On explosive boiling of a multicomponent Leidenfrost drop

The gasification of multicomponent fuel drops is relevant in various energy-related technologies. An interesting phenomenon associated with this process is the self-induced explosion of the drop, producing a multitude of smaller secondary droplets, which promotes overall fuel atomization and, consequently, improves the combustion efficiency and reduces emissions of liquid-fueled engines. Here, we study a unique explosive gasification process of a tricomponent droplet consisting of water, ethanol, and oil ("ouzo"), by high-speed monitoring of the entire gasification event taking place in the well-controlled, levitated Leidenfrost state over a superheated plate. It is observed that the preferential evaporation of the most volatile component, ethanol, triggers nucleation of the oil microdroplets/nanodroplets in the remaining drop, which, consequently, becomes an opaque oil-in-water microemulsion. The tiny oil droplets subsequently coalesce into a large one, which, in turn, wraps around the remnant water. Because of the encapsulating oil layer, the droplet can no longer produce enough vapor for its levitation, and, thus, falls and contacts the superheated surface. The direct thermal contact leads to vapor bubble formation inside the drop and consequently drop explosion in the final stage.Comment: 8 pages, 5 figure

Study on the treatment of fluorine-containing wastewater by precipitation-adsorption process

Fluorine-containing wastewater from the Yuncheng Sewage Treatment Plant in Heze City, Shan-dong Province was treated by coagulation and precipitation with poly aluminum sulfate, and CaO chemical precipitation-activated carbon adsorption, with a view to reducing fluoride ions concentration in the wastewater to below the discharge standard. The results showed that the optimum conditions for the coagulation-sedimentation test of poly aluminum sulfate were as follows: the dosage of poly aluminum sulfate 0.3 g/dm3, initial pH value 4.0, the removal rate of fluoride ion in the fluorine-containing wastewater reached 98.46%, and the concentration of fluoride ion was 0.462 mg/ dm3, which reached the discharge standard (1.5 mg/ dm3); The optimum conditions for the CaO chemical precipitation, and lanthanum loaded activated carbon adsorption method were as follows: the amount of CaO 20 g/ dm3, initial pH of the chemical precipitation test 8.0, the dosage of lanthanum loaded activated carbon 10 g/ dm3, and the initial pH of the adsorption test 6.0. At this time, the removal rate of fluoride ions in the fluorine-containing wastewater reached 95.81%, and the concentration of fluoride ions was 1.26 mg/ dm3, which also met the discharge standard

Structure and dynamics of water adsorbed on the lignite surface: Molecular dynamics simulation

The effects of oxygen-containing functional groups on the structure and dynamic properties of water molecules near a lignite surface were investigated through molecular dynamics (MD) simulations. Because of its complex composition and structure, a graphite surface containing hydroxyl, carboxyl, and carbonyl groups was used to represent the lignite surface model. According to X-ray photoelectron spectroscopic (XPS) results, the composing proportion of hydroxyl, carbonyl and carboxyl is 21:13:6. The density profiles of oxygen and hydrogen atoms indicate that the brown coal surface characteristics influence the structural and dynamic properties of water molecules. The interfacial water is much more ordered than bulk water. The results of the radial distribution functions, mean square displacements, and local self-diffusion coefficients for the water molecules in the vicinity of three oxygen-containing functional groups confirmed that carboxyl groups are the preferential adsorption sites

Adsorption behavior and XPS analysis of nonylphenol ethoxylate on low rank coal

In this work, low rank coal was used for the removal of nonylphenol ethoxylate with fifteen ethylene oxide groups (NPEO15) from aqueous solutions at different contact times, temperatures, and initial adsorbent concentrations. The adsorption isotherms showed good fit with the Langmuir equation. Maximum adsorption capacities calculated at 308, 318, and 328 K were 23.64, 29.41, and 35.71 mg g–1, respectively. The changes in the free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were calculated in order to predict the nature of adsorption. The results of the thermodynamic analysis indicated that a spontaneous process took place, driven synergistically by both enthalpy and entropy. The adsorption kinetics of NPEO15 were consistent with a pseudo-second order reaction model. XPS results showed that the oxygen functional groups on the low rank coal surface were significantly covered by NPEO15. Furthermore, while the content of C–C/C–H functional groups increased significantly, that of C–O functional groups decreased after absorption. These results clearly indicate that low rank coal is more hydrophobic and displays better floatability

