Search2019 Vol. 26, No. 1
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2019, vol. 26, no. 1, pp.
1-10.
https://doi.org/10.1007/s12613-019-1704-1
Abstract:
In this study, pentlandite was selectively separated from serpentine using magnetic coating technology by adjusting and optimizing pH, stirring speeds, magnetic field intensities, and dosages of sodium hexametaphosphate (SHMP) and sodium oleate (SO). A magnetic concentrate with Ni grade of 20.8% and Ni recovery of 80.5% was attained under the optimized operating conditions. Considering the above, the adsorption behaviors of SHMP and SO and the surface properties of minerals after the magnetic coating were studied by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that magnetite was preferentially coated on the pentlandite surfaces and sparingly coated on the serpentine surfaces in the presence of SHMP and SO. Furthermore, calculations by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory indicate that the preferential adsorption of magnetite on the pentlandite surfaces is due to the presence of a hydrophobic interaction between the magnetite and pentlandite, which is much stronger than the interaction between magnetite and serpentine.
In this study, pentlandite was selectively separated from serpentine using magnetic coating technology by adjusting and optimizing pH, stirring speeds, magnetic field intensities, and dosages of sodium hexametaphosphate (SHMP) and sodium oleate (SO). A magnetic concentrate with Ni grade of 20.8% and Ni recovery of 80.5% was attained under the optimized operating conditions. Considering the above, the adsorption behaviors of SHMP and SO and the surface properties of minerals after the magnetic coating were studied by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that magnetite was preferentially coated on the pentlandite surfaces and sparingly coated on the serpentine surfaces in the presence of SHMP and SO. Furthermore, calculations by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory indicate that the preferential adsorption of magnetite on the pentlandite surfaces is due to the presence of a hydrophobic interaction between the magnetite and pentlandite, which is much stronger than the interaction between magnetite and serpentine.
2019, vol. 26, no. 1, pp.
11-20.
https://doi.org/10.1007/s12613-019-1705-0
Abstract:
In this study, strontium nitrate extraction from celestite in nitric acid solutions was investigated using the leaching method. The influences of acid concentration, solid-to-liquid ratio, stirring speed, and reaction temperature on the leaching of strontium from celestite concentrate were studied. The results showed that the leaching rate increased with increasing acid concentration, stirring speed, and temperature and decreased with increasing solid-to-liquid ratio. The particle size was fixed in all of the dissolution experiments. The results showed that the stirring speed and the temperature were the most influential parameters with respect to the leaching process. The kinetic model best fit control by diffusion through the product layer. The activation energy of the dissolution celestite in nitric acid solutions was calculated to be 42.22 kJ/mol.
In this study, strontium nitrate extraction from celestite in nitric acid solutions was investigated using the leaching method. The influences of acid concentration, solid-to-liquid ratio, stirring speed, and reaction temperature on the leaching of strontium from celestite concentrate were studied. The results showed that the leaching rate increased with increasing acid concentration, stirring speed, and temperature and decreased with increasing solid-to-liquid ratio. The particle size was fixed in all of the dissolution experiments. The results showed that the stirring speed and the temperature were the most influential parameters with respect to the leaching process. The kinetic model best fit control by diffusion through the product layer. The activation energy of the dissolution celestite in nitric acid solutions was calculated to be 42.22 kJ/mol.
2019, vol. 26, no. 1, pp.
21-32.
https://doi.org/10.1007/s12613-019-1706-z
Abstract:
This study aims to investigate the leaching behavior and filtration performance of zinc refinery residue under hydrothermal conditions. The relationships between the structure and morphology of silicon in the leaching residue and the pulp filtration performance were explored by determining the pulp filtration speed, analyzing quantitatively the silicon content in the leachate, and characterizing the leaching residue structure. The results show that hydrothermal leaching induces the coagulation-hydrolysis of the silicon in solution, consequently altering the microstructure of the leaching residue, and that silicon oxygen tetrahedra ([SiO4]4-) form the main skeleton structure of the residue. The results obtained also show that the leaching rates of zinc and copper are 98.1% and 98.7%, respectively, and that the filtration speed is 526.32 L/(m2·h) under the conditions of sulfuric acid concentration of 140 g/L, leaching temperature of 160℃, leaching time of 3.0 h, oxygen partial pressure of 0.75 MPa, stirring speed of 600 r/min, and a liquid-to-solid ratio of 10 mL/g.
