A study on the melting and viscosity properties of the chromium-containing high-titanium melting slag(CaO–SiO2–MgO–Al2O3–TiO2–Cr2O3) with TiO2 contents ranging from 38.63 wt% to 42.63 wt% was conducted. The melti...A study on the melting and viscosity properties of the chromium-containing high-titanium melting slag(CaO–SiO2–MgO–Al2O3–TiO2–Cr2O3) with TiO2 contents ranging from 38.63 wt% to 42.63 wt% was conducted. The melting properties were investigated with a meltingpoint apparatus, and viscosity was measured using the rotating cylinder method. The FactSage 7.1 software and X-ray diffraction, in combination with scanning electron microscopy–energy-dispersive spectroscopy(SEM–EDS), were used to characterize the phase equilibrium and microstructure of chromium-containing high-titanium melting slags. The results indicated that an increase in the TiO2 content led to a decrease in the viscosity of the chromium-containing high-titanium melting slag. In addition, the softening temperature, hemispheric temperature, and flowing temperature decreased with increasing TiO2 content. The amount of crystallized anosovite and sphene phases gradually increased with increasing TiO2 content, whereas the amount of perovskite phase decreased. SEM observations revealed that the distribution of the anosovite phase was dominantly influenced by TiO2.展开更多
The effects of basicities and equilibrium temperatures on the enrichment of chromium in different mineral phases of synthesized argon-oxygen decarburization slags were investigated to understand the Cr concentrating b...The effects of basicities and equilibrium temperatures on the enrichment of chromium in different mineral phases of synthesized argon-oxygen decarburization slags were investigated to understand the Cr concentrating behavior into Mg(Cr,Al)2O4 spinel phase and to determine the leaching stability of Cr-containing slag.The results showed that when the basicity decreased from 1.0 to 0.6 and temperatures decreased from 1600 to 800℃,the Cr content of amorphous phase and crystalline phase gradually decreased,with a subsequent increase in the Cr content of spinel phase.The range of Cr enrichment in spinel of slags S1,S2,and S3 is 92.03-96.89,91.63-96.36,and 90.67-95.42,respectively.The mass fraction and the size of spinel increased with the decreasing equilibrium temperatures,and the Cr leaching values decreased simultaneously.Therefore,the trend of the amount of Cr-related ions in the leachate was consistent with the trend of Cr in the amorphous phase,diopside,and akermanite.The results suggest that the lower basicity and equilibrium temperatures could be conducive to stabilizing Cr into spinel phase to minimize Cr leaching into the environment.展开更多
Laser surface remelting of steels with different Cr contents has been performed by using a CO_2 laser. The results of oxidation tests showed that the effects of laser remelting on the oxidation resistance of Cr-contai...Laser surface remelting of steels with different Cr contents has been performed by using a CO_2 laser. The results of oxidation tests showed that the effects of laser remelting on the oxidation resistance of Cr-containing steels have close relation to the Cr contents and microstructures of the steels. The re- sistance to high temperature oxidation of 18-8 and HK40 at 1273 K can be obviously improved by laser remelting, whereas laser remelting showed little effect on the oxidation resistance of Fe-6Cr and Cr30 at 1173-1273 K.展开更多
Chromium (Cr), as a transition metal material with multiple redox states, has exhibited the catalysis toward Fenton-like reactions over a wide pH range. Although it is not sensible to add Cr reagents as catalysts due ...Chromium (Cr), as a transition metal material with multiple redox states, has exhibited the catalysis toward Fenton-like reactions over a wide pH range. Although it is not sensible to add Cr reagents as catalysts due to its toxicity, it is highly promising to remediate Cr-containing wastewater through Cr-initiated advanced oxidation processes (Cr-initiated AOPs), which are clean and low-cost. Moreover, the widely concerned Cr-complexes, considered as obstacles in the remediation process, can be effectively destroyed by AOPs. Cr self-catalysis is defined as Cr species is both substrate and catalyst. However, the full understanding of Cr self-catalysis, including the generation of intermediates Cr(IV)/Cr(V), the synergetic effects with co-existing ions, and the accumulation of toxic Cr(VI), remains a challenge for the practical application of Cr-initiated AOPs. In this review, relevant researches on Cr self-catalysis during Cr-initiated AOPs are summarized. Specifically, the Cr-Fenton-like reaction, Cr substituted materials, and Cr-sulfite reactions are explored as key mechanisms contributing to Cr self-catalysis. Moreover, Cr transformation processes, including synchronously Cr removal, Cr redox reactions, and Cr(VI) accumulation, in AOPs-based synergistic systems are systematically analyzed. Detailed approaches for the detection of active species in AOPs-based systems are also presented. The primary objective of this review is to explore the application of AOPs for Cr-containing wastewater remediation based on Cr self-catalysis, and provide fundamental insights and valuable information for future research on Cr-initiated AOPs.展开更多