Preparation of Portland Cement with Gold Ore Tailings

The disposal of gold ore tailings (GTs) has been a very difficult problem for a long time. Thus, this study explored a new approach to the management of GTs by preparing Portland cement. Physical properties, reaction mechanisms, and hydration product types of cement prepared with GTs (C-GTs) and ordinary Portland cement (C-SS) were compared. X-ray diffraction (XRD), thermogravimetric (TG), and scanning electron microscope energy-dispersive spectroscopy (SEM-EDS) analysis techniques were used to study the mineralogical phases of the clinker and raw materials, hydration product types, and microtopography. The consistency, setting time, flexural strength and compressive strength values of the cement samples (C-GTs and C-SS), and burnability of the raw materials were also studied. The burnability analysis indicated that GTs provided a higher reactivity. The XRD results showed that the clinker phases of the C-GTs were C3S, C2S, C3A, and C4AF. The XRD, TG, and SEM-EDS results showed that the hydration products were flaky calcium hydroxide, rod-shaped ettringite, and granular C-S-H gels. Its compressive strength and flexural strength were, respectively, 30.4 MPa and 6.1 MPa at the curing age of 3 days and 59.1 MPa and 9.8 MPa at the curing age of 28 days, which were slightly higher than those of the C-SS. Furthermore, the results showed that the consistency, initial setting time, and final setting time for the two kinds of cement were similar, which further suggested that GTs could be used to prepare Portland cement

Effect of protein oxidation on the structural characteristics of hazelnut protein isolate

Abstract The oxidation and structural properties of hazelnut protein prepared from a low-temperature cold-pressed hazelnut meal were evaluated using three oxidative modification methods: AAPH (2,2'-azo(2-methylpropionamidine)dihydrochloride), MDA (malondialdehyde), and H2O2. The three different oxidants gradually increased the carbonyl content of the proteins, MDA from 1.91 to 8.87 nmol/m, AAPH (from 2.13 to 12.18 nmol/mg, and H2O2 from 2.28 to 13.72 nmol/mg, indicating that the hazelnut protein was oxidized. The carbonyl content of H2O2-modified hazelnut proteins was the highest, implying that the proteins were more susceptible to oxidation by hydroxyl radicals. FT-IR, intrinsic fluorescence spectra, surface hydrophobicity, and protein electrophoresis implied that oxidative modifications altered the secondary structure of hazelnut proteins, and promoted protein aggregation and cross-linking. In addition, the oxidative modification resulted in a larger particle size distribution of hazelnut proteins and a decrease in the zeta potential absolute value, indicating a decrease in the hazelnut proteins stability and the formation of soluble aggregates. Overall, incubation with AAPH, MDA, and H2O2 significantly affected the structure of hazelnut proteins, demonstrating that hazelnut proteins in food processing systems are susceptible to structural and property changes due to different oxidation products

Study on Microstructure Evolution of Oolitic Hematite during Microwave Fluidization Roasting

To explore the microstructure evolution of oolitic hematite during microwave fluidization roasting, COMSOL multiphysics and scanning electron microscopy (SEM)–energy-dispersive spectrometry (EDS) were used to simulate and explore the microstructure evolution. The simulation results indicated that with the extension of microwave heating time and the increase of microwave power, the surface temperature in the particle model progressively increased, and the heating rate of hematite was the fastest, followed by quartz and apatite; simultaneously, the temperature stress and difference between the three mineral interfaces in the model were increased. The SEM–EDS results illustrated that there were microcracks at the interface between iron minerals and gangue minerals, such as quartz and apatite, and the microcracks were more obvious at the interface between iron minerals and quartz minerals. With the extension of microwave treatment time, the microcracks were gradually extended and expanded inward along the outer edge of oolitic and gradually formed in the core of the oolitic structure. Appropriately increasing the roasting temperature, prolonging the roasting time, and increasing the CO concentration made the particle surface more loose and rough, and produced more cracks and pores, while the ore surface presented a honeycomb morphology

Cost-Effective and High Purity Valuable Metals Extraction from Water Leaching Solid Residues Obtained as a By-Product from Processing the Egyptian Boiler Ash