This study aims to investigate the leaching behavior and filtration performance of zinc refinery residue under hydrothermal conditions. The relationships between the structure and morphology of silicon in the leaching residue and the pulp filtration performance were explored by determining the pulp filtration speed, analyzing quantitatively the silicon content in the leachate, and characterizing the leaching residue structure. The results show that hydrothermal leaching induces the coagulation-hydrolysis of the silicon in solution, consequently altering the microstructure of the leaching residue, and that silicon oxygen tetrahedra ([SiO4]4-) form the main skeleton structure of the residue. The results obtained also show that the leaching rates of zinc and copper are 98.1% and 98.7%, respectively, and that the filtration speed is 526.32 L/(m2·h) under the conditions of sulfuric acid concentration of 140 g/L, leaching temperature of 160℃, leaching time of 3.0 h, oxygen partial pressure of 0.75 MPa, stirring speed of 600 r/min, and a liquid-to-solid ratio of 10 mL/g.
Recovery of vanadium and molybdenum from spent petrochemical catalyst by microwave-assisted leaching
2019, vol. 26, no. 1, pp.
33-40.
https://doi.org/10.1007/s12613-019-1707-y
Abstract:
The study of the leaching of vanadium (V) and molybdenum (Mo) from spent petrochemical catalysts in sodium hydroxide (NaOH) medium was performed using two approaches, namely, conventional leaching and microwave-assisted leaching methods. The influence of microwave power, leaching time, leaching temperature, and NaOH concentration on the leaching efficiency of spent petrochemical catalyst was investigated. Under microwave-assisted conditions (600 W, 10 min, 90℃, 2.0 mol·L-1 NaOH, and 0.20 g·mL-1 solid-liquid ratio), the leaching efficiencies of V and Mo reached 94.35% and 96.23%, respectively. It has been confirmed that microwave energy has considerable potential to enhance the efficiency of the leaching process and reduce the leaching time. It is suggested that the enhancement of the leaching efficiencies of V and Mo can be attributed to the existence of a thermal gradient between solid and liquid and the generation of cracks on the mineral surface.
The study of the leaching of vanadium (V) and molybdenum (Mo) from spent petrochemical catalysts in sodium hydroxide (NaOH) medium was performed using two approaches, namely, conventional leaching and microwave-assisted leaching methods. The influence of microwave power, leaching time, leaching temperature, and NaOH concentration on the leaching efficiency of spent petrochemical catalyst was investigated. Under microwave-assisted conditions (600 W, 10 min, 90℃, 2.0 mol·L-1 NaOH, and 0.20 g·mL-1 solid-liquid ratio), the leaching efficiencies of V and Mo reached 94.35% and 96.23%, respectively. It has been confirmed that microwave energy has considerable potential to enhance the efficiency of the leaching process and reduce the leaching time. It is suggested that the enhancement of the leaching efficiencies of V and Mo can be attributed to the existence of a thermal gradient between solid and liquid and the generation of cracks on the mineral surface.
2019, vol. 26, no. 1, pp.
41-51.
https://doi.org/10.1007/s12613-019-1708-x
Abstract:
Molasses was used as an alternative binder to the bentonite binder. The change in moisture absorption by pellets prepared with different iron ores and different molasses contents were investigated. Iron ore properties exerted the major effect on pellet behavior and final pellet quality. The absorbed moisture content of pellets prepared without binder, bentonite-added pellets, and molasses-added pellets were in the range of 7.72%-9.95%, 9.62%-10.84%, and 6.14%-6.69%, respectively. The wet pellet compressive strength of molasses-added pellets (43-230 N/pellet) was superior to that of bentonite-added pellets (9.47-11.92 N/pellet). The compressive strength of dried molasses-modified pellets increased to 222-394 N/pellet, which is currently the highest value achieved for dried pellets.