Under a suitable condition of crystallization, dark brown rhombohedron crystals (the lengths of the longest two diagonals were 0.25 and 0.12 mm, respectively) could be obtained from nitrogenase CrFe protein purified f...Under a suitable condition of crystallization, dark brown rhombohedron crystals (the lengths of the longest two diagonals were 0.25 and 0.12 mm, respectively) could be obtained from nitrogenase CrFe protein purified from a mutant UW3 of Azotobacter vinelandii Lipmann grown in Cr-containing but NH3-free Medium, The possibility of crystallization, as well as the. number, size and quality of crystals obviously depended on the concentrations of PEG 8000, MgCl2, NaCl, Tris and Hepes buffer, and methods of crystallization. The optimum concentrations of the chemicals for crystallization of CrFe protein were slightly different from those for crystallization of MnFe protein from UW3 grown in Mn and DeltanifZ MoFe protein from a nifZ deleted strain of A. vinelandii. The crystal seemed to be formed from CrFe protein.展开更多
The effect of Al_(2)O_(3) content on the viscosity and structure of CaO-SiO_(2)-Cr_(2)O_(3)Al_(2)O_(3) slags was investigated to facilitate recycling of Cr in steelmaking slags.The slags exhibit good Newtonian behavio...The effect of Al_(2)O_(3) content on the viscosity and structure of CaO-SiO_(2)-Cr_(2)O_(3)Al_(2)O_(3) slags was investigated to facilitate recycling of Cr in steelmaking slags.The slags exhibit good Newtonian behavior at high temperature.The viscosity of acidic slag first increases from 0.825 to 1.141 Pa·s as the Al_(2)O_(3) content increases from 0 to 10wt%and then decreases to 1.071 Pa·s as the Al_(2)O_(3) content increases further to 15wt%.The viscosity of basic slag first increases from 0.084 to 0.158 Pa·s as the Al_(2)O_(3) content increases from 0 to 15wt%and then decreases to 0.135 Pa·s as the Al_(2)O_(3) content increases further to 20wt%.Furthermore,Cr_(2)O_(3)containing slag requires less Al_(2)O_(3) to reach the maximum viscosity than Cr_(2)O_(3)free slag;the Al_(2)O_(3) contents at which the behavior changes are 10wt%and 15wt%for acidic and basic slags,respectively.The ac-tivation energy of the slags is consistent with the viscosity results.Raman spectra demonstrate that[AlO_(4)]tetrahedra appear initially and were replaced by[AlO_(6)]octahedra with further addition of Al_(2)O_(3).The dissolved organic phosphorus content of the slag first increases and then de-creases with increasing Al_(2)O_(3) content,which is consistent with the viscosity and Raman results.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51904066)the Fundamental Research Funds for the Central Universities,China(No.N182503032)+1 种基金the Postdoctoral Foundation of Northeastern University,China(No.20190201)the Postdoctoral International Exchange Program,China(Dispatch Project,20190075)
文摘A study on the melting and viscosity properties of the chromium-containing high-titanium melting slag(CaO–SiO2–MgO–Al2O3–TiO2–Cr2O3) with TiO2 contents ranging from 38.63 wt% to 42.63 wt% was conducted. The melting properties were investigated with a meltingpoint apparatus, and viscosity was measured using the rotating cylinder method. The FactSage 7.1 software and X-ray diffraction, in combination with scanning electron microscopy–energy-dispersive spectroscopy(SEM–EDS), were used to characterize the phase equilibrium and microstructure of chromium-containing high-titanium melting slags. The results indicated that an increase in the TiO2 content led to a decrease in the viscosity of the chromium-containing high-titanium melting slag. In addition, the softening temperature, hemispheric temperature, and flowing temperature decreased with increasing TiO2 content. The amount of crystallized anosovite and sphene phases gradually increased with increasing TiO2 content, whereas the amount of perovskite phase decreased. SEM observations revealed that the distribution of the anosovite phase was dominantly influenced by TiO2.
基金supported by the National Key R&D Program of China(2019YFC1905701)the National Natural Science Foundation of China(U1960201).
文摘The effects of basicities and equilibrium temperatures on the enrichment of chromium in different mineral phases of synthesized argon-oxygen decarburization slags were investigated to understand the Cr concentrating behavior into Mg(Cr,Al)2O4 spinel phase and to determine the leaching stability of Cr-containing slag.The results showed that when the basicity decreased from 1.0 to 0.6 and temperatures decreased from 1600 to 800℃,the Cr content of amorphous phase and crystalline phase gradually decreased,with a subsequent increase in the Cr content of spinel phase.The range of Cr enrichment in spinel of slags S1,S2,and S3 is 92.03-96.89,91.63-96.36,and 90.67-95.42,respectively.The mass fraction and the size of spinel increased with the decreasing equilibrium temperatures,and the Cr leaching values decreased simultaneously.Therefore,the trend of the amount of Cr-related ions in the leachate was consistent with the trend of Cr in the amorphous phase,diopside,and akermanite.The results suggest that the lower basicity and equilibrium temperatures could be conducive to stabilizing Cr into spinel phase to minimize Cr leaching into the environment.
