective is to enhance OSN performance by incorporating terephthalate metal-organic frameworks (M-BDC, where M = Zr or Cu) into a P84 matrix to fabricate M-BDC/P84 composite MMMs. This work focuses on the influence of metal cluster variation on particle size, pore size distribution, and specific surface area of M-BDC, while systematically investigating the impact of M-BDC addition on OSN performance and underlying separation mechanisms. The synthesized membranes underwent comprehensive characterization using SEM, XRD, ATR-FTIR, contact angle, zeta potential, and thermogravimetric analysis. Significantly, all MMMs exhibited superior permeance and methyl blue (MB) rejection compared to P84 membranes. This enhancement is attributed to the improved interfacial contact between M-BDC and P84, as well as their effective dispersion within the membrane matrix. Interestingly, comparative analysis between Cu-BDC/P84 and Zr-BDC/P84 MMMs revealed the latter's superior permeance, attributed to its larger pore size and surface area. The resulting MMMs demonstrated outstanding MB rejection (>96.7%) with ethanol permeance of 21.5 and 19.0 LMH/Bar for Zr-BDC/P84 and Cu-BDC/P84 MMMs, respectively. Furthermore, the stable performance of M-BDC-based MMMs during prolonged MB/ethanol operation underscores their potential significance in the field of OSN, providing valuable insights for future membrane design and application.

Investigation of synergistic mechanism of magnesium ions and cationic surfactant in low-rank coal flotation

The effect of magnesium ions on the adsorption of DTAB (Dodecyltrimethylammonium Bromide) surfactants by low-rank coal using adsorption experiments and microscopic mechanism analysis. In addition, the flotation recovery of coal was summarized for application by micro flotation test. The results of adsorption experiments showed that 0.1 mM magnesium ions concentration is optimal, with 12.55 mg/g adsorption capacity. Besides, correlation analysis reveals that the adsorption capacity is positively correlated with temperature, surfactant concentration, reaction time and the magnesium ions density. Adsorption thermodynamics and kinetics experiments indicate that magnesium ions promote adsorption by increasing the adsorption active sites of coal and accelerating the adsorption rate of DTAB on coal. Furthermore, the results of contact angle, zeta potential, model calculations and FTIR (Fourier transform infrared spectroscopy) analyses reveal that magnesium ions and its hydrolysates can adsorb on the coal as a bridge and destroy the stable hydrogen bond on the coal to activate the adsorption, which enhance the negatively charged coal to electrostatically adsorb positively charged DTAB. Moreover, the recovery rate of low-rank coal flotation using DTAB combined with magnesium ions was tested by a micro flotation apparatus, which provides a guidance for the flotation application by saline surfactant solution on coal.

Eggshell membrane as a novel and green platform for the preparation of highly efficient and reversible curcumin-based colorimetric sensor for the monitoring of chicken freshness

Herein, for the very first time, we report a paper-like biomass, eggshell membrane (ESM), as a suitable platform for the fabrication of a colorimetric sensor (E-Cot). Green ethanolic extract, curcumin (CUR), was used as a sensing material to coat with the ESM. The present E-Cot effectively changed its color (yellow to red) in the real-time monitoring for chicken spoilage. The E-Cot exhibits barrier properties due to its inherent semi-permeability characteristics. Interestingly, the E-Cot showed a significant change in total color difference value (ΔE, 0 days - 0.0-39.6, after 1 day – 39.6-42.1, after 2 days – 42.1-53.6, after 3 days- 53.6-60.1, and after 4 days – 60.1-66.3, detectable by the naked eye) in the real-time monitoring for chicken freshness. In addition, the present E-Cot smart colorimetric sensor is reversible with a change in pH, and the sensor can be reused. Further, the hydrophobic nature of the E-Cot was confirmed by water contact angle analysis (WCA, contact angle of 101.21 ± 8.39). Good antibacterial, barrier, and optical properties of the present E-Cot were also found. Owing to the advantages such as green, efficient, cost-effective, biodegradable, reusable, sustainable, and simple preparation, we believe that the present E-Cot would be a more attractive candidate.

