Diffusion kinetics of CO2 in amine-impregnated MIL-101, alumina,and silica adsorbents

CO₂ sorption kinetics of poly(ethylenimine) (PEI)-impregnated MIL-101, γ-alumina, and UVM-7 silica were investigated by the zero-length column technique for the purpose of understanding the effect of amine content, adsorbent porosity, and adsorption temperature on CO₂ sorption rates. Each of the adsorbents was impregnated with three different amine contents (20, 35, and 50 wt%) and the effective diffusion time constants were determined at 25°C. For each respective adsorbent, it was found that increasing the amine content results in diminished diffusion rates. Additionally, it was found that the pore size of the support has a profound effect on diffusional kinetics, where microporous MIL-101 yielded substantially slow desorption rates upon amine-functionalization compared to mesoporous γ-alumina. PEI-impregnated UVM-7 silica was further investigated at 50 and 75°C in order to provide insight into the effect of temperature on sorption kinetics. The results indicated that PEI-impregnated UVM-7 exhibited faster sorption kinetics at higher temperatures. Upon desorption, PEI-UVM-7 silica exhibited two distinct regions of mass-transfer control that occur at different sorption times. This is best explained by first the occurrence of surface diffusion followed by diffusion out of the bulky PEI polymer chains. The findings of this study provide novel kinetic characterizations on promising amino-adsorbents for carbon capture applications.     

Analysis of dynamic CO2 capture over 13X zeolite monoliths in the presence of SOx,NOx and humidity

In this investigation, the CO₂ capture performances of zeolite 13X monoliths with 600 and 800 cells per square inch (cpsi) in the presence of SO₂/NO impurities under dry and humid conditions were evaluated and compared with that of 13X beads. Dynamic breakthrough tests demonstrated a drastic reduction in CO₂ capture capacity and deterioration of kinetics under dry-clean conditions, whereas, upon switching the feed from a clean gas to contaminated gas which contained SO₂ and NO, different adsorption performance was observed. Specifically, in dry-contaminated mode, the adsorbents retained their capture capacities with comparable kinetics to that of dry-clean feed conditions, however, in humid-contaminated mode, the adsorbents experienced improved CO₂ uptake and CO₂/N₂ selectivity, albeit at the expense of deteriorated kinetics. These findings indicate that the presence of SO₂ and NO contaminants, especially SO₂ contaminants, lead to dramatic changes in the adsorption performance of zeolite 13X monoliths, indicating the importance of evaluating adsorbent materials under realistic conditions.     

Surface nanostructure modification of Al substrates by N+ ion implantation and their corrosion inhibition

The influence of implantation of N⁺ ions of different energies on the nanostructure of 7049 Al substrates and the corrosion inhibition of produced Al samples in a 3.5% NaCl solution was studied. The X-ray diffraction (XRD) results confirmed the formation of AlN as a result of N⁺ ion implantation. The atomic force microscope (AFM) results showed that grains of larger scale are formed by increasing N⁺ energy which can be due to heat accumulation in the sample during implantation causing higher rate of diffusion in the sample, hence decreasing the number of defects. Corrosion resistance of the samples was studied by the electrochemical impedance spectroscopy (EIS) measurements. Results showed that corrosion resistance of implanted Al increases with increasing N⁺ ion energy. The equivalent circuits for the N⁺ implanted Al samples with different energies were obtained, using the EIS data which showed strong dependence of the equivalent circuit elements on the surface morphology of the samples. Finally, the relationship between corrosion inhibition and equivalent circuit elements was investigated.     

Thin film graphene oxide membrane: Challenges and gas separation potential

Graphene oxide membranes were prepared by vacuum and pressurized ultrafiltration methods on the 12% modified Polyacrylonitrile (12mPAN) substrate to specify challenges, salient features, future directions, and potential of GO membrane for separation fields using characterization techniques and gas separation test (studied gases are CO₂, He and N2), which is an efficient tool for better understanding of GO membrane behavior. GO membrane structure was examined over a wide range of parameters, such as pore size range of substrate and its surface properties, pH of GO dispersion, GO content, synthesis pressure, operating pressure and temperature. The results show that the GO content does not hold a linear relationship with the permeance and selectivity. Film thickness, aggregates, synthesis pressure defects and interlayer spacing have significant effects on the gas separation performance of GO membranes which originate from the synthesis method and its conditions.     

Effect of heat treatment and solution preparation procedure on colloidal stability of whey protein sour cherry beverage

In this study, a whey protein sour cherry beverage was prepared using whey protein concentrate, sour cherry concentrate, Angum gum, water and sugar as initial ingredients. Whey protein concentrate and gum solutions were prepared by four methods. Heat treatment of the solutions led to denaturation of proteins, a change in the solubility of proteins and sediment formation. Our results showed that denaturation of proteins made the peptide fragments of the proteins to bind the gum, thus preventing the separation of the serum.     

Fuzzy sliding-mode control of a human arm in the sagittal plane with optimal trajectory

Patients with spinal cord injuries cannot move their limbs using their intact muscles. A suitable controller can be used to move their arms by employing the functional electrical stimulation method. In this article, a fuzzy exponential sliding-mode controller is designed to move a musculoskeletal human arm model to track an optimal trajectory in the sagittal plane. This optimal arm trajectory is obtained by developing a policy for the central nervous system. In order to specify the optimal trajectory between two points, two dynamic and static optimal criteria are applied simultaneously. The first dynamic objective function is defined to minimize the joint torques, and the second static optimization is offered to minimize the muscle forces at each moment. In addition, fuzzy logic is used to tune the sliding-surface parameter to enable an appropriate tracking performance. Simulation results are evaluated and compared with experimental data for upward and downward movements of the human arm.     

Modeling truck scheduling problem at a cross-dock facility through a bi-objective bi-level optimization approach

Uncertainty and non-deterministic nature of the real world makes planning and scheduling in cross-docks a very complicated task for decision makers. These constant changes that happen all the time, often, lead to an increase in costs and/or a decrease in efficiency. Most of the uncertainty in cross-docks is caused by un-known truck arrival times. In this study we address the problem of scheduling incoming and outgoing trucks at a cross-dock facility, when vehicle arrival times are unknown, through a cost-stable scheduling strategy. Two meta-heuristics, MODE and NSGA-II, are used for solving the designed sample problems and are compared with a random search based genetic algorithm existing in the literature. Finally, performance of each algorithm is measured and analyzed using four metrics: quality, spacing, diversification and mean ideal distance. The results indicate that the proposed model MODE algorithm performs better in comparison with the other two methods.     

Precursor route poly(thienylene vinylene) for organic solar cells: Photophysics and photovoltaic performance

Photophysical studies and photovoltaic devices on a low bandgap, high-charge carrier mobility poly(thienylene vinylene) (PTV), prepared from a soluble precursor polymer synthesised via the “dithiocarbamate route”, are reported. In composites with an electron acceptor ([6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM), a soluble fullerene derivative), photoinduced absorption characteristic for charged excitations together with photoluminescence quenching are observed indicating photoinduced electron transfer. The “bulk heterojunction” photovoltaic devices using PTV and PCBM composites show short-circuit currents up to 4 mA/cm² under AM 1.5 white-light illumination. The photocurrent spectrum of the photovoltaic device shows an onset about 1.65 eV (750 nm), which corresponds to the absorption spectrum of the polymer.