文摘Laser surface remelting of steels with different Cr contents has been performed by using a CO_2 laser. The results of oxidation tests showed that the effects of laser remelting on the oxidation resistance of Cr-containing steels have close relation to the Cr contents and microstructures of the steels. The re- sistance to high temperature oxidation of 18-8 and HK40 at 1273 K can be obviously improved by laser remelting, whereas laser remelting showed little effect on the oxidation resistance of Fe-6Cr and Cr30 at 1173-1273 K.
基金supported by the National Natural Science Foundation of China(No.22278247)the Shandong Natural Science Foundation(China)(No.ZR2020MB092).
文摘Chromium (Cr), as a transition metal material with multiple redox states, has exhibited the catalysis toward Fenton-like reactions over a wide pH range. Although it is not sensible to add Cr reagents as catalysts due to its toxicity, it is highly promising to remediate Cr-containing wastewater through Cr-initiated advanced oxidation processes (Cr-initiated AOPs), which are clean and low-cost. Moreover, the widely concerned Cr-complexes, considered as obstacles in the remediation process, can be effectively destroyed by AOPs. Cr self-catalysis is defined as Cr species is both substrate and catalyst. However, the full understanding of Cr self-catalysis, including the generation of intermediates Cr(IV)/Cr(V), the synergetic effects with co-existing ions, and the accumulation of toxic Cr(VI), remains a challenge for the practical application of Cr-initiated AOPs. In this review, relevant researches on Cr self-catalysis during Cr-initiated AOPs are summarized. Specifically, the Cr-Fenton-like reaction, Cr substituted materials, and Cr-sulfite reactions are explored as key mechanisms contributing to Cr self-catalysis. Moreover, Cr transformation processes, including synchronously Cr removal, Cr redox reactions, and Cr(VI) accumulation, in AOPs-based synergistic systems are systematically analyzed. Detailed approaches for the detection of active species in AOPs-based systems are also presented. The primary objective of this review is to explore the application of AOPs for Cr-containing wastewater remediation based on Cr self-catalysis, and provide fundamental insights and valuable information for future research on Cr-initiated AOPs.
文摘Under a suitable condition of crystallization, dark brown rhombohedron crystals (the lengths of the longest two diagonals were 0.25 and 0.12 mm, respectively) could be obtained from nitrogenase CrFe protein purified from a mutant UW3 of Azotobacter vinelandii Lipmann grown in Cr-containing but NH3-free Medium, The possibility of crystallization, as well as the. number, size and quality of crystals obviously depended on the concentrations of PEG 8000, MgCl2, NaCl, Tris and Hepes buffer, and methods of crystallization. The optimum concentrations of the chemicals for crystallization of CrFe protein were slightly different from those for crystallization of MnFe protein from UW3 grown in Mn and DeltanifZ MoFe protein from a nifZ deleted strain of A. vinelandii. The crystal seemed to be formed from CrFe protein.
基金This work was financially supported by the National Natural Science Foundation of China(No.U1960201)the National Key R&D Program of China(No.2019YFC 1905701).
文摘The effect of Al_(2)O_(3) content on the viscosity and structure of CaO-SiO_(2)-Cr_(2)O_(3)Al_(2)O_(3) slags was investigated to facilitate recycling of Cr in steelmaking slags.The slags exhibit good Newtonian behavior at high temperature.The viscosity of acidic slag first increases from 0.825 to 1.141 Pa·s as the Al_(2)O_(3) content increases from 0 to 10wt%and then decreases to 1.071 Pa·s as the Al_(2)O_(3) content increases further to 15wt%.The viscosity of basic slag first increases from 0.084 to 0.158 Pa·s as the Al_(2)O_(3) content increases from 0 to 15wt%and then decreases to 0.135 Pa·s as the Al_(2)O_(3) content increases further to 20wt%.Furthermore,Cr_(2)O_(3)containing slag requires less Al_(2)O_(3) to reach the maximum viscosity than Cr_(2)O_(3)free slag;the Al_(2)O_(3) contents at which the behavior changes are 10wt%and 15wt%for acidic and basic slags,respectively.The ac-tivation energy of the slags is consistent with the viscosity results.Raman spectra demonstrate that[AlO_(4)]tetrahedra appear initially and were replaced by[AlO_(6)]octahedra with further addition of Al_(2)O_(3).The dissolved organic phosphorus content of the slag first increases and then de-creases with increasing Al_(2)O_(3) content,which is consistent with the viscosity and Raman results.
