ACS Engineering Au最新文献

Omega-3 polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA, C20:5), are crucial dietary fats known for their numerous health benefits. However, traditional sources of EPA, like fish oil, raise sustainability and environmental concerns, underscoring the need for alternative production methods. The engineered oleaginous yeast Yarrowia lipolytica has emerged as a promising candidate for sustainable production of EPA. This study explores the efficient production of EPA with an earlier engineeredY. lipolytica strain Y8412, utilizing waste cooking oil (WCO) as an alternative carbon source. While cofeeding WCO resulted in increased total lipid content, it also caused an increase in intracellular free fatty acid (FFA) levels, which can be toxic to cells and reduce EPA synthesis. To solve this issue, we first overexpressed FAA1 and GPD1 genes converting excess FFAs into triglycerides (TAGs). Additionally, we knocked out TGL3/4 genes, which encode lipases linked to lipid bodies, to minimize the degradation of TAGs back into FFAs. The modified strains significantly reduced intracellular FFA levels and improved EPA production. Notably, the TGL4 knockout strain Y8412T4^- showed 57% increase in EPA production titer and nearly 50% increase in carbon conversion yield compared to the parental strain Y8412 fed with glucose only. These findings suggest that preventing TAG degradation by knocking out TGL4 is an effective approach for enhanced EPA production when WCO is used to partially replace glucose as the carbon source. This study offers an effective engineering strategy for low-cost, high-yield, and sustainable production of omega-3 fatty acids from waste feedstocks.

We demonstrate optical coherence tomography (OCT) velocimetry with in-line processing of complex fluids for the first time. The OCT measurements were performed on a perspex section of a test rig containing ∼40 L of complex fluids, analogous to real-world manufacturing conditions. Opaque solutions of lamellar surfactant gel networks (LGNs) and powdered milk were explored. Velocity profiles characteristic of power law fluids were found in the LGNs, in good agreement with independent measurements of the flow rate and off-line determination of viscosity. The velocity fluctuations of 3.4 pL volumes of the fluids in the test rig were also explored. LGNs demonstrated smooth, steady flows, whereas the powdered milk demonstrated marked instability, both showing intermittent behavior and Kolmogorov scaling for fully developed classical turbulence of Newtonian fluids (P(ω) ∼ ω^-5/3, where P(ω) is the power spectral density of the velocity fluctuations, and ω is the frequency). The effects of dynamic changes in formulation on velocimetry measurements could be observed with LGNs during the addition of salt and with the milk powder due to biofouling.

The utilization of single-atom and nanocluster catalysis in various chemical processing industries and applications is well-established. Their monodispersity and well-defined arrangement facilitate their interrogation of the fundamental physical properties necessary for the significant application in structural composites, electrical devices and catalytic chemical reactions, particularly in high-temperature environments. Hydrogen peroxide (H₂O₂) stands out as a highly effective oxidizing agent, distinguished by its environmentally benign nature, as it yields only water as a byproduct postredox process. Their versatility of H₂O₂ spans diverse fields including pulp and paper bleaching, disinfection, detergent formulation, chemical synthesis, textile manufacturing and electronic production. This paper aims to elucidate recent advancements in engineering single-atoms and nanocluster-based photocatalysts, emphasizing their evolving structural modification strategies, catalytic mechanisms, synthesis methodologies and the mechanisms underlying H₂O₂ production. Furthermore, this review underscores the potential future application of these catalysts in environmental treatment, particularly in the context of H₂O₂ production. By focusing on the functionality and efficacy of employing SACs for H₂O₂ production, this study aims to inform the development of future implementations to mitigate environmental impacts. Consequently, these materials emerge as promising candidates for environmentally friendly applications including refined fuel production and associated environmental treatment processes.

Conventional leaching, the standard method for gold extraction, involves using a cyanide solution to dissolve gold from the ore. However, this process is often ineffective for refractory ores due to the presence of sulfide minerals. This study aims to improve the efficiency of gold extraction from refractory ores by introducing an oxidative pretreatment step using a calcium hypochlorite. This compound plays a crucial role in the process as it facilitates the oxidation of the sulfide minerals, mainly pyrite and quartz. The study also investigates how this approach affects oxidation at different temperatures and pressures inside a titanium reactor at 600 rpm. After the pretreatment, the mineral is in contact with a solution of sodium cyanide (1000 ppm) inside a stirred reactor (300 rpm) under atmospheric conditions. Some results obtained were more than 60% extraction of gold, but there were conditions under which gold extraction was less than 40%. The effect of the concentration of calcium hypochlorite 10 and 30 wt % was more significant compared with the temperature (25, 60, and 80 °C) and oxygen pressure (80 and 120 psi). This effect is due to a protective layer confirmed in the characterization using scanning electron microscopy (SEM-EDS) of the solid material previously leached.