Molasses was used as an alternative binder to the bentonite binder. The change in moisture absorption by pellets prepared with different iron ores and different molasses contents were investigated. Iron ore properties exerted the major effect on pellet behavior and final pellet quality. The absorbed moisture content of pellets prepared without binder, bentonite-added pellets, and molasses-added pellets were in the range of 7.72%-9.95%, 9.62%-10.84%, and 6.14%-6.69%, respectively. The wet pellet compressive strength of molasses-added pellets (43-230 N/pellet) was superior to that of bentonite-added pellets (9.47-11.92 N/pellet). The compressive strength of dried molasses-modified pellets increased to 222-394 N/pellet, which is currently the highest value achieved for dried pellets.
2019, vol. 26, no. 1, pp.
52-63.
https://doi.org/10.1007/s12613-019-1709-9
Abstract:
Five advanced high-strength transformation-induced plasticity (TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets. Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the JMatPro© software. Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques. The nonmetallic inclusions were characterized by scanning electron microscopy. The results show that the contents of Si, C, Al, and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents. We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process. The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets.
Five advanced high-strength transformation-induced plasticity (TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets. Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the JMatPro© software. Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques. The nonmetallic inclusions were characterized by scanning electron microscopy. The results show that the contents of Si, C, Al, and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents. We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process. The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets.
2019, vol. 26, no. 1, pp.
64-75.
https://doi.org/10.1007/s12613-019-1710-3
Abstract:
Two austenitic Mn steels (Fe-17Mn and Fe-17Mn-3Al (wt%, so as the follows)) were subjected to thermomechanical processing (TMP) consisting of forging followed by solutionization and hot rolling. The rolled samples were annealed at 650 and 800℃ to relieve the internal stress and to induce recrystallization. The application of TMP and heat treatment to the Fe-17Mn/Fe-17Mn-3Al steels refined the austenite grain size from 169 μm in the as-solutionized state to 9-13 μm, resulting in a substantial increase in hardness from HV 213 to HV 410 for the Fe-17Mn steel and from HV 210 to HV 387 for the Fe-17Mn-3Al steel. The elastic modulus values, as evaluated by the nanoindentation technique, increased from (175±11) to (220±12) GPa and from (163±15) to (205±13) GPa for the Fe-17Mn and Fe-17Mn-3Al steels, respectively. The impact energy of the thermomechanically processed austenitic Mn steels was lower than that of the steels in their as-solutionized state. The addition of Al to the Fe-17Mn steel decreased the hardness and elastic modulus but increased the impact energy.
Two austenitic Mn steels (Fe-17Mn and Fe-17Mn-3Al (wt%, so as the follows)) were subjected to thermomechanical processing (TMP) consisting of forging followed by solutionization and hot rolling. The rolled samples were annealed at 650 and 800℃ to relieve the internal stress and to induce recrystallization. The application of TMP and heat treatment to the Fe-17Mn/Fe-17Mn-3Al steels refined the austenite grain size from 169 μm in the as-solutionized state to 9-13 μm, resulting in a substantial increase in hardness from HV 213 to HV 410 for the Fe-17Mn steel and from HV 210 to HV 387 for the Fe-17Mn-3Al steel. The elastic modulus values, as evaluated by the nanoindentation technique, increased from (175±11) to (220±12) GPa and from (163±15) to (205±13) GPa for the Fe-17Mn and Fe-17Mn-3Al steels, respectively. The impact energy of the thermomechanically processed austenitic Mn steels was lower than that of the steels in their as-solutionized state. The addition of Al to the Fe-17Mn steel decreased the hardness and elastic modulus but increased the impact energy.