Fabrication of high-performance and high-fouling resistance reverse osmosis membrane by a natural deep eutectic solvent (NDES) as a new generation of co-solvents

Here, we modify the RO membrane employing thymol:acetic acid (Th:AA) natural deep eutectic solvent (NDES) as a new generation of the co-solvent. The Th:AA NDES was synthesized with the heating method. The co-creation of the NDES synthesis was confirmed by FTIR and NMR spectroscopy. For the impact assessment of Th:AA in the CAIP process, the dosage of the NDES as a co-solvent in the organic phase was initially optimized. Then, in the second step, the effect of the AA molar ratio on the membrane performance was investigated. Alteration changes in the morphology of PA/NDES membranes were investigated by SEM, AFM, ATR-FTIR, zeta potential, and water contact angle analyses. PA/NDES membranes have thinner selective layers, smoother surfaces, and a more hydrophilic nature without changes in the chemical structure. The performance of different types of PA/NDES RO membranes was assessed by the pure water flux and NaCl rejection experiments. The results indicated that at the optimum amount and molar ratio of the Th:AA NDES, the permeability reached 5.35 LMH/bar while the rejection didn't reduce and was constant at 98%. Also, the antifouling performance was explored by the NaCl/HA solution with the 2000/10 mg/L concentration. The outcomes of this experiment showed the PA/NDES13 membrane with a 1.5% flux decline had the best antifouling features. Moreover, the long-term test indicated the PA/NDES13 membrane has long-time stability. Also, the chlorine resistance of this membrane was much better than unmodified PA and commercial membranes. In the end, it was found that using Th:AA NDES as a co-solvent in the CAIP process produced a RO membrane with high permeability and high fouling resistance features along with better features than a commercial BWRO membrane, making it an excellent candidate for industrial application due to the ease of NDES synthesis and membrane fabrication.

Thermo‐responsive polymer to clean fouled forward osmosis membrane after wastewater treatment: Excellent flux recovery

AbstractThermally responsive polymers (TRPs) have gained significant attention in the past decade due to their unique phase transition behavior, those exhibiting changes in properties with temperature variations. In water, hydrophilic block copolymers form helical structures that can transform into hydrophobic globules above the lower critical solution temperature (LCST). Fouling is one of the limiting issues for the forward osmosis (FO) process in wastewater treatment. In this work, after the treatment of wastewater from the paper and pulp industries, foulants were removed from the surface of the commercial polyamide thin‐film composite membrane of the FO process using polyvinyl methyl ether (PVME), a TRP with an LCST of 35–37°C. PVME was mixed with different aqueous solutions to form cleaning solutions. Foulant cleaning experiments utilized a 1% PVME (w/v) solution in 300 mL of de‐ionized (DI) water, while 1 M NaCl solution served as the draw solution (DS) in the FO process. Comparing the water flux (J) and change in membrane hydraulic resistance (Rf) among pristine, fouled, and cleaned membranes revealed a 56.67% increase in water flux and a 51.68% decrease in membrane resistance after PVME mixed with DI water cleaning solution showcasing its effectiveness in improving membrane performance and reducing fouling. The cleaning efficiency of two solutions, that is, 1% PVME mixed in DI water and 1% PVME mixed in 1 M aqueous urea solution, is compared. Results showed that the former cleaning solution helped to obtain 32.62% higher water flux and 56.05% less membrane resistance. Various membrane characterizations are performed, such as field emission scanning electron microscopy (FE‐SEM), which characterizes the membrane's pore structure and surface morphology, while a contact angle analyzer assesses hydrophilicity. This research highlights the use of TRPs as effective cleaning agents, enhancing membrane performance by effectively removing foulants on the membrane surface. Investigating alternative cleaning solutions also provides insights for optimizing water treatment processes.Highlights Cleaning of fouled thin‐film composite membrane using thermal‐responsive polymers (TRPs). Polyvinyl methyl ether, a TRP with an lower critical solution temperature of 35–37°C used as a cleaning agent. 60% increase in water flux was observed after the single‐step cleaning process. Multiple uses of TRP for cleaning performed with no membrane damage.

Flotation recovery of barite from high-density waste drilling fluid using β-cyclodextrin as a novel depressant and its mechanism.

