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A comprehensive study was conducted on the performance of M-promoted (M = 1%Ru, 1%Rh, 5%Ni) upgraded slag oxide metallurgical waste catalysts (M-UGSO) for hydrogen production by glycerol steam reforming (GSR). The results confirmed that the tendency of the incorporated metal to interact with Mg/Fe containing species within UGSO plays a key role in the surface availability of the corresponding metal, structural changes after reduction, and catalyst stability. Aside its best stability, 5% Ni-UGSO showed a performance (glycerol conversion to gaseous products of 100% and H2 yield of 74%) comparable with 1% Rh-UGSO (100% and 78%, respectively) or even surpassing that of 1% Ru-UGSO (94% and 71%, respectively), as noble metal-based catalysts. Synergistic cooperation was achieved by incorporated metals (M) and Fe/Mg containing species within UGSO, resulting in enhanced glycerol and water activation. The weakest results of Ru-UGSO could be justified by lack of propensity for MgO–RuO2 interaction on UGSO surface.

The intracellular level of nicotinamide adenine dinucleotide (NAD+) decreases with age, and this depletion seems to worsen during complex SARS-CoV-2 infections. Increasing the level of NAD+ via nicotinamide and nicotinamide riboside kinase routes may re-establish the antiviral poly-ADP-ribose polymerase functions of infected elderly persons and may potentially restrict SARS-CoV-2 infection by boosting innate immunity. In this work, we simulated nicotinamide synthesis in laminar flow microreactors with nitrile hydratase enzyme uniformly attached on the microchannel wall and/or immobilized on the surface of microparticles dispersed in the liquid phase. Hydrodynamic/diffusional limitations of laminar flow microreactors are greatly alleviated in intensified flow microreactors and microreactors with an enhanced enzymatic process, which greatly improves when nitrile hydratase loading on the surface of microparticles increases (more enzyme works as a free solution-phase enzyme). Enhanced nicotinamide synthesis in intensified flow microreactors generates high conversions even if an enzymatic module (attached enzyme on the channel wall or microparticle surface) does no work at optimal parameters. ©

Revalorization of mining residues is of central concerns to the mining industry and the environment. Specifically, environmental management of residual products from the exploitation of chrysotile in the Thetford Mines region is one of the government concerns in Quebec and Canada. This work uses mining wastes in a second resource generation for production of magnesium from cheap and health-friendly mineral sources; the goal being to produce chrysotile-depleted pre-concentrates for a use as precursors in the leach off extraction of magnesium. The concentration of lizardite/antigorite from chrysotile containing serpentine rock mine tailings originating from the Carey Mine site in East-Broughton (Québec) was carried out using a suite of hydrocyclone, settling/decantation and magnetic separations. Four size classes of the mining residue, namely (−3150,+1580), (−1580, +600), (−600, +300) and (−300, +150) μm, were tested with an aim to reduce the level of objectionable asbestos fibers to allow access to the safer Mg-bearing minerals contained in the mine waste sources. The asbestos fibers clean-up consisted of subjecting the sieved fractions to two hydrocyclone steps, six settling/decantation steps and two magnetic separation steps. The best results were achieved when the hydrocyclone separators led to Mg recovery of 85% (±4) for the coarsest size fraction size. Both hydrocyclone underflow streams underwent settling/decantation separations. The settling tests lasted 30 min and led to Mg recoveries of 82.5% (±1.8) of Mg in the ultimate concentrate. SEM characterizations revealed that it was possible to reduce substantially the amount of chrysotile fibers to render the coarse-sized fraction in the mining waste usable while significantly lowering the health risk of the fibers. A two-step magnetic separation was applied to the final settling/decantation underflow to remove magnetic minerals such as magnetite from the lizardite/antigorite concentrate. The final quasi-non-magnetic chrysotile-depleted lizardite/antigorite concentrate allowed sample recovery of 62.5% (±0.9) wt. of Mg. These preliminary results are intended as a first compulsory step in support of viable restoration and sustainable development scenarios for the Thetford Mines mining sites as second-breath sources for valuable magnesium.

