Because CaSi core wire was not fed in external refining process for 26CrMo4S/2 steel making, it was found that the molar ratio of calcium versus alumina was very low and subsequently resulted in generation of much more non-metallic inclusions. Hence, it was reasonable to sugguest feeding appropriate amount of Ca core wire. Before the performance, the thermodynamic calculation had been carried out to obtain the theoretical amount of Ca wire to be fed. According to the practical data from steel plant and the thermodynamic data, it was calculated that only when 5 2/34.97 10 [%Al]T-≥×4 2/31.38 10 [%Al] [%Ca]T T-×≥≥in molten steel the Al2O3 inclusions could be properly modified.
The addition of silica to steelmaking slags to decrease the binary basicity can promote phosphate enrichment in quenched slag samples. In this study, we experimentally investigated phosphate enrichment behavior in CaO–SiO_2–FeO–Fe_2O_3–P_2O_5 slags with a P_2O_5 content of 5.00% and the binary basicity B ranging from 1.0 to 2.0, where the(%FetO)/(%Ca O) mass percentage ratio was maintained at 0.955. The experimental results are explained by the defined enrichment degree 2 3C S C PR- of solid solution 2CaO·SiO_2–3CaO·P_2O_5(C_2S–C_3P), where 2 3C S C PR- is a component of the developed ion and molecule coexistence theory(IMCT)–Ni model for calculating the mass action concentrations Ni of structural units in the slags on the basis of the IMCT. The asymmetrically inverse V-shaped relation between phosphate enrichment and binary basicity B was observed to be correlated in the slags under applied two-stage cooling conditions. The maximum content of P_2O_5 in the C_2S–C_3P solid solution reached approximately 30.0% when the binary basicity B was controlled at 1.3.
A simple and practical method for the synthesis of zeolite 4A from bauxite tailings is presented in this paper. Systematic investigations were carried out regarding the capacity of zeolite 4A to remove Cr(III) from aqueous solutions with relatively low initial concentrations of Cr(III)(5–100 mg·L^(-1)). It is found that the new method is extremely cost-effective