High-density waste drilling fluid contains an abundance of recyclable weighting reagents, direct disposal can pollute the environment. In this paper, the primary mineral composition of a high-density waste drilling fluid from a well in the southwest oil and gas field was analyzed. This paper proposes β-cyclodextrin (β-CD) as a depressant for the recovery of barite from waste drilling fluid. The recovery process was investigated through inverse flotation experiments, and the mechanism was analyzed using zeta potential, contact angle analysis, and FTIR. The flotation experiments showed that under the SDS flotation system, when the pH was 9.0 and the amount of depressant β-CD was 900 g/t, the barite recovery and density reached the highest values, which were 87.41% and 4.042 g/cm3, respectively. Zeta potential experiments, contact angle analysis, and FTIR analysis indicate that β-CD adsorbed onto barite through enhancing the hydrophilicity of barite, electrostatic force adsorption, and strong adsorption, which could not be displayed by SDS through competitive adsorption. Furthermore, β-CD exhibited a selective inhibitory effect on barite and enabled reverse flotation. The mechanism model of the flotation separation process was established.

Flexible Composite Hydrogels Based on Polybenzoxazine for Supercapacitor Applications.

Polybenzoxazines (Pbzs) are advanced forms of phenolic resins that possess many attractive properties, including thermal-induced self-curing polymerization, void-free polymeric products and absence of by-product formation. They also possess high Tg (glass transition temperature) and thermal stability. But the produced materials are brittle in nature. In this paper, we present our attempt to decrease the brittleness of Pbz by blending it with polyvinylalcohol (PVA). Benzoxazine monomer (Eu-Ed-Bzo) was synthesized by following a simple Mannich condensation reaction. The formation of a benzoxazine ring was confirmed by FT-IR and NMR spectroscopic analyses. The synthesized benzoxazine monomer was blended with PVA in order to produce composite films, PVA/Pbz, by varying the amount of benzoxazine monomer (1, 3 and 5 wt. % of PVA). The property of the composite films was studied using various characterization techniques, including DSC, TGA, water contact angle analysis (WCA) and SEM. WCA analysis proved that the hydrophobic nature of Pbz (value) was transformed to hydrophilic (WCA of PVA/Pbz5 is 35.5°). These composite films could play the same role as flexible electrolytes in supercapacitor applications. For this purpose, the composite films were immersed in a 1 M KOH solution for 12 h in order to analyze their swelling properties. Moreover, by using this swelled gel, a symmetric supercapacitor, AC//PVA/Pbz5//AC, was constructed, exhibiting a specific capacitance of 170 F g-1.

Manifestation of UiO-66-Zr MOF-enabled photocatalytic membranes for successive separation and degradation of dye mixtures in water remediation

The use of metal-organic framework (MOF) nanoparticles both as a separation-enhancer and as a photocatalyst has been demonstrated by suitably embedding them into polysulfone (PSU) membranes. These MOF-nanoparticles with Zr-metal and 2-aminoterephthalic-ligand, namely UiO-66-NH2, are synthesized via solvothermal and embedded into the PSU-membranes via solvent-casting process, confirmed via XRD and IR analysis. The skin-deep presence of MOFs and enhancements in the depth of pore-channels within membrane are confirmed through FESEM images. A favorable surface-charge and hydrophilic nature of the MOF-membrane are confirmed via zeta-surface potential and water contact angle analysis, respectively. Consequently, the water-flux efficacy of the optimized MOF-embedded membrane is estimated to be ∼59 L/m2h, while it is ∼20 L/m2h for pristine-membrane. The flux of MOF-membrane against the dye solutions containing rhodamine B (RhB), Congo red (CR), and their mixtures (RhB+CR) is estimated to be ∼39.9, 42.7 and 28.8 L/m2h, which is ∼3.6 times more than the pristine-membrane. Correspondingly, a rejection of ∼81.6, 77.6, and (87.2+79.2%) is estimated for RhB, CR and RhB+CR, respectively, which is ∼2.3 times higher the pristine-membrane. Furthermore, under sunlight irradiation, the MOF-membrane degrades ∼10.1, 7.1 and (7.3+4.2%) of RhB, CR and (RhB+CR) dyes, respectively. The parameters indicating regenerative efficiency, such as flux recovery ratio, reversible, irreversible, and total fouling are found to be enhanced for MOF-membranes compared to pristine-membrane. Overall, the incorporation of MOFs as additives enhances both separation and regeneration efficiency of membranes through photocatalytic process. This process holds promise as a reliable strategy for developing smart-membranes for energy-efficient real-time water treatment applications.