The present work focuses on the gasification of a single carbon-anode particle with CO2, using a detailed reaction-transport model based on the reaction intrinsic kinetics and transport of gaseous species. The model includes the mass conservation equations for the gas components and solid carbon particles, resulting in a set of nonlinear partial differential equations, being solved using numerical techniques. The model may predict the gas generation rate, the gas compositions, and the carbon consumption rate during the gasification of a carbon particle. Five kinetic models were compared to describe the gasification behavior of carbon particles. It was found that the random pore model (RPM) provided the best description of the reactivity of anode particles. The model also predicted the particle shrinkage during the gasification process. The model was validated using experimental results obtained with different particle size ranges, being gasified with CO2 at 1233 K. The experiments were performed in a thermogravimetric analyzer (TGA). Good agreement between the model results and the experimental data showed that this approach could quantify with success the gasification kinetics and the gas distribution within the anode particle. In addition, the Langmuir–Hinshelwood (L–H) model is used in order to capture the inhibition effect of carbon monoxide on the gasification reaction. The effectiveness factor and Thiele modulus simulated for various particle sizes helped assess the evolution of the relative dominance of diffusion and chemical reactions during the gasification process.

A marinization test rig comprising a hexapod/column/wire-mesh-sensor assemblage was used to emulate the liquid drainage onboard floating packed columns. Single and compounded rotations and translat...

In the flotation process, surface–reagent reactions occur on water precovered surfaces; therefore, investigation on the mineral–water interactions is essential in such systems. In the present study...

Reliance on harmless and renewable resources to mitigate process environmental footprint has become increasingly important for the design and operation of sustainable processes. One challenge that is prevalent in marine water surface contamination concerns treatment and recovery from oil spills where efforts are needed to design emergency units adapted to marine conditions. Potential candidates are naturally-grown porous loofa (bio-foam) materials which can be integrated in floating units transportable to the contamination area. For this purpose, a hexapod platform motion simulator was employed to emulate sea-driven floating movements of a column packed with two loofa bio-foam packings (dense and open-cell samples) and operated in cocurrent gas-liquid upflow mode. The column hydrodynamic behaviour was monitored by means of capacitance wire mesh sensors and electrical capacitance tomography for various inclination and rolling parameters. In the case of dense bio-foam packing, the relatively even distribution of gas and liquid in the vertical bed tended to degrade as the bed tilted up to 15°. Column rolling prompted fluid displacements in bed crosswise planes inducing notable amplitude oscillations of the local liquid saturation. Kerosene exhibited a strong foaming behavior with promotion of earlier inception of pulsing flow as a function of column inclination as compared to water.

The study provides insights for adapting commercially available packings to work on floating vessels in the marine context aiming at preserving performances similar to land-based packed-bed reactors. Specifically, liquid distribution for cocurrent gas-liquid downflow (Ug = 0.0065-0.131 m/s and Ul = 0.001-0.0078 m/s) inside monolith packings embarked on a hexapod emulator was compared against glass-bead containing trickle bed and open-cell foam packings using wire-mesh sensors under vertical, inclined and rolling column conditions. Sensitivity of the tested internals with regard to liquid maldistribution was diagnosed and analyzed in terms of a maldistribution factor for the vertical/inclined and rolling columns. Liquid maldistribution was found to prevail at high gas and low liquid superficial velocities for the tested three packings regardless of column conditions. Monolith packed beds demonstrated superior robustness to counteract liquid maldistribution induced by bed static inclinations and roll motion...