2019, vol. 26, no. 1, pp.
76-85.
https://doi.org/10.1007/s12613-019-1711-2
Abstract:
Flexible rolling is a forming process based on thickness reduction, and the precision of thickness reduction is the key factor affecting bending deformation. The major purpose of the present work is to solve the problem of bending deformation error caused by insufficient thickness reduction. Under the condition of different rolling reductions with the same sheet thickness and the same thickness reduction with different sheet thicknesses, the thickness reduction error of sheet metal is analyzed. In addition, the bending deformation of sheet metal under the same conditions is discussed and the influence of the multi-step forming process on the thickness reduction error is studied. The results show that, under the condition of the same sheet thickness, the thickness reduction error increases with increasing rolling reduction because of an increase in work hardening. As rolling reduction increases, the longitudinal bending deformation decreases because of the decrease of the maximum thickness difference. Under the condition with the same thickness reduction, the thickness reduction error increases because of the decrease of the rolling force with increasing sheet thickness. As the sheet thickness increases, the longitudinal bending deformation increases because of the increase in the maximum thickness difference. A larger bending deformation is divided into a number of small bending deformations in a multi-step forming process, avoiding a sharp increase in the degree of work hardening; the thickness reduction error is effectively reduced in the multi-step forming process. Numerical simulation results agree with the results of the forming experiments.
Flexible rolling is a forming process based on thickness reduction, and the precision of thickness reduction is the key factor affecting bending deformation. The major purpose of the present work is to solve the problem of bending deformation error caused by insufficient thickness reduction. Under the condition of different rolling reductions with the same sheet thickness and the same thickness reduction with different sheet thicknesses, the thickness reduction error of sheet metal is analyzed. In addition, the bending deformation of sheet metal under the same conditions is discussed and the influence of the multi-step forming process on the thickness reduction error is studied. The results show that, under the condition of the same sheet thickness, the thickness reduction error increases with increasing rolling reduction because of an increase in work hardening. As rolling reduction increases, the longitudinal bending deformation decreases because of the decrease of the maximum thickness difference. Under the condition with the same thickness reduction, the thickness reduction error increases because of the decrease of the rolling force with increasing sheet thickness. As the sheet thickness increases, the longitudinal bending deformation increases because of the increase in the maximum thickness difference. A larger bending deformation is divided into a number of small bending deformations in a multi-step forming process, avoiding a sharp increase in the degree of work hardening; the thickness reduction error is effectively reduced in the multi-step forming process. Numerical simulation results agree with the results of the forming experiments.
2019, vol. 26, no. 1, pp.
86-97.
https://doi.org/10.1007/s12613-019-1712-1
Abstract:
Azole derivatives such as 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBI) were introduced as corrosion inhibitors into the interlayer space of sodium montmorillonite clay (Na+-MMT). The corrosion protection behavior of mild steel in solutions containing MBT, MBI, MMT+MBT, MMT+MBI, Na+-MMT, and NaCl (3.5wt%) was evaluated using polarization and electrochemical impedance spectroscopy (EIS). Also, the release of penetrated species into the medium from the clay nanocarriers was evaluated using ultraviolet-visible (UV-Vis) spectroscopy. Small-angle X-ray scattering (SAXS) confirmed the insertion of MBT and MBI into the inner space of the clay layers and the interaction between two organic and inorganic phases. Scanning electron microscopy (SEM) was used to assess the morphology of the surface of the steel samples after the samples had been immersed for 24 h in the extraction solution. The corrosion protection in the solutions with clay nanocarriers containing MBT and MBI was better than that in solutions without MMT. The UV-Vis results showed that the release of MBI species from Na+-MMT nanocarriers in neutral pH was far lower than that of MBT species.
