Zwitterionic Polysulfone Copolymer/Polysulfone Blended Ultrafiltration Membranes with Excellent Thermostability and Antifouling Properties

Membrane fouling has been one of the most important challenges in membrane separation operations. In this study, we report a facile strategy to prepare antifouling polysulfone (PSf) UF membranes by blending amphiphilic zwitterion polysulfone-co-sulfobetaine polysulfone (PSf-co-SBPSf) copolymer. The copolymer chemical structure was characterized by 1HNMR spectroscopy. The PSf/PSf-co-SBPSf blend membranes with various zwitterionic SBPSf segment contents exhibited better surface hydrophilicity and excellent antifouling ability compared to PSf and PSf/PEG membranes. The significant increase of both porosity and water permeance indicates that the PSf-co-SBPSf has a pore-forming effect. The pure water flux and flux recovery ratio of the PSf/PSf-co-SBPSf blend membranes were both remarked to improve 286.43 L/m2h and 92.26%, while bovine serum albumin (BSA) rejection remained at a high level (97.66%). More importantly, the water flux and BSA rejection see minimal variance after heat treatment, indicating excellent thermostability. Overall, the PSf/PSf-co-SBPSf blend membranes achieved a comprehensive performance of sustainable hydrophilic, high permeation flux, and remarkable antifouling ability, thus becoming a promising candidate in high-temperature separation application.

THE DUFOUR EFFECT IN FILM COOLING EXPERIMENTS WITH FOREIGN GASES

In typical film cooling experiments, the adiabatic wall temperature may be determined from surface temperature measurements on a low thermal conductivity model in a low temperature wind tunnel. In such experiments, it is generally accepted that the adiabatic wall temperature must be bounded between the coolant temperature and the freestream recovery temperature as they represent the lowest and highest temperature introduced into the experiment. Many studies have utilized foreign gas coolants to alter the coolant properties such as density and specific heat to more appropriately simulate engine representative flows. In this paper, we show that the often ignored Dufour effect can alter the thermal physics in such an experiment from those relevant to the engine environment that we generally wish to simulate. The Dufour effect is an off-diagonal coupling of heat and mass transfer that can induce temperature gradients even in what would otherwise be isothermal experiments. These temperature gradients can result in significant errors in calibration of various experimental techniques, as well as lead to results that at first glance may appear non-physical such as adiabatic effectiveness values not bounded by zero and one. This work explores Dufour effect induced temperature separation on two common cooling flow schemes, a leading edge with compound injection through a cylindrical cooling hole, and a flat plate with axial injection through a 7-7-7 shaped cooling hole. Air, argon, carbon dioxide, helium, and nitrogen coolant were utilized due to their usage in recent film cooling studies.

AN EXPERIMENTAL INVESTIGATION OF THE GOVERNING PROPERTIES IN A VORTEX TUBE

Although awareness of the phenomenon of temperature separation in Ranque-Hilsch vortex tubes dates back at least nine decades, some mystery surrounding the phenomenon remains to this day. These devices split an incoming stream of fluid into two streams—one with a greater total temperature than the incoming fluid and the other with a lower total temperature. This temperature separation is accomplished with no moving parts and no external sources of energy including heat transfer to or from the device. In attempts to understand the physics of the temperature separation, previous researchers have characterized the effect through various inlet temperatures and pressures as well as various gases with different properties. Unfortunately, the findings documented in the literature are sometimes inconsistent indicating the possibility that previously uncontrolled properties and flow conditions govern temperature separation to an unappreciated degree. In the present research, two new flow characteristics are examined for their role in temperature separation—volumetric heat capacity, ρC_p, and nozzle velocity. In the present experiments with air, it was found that by matching nozzle velocity and ρC_p—even with disparate pressures, temperatures, Reynolds numbers, and Mach numbers—the resulting temperature separation curves are identical. This is the first known documentation of such a finding. The results suggest that nozzle velocity is fundamental to scaling the performance of a vortex tube, while the nozzle volumetric heat capacity is also relevant to its behavior.

Rapid Adsorption of Magnetite Nanoparticles from Recycled Mill Scale Waste as Potential Adsorbent for Removal of Cu(II) Ions

The present study was conducted to establish adsorbent potential of magnetite nanoparticle ferrous ferric oxide (Fe3O4) for removal of Cu(ll) ions in wastewater. In the study, Fe3O4 was prepared by synthesizing low-cost recycled mill scale waste in an aqueous solution. Samples of scale wastes were milled and ground using high-energy ball milling (HEBM) at three milling times of 5, 7 and 9 hours. Extraction of Fe3O4 was accomplished by magnetic separation technique (MST) and Curie temperature separation technique (CTST). The morphologies and structural properties of Fe3O4 were characterized by using X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and Fourier-transform infrared spectroscopy (FTIR). HRTEM yielded images in the range of 10-22 nm. Maximum adsorption capacity, qe,and percentage removal of Cu(II) ions were achieved at 4.45 mg/g and 62.61% respectively after 7 hours of milling time. The present study recorded the smallest particle size of Fe3O4 imparting high qe, and percentage removal of Cu (II) ion in an aqueous solution, suggesting its high adsorbent potential.