Gas solubility can go beyond classical bulk-liquid Henry's law saturation under the nanoconfinement of a liquid phase. This concept establishes the foundation of the current study for developing a novel catalytic system for transformation of carbon dioxide to cyclic carbonates at mild conditions with major emphasis on application for CO2 capture and utilization. A series of mesoporous silica-based supports of various pore sizes and shapes grafted with a quaternary ammonium salt is synthesized and characterized. CO2 sorption in styrene oxide, either in bulk or nanoconfined state, as well as catalytic reactivity for CO2 transformation into styrene carbonate, are experimentally evaluated. The family of mesoporous catalysts with aligned cylindrical pores (MCM-41 and SBA-15) with pore sizes ranging from 3.5 to 9 nm exhibit enhanced sorption of CO2 in nanoconfined styrene oxide with maximum sorption capacity taking place in MCM-41 with the smallest pore size. The catalysts with interconnected cylindrical pores (KIT-6) with pore sizes ranging from 4.5 to 8.7 nm showed CO2 solubilities almost equal to the bulk solubility of styrene oxide. Monte Carlo simulations revealed that the oversolubility in styrene oxide confined complex is directly related to the density of adsorbed solvent in the nanopore, which is less than its bulk density. Catalytic reactivities correlate with CO2 sorption enhancement, showing higher turnover frequencies for catalysts having higher CO2 sorption capacity. The turnover frequency is increased by a factor of 7.5 for grafted MCM-41 with the smallest pore size with nanoconfined styrene oxide in comparison to the homogeneous reaction implemented in bulk.

An integrated process combining CO2 reduction with hydrogen under plasma conditions and catalytic methanol synthesis offers an encouraging option for the conversion of CO2 from exhaust gas marine e...

The present work aims to investigate, experimentally, analytically and computationally, the removal of a light yield stress fluid displaced by a slightly heavier Newtonian fluid, in a long vertical pipe. The fluids of interest are miscible and the displacement flow is downward. In general, the flow is controlled by at least four dimensionless numbers, and their combinations, namely the Newtonian Bingham number, 0 ≤ BN ≤ 18600, the viscosity ratio, 1 χ = 2 R e N / F r 2 ≈ 120 . Third, for fluid flows with BN ≳ 100, the residual layer patterns can be classified into three distinct sub-regimes, including corrugated, wavy and smooth regimes, as a function of R e N / ( B N + m ) and ReN/Fr. Fourth, to analyse secondary displacement front features, the experiments are phenomenologically classified into central and periphery displacements, for which the transition can be reasonably predicted by an appropriate analytical model. However, the long time displacing front velocities cannot be estimated by the analytical model. Finally, computational fluid dynamics simulations in a simpler channel geometry demonstrate that some of the complex displacement flow features may be predicted computationally.

Dissolution in choline-chloride based deep eutectic solvents (DES) of rare earth elements (REE) from high-purity single carbonate salts of Y, La, Ce, Nd and Sm and from their multicomponent mixtures and also bastnasite mineral was assessed with a prospect to gain an understanding on the leaching behavior of bastnasite ores as REE source from DES suspensions. Urea, malonic acid and citric acid were used in different proportions with choline chloride in order to form deep eutectic solvents with desired viscosity and functionality. The results obtained prove promising for use insolvato-metallurgical processes in terms of selective dissolution of the higher-atomic-number (Z) rare earth elements at the expense of the lower-ZREEs and the gangue-originating metal impurities, thus initiating separation among the different REE members from the early hydrometallurgical steps.

Offshore oil/gas industries have been employing multiphase scrubbers and reactors to treat hydrocarbons extracted from undersea reservoirs. Operation of floating scrubbers and reactors on nonstationary platforms undergoes remarkable technical and operational challenges stemming from the complex sea states. Indeed, ship tilts and motions affect the reactor hydrodynamics and consequently its chemical performance. Therefore, imperatives for predicting and controlling the performance of offshore reactors by accounting for the contribution of marine swells have opened up considerable opportunities for research. This contribution presents an extensive chemical engineering overview on experimental and theoretical studies related to the effect of floating vessel motions on the performance of multiphase reactors and scrubbers. Cocurrent downflow, cocurrent upflow, and countercurrent gas–liquid packed beds, spinning gas–liquid packed beds, gas–solid fluidized bed, and bubble columns are reviewed with an emphasis on...