Azole derivatives such as 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBI) were introduced as corrosion inhibitors into the interlayer space of sodium montmorillonite clay (Na+-MMT). The corrosion protection behavior of mild steel in solutions containing MBT, MBI, MMT+MBT, MMT+MBI, Na+-MMT, and NaCl (3.5wt%) was evaluated using polarization and electrochemical impedance spectroscopy (EIS). Also, the release of penetrated species into the medium from the clay nanocarriers was evaluated using ultraviolet-visible (UV-Vis) spectroscopy. Small-angle X-ray scattering (SAXS) confirmed the insertion of MBT and MBI into the inner space of the clay layers and the interaction between two organic and inorganic phases. Scanning electron microscopy (SEM) was used to assess the morphology of the surface of the steel samples after the samples had been immersed for 24 h in the extraction solution. The corrosion protection in the solutions with clay nanocarriers containing MBT and MBI was better than that in solutions without MMT. The UV-Vis results showed that the release of MBI species from Na+-MMT nanocarriers in neutral pH was far lower than that of MBT species.
2019, vol. 26, no. 1, pp.
98-107.
https://doi.org/10.1007/s12613-019-1713-0
Abstract:
Lithium and cobalt recovery from spent lithium-ion batteries (LIBs) is a major focus because of their increased production and usage. The conventional method for recycling spent LIBs using inorganic acids produces harmful byproducts. In this work, the leaching agent was substituted with a less expensive and more environmentally friendly alternative-acetic acid-and a mathematical model was developed to describe the kinetics of the recovery process. The variables used were the pH value, temperature, H2O2 concentration, and the solid-to-liquid (S/L) ratio. The mathematical model used was the shrinking core model, which was modified to accommodate an equilibrium reaction. The experimental results show that the rate of recovery of Li and Co over time was only affected by temperature. The leaching behaviors of Li and Co were found to oppose each other. An increase in temperature resulted in increased recovery of Li but decreased recovery of Co because of the product-favoring endothermic reaction of Li and the reactant-favoring exothermic reaction of Co. The product of Li has a lower entropy value than the reactant as a free-moving ion, whereas the product of Co leaching has a higher entropy value as a stiff crystal complex. Thus, temperature conditioning is a pivotal factor in the leaching of spent LIBs.
Lithium and cobalt recovery from spent lithium-ion batteries (LIBs) is a major focus because of their increased production and usage. The conventional method for recycling spent LIBs using inorganic acids produces harmful byproducts. In this work, the leaching agent was substituted with a less expensive and more environmentally friendly alternative-acetic acid-and a mathematical model was developed to describe the kinetics of the recovery process. The variables used were the pH value, temperature, H2O2 concentration, and the solid-to-liquid (S/L) ratio. The mathematical model used was the shrinking core model, which was modified to accommodate an equilibrium reaction. The experimental results show that the rate of recovery of Li and Co over time was only affected by temperature. The leaching behaviors of Li and Co were found to oppose each other. An increase in temperature resulted in increased recovery of Li but decreased recovery of Co because of the product-favoring endothermic reaction of Li and the reactant-favoring exothermic reaction of Co. The product of Li has a lower entropy value than the reactant as a free-moving ion, whereas the product of Co leaching has a higher entropy value as a stiff crystal complex. Thus, temperature conditioning is a pivotal factor in the leaching of spent LIBs.
2019, vol. 26, no. 1, pp.
108-113.
https://doi.org/10.1007/s12613-019-1714-z
Abstract:
The effects of partial substitution of La by Ce and Ni by Al, Fe, or Co in LaNi5-based alloys on hydrogen storage performance were systematically studied. All samples were prepared using vacuum arc melting in an argon atmosphere. The results showed that for La-Ni5-xMx (M=Al, Fe, or Co) alloys, the lattice constants and unit cell volumes increased with an increasing amount of Al and Fe. On the other hand, these parameters decreased upon partial substitution of La by Ce. In addition, the lattice constant remained almost constant in the La0.6Ce0.4Ni5-xCox alloys regardless of the value of x (x=0.3, 0.6, or 0.9), as Ce might enhance the homogeneity of the CaCu5-type phase in Co-containing alloys. The hydrogen storage properties of the alloys were investigated using pressure, composition, and temperature isotherms. The experimental results showed that the plateau pressure decreased with an increasing content of Al, Fe, or Co, but it increased with Ce addition. Furthermore, the plateau pressures of all Co-containing alloys were almost identical upon substitution with Ce. Finally, the enthalpy (ΔH) and entropy (ΔS) values for all alloys were calculated using van't Hoff plots. The relationship between the lattice parameters and enthalpy changes for hydrogenation will be discussed.