Numerical Simulations of Cryogenic Hydrogen Cooling in Vortex Tubes with Smooth Transitions

Improving efficiency of hydrogen cooling in cryogenic conditions is important for the wider applications of hydrogen energy systems. The approach investigated in this study is based on a Ranque-Hilsch vortex tube (RHVT) that generates temperature separation in a working fluid. The simplicity of RHVT is also a valuable characteristic for cryogenic systems. In the present work, novel shapes of RHVT are computationally investigated with the goal to raise efficiency of the cooling process. Specifically, a smooth transition is arranged between a vortex chamber, where compressed gas is injected, and the main tube with two exit ports at the tube ends. Flow simulations have been carried out using STAR-CCM+ software with the real-gas Redlich-Kwong model for hydrogen at temperatures near 70 K. It is determined that a vortex tube with a smooth transition of moderate size manifests about 7% improvement of the cooling efficiency when compared vortex tubes that use traditional vortex chambers with stepped transitions and a no-chamber setup with direct gas injection.

Alkali Activation of Metallurgical Slags: Reactivity, Chemical Behavior, and Environmental Assessment

Alkali-activated materials (AAMs) represent a promising alternative to conventional building materials and ceramics. Being produced in large amounts as aluminosilicate-rich secondary products, such as slags, they can be utilized for the formulation of AAMs. Slags are partially crystalline metallurgical residues produced during the high temperature separation of metallic and non-metallic materials in the steelmaking processes. In the present study, the electric arc furnace carbon or stainless steel slag (EAF) and secondary metallurgical slag such as ladle furnace basic slag (LS) were used as precursors in an alkali-activation process. EAF slag, with its amorphous fraction of about 56%, presented higher contents of soluble Si and Al species with respect to ladle slag R (35%). However, both are suitable to produce AAM. The leaching behavior shows that all the release values are below the regulation limit. All the bivalent ions (Ba, Cd, Cu, Ni, Pb, and Zn) are well immobilized in a geopolymeric matrix, while amphoteric elements, such as As and Cr, show a slight increase of release with respect to the corresponding slag in alkaline and aqueous environments. In particular, for Sb and As of AAM, release still remains below the regulation limits, while Mo presents an increase of leaching values that slightly exceeds the limit for landfill non-dangerous waste.

Quantifying the High-Temperature Separation Behavior of Lamellar Interfaces in γ-Titanium Aluminide Under Tensile Loading by Molecular Dynamics

γ-titanium aluminide (TiAl) alloys with fully lamellar microstructure possess excellent properties for high-temperature applications. Such fully lamellar microstructure has interfaces at different length scales. The separation behavior of the lamellae at these interfaces is crucial for the mechanical properties of the whole material. Unfortunately, quantifying it by experiments is difficult. Therefore, we use molecular dynamics (MD) simulations to this end. Specifically, we study the high-temperature separation behavior under tensile loading of the four different kinds of lamellar interfaces appearing in TiAl, namely, the γ/α2, γ/γPT, γ/γTT, and γ/γRB interfaces. In our simulations, we use two different atomistic interface models, a defect-free (Type-1) model and a model with preexisting voids (Type-2). Clearly, the latter is more physical but studying the former also helps to understand the role of defects. Our simulation results show that among the four interfaces studied, the γ/α2 interface possesses the highest yield strength, followed by the γ/γPT, γ/γTT, and γ/γRB interfaces. For Type-1 models, our simulations reveal failure at the interface for all γ/γ interfaces but not for the γ/α2 interface. By contrast, for Type-2 models, we observe for all the four interfaces failure at the interface. Our atomistic simulations provide important data to define the parameters of traction–separation laws and cohesive zone models, which can be used in the framework of continuum mechanical modeling of TiAl. Temperature-dependent model parameters were identified, and the complete traction–separation behavior was established, in which interface elasticity, interface plasticity, and interface damage could be distinguished. By carefully eliminating the contribution of bulk deformation from the interface behavior, we were able to quantify the contribution of interface plasticity and interface damage, which can also be related to the dislocation evolution and void nucleation in the atomistic simulations.