The water leaching solid residues (WLSR) obtained from salt-roasting Egyptian boiler ash are considered an essential secondary resource for (13%) nickel and (5.6%) zinc extraction. Hence, the current study aims for the cost-effective and high purity Ni, Zn, Fe and Mg metal ion extraction from (WLSR) using a sulfuric acid leaching process. The factors affecting the percentage recovery of Ni, Zn, Fe and Mg from WLSR, including leaching temperature, time, acid concentration and solid/liquid ratio, have been investigated. The obtained leaching solutions were analyzed chemically using ICP, and the different precipitates were analyzed mineralogically using XRD and EDX analysis and chemically using XRF. The maximum percentage recovery of Ni, Zn, Fe and Mg was 95.02%, 90.13%, 66.29% and 75.73%, which was obtained under the optimum leaching conditions of 8% H2SO4 concentration and 1/15 solid/liquid ratio at 85 °C for 240 min. The effect of pH, Fe2O3 dosage as nucleating agent and the precipitation duration on iron removal and Ni and Zn loss have been thoroughly studied. It has been found that >95% of the contained iron impurity can be removed, while nickel and zinc losses are around 4.2% and 3.8%, respectively. Additionally, a pH of 6 and 0.45 mol/L concentration of H2C2O4 was utilized to precipitate Mg as MgC2O4.2H2O, demonstrating that the precipitation efficiency of Mg reaches 96.9%. Nickel and zinc precipitation efficiency was 92.25% and 85.51%, respectively, by raising the solution pH to approximately 9. The kinetic of Ni and Zn dissolution has been investigated to explain the mechanism prevalent and the factors influencing the leaching process. It has been found that the nickel leaching kinetic is controlled by both diffusion through an inert porous layer and by chemical reaction with an activation energy of 20.25 kJ.mol−1. Meanwhile, the kinetic of zinc leaching is controlled by solid product layer diffusion with an activation energy of 11.67 kJ mol−1

Electrochemical behaviour of the oxidative dissolution of arsenopyrite catalysed by Ag+ in 9K culture medium

Arsenopyrite (FeAsS) is the most common As-containing sulphide mineral in gold deposits. Most auriferous arsenopyrite ores are refractory necessitating pre-treatments before gold extraction. Bio-oxidation pre-treatment is simple and eco-friendly technology that has attracted significant attention in the past decade. Slow leaching kinetics of bioleaching is, however, a critical impedance to its large-scale application. The addition of metal cations has previously been found to expedite the leaching process. The electrochemical behaviour of Ag+ in the dissolution of arsenopyrite in 9 K culture medium was investigated in depth by a series of electrochemical and analytical techniques. Electrochemical results suggested that Ag+ could significantly improve the oxidative dissolution of arsenopyrite. Analytical results demonstrated that, with Ag+, only a discontinuous, porous and non-passivating film was formed on the arsenopyrite surface. The catalytic effect of silver is largely attributed to that Ag+ can enhance the oxidative dissolution of not only arsenopyrite but also the passive film by forming conducting Ag2S on the arsenopyrite surface, which explains why Ag+ can remove the passive film on the surface of arsenopyrite during bioleaching and thus effectively shorten its bioleaching period

Cost-Effective and High Purity Valuable Metals Extraction from Water Leaching Solid Residues Obtained as a By-Product from Processing the Egyptian Boiler Ash

The water leaching solid residues (WLSR) obtained from salt-roasting Egyptian boiler ash are considered an essential secondary resource for (13%) nickel and (5.6%) zinc extraction. Hence, the current study aims for the cost-effective and high purity Ni, Zn, Fe and Mg metal ion extraction from (WLSR) using a sulfuric acid leaching process. The factors affecting the percentage recovery of Ni, Zn, Fe and Mg from WLSR, including leaching temperature, time, acid concentration and solid/liquid ratio, have been investigated. The obtained leaching solutions were analyzed chemically using ICP, and the different precipitates were analyzed mineralogically using XRD and EDX analysis and chemically using XRF. The maximum percentage recovery of Ni, Zn, Fe and Mg was 95.02%, 90.13%, 66.29% and 75.73%, which was obtained under the optimum leaching conditions of 8% H2SO4 concentration and 1/15 solid/liquid ratio at 85 °C for 240 min. The effect of pH, Fe2O3 dosage as nucleating agent and the precipitation duration on iron removal and Ni and Zn loss have been thoroughly studied. It has been found that >95% of the contained iron impurity can be removed, while nickel and zinc losses are around 4.2% and 3.8%, respectively. Additionally, a pH of 6 and 0.45 mol/L concentration of H2C2O4 was utilized to precipitate Mg as MgC2O4.2H2O, demonstrating that the precipitation efficiency of Mg reaches 96.9%. Nickel and zinc precipitation efficiency was 92.25% and 85.51%, respectively, by raising the solution pH to approximately 9. The kinetic of Ni and Zn dissolution has been investigated to explain the mechanism prevalent and the factors influencing the leaching process. It has been found that the nickel leaching kinetic is controlled by both diffusion through an inert porous layer and by chemical reaction with an activation energy of 20.25 kJ.mol−1. Meanwhile, the kinetic of zinc leaching is controlled by solid product layer diffusion with an activation energy of 11.67 kJ mol−1