[This corrects the article DOI: 10.1021/acsengineeringau.4c00027.].

The counter-current downers have the potential to combine the hydrodynamic characteristics of co-current risers and downers with less back-mixing and improved solid holdup. However, flooding may occur when particles suspend or reverse the flowing direction under increasing superficial gas velocity or solid mass flux. Here, we evaluate transported bed configurations by coupling the counter-current downer with a riser reactor to take advantage of the flooding behaviors. We analyze the theoretical hydrodynamics in risers and co- and counter-current downers from particle mechanics to cluster development. By validation with experimental results from the literature, we determine the proper simulation strategy for counter-current downers using computational particle fluid dynamics by replacing the particle size with empirically calculated cluster size. We investigate the effects of superficial gas velocity and solid mass flux with Geldart group A particles until beyond the flooding point of the counter-current downer. The coupled riser–counter-current downer reactor configuration offers more uniform axial and dynamic radial solid distribution while keeping a relatively high solid holdup to better utilize the reactor volume for enhanced gas–solid contact. The fluidization regime diagram by the Richardson–Zaki equation fails to capture the counter-current operation, so we provide a separate graph to mark the limitation of the coupled and decoupled riser and counter-current downer reactor configurations.

Decentralized electrochemical reduction of nitrate into ammonium is explored as a viable approach to mitigate nitrate accumulation in groundwater. In this study, tubular porous electrodes made of titanium (termed hollow fiber electrodes or HFEs) were successfully modified with silver (Ag) nanoparticles through electrodeposition. Under galvanostatic control and in acidic electrolyte, Ag deposition on Ti HFE resulted in an increase in the Faradaic efficiency for ammonium formation from low concentrations of nitrate (50 mM), but only under reaction conditions of restricted mass transport. For conditions of favorable transport, facilitated by an inert gas flow (Ar) exiting the pores, a higher nitrate conversion but an increase in hydroxylamine selectivity at the expense of the ammonium selectivity are observed for Ti/Ag hollow fiber electrodes. For Ti/Ag electrodes, it is concluded that ammonium formation is prevented by effective removal of surface intermediates. Remarkably, for unmodified Ti hollow fiber electrodes, the Faradaic efficiency to ammonium is significantly improved when operated at high current densities and in conditions of high mass transport. The selectivity to liquid products even surpasses the selectivity of Ti/Ag electrodes. These findings indicate that nitrate reduction to ammonium at Ti and Ti/Ag hollow fiber electrodes can be achieved at comparable rates but under distinctly different process conditions. In fact, for Ti electrodes, operation at a lower applied potential compared to Ti/Ag electrodes is feasible, ultimately resulting in reduced energy consumption. This study thus highlights the importance of controlling the interfacial electrode environment, particularly when comparing and evaluating the effectiveness of electrode materials in electrochemical nitrate reduction. The study also reveals that transport phenomena affect electrode material-dependent activity-selectivity correlations and must be considered in ongoing material development efforts.

On account of the use of platinum group metals (PGMs) as active materials in proton exchange membrane water electrolyzer (PEMEL) cells, development of recycling processes for fine catalyst materials is indispensable for further scale-up of hydrogen production. By applying a contrast in (de)wetting ability of the materials, ultrafine particles have the potential to be separated for recycling. The limitation of particle size in froth flotation technology can be overcome by adding oil droplets to the system. This study investigates the selective separation of ultrafine particles by applying hydrophobic high internal phase (HIP) water-in-oil emulsion containing only 5% of organic liquid emulsified as a double emulsion in the particle dispersion. Hydrophobic cathode particles (i.e., carbon black) are selectively agglomerated in this system, allowing 90% of the feed to be recovered in the froth phase. The recovery rate was also significantly higher than that using the same amount of pure oil promoter, kerosene. In the binary particle system, 70% of the target particles are recovered with 90% grade by adding 2.8% hydrophobic double emulsion.