Low fouling and pH-responsive poly(N-vinyl imidazole)/poly(ethylene glycol) methacrylate copolymer gels for colon targeted diclofenac sodium delivery

Protein and cell adhesion onto drug delivery matrices interferes with the predesigned drug delivery profile to the targeted site. Antifouling surfaces are needed to overcome this problem and improve the effectiveness and efficiency of drug delivery systems. Copolymers of N-vinyl imidazole (NVI) with poly(ethylene glycol methacrylate) (PEGMA) were synthesized via free radical polymerization under cryogenic conditions as potential pH-responsive drug delivery systems resistant to protein and cell adhesion. FTIR spectroscopy, elemental analysis, thermal analysis (DSC), mechanical tests, contact angle, surface energy, and SEM analysis provide the physicochemical properties of the samples. Static adsorption/adhesion experiments show that the copolymer cryogels resist BSA adhesion. Furthermore, the copolymer cryogels demonstrate anti-cell adhesion behavior against colon colorectal carcinoma (HCT-116) cells. They are non-cytotoxic toward HDFa fibroblasts. Diclofenac sodium (DS) - loaded copolymer cryogels show pH-dependent sustained drug delivery. The release studies show a limited release in stomach pH (2.0). On the other hand, enhanced release is observed in pH 5.0 and pH 7.4 within 15 h. The quantities of diclofenac sodium released from the copolymer cryogels are sufficient to show anti-inflammatory activity.

Halogen‐free boron‐based hybrid system for enhancing flame retardancy, mechanical and thermal properties of epoxy

AbstractThis study aims to increase the flame retardancy of epoxy‐based composites by using various flame retardants together with colemanite filler (CLM), which is a very mineral‐rich boron type. As a flame retardant, aluminum hydroxide (Al(OH)3) and boron‐containing compounds: borax (BRX) and natural minerals (tincal (TNC) and colemanite (CLM)), as well as barium metaborate (BaMB) synthesized by us were used. Scanning electron microscopy (SEM), x‐ray powder diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), contact angle (CA), and particle size analysis were used to characterize the composites and additives. All boron compounds increased the thermal stability of the composites. Except for the ER/CLM‐BaMB composite, other composites' surface contact angles were over 90°. In terms of both combustion and thermal properties, the best CLM‐BaMB‐Al(OH)3‐TNC ratio was determined as 15:5:15:15. The tensile strength, self‐extinguishing time, estimated and experimental Limited Oxygen Index (LOI) values for this composite were determined as 96 MPa, 65 s, 29.6%, and 25%, respectively. In addition, ANOVA was applied to determine the effect of hybrid filler type and different weight ratios on the mechanical properties of composites.

Fabrication of porous beta-cyclodextrin functionalized PVDF/Fe–MOF mixed matrix membrane for enhanced ciprofloxacin removal

Herein, we demonstrate the synthesis of beta-cyclodextrin (β–CD) functionalized polyvinylidene fluoride (PVDF) and iron-based metal-organic framework (Fe–MOF) mixed matrix membrane (MMM) for the enhanced removal of ciprofloxacin (CIP) from water. The membranes were prepared using the phase inversion technique with PVDF as the polymer matrix, Fe–MOF as the filler, and polyvinylpyrrolidone (PVP) as the porogen. The optimized MMM with 7% wt. Fe–MOF exhibited excellent performance with 87.6% removal efficiency. Moreover, the maximum adsorption capacity was 6.43 mg g–1. The β–CD functionalization improved the MMM hydrophilicity exhibited by the water contact angle (WCA) analysis (WCA = 55°). Furthermore, excellent adsorption performance can be attributed to the large Fe–MOF specific surface area (682.5 m2 g–1), the high porosity (77%), and the average pore diameter (395 nm) of the membrane. The inclusion of PVP (1% wt.) enhanced the porous nature of the MMM and, consequently, the adsorption performance for CIP. Notably, the hydrophilic and macroporous membrane showed good reusability with over 70% removal efficiency after five sequential adsorption–desorption cycles. The insights from this study suggest that the PMC–7 membrane can be an excellent candidate for the remediation of organic contaminants from aquatic environments.

