Nanocomposites containing graphene oxide (GO), polyethyleneimine (PEI), and chitosan (CS) were synthesized for chromium(VI) and copper(II) removal from water. Response surface methodology (RSM) was used for the optimization of the synthesis of the CS-PEI-GO beads to achieve simultaneous maximum Cr(VI) and Cu(II) removals. The RSM experimental design involved investigating different concentrations of PEI (1.0-2.0%), GO (500-1500 ppm), and glutaraldehyde (GLA) (0.5-2.5%), simultaneously. Batch adsorption experiments were performed to obtain responses in terms of percent The optimum bead composition contained 2.0% PEI, 1500 ppm GO, and 2.08% GLA, and allowed Cr (VI) and Cu(II) removals of up to 91.10% and 78.18%, respectively. Finally, characterization of the structure and surface properties of the optimized CS-PEI-GO beads was carried out using X-ray diffraction (XRD), porosity and BET surface area analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), which showed favorable adsorbent characteristics as given by a mesoporous structure with high surface area (358 m 2 g À1 ) and plenty of surface functional groups. Overall, the synthesized CS-PEI-GO beads were proven to be effective in removing both cationic and anionic heavy metal pollutants.

Selenium in water is becoming of increasing risk to human exposure because only recently serious health effects have been associated with their presence in water resources. The present study investigated the development and optimization of the composition of graphene oxide polymeric nanocomposite hydrogel beads by using response surface methodology. The use of polymers such as chitosan and polyethylenimine, which are rich in amine and alcoholic functional groups, provided enhanced removal of anionic selenium species from the water. Experimentally validated polymeric beads were used to perform batch adsorptions of selenium under different conditions such as pH, bead dosage, and diverse selenium concentrations to investigate their potential use, adsorption kinetics, and selenium removal mechanisms. Acidic conditions were found to best remove negatively charged selenium ions from aqueous solutions via −OH, −COOH, and amine functional groups present in the beads. The adsorption kinetic mechanism was better described by the pseudo-second-order adsorption kinetics, indicating that the beads remove selenium via chemisorption mechanisms. The isotherm studies showed an adsorption capacity of 1.62 mg/g based on the Langmuir isotherms at 25 °C. Regeneration studies showed loss of available adsorption sites after the first desorption treatment with different concentrations of NaOH and HCl. The mathematically optimized nanocomposite was further used to treat selenium spiked in real environmental water samples, which confirmed that the best removal of selenium occurs in acidic conditions.

Analysis of the probability distribution of induction times for acetaminophen and glycine supersaturated solutions showed that reduction in sample volume results in an exponential increase in induction times. It approximately increased by a factor of 55 when the volume was reduced from 1000 to 25 μL. To elucidate the use of confinement as an approach to nanocrystal development and polymorph access, we demonstrated the effect of volume reduction on the nucleation of two model compounds, acetaminophen and glycine. Using supersaturated solutions of both compounds at volumes ranging from 1000 to 25 μL, induction time statistics were obtained experimentally. Image analysis revealed that form I acetaminophen and β-glycine formed as the initial primary nucleation event, with β-glycine sometimes followed by a polymorph transformation to γ-glycine shortly after. Image analysis showed no variation in polymorphism occurring for acetaminophen systems across all volumes. However, it was revealed that at volume sizes below 100 μL, primary nucleation in glycine systems shifts toward γ-glycine nucleation. These results demonstrate the effects of volume reduction on nucleation induction times, its implications on polymorphism, and the extent of lessening the probability of a nucleation event.

