Selective water‐permeable channels induced by polystyrene brushes within hairy nanocellulose/cellulose acetate membrane

Hairy nanocellulose (NC) was prepared by in‐situ admicellar polymerization of styrene on NC surface in the presence of cetyltrimethylammonium bromide through a stepwise fashion. It was also tried to achieve three hairy NCs with different polystyrene (PS) brush contents (i.e. 40, 50, and 80%) through altering monomer initial concentration. Then, NC and three hairy NCs were separately added into cellulose acetate (CA) solutions to fabricate membranes via the phase inversion technique. Transmission electron microscope images show that NC and three hairy NCs are spherical‐shaped nanoparticles. Results of Fourier transform infrared spectra provide clear evidence of PS brush being attached to the NC surfaces. Thermal gravimetric analysis confirms that increasing styrene initial concentration leads to enhanced PS content of hairy NCs. Results also elucidate that dispersions of prepared hairy NCs are highly stable even at high loading levels. It was found that incorporation of 1 wt% hairy NC with optimum brush content of 50% within CA membranes results in the increasing membrane water permeability from 7 to 40 l/m² hr with no change in its selectivity. Indeed, new interactions induced by PS brushes at hairy NC/CA interfaces result in the creation of connected channels at the interfaces which facilitate water transport through the membrane. This study provides insights into the key role that PS brushes play in overcoming the dispersion problems of NC in nonpolar media and offers guidelines to tailor channels within hairy NC/CA membrane for enhanced filtration performance. Copyright © 2017 John Wiley & Sons, Ltd.     

Modification and characterization of semi-crystalline poly(vinyl alcohol) with interpenetrating poly(acrylic acid) by UV radiation method for alkaline solid polymer electrolytes membrane

Semi-crystalline poly(vinyl alcohol) was modified by UV radiation with acrylic acid monomer to get interpenetrating poly(acrylic acid) modified poly(vinyl alcohol), PVAAA, membrane. The stability of various PVAAA membranes in water, 2 M CH₃OH, 2 M H₂SO₄, and 40 wt% KOH aqueous media were evaluated. It was found that the stability of PVAAA membrane is stable in 40 wt% KOH solution. The PVAAA membranes were characterized by differential scanning calorimetry, X-ray diffraction, and thermogravimetry analysis. These results show that (1) the crystallinity in PVAAA decreased with increasing the content of poly(acrylic acid) in the PVAAA membranes. (2) The melting point of the PVAAA membrane is reduced with increasing the content of poly(acrylic acid) in the membrane. (3) Three stages of thermal degradation were found for pure PVA. Compared to pure PVA, the temperature of thermal degradation increased for the PVAAA membrane. The various PVAAA membranes were immersed in KOH solution to form polymer electrolyte membranes, PVAAA-KOH, and their performances for alkaline solid polymer electrolyte were conducted. At room temperature, the ionic conductivity increased from 0.044 to 0.312 S/cm. The result was due to the formation of interpenetrating polymer chain of poly(acrylic acid) in the PVAAA membrane and resulting in the increase of charge carriers in the PVA polymer matrix. Compared to the data reported for different membranes by other studies, our PVAAA membrane are highly ionic conducting alkaline solid polymer electrolytes membranes.     

Versatility of hydrophilic and antifouling PVDF ultrafiltration membranes tailored with polyhexanide coated copper oxide nanoparticles