Fabrication of a laser-directed electrochemical paper analytical device and its deployment for multi-functional electrochemical sensing

The demand for eco-friendly, disposable, and affordable electrochemical sensors stimulates the fabrication of laser-directed paper-based electrodes. This work reports the fabrication of laser-derived patterns on the paper substrate and its multi-functional sensing applications. For this, a computer-aided design (CAD) software-driven computer numerical control (CNC) manufacturing method was developed to engrave a three-electrode design on a paper substrate. The fabricated Laser-Directed electrochemical Paper Analytical Device (LD-ePAD) was thoroughly characterized by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), contact angle analysis, electrochemical impedance spectroscopy (EIS), and the cyclic voltammetry (CV). After that, we demonstrated the multi-functional sensing ability of the LD-ePADs by detecting diverse model analytes, including small molecules (i.e., lead ions [Pb2+]), free radicals (i.e., peroxide [H2O2]), and macromolecules (i.e., Alkaline phosphatase [ALP]). Upon investigation, it exhibits a fair detection limit of 5.19 (±0.21) µM for Pb2+, 48.66 (±0.31) µM for H2O2, and 0.48 (±0.02) U/L for ALP. The LD-ePADs' outstanding repeatability, stability, abundance of catalytic active sites, remarkable tunability, and potential for nano-bioengineering emphasized their tremendous commercial feasibility. To the best of our knowledge, this is the first study to use controlled one-step laser direct engraving to fabricate a three-electrode setup on a paper-substrate that can sense three heterogeneous molecules electrochemically.

Electrospun Materials Based on Cellulose Acetate Loaded with Rosmarinic Acid with Antioxidant and Antifungal Properties.

Fibrous cellulose acetate (CA) materials loaded with rosmarinic acid (RA) were successfully created by one-pot electrospinning. In order to improve the water solubility of the polyphenolic acid and to facilitate its release from the fibrous materials, the non-ionic water-soluble polyethylene glycol (PEG) was added. Detailed characterization of the fabricated fibrous CA/RA and CA/PEG/RA materials was performed using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), UV-Vis spectroscopy and water contact angle analysis. The optimal ratio between CA, RA and PEG for preparation of defect-free and uniform fibers was accomplished by varying their concentrations. Furthermore, the incorporation of the PEG improved the hydrophilicity and wettability of the fibrous CA materials. Moreover, PEG facilitated the RA release and over 360 min, the amount released from fibrous CA/PEG/RA fibers was 91%, while that released from CA/RA materials was 53%. Both of the RA-containing fibrous materials, with and without PEG, manifested high antioxidant activity as determined by the DPPH free radical-scavenging method. In addition, the electrospun CA/PEG/RA materials displayed good antifungal activity against C. albicans. These features make the fibrous CA/PEG/RA materials promising candidates for treatment of wound infections.

Effect of Sulfuric Acid Corrosion on Flotation Performance of Calcite by Changing Surface Roughness.

Surface roughness is a crucial factor that affects the flotation performance of minerals. In this study, the effect of sulfuric acid corrosion on the surface roughness of calcite flotation was investigated through microflotation tests, scanning electron microscopy (SEM-EDS), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and contact angle analysis. Microflotation test results show that sulfuric acid treatment has a serious negative effect on the floatability of calcite. When the sulfuric acid dosage was 4 mL (3 mol/L), the flotation recovery of calcite was reduced to less than 19%. SEM-EDS and AFM results verified that the sulfuric acid treatment significantly changed the surface morphology of calcite, reduced the average surface roughness and surface area, and reduced the amount of active Ca2+ sites on the calcite surface. As characterized by FT-IR and contact angle analyses, the sulfuric acid treatment enhanced the hydrophilicity of the calcite surface and reduced the amount of sodium oleate adsorbed on the calcite surface. Consequently, sulfuric acid corrosion can reduce the average surface roughness of calcite and have a serious negative effect on the flotation performance of calcite.

Ciprofloxacin-, Cefazolin-, and Methicilin-Soaked Graphene Paper as an Antibacterial Medium Suppressing Cell Growth.

This paper presents the results of research on the impact of graphene paper on selected bacterial strains. Graphene oxide, from which graphene paper is made, has mainly bacteriostatic properties. Therefore, the main goal of this research was to determine the possibility of using graphene paper as a carrier of a medicinal substance. Studies of the degree of bacterial inhibition were performed on Staphylococcus aureus and Pseudomonas aeruginosa strains. Graphene paper was analyzed not only in the state of delivery but also after the incorporation of the antibiotics ciprofloxacin, cefazolin, and methicillin into its structures. In addition, Fourier-Transform Infrared Spectroscopy, contact angle, and microscopic analysis of bacteria on the surface of the examined graphene paper samples were also performed. Studies have shown that graphene paper with built-in ciprofloxacin had a bactericidal effect on the strains of Staphylococcus aureus and Pseudomonas aeruginosa. In contrast, methicillin, as well as cefazolin, deposited on graphene paper acted mainly locally. Studies have shown that graphene paper can be used as a carrier of selected medicinal substances.