Using a hexapod ship motion emulator, the influence of floating vessel motion on the trajectory and velocity profile of single ellipsoidal bubbles is investigated from the images provided by a high...

Aqueous mineral carbonation of brucite is an important mineralization route for carbon capture and sequestration. Prerequisite to mineral carbonation are the simultaneous CO2 absorption and brucite...

Common rare earth (RE) minerals, such as bastnasite and monazite, may be formed in deposits associated with carbonate gangue, such as calcite and dolomite. Sodium oleate is a widely used collector for the flotation of both RE and gangue minerals, which might, therefore, be an inefficient process due to the lack of selectivity of this collector. Since these minerals are also sparingly soluble in solution, they could release their constituent ions into the solution, which could affect the floatability of other minerals. In this study, the interactions of sodium oleate with bastnasite and monazite in the presence of dissolved dolomite species have been investigated. Microflotation tests were carried out to explore the effects of these dissolved species on the floatability of the RE minerals. Zeta potential measurements and XPS characterization were carried out to understand how the species affect the collector adsorption. To complement these characterizations, density functional theory (DFT) simulations were conducted to investigate the collector-mineral and collector-adsorbed species (on the mineral surface) interactions. The results show that collector-dolomite interaction energy is greater than that of collector-adsorbed species, but lower than collector-monazite interaction energy, explaining the decrease in the minerals' recovery upon exposure to the dissolved mineral species. It is also shown that oleate ions (Ol–) have the strongest interaction with the minerals compared to other oleate species such as acid soap (HOl2–) and oleate dimer (Ol22−). The behavior (strength and selectivity) of sodium oleate towards RE minerals and dolomite, as compared to other RE mineral collectors (such as aromatic hydroxamate), is attributed mainly to the collector's and the minerals' structure. The long hydrocarbon chain of sodium oleate which imparts hydrophobic characteristic to the minerals, makes it stronger collector than benzohydroxamate. Moreover, sodium oleate (with linear structure), unlike the aromatic hydroxamate, can approach the mineral easier due to lesser steric hindrance effect and higher reactivity of O involved in the interaction, making it less selective. In addition, it can interact easily with dolomite due to the presence of more exposed active sites than RE minerals.

Gold-bearing ores, especially the sulphidic ones, are often treated by flotation prior to cyanidation. Following flotation process, the flotation concentrate or tailings are redirected to the cyanidation circuit for gold extraction that may contain appreciable amounts of collector used in flotation, and also remained sulfide minerals, i.e., predominantly pyrite. This current research examines the effect of collector on gold leaching by conditioning gold prior to cyanidation and direct addition in cyanidation in a packed bed leach reactor. Effects of pyrite, and solid-liquid separation on gold leaching and its electrochemical behaviour in presence of collector were also investigated. It was found that conditioning of gold with Aerophine 3418A in absence of pyrite has a detrimental effect especially on leach kinetics of gold since it adsorbs onto gold and decreases its further dissolution. In presence of pyrite, a significant improvement was obtained in gold leaching due to the positive galvanic interactions. These findings suggest that although collector adsorption adversely affects gold leaching, i.e., partial passivation, yet galvanic interactions could continue to enhance its extraction. Following conditioning, solid-liquid separation prior to cyanidation is shown to moderately increasing gold leaching by up to 10%. When Aerophine 3418A was added directly during cyanidation, gold leaching showed a slight increase in absence of pyrite. Conversely, in presence of pyrite, a significant increase in gold leaching was observed. Moreover, if collector was added after the first one hour of cyanidation, gold leaching kinetics was enhanced. Cyclic voltammetry tests within open circuit potential findings support the cyanide leaching results. SEM-EDS analysis of leach residues has demonstrated that there is less amount of gold in the residue both when pyrite is present and collector is added directly. XPS analyses have confirmed the presence of metallic gold in leach residues. These results have revealed the effect of Aerophine 3418A on gold leaching is different when it is directly added than that of conditioning and the positive galvanic effect of pyrite occurs even in the presence of collector.