Hydrophilic poly(vinylidene fluoride) (PVDF) nanocomposite ultrafiltration (UF) membranes with excellent antifouling and antibiofouling characteristics are fabricated by employing polyhexanide coated copper oxide nanoparticles (P–CuO NPs). The presence of P–CuO NPs is played a significant role in altering the PVDF membrane matrix and probed by XRD, FTIR, FESEM and contact angle analysis. The PVDF/P–CuO nanocomposite membranes exhibited an outstanding antifouling performance indicated by the superior pure water flux, effective foulant separation and maximum flux recovery ratio during UF experiments as a result of the formation of the hydrophilic and more porous membrane due to the uniform distribution of P–CuO NPs. Particularly, the PVDF/P–CuO-3 membrane showed higher PWF of 152.5 ± 2.4 lm⁻²h⁻¹ and porosity of 64.5% whereas the lower contact angle of 52.5°. Further, it showed the higher rejection of 99.5 and 98.4% and the flux recovery ratio of 99.5 and 98.5% respectively for BSA and HA foulants, demonstrated its increased water permeation, foulant separation and antifouling behavior. Further, the decent antibacterial activity is showed by the PVDF/P–CuO nanocomposite membranes with the formation of halo-zone around the membrane when exposed to the bacterial medium demonstrated that, by this process an antibacterial water treatment membrane can be developed by simple phase inversion technique with good membrane stability.     

Recovery of H2SO4 from wastewater in the presence of NaCl and KHCO3 through pH responsive polysulfone membrane: Optimization approach

Through the phase inversion technique, asymmetric flat sheet pH-responsive Polysulfone (PSF) membrane was prepared and utilized for recovering H₂SO₄ in the presence of NaCl and KHCO₃ from wastewater. Hydrophilic and pH-responsive characteristics were incorporated within the membrane by blending Polyethylene glycol methyl ether (PEGME) and Humic acid (HA). The modification in membrane morphology with pH was characterized by Field Emission Scanning Electron Microscopy (FESEM), Differential scanning calorimetry (DSC) and Fourier Transform Infrared Studies (FTIR) method. The ion exchange capacity of the prepared pH-responsive membrane increased from 0.145 to 0.25 mmol/g when compared to the pristine PSF membrane. Pure water flux (PWF) of 113.8–46.8 L/m²h, water uptake of 25.9%–6.8% were obtained for pH-responsive membrane when pH varied from 4 to 12. Recovery of H₂SO₄ was optimized by design expert software 9.0 TRIAL and was found to be a maximum of 76.57 ± 1.5% in the presence of 0.32 M NaCl and 0.5 M KHCO₃ at pH ~8.4, through the pH-responsive PSF membrane by diffusion dialysis process. The influencing parameters (pH, NaCl (M) and KHCO₃ (M)) were optimized and acid recovery modeling was performed through response surface methodology (RSM) and central composite design (CCD). F value of 6573.40 through ANOVA study indicated the significance of the quadratic model chosen, whereas an insignificant lack of fit (prob > F = 0.0519) confirmed the goodness of fit between the model and obtained experimental data's.     

Thermostable ultrafiltration and nanofiltration membranes from sulfonated poly(phthalazinone ether sulfone ketone)

Modification of poly(phthalazinone ether sulfone ketone) (PPESK) by sulfonation with concentrated or fuming sulfuric acid was carried out in order to prepare thermally stable polymers as membrane materials having increased hydrophilicity and potentially improved fouling-resistance. The sulfonated poly(phthalazinone ether sulfone ketone)s (SPPESK) were fabricated into ultrafiltration (UF) and nanofiltration (NF) asymmetric membranes. The effects of SPPESK concentration and the type and concentration of additives in the casting solution on membrane permeation flux and rejection were evaluated by using an orthogonal array experimental design in the separation of polyethyleneglycol (PEG12000 and PEG2000) and Clayton Yellow (CY, MW 695). One UF membrane formulation type had a 98% rejection rate for PEG12000 and a high pure water flux of 867 kg m⁻² h⁻¹. All the NF membranes made in the present study had rejections of ≥96%, and one had a high water flux of 160 kg m⁻² h⁻¹. Several of the NF membrane formulation types had ∼90% rejection for CY. When the membranes were operated at higher temperatures (80°C), the rejection rates declined slightly and pure water flux was increased more than two-fold. Rejection and flux values returned to previous values when the membranes were operated at room temperature again. Mono- and divalent salt rejections and fluxes were studied on an additional NF membrane set.     