PFAS-free superhydrophobic chitosan coating for fabrics

In view of health and environmental concerns, together with the upcoming restrictive regulations on per- and polyfluoroalkyl substances (PFAS), less impactful materials must be explored for the hydrophobization of surfaces. Polysaccharides, and especially chitosan, are being explored for their desirable properties of film formation and ease of modification. We present a PFAS-free chitosan superhydrophobic coating for textiles deposited through a solvent-free method. By contact angle analysis and drop impact, we observe that the coating imparts hydrophobicity to the fabrics, reaching superhydrophobicty (θA = 151°, θR = 136°) with increased amount of coating (from 1.6 g/cm2). This effect is obtained by the combination of chemical water repellency of the modified chitosan and the nano- and micro-roughness, assessed by SEM analysis. We perform a comprehensive study on the durability of the coatings, showing good results especially for acidic soaking where the hydrophobicity is maintained until the 8th cycle of washing. We assess the degradation of the coating by a TGA-IR investigation to define the compounds released with thermal degradation, and we confirm the coating's biodegradability by biochemical oxygen consumption. Finally, we demonstrate its biocompatibility on keratinocytes (HaCaT cell line) and fibroblasts (HFF-1 cell line), confirming that the coating is safe for human skin cells.

Upgrading of talc-bearing copper-nickel sulfide ore by froth flotation using sodium phytate as depressant

Copper-nickel sulfide ores, as important sources of copper and nickel metals, always have large amount of clay-type gangue minerals like talc. In this work, selective flotation of copper-nickel sulfide ore was achieved by using a selective depressant of sodium phytate. Microscale flotation results show that sodium phytate can selectively and effectively depress talc flotation, but has a minor effect on the floatability of chalcopyrite and pentlandite. In batch-scale flotation tests of feed ore, containing 0.35% Cu, 0.68% Ni and 24.57% MgO, potassium butyl xanthate was employed as the collector in rougher (200 g/t), scavenger-1 (100 g/t), scavenger-2 (50 g/t) and scavenger-3 (25 g/t), and sodium phytate depressant was used in rougher (300 g/t) and cleaner-1 (100 g/t) stages of closed-circuit flotation to obtain a concentrate containing 2.66% Cu (79.7% recovery), 5.38% Ni (83.01% recovery), and only 6.39% MgO. The contact angle analysis showed that sodium phytate significantly improved the hydrophilicity of talc, but it only slightly increased the hydrophilicity of chalcopyrite and nickelpyrite. The FTIR and XPS tests showed that chemisorption of sodium phytate occurred on talc surface by the interaction between P-O/PO and Mg active sites. This work indicates that sodium phytate has strong potential as an inhibitor for the selective separation of talc from copper-nickel sulfide ores.

Trace polymer coated clarithromycin spherulites: Formation mechanism, improvement in pharmaceutical properties and development of high-drug-loading direct compression tablets

Clarithromycin (CLA) is a high dose antibiotic drug exhibiting poor flowability and tabletability, making the tablet development challenging. This study aims to develop spherulitic CLA by introducing trace amount of polymer in crystallization solution. Its formation mechanism, physicochemical properties and potential for the direct compression (DC) tablets development were also investigated. Morphological analyses and the in situ observation on crystallization process revealed that the CLA spherulites are formed by fractal branching growth from both sides of the threadlike precursor fibers. 1H NMR analysis and nucleation time monitoring indicated that the existence of hydroxypropyl cellulose in solution slowed down the crystal nucleation and growth rate by forming hydrogen bonding interactions with CLA molecules, making the system maintain high supersaturation, providing high driving forces for CLA spherulitic growth. In comparison to commercial CLA, the CLA spherulites exhibit profoundly improved flowability, tabletability and dissolution behaviors. XPS, contact angle and Raman mapping analysis confirmed the presence of a thin HPC layer on the surfaces and interior of CLA spherulitic particles, resulting in increasing powder plasticity, interparticulate bonding strength and powder wettability, thus better tabletability and dissolution performances. The improved flowability and tabletability of CLA spherulites also enabled the successful development of DC tablet formulation with a high CLA loading (82.8 wt%) and similar dissolution profiles to reference listed drug. This study provides a novel solid form of CLA with superior manufacturability for further development.