Cytochromes P450 are a vast and important class of heme monooxygenases with a broad range of substrates and corresponding functions. Decades of studies attest that enzymatic processes with many mem...

Two-phase countercurrent flow dynamics and simultaneous CO2 and H2S removal performance were studied in countercurrent randomly packed-bed columns with fourth generation Raschig super-Rings exposed to static inclination and heaving motion via an unsteady-state comprehensive three-dimensional model. Gas-liquid countercurrent flow displays a gradual deviation to axial symmetry with the increase of angle of the packed-bed column inclination. CO2 absorption process is negatively impacted in inclined packed-bed columns and the deficit in CO2 removal performance increases with the increase of H2S concentration in gas phase. H2S removal efficiency is marginally reduced and mostly at considerable packed bed inclinations. Under heaving motion of the packed-bed column, an oscillatory two-phase flow and CO2-monoethanolamine (MEA) absorption process performance develop around the steady-state solution of the column stationary state prior to heaving application. As externally-generated packed-bed column oscillations, the heaving motion impacts more CO2 absorption because of very high rate constant of the reaction between H2S and MEA and because the packed-bed column is exposed only to small episodes of time to maximum/minimum heaving acceleration where H2S removal efficiency can be affected.

Understanding the interactions of amino acids with minerals is crucial for selecting the peptide-based reagents of interest in environmentally friendly ore separation applications. This study aimed to simulate archetypal alanine/water/ZnS complexes through DFT by including explicit water molecules on defectless and sulfur-deficient sphalerite. Swarms of water molecules up to a multilayer were introduced into the simulation cells in order to examine the different types of surface interactions in the solvated mode. Using the grand canonical Monte Carlo method, an efficient strategy was also proposed to diversify the highly plausible initial configurations. Our results revealed that solvated alanine disinclines to form a covalent bond with the defect-free sphalerite surface, thereby the higher affinity toward the neighboring water molecules. On the contrary, sulfur-depleted ZnS surfaces were the siege of stable monodentate bonds between the solvated alanine and Zn atoms around the pruned vacancy site. In particular, our study suggests that the level of interactions between solvated alanine and ZnS can be controlled by tuning the density of sulfur vacancy on the ZnS surface.

Selective solvent extraction of molybdenum over rhenium from molybdenite (MoS2) flue dust leaching solution was studied. In the present work, thermodynamic calculations of the chemical equilibria in aqueous solution were first performed, and the potential–pH diagram for the Mo–Re–SO42−–H2O system was constructed. With the gained insight on the system, 2-ethylhexyl phosphonic acid mono-(2-ethylhexyl)-ester (PC88A) diluted in kerosene was used as the extractant agent. Keeping constant the reaction temperature and aqueous-to-organic phase ratio (1:1), organic phase concentration and pH were the studied experimental variables. It was observed that by increasing the acidity of the solution and extractant concentration, selectivity towards Mo extraction increased, while the opposite was true for Re extraction. Selective Mo removal (+95%) from leach solution containing ca. 9 g/L Mo and 0.5 g/L Re was achieved when using an organic phase of 5% PC88A at pH = 0. No rhenium was coextracted during 10 min of extraction time at room temperature. Density functional theory (DFT) calculations were performed in order to study the interactions of organic extractants with Mo and Re ions, permitting a direct comparison of calculation results with the experimental data to estimate selectivity factors in Mo–Re separation. For this aim, PC88A and D2EHPA (di-(2-ethylhexyl) phosphoric acid) were simulated. The interaction energies of D2EHPA were shown to be higher than those of PC88A, which could be due to its stronger capability for complex formation. Besides, it was found that the interaction energies of both extractants follow this trend considering Mo species: MoO22+ > MoO42−. It was also demonstrated through DFT calculations that the interaction energies of D2EHPA and PC88A with species are based on these trends, respectively: MoO22+ > MoO42− > ReO4− and MoO22+ > ReO4− > MoO42−, in qualitative agreement with the experimental findings.