Selective Hg2+ sensor performance based various carbon‐nanofillers into CuO‐PMMA nanocomposites

Ternary nanocomposites (NCs) containing copper oxide (CuO)/poly(methyl methacrylate)/various carbon‐based nanofillers have been successfully prepared as thin films by an ex situ method as a selective Hg⁺² sensor. The structural, morphological, and electrochemical properties of the NCs were identified by all common characterization tools. The FT‐IR curves of these NCs proved the efficiency of CuO mixed with single‐walled CNTs (CuO/SWCNTs), multi‐walled CNTs (CuO/MWCNTs), or graphene (CuO/G) nanoparticles in the PMMA polymer matrix. The mixed nanofillers significantly improved the properties of the PMMA film. The thermal characteristics of the pure PMMA polymer matrix were highly developed by adding nanofillers in the form of NCs. The maximum composite degradation temperature (CDT_max) values were comparable for all the NCs and were in the range of 345 to 406°C. For fabrication, the CuO‐PMMA‐SWCNT, CuO‐PMMA‐MWCNT, and CuO‐PMMA‐GNCs were coated onto a glassy carbon electrode (GCE) to form a tiny layer with orderly thickness using a conductive 5% Nafion chemical binder. During the electrochemical investigation, it was found that CuO‐PMMA‐SWCNT had the maximum response toward Hg²⁺ ions compared to the other nanofillers in a buffer medium (phosphate type). To calibrate the Hg²⁺ ionic sensor, the data were plotted against Hg²⁺ ion concentration and the proposed sensor showed linearity over a wide range of concentrations (0.1‐0.01 mM), which is called the linear dynamic range (LDR). The analytical parameters, such as sensitivity (1.70 × 102 μAμM^‐1 cm^?2), detection limit (55.76 ± 2.79 pM), and limit of quantification (185.87 pM) were calculated from the calibration curve. Moreover, it showed good reproducibility, fast response time, good linearity, large LDR, and good stability. The CuO‐PMMA‐SWCNT NC‐modified GCE offers a new route to fabricate novel heavy metal ionic sensors, which might be used in green environment and health development applications.     

Performance improvement of polysulfone ultrafiltration membrane by blending with polyaniline nanofibers

Polyaniline (PANI) nanofibers were used to improve hydrophilic property and permeability of polysulfone (PS) membrane. PS membrane and PS/PANI nanofibers blended membranes with different PANI–PS mass ratios (1, 5, 10, and 15 wt.%) were prepared by phase inversion process. The blended membranes showed similar bovine serum albumin (BSA) and albumin egg (AE) rejections to PS membrane. The blended membranes had larger porosity and better hydrophilic property than PS membrane, which caused the improvement of their permeability. Pure water fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 1.6 and 2.4 times that of PS membrane, respectively. During the filtration of BSA solution, the blended membranes had slower flux decline rate than PS membrane. Moreover, stable permeate fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 2.0 and 2.5 times that of PS membrane, respectively. Compared with PS membrane, mechanical property and thermal stability of the blended membranes with less PANI–PS mass ratio, e.g. 1 wt.%, had no obvious change. For the blended membrane with PANI–PS mass ratio of 15 wt.%, breaking strength increased 28% and elongation at break decreased 30.6%.     

Preparation and characterization of NF composite membrane

With a view to be able to prepare high performance nanofiltration membranes, we made experiments where NF composite membranes were prepared by interfacial polymerization, using ultrafilitration membrane as substrate and their performances such as water flux, retention of Na₂SO₄ and PEG 600 were studied. The results show that under an operational pressure of 0.6 MPa, water fluxes of NF-1, NF-2 and NF-3 are 4.1, 6.0 and 26.5 l/m² h, respectively, while the retentions of Na₂SO₄ are 78, 94 and 94%, respectively. The chemical composition and the surface image of NF membranes are obtained by using IR and atomic force microscope Also explored are the prospects of their applications in the dyeing industry.     