The effects of partial substitution of La by Ce and Ni by Al, Fe, or Co in LaNi5-based alloys on hydrogen storage performance were systematically studied. All samples were prepared using vacuum arc melting in an argon atmosphere. The results showed that for La-Ni5-xMx (M=Al, Fe, or Co) alloys, the lattice constants and unit cell volumes increased with an increasing amount of Al and Fe. On the other hand, these parameters decreased upon partial substitution of La by Ce. In addition, the lattice constant remained almost constant in the La0.6Ce0.4Ni5-xCox alloys regardless of the value of x (x=0.3, 0.6, or 0.9), as Ce might enhance the homogeneity of the CaCu5-type phase in Co-containing alloys. The hydrogen storage properties of the alloys were investigated using pressure, composition, and temperature isotherms. The experimental results showed that the plateau pressure decreased with an increasing content of Al, Fe, or Co, but it increased with Ce addition. Furthermore, the plateau pressures of all Co-containing alloys were almost identical upon substitution with Ce. Finally, the enthalpy (ΔH) and entropy (ΔS) values for all alloys were calculated using van't Hoff plots. The relationship between the lattice parameters and enthalpy changes for hydrogenation will be discussed.
2019, vol. 26, no. 1, pp.
114-123.
https://doi.org/10.1007/s12613-019-1715-y
Abstract:
The Ni samples were electroformed from additive-free (AF) and saccharin-containing (SC) sulfamate solutions, respectively. In situ backscattered electron (BSE) imaging, electron backscatter diffraction (EBSD), and electron-probe microanalysis (EPMA) were used to investigate the effect of annealing on the deformation behaviors of the AF and SC samples. The results indicate that columnar grains of the as-deposited AF sample had an approximated average width of 3 μm and an approximated aspect ratio of 8. The average width of columnar grains of the as-deposited SC sample was reduced to approximately 400 nm by the addition of saccharin to the electrolyte. A few very-large grains distributed in the matrix of the SC sample after annealing. No direct evidence indicated that S segregated at the grain boundaries before or after annealing. The average value of the total elongations of the SC samples decreased from 16% to 6% after annealing, whereas that of the AF samples increased from 18% to 50%. The dislocation recovery in grain-boundary areas of the annealed AF sample was reduced, which contributed to the appearance of microvoids at the triple junctions. The incompatibility deformation between very-large grains and fine grains contributed to the brittle fracture behavior of the annealed SC Ni.
The Ni samples were electroformed from additive-free (AF) and saccharin-containing (SC) sulfamate solutions, respectively. In situ backscattered electron (BSE) imaging, electron backscatter diffraction (EBSD), and electron-probe microanalysis (EPMA) were used to investigate the effect of annealing on the deformation behaviors of the AF and SC samples. The results indicate that columnar grains of the as-deposited AF sample had an approximated average width of 3 μm and an approximated aspect ratio of 8. The average width of columnar grains of the as-deposited SC sample was reduced to approximately 400 nm by the addition of saccharin to the electrolyte. A few very-large grains distributed in the matrix of the SC sample after annealing. No direct evidence indicated that S segregated at the grain boundaries before or after annealing. The average value of the total elongations of the SC samples decreased from 16% to 6% after annealing, whereas that of the AF samples increased from 18% to 50%. The dislocation recovery in grain-boundary areas of the annealed AF sample was reduced, which contributed to the appearance of microvoids at the triple junctions. The incompatibility deformation between very-large grains and fine grains contributed to the brittle fracture behavior of the annealed SC Ni.