We are currently witnessing the dawn of hydrogen (H 2 ) economy, where H 2 will soon become a primary fuel for heating, transportation, and longdistance and long-term energy storage. Among diverse possibilities, H 2 can be stored as a pressurized gas, a cryogenic liquid, or a solid fuel via adsorption onto porous materials. Metal−organic frameworks (MOFs) have emerged as adsorbent materials with the highest theoretical H 2 storage densities on both a volumetric and gravimetric basis. However, a critical bottleneck for the use of H 2 as a transportation fuel has been the lack of densification methods capable of shaping MOFs into practical formulations while maintaining their adsorptive performance. Here, we report a high-throughput screening and deep analysis of a database of MOFs to find optimal materials, followed by the synthesis, characterization, and performance evaluation of an optimal monolithic MOF ( mono MOF) for H 2 storage. After densification, this mono MOF stores 46 g L −1 H 2 at 50 bar and 77 K and delivers 41 and 42 g L −1 H 2 at operating pressures of 25 and 50 bar, respectively, when deployed in a combined temperature− pressure (25−50 bar/77 K → 5 bar/160 K) swing gas delivery system. This performance represents up to an 80% reduction in the operating pressure requirements for delivering H 2 gas when compared with benchmark materials and an 83% reduction compared to compressed H 2 gas. Our findings represent a substantial step forward in the application of high-density materials for volumetric H 2 storage applications.

Small Angle X-ray Scattering has been used to characterize nanoparticles generated by electrical arcing between metallic (AgSnO2) electrodes. The particles are found to have diameters between 30 and 40 nm and display smooth surfaces suggesting that they are either in liquid form or have solidified from the liquid state. Particles collected around the electrodes were analyzed by Transmission Electron Microscopy and were seen to be much larger than those seen in the SAXS measurement, to be spherical in form and composed of silver metal with irregular tin oxide particles deposited on their surface. Mixed metal nanoparticles can have important practical applications and the use of mixed sintered electrodes may be a direct method for their production

International audienceThe influence of a reactive atmosphere on the formation of nanoparticles (NPs) in the plasma plume generated by nanosecond pulsed laser irradiation of metal targets (Ti, Al, Ag) was probed in-situ using Small Angle X-ray Scattering (SAXS). Air and different O2-N2 gas mixtures were used as reactive gas within atmospheric pressure. SAXS results showed the formation of NPs in the plasma-plume with a mean radius varying in the 2-5 nm range. A decrease of the NPs size with increasing the O2 percentage in the O2-N2 gas mixture was also showed. Ex-situ observations by transmission electron microscopy and structural characterizations by x-ray diffraction and Raman spectroscopy were also performed for powders collected in experiments done using air as ambient gas. The stability of the different metal oxides is discussed as being a key parameter influencing the formation of NPs in the plasma-plume (E-MRS 2015 Spring Meeting Symposium CC: “Laser and plasma processing for advanced applications in material science”, 11-15 May 2015, Lille (France

We are currently witnessing the dawn of the hydrogen (H2) economy, where H2 will become a primary fuel for heating, transportation, and long-distance and long-term energy storage. Among the diverse possibilities, H2 can be stored as a pressurized gas, cryogenic liquid, or solid fuel via adsorption onto porous materials. Metal-organic frameworks (MOFs) have emerged as the adsorbent materials with the theoretical highest H2 storage densities on both a volumetric and gravimetric basis. However, a critical bottleneck for the use of H2 as a transportation fuel has been the lack of densification methods capable of shaping MOFs into practical formulations whilst maintaining their adsorptive performance. Here, we report a high-throughput screening and deep analysis of a database of MOFs to find optimal materials, followed by the synthesis, characterisation, and performance evaluation of an optimal monolithic MOF (monoMOF) for H2 storage. After densification, this monoMOF stores 46 g L-1 H2 at 50 bar, 77 K, and delivers 41 and 42 g L-1 H2 at operating pressures of 25 and 50 bar, respectively, when deployed in a combined temperature–pressure (25-50 bar/77 K → 5 bar/160 K) swing gas delivery system. This performance represents up to an 80% reduction in the operating pressure requirements for delivering H2 gas when compared with benchmark materials, and an 83% reduction compared to compressed H2 gas. Our findings represent a substantial step forward in the application of high-density materials for volumetric H2 storage applications.

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