Using PDMS coated TFC-RO membranes for CO2/N2 gas separation: Experimental study,modeling and optimization

Thin film composite (TFC) reverse osmosis (RO) membranes are semipermeable membranes that are utilized in water purification or water desalination systems. Discarding these membranes after end-of-life leads to environmental problems. Reusing old TFC-RO membranes is one way to solve this problem. For this reason, in this study, used TFC-RO membranes were coated with polydimethylsiloxane (PDMS) for CO₂/N₂ gas separation application. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was utilized to confirm the crosslinking of coated PDMS. The morphology of PDMS/TFC-RO membranes was characterized using scanning electron microscopy (SEM). The parameters that can affect performance of prepared membranes (N₂ permeance and CO₂/N₂ selectivity) are concentration of PDMS solution, coating time, solvent evaporation time and curing temperature and time. Given that the used membranes don't have uniform surfaces, the first step of this study was to investigate the effect of the above mentioned factors on virgin membranes using fractional factorial design (FFD) of experiments. The results obtained showed that PDMS concentration is the most significant factor that has a negative effect on N₂ permeance and positive effect on CO₂/N₂ selectivity. The reported CO₂/N₂ selectivity of PDMS membranes was 11–12, but this selectivity for prepared PDMS/TFC-RO membranes was in the range of 6.7–22.5. After determining optimum conditions, the gas separation performance of PDMS coated used TFC-RO membrane under these conditions was finally determined. The results showed that the used membranes had a better performance than virgin membranes.     

Synthesis of Fe3O4/CuO/ZnO/RGO and its catalytic degradation of dye wastewater using dielectric barrier discharge plasma

The design of an efficient and green dye degradation technology is of great significance to mitigate water pollution as well as ecological damage. Fe₃O₄/CuO/ZnO/RGO was prepared by solvothermal synthesis and homogeneous precipitation. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), and vibrating-sample magnetometry (VSM) were used to characterize the samples, to explore the morphology and structural composition of the composites. To enhance the degradation efficiency, a dielectric barrier discharge (DBD)–Fe₃O₄/CuO/ZnO/RGO co-catalytic system was created based on the DBD plasma technology. Response surface methodology analysis results demonstrate that the degradation effect of DBD–Fe₃O₄/CuO/ZnO/RGO is optimal and the decolorization rate is 95.06 % when the solution pH is 3, conductivity is 0.5 mS/cm, the input voltage is 90 V, and Fe₃O₄/CuO/ZnO/RGO concentration is 0.18 g/L. Therefore, this study offers a novel method for dye degradation and confirms the viability of a DBD–Fe₃O₄/CuO/ZnO/RGO synergistic catalytic system.     

Hydrothermal synthesis and photocatalytic property of porous CuO hollow microspheres via PS latex as templates

Porous copper oxide (CuO) hollow microspheres have been fabricated through a simple hydrothermal method using PS latex as templates. The as-obtained samples were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). The influences of the mole ratio of Ethylenediamine (C₂H₈N₂) and copper acetate (Cu(Ac)₂·H₂O), hydrothermal temperature and time on the size and morphologies of the final products have been investigated. The possible formation mechanism of porous CuO hollow microspheres has been proposed and the specific surface area of the hollow microspheres with 81.71 m²/g is measured by BET method. The band gap value calculated from a UV–vis absorption spectrum of porous CuO hollow microspheres is 2.71 eV. The as-synthesized product exhibits high photocatalytic activity during the photodegradation of an organic dyestuff, rhodamine B (RhB), under UV-light illumination.     

Synthesis,characterization and kinetic computations of fullerene (C60)–CuO on the mechanism decomposition of ammonium perchlorate

CuO, C₆₀–CuO, and Al/C₆₀–CuO nanostructures were synthesized and characterized by scanning electron microscope (SEM)/energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA) measurements were performed to study the influence of these additives on ammonium percolate (AP) thermal decomposition. From the comparison of DSC and TGA plots, the catalytic effect of CuO and C₆₀–CuO has been clearly noticed in which the lower temperature decomposition of AP was decreased from 331 °C to 315 °C, 310 °C, and 303 °C (in the presence of CuO, C₆₀–CuO, and Al/C₆₀–CuO, respectively) and the HTD was dropped from 430 °C (pure AP) to 352 °C, 335 °C, and 317 °C (for the compounds AP/CuO, AP/C₆₀–CuO, and AP/Al/C₆₀–CuO, respectively). The kinetics of the samples were investigated by isoconversional models and compared with an iterative procedure. The results of pure AP indicated a complex decomposition process involving three decomposition steps with specific reaction mechanism. The nanocatalysts incorporated in the AP have clearly affected its decomposition process in which the reaction mechanism and the number of stages were changed.     

Insight into the performance of novel kaolinite-cellulose/cobalt oxide nanocomposite as green adsorbent for liquid phase abatement of heavy metal ions: Modelling and mechanism

A cost-efficient kaolinite-cellulose/cobalt oxide green nanocomposite (Kao-Cel/Co₃O₄ NC) was successfully synthesized, and utilized as a promising material for removing Pb²⁺ and Cd²⁺ from aqueous solution. The fabricated nanocomposite has been characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy-energy dispersive X-ray, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller analysis. The batch methodology was exploited for optimization of process parameters and the optimized conditions were found to be adsorbent dosage (2.0 g/L), extraction time (50 min), initial concentration (60 mg/L), and initial solution pH (6). Kao-Cel/Co₃O₄ NC displayed excellent adsorption properties and achieved maximum saturation capacity (Q_m) of 293.68 mg Pb²⁺/g and 267.85 mg Cd²⁺/g, with an equilibration time of 50 min at 323 K. The Langmuir model best expressed the isotherm data recommending the adsorption onto energetically homogeneous NC surface, while the compatibility of kinetics data with pseudo-second-order model revealed the dependency of adsorption rate on adsorption capacity, and probable involvement of chemisorption in the rate-controlling step. Electrostatic interaction and ion exchange mechanism were responsible for the uptake of Pb²⁺ and Cd²⁺ by Kao-Cel/Co₃O₄ NC as demonstrated by Fourier transform infrared spectroscopy and pH studies. Thermodynamic parameters confirmed the physical, spontaneous, and endothermic sequestration processes. Real water investigation specified that the present adsorbent could be effectively used for liquid phase decontamination of Pb²⁺ and Cd²⁺. The nanocomposite exhibited high reusability, which could be utilized efficiently for five runs with sustainable results. In summary, this study portrayed the present nanocomposite as an emerging material for the adsorption of heavy metal ions particularly Pb²⁺ and Cd²⁺.     

PEG modified poly(amide-b-ethylene oxide) membranes for CO2 separation

In the present work, membranes from commercially available Pebax^® MH 1657 and its blends with low molecular weight poly(ethylene glycol) PEG were prepared by using a simple binary solvent (ethanol/water). Dense film membranes show excellent compatibility with PEG system up to 50 wt.% of content. Gas transport properties have been determined for four gases (H₂, N₂, CH₄, CO₂) and the obtained permeabilities were correlated with polymer properties and morphology of the membranes. The permeability of CO₂ in Pebax^®/PEG membrane (50 wt.% of PEG) was increased two fold regarding to the pristine Pebax^®. Although CO₂/N₂ and CO₂/CH₄ selectivity remained constant, an enhancement of CO₂/H₂ selectivity (∼11) was observed. These results were attributed to the presence of EO units which increases CO₂ permeability, and to a probable increase of fractional free-volume. Furthermore, for free-volume discussion and permeability of gases, additive and Maxwell models were used.     

Effect of preparation variables on morphology and pure water permeation flux through asymmetric cellulose acetate membranes

In this study, cellulose acetate (CA) ultrafiltration (UF) membranes were prepared using the phase inversion method. Effects of CA and polyethylene glycol (PEG) concentrations in the casting solution and coagulation bath temperature (CBT) on morphology of the synthesized membranes were investigated. Based on L₉ orthogonal array of Taguchi experimental design 18 membranes were synthesized (with two replications) and pure water permeation flux through them were measured. It was found out that increasing PEG concentration in the casting solution and CBT, accelerate diffusional exchange rate of solvent 1-methyl-2-pyrrolidone (NMP) and nonsolvent (water) and consequently facilitate formation of macrovoids in the membrane structure. Increasing CA concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. Rate of water flux through the synthesized membranes is directly dependent on the size and number of macrovoids in the membrane structure. Thus, maximum value of flux is obtained at the highest levels of PEG concentration and CBT (10 wt.% and 23 °C, respectively) and the lowest level of CA concentration (13.5 wt.%). Analysis of variance (ANOVA) showed that all parameters have significant effects on the response. However, CBT is the less influential factor than CA and PEG concentrations on the response (flux).     

Enhancing the performance of TFC nanofiltration membranes by adding organic acids in polysulfone support layer

Throughout this study, the effect of certain organic acids, methacrylic acid, lactic acid and tartaric acid, doped in polysulfone (PSF) casting solution onto the performance of nanofiltration (NF) membranes was investigated. Different NF membranes have been prepared from m-phenylenediamine and trimesoylchloride onto the top surface of the acid-modified PSF membranes through regulating the concentration and contact time of the conventional interfacial polymerization process. The study of scanning electron microscopy (SEM) was used to investigate the influence of acids on the morphology of membranes and cross-sectional structures. The functional groups, hydroxyl and carboxylic acid, of the acids have resulted in a significant increase in membrane thickness, porosity and hydrophilicity, with a decrease in macrovoid capacity of the PSF layer. The acid-modified PSF/TFC membranes showed higher rejection of salt, with an increment in water flux compared to the neat membrane. Water flux and salt rejection (R_s %) of the control membrane was 7.6 L/m² h and 65.4%, whereas polysulfone/methacrylic acid (PSF/MAAc), polysulfone/tartaric acid (PSF/TAc), and polysulfone/lactic acid (PSF/LAc) were 16.8, 18.5, and 20.2 L/m² h and 88, 88.2 and 94.1%, respectively. Efficiency of prepared NF membranes under various inlet pressures and specific salts was investigated with selectivity and salt rejection. The salt rejection of a mixed salt solution was found to meet the order of R_s % CaSO₄ ≥ R_s % Na₂SO₄ ˃ R_s % MgSO₄ ˃ R_s MgCl₂ ˃ Rs % NaCl.     

Compatibility study of 1,3,3-trinitroazetidinewith some energetic components and inert materials

The compatibility of 1,3,3-trinitroazetidine (TNAZ) with some energetic components and inert materials of solid propellants was studied by using the pressure DSC method. Where, cyclotetramethylenetetranitroamine (HMX), cyclotrimethylenetrinitramine (RDX), nitrocellulose (NC), nitroglycerine (NG), 1.25/1-NC/NG mixture, lead 3-nitro-1,2,4-triazol-5-onate (NTO-Pb), aluminum powder (Al powder) and N-nitrodihydroxyethylaminedinitrate (DINA) were used as energetic components and hydroxyl terminated polybutadiene (HTPB), carboxyl terminated polybutadiene (CTPB), polyethylene glycol (PEG), polyoxytetramethylene- co-oxyethylene (PET), addition product of hexamethylene diisocyanate and water (N-100), 2-nitrodianiline (2-NDPA), 1,3-dimethyl-1,3-diphenyl urea (C₂), carbon black (C.B.), aluminum oxide (Al₂O₃), cupric 2,4-dihydroxybenzoate (β-Cu), cupric adipate (AD-Cu) and lead phthalate (φ-Pb) were used as inert materials. The results showed that the binary systems of TNAZ with HMX, NC, NG, NC+NG and DINA are compatible, with RDX and Al powder are slightly sensitive, with NTO-Pb, β-Cu, AD-Cu, C.B. and Al2O3 are sensitive, and with HTPB, CTPB, PEG, PET, N-100, 2-NDPA, C₂ and φ-Pb are incompatible.     