2019, vol. 26, no. 1, pp.
124-132.
https://doi.org/10.1007/s12613-019-1716-x
Abstract:
Because of the potential carcinogenic effects and difficult degradation of azo dyes, their degradation has been a longstanding problem. The degradation of azo dye Direct Blue 6 (DB6) using ball-milled (BM) high-entropy alloy (HEA) powders was characterized in this work. Newly designed AlFeMnTiM (M=Cr, Co, Ni) HEAs synthesized by mechanical alloying (MA) showed excellent performance in the degradation of azo dye DB6. The degradation efficiency of AlFeMnTiCr is approximately 19 times greater than that of the widely used commercial Fe-Si-B amorphous alloy ribbons and more than 100 times greater than that of the widely used commercial zero-valent iron (ZVI) powders. The galvanic-cell effect and the unique crystal structure are responsible for the good degradation performance of the BM HEAs. This study indicates that BM HEAs are attractive, valuable, and promising environmental catalysts for wastewater contaminated by azo dyes.
Because of the potential carcinogenic effects and difficult degradation of azo dyes, their degradation has been a longstanding problem. The degradation of azo dye Direct Blue 6 (DB6) using ball-milled (BM) high-entropy alloy (HEA) powders was characterized in this work. Newly designed AlFeMnTiM (M=Cr, Co, Ni) HEAs synthesized by mechanical alloying (MA) showed excellent performance in the degradation of azo dye DB6. The degradation efficiency of AlFeMnTiCr is approximately 19 times greater than that of the widely used commercial Fe-Si-B amorphous alloy ribbons and more than 100 times greater than that of the widely used commercial zero-valent iron (ZVI) powders. The galvanic-cell effect and the unique crystal structure are responsible for the good degradation performance of the BM HEAs. This study indicates that BM HEAs are attractive, valuable, and promising environmental catalysts for wastewater contaminated by azo dyes.
2019, vol. 26, no. 1, pp.
133-141.
https://doi.org/10.1007/s12613-019-1717-9
Abstract:
A homogeneous and compact super-aligned carbon nanotube (SACNT)-reinforced nickel-matrix composite was successfully prepared by electrodeposition. The mechanical properties of the laminar SACNT/Ni composites were substantially improved compared with those of pure nickel. With increasing content of SACNTs, the tensile strength of the composite increased and the elongation decreased because of the high-strength SACNTs bearing part of an applied load and the fine-grained strengthening mechanism. The nanohardness of the SACNT/Ni composites was improved from 3.92 GPa (pure nickel) to 4.62 GPa (Ni-4vol%SACNTs). The uniform distribution of SACNTs in the composites and strong interfacial bonding between the SACNTs and the nickel matrix resulted in an improvement of the mechanical properties of the SACNT/Ni composites. The introduced SACNTs refined the nickel grains, increased the amount of crystal twins, and changed the preferred orientation of grain growth.
A homogeneous and compact super-aligned carbon nanotube (SACNT)-reinforced nickel-matrix composite was successfully prepared by electrodeposition. The mechanical properties of the laminar SACNT/Ni composites were substantially improved compared with those of pure nickel. With increasing content of SACNTs, the tensile strength of the composite increased and the elongation decreased because of the high-strength SACNTs bearing part of an applied load and the fine-grained strengthening mechanism. The nanohardness of the SACNT/Ni composites was improved from 3.92 GPa (pure nickel) to 4.62 GPa (Ni-4vol%SACNTs). The uniform distribution of SACNTs in the composites and strong interfacial bonding between the SACNTs and the nickel matrix resulted in an improvement of the mechanical properties of the SACNT/Ni composites. The introduced SACNTs refined the nickel grains, increased the amount of crystal twins, and changed the preferred orientation of grain growth.
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