Colorimetric detection of hydrogen peroxide and lactate based on the etching of the carbon based Au-Ag bimetallic nanocomposite synthesized by carbon dots as the reductant and stabilizer

In this report, carbon-based gold core silver shell Au-Ag bimetallic nanocomposite (Au-Ag/C NC) was synthesized using carbon dots (C-dots) as the reductant and stabilizer by a facile green sequential reduction approach. The structure and morphology of the nanocomposite are characterized by ultraviolet–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The as synthesized Au-Ag/C NC exhibits good optic response toward hydrogen peroxide (H₂O₂) without adding any other chromogenic agents. The characteristic surface plasmon resonance (SPR) absorbance peak of Au-Ag/C NC declined and red-shifted with the solution color changing from reddish orange to light pink when adding H₂O₂ owing to the etching effect of H₂O₂ towards Ag. Thus, a simple colorimetric and UV strategy for sensitive detection of H₂O₂ is proposed. It provides the wide linear range for detection of H₂O₂ from 0.8–90 μM and 90–500 μM, and the detection limit was as low as 0.3 μM (S/N = 3). In addition, this colorimetric strategy can also be applied to directly distinguish and detect of lactate by naked eye and UV–Vis. The linear range of colorimetric sensing towards lactate was 0.1–22 μM and 22–220 μM, which was successfully applied in the analysis of lactate in human serum.     

Investigating the effect of PEG200 and two-dimensional h-BN on PVDF membrane performance for membrane distillation–crystallization

Although water supplies are prominently dependent on desalination technology, desalination plant facing severe issues of discharged brine concentrate. Membrane distillation crystallization is an emerging synergistic technology that resolves the issue of brine concentrate by recovering clean water and value-added minerals simultaneously. In the present study, properties of polyvinylidene fluoride (PVDF) membrane were modified by incorporation of exfoliated fillers of hexagonal boron nitride and polyethylene glycol. The changes in morphology, surface roughness, hydrophobicity, thermal stability, and chemical composition of the prepared membranes were evaluated by scanning electron microscopy, atomic force microscopy, contact angle, thermogravimetric analysis, Fourier-transform infrared spectroscopy, respectively. Membrane distillation crystallization experiments were conducted to observe the effect of modified membranes on the permeate flux and salts recovery at different feed temperatures. The results showed a significant improvement in the permeate flux with modified membranes compared with pure PVDF membrane. It was found that hexagonal boron nitride/polyethylene glycol200 incorporated PVDF membrane gave the higher permeate flux (3.41 kg/m² h for K₂SO₄ and 2.62 kg/m² h for KNO₃) at a temperature of 80 °C along with higher salts recovery than pure PVDF membranes. A 100 h long run test was conducted on modified membranes, which showed consistency in permeate flux with a marginal increase in conductivity.     

Studies on the interactions of diglycine and triglycine with polyethylene glycol 400 in aqueous solutions by density and ultrasound speed measurements

Density and ultrasound speed were measured accurately for diglycine + water, triglycine + water, diglycine + water-polyethylene glycol 400 (PEG400) and triglycine + water-PEG400 solutions at T = (293.15, 298.15, 303.15 and 308.15) K. The results were used in evaluating thermodynamic properties as apparent molar volumes (V_Ø) and apparent molar isentropic compressions (K_SΦ) of diglycine and triglycine in water and in PEG400 solutions. Infinite dilution values of these parameters, V^o_Ø, and K^o_SΦ, were obtained from their plots as a function of molality by extrapolation and have been utilized in obtaining transfer volumes and transfer compressions at infinite dilution. All transfer volumes and transfer compressions were found to increase with increasing molality of PEG400. Apparent molar isobaric expansions were derived from the temperature dependence of V_Ø values at infinite dilution and at finite concentrations. All the results were interpreted in terms of solute (diglycine or triglycine) and co-solute (PEG400) and solvent (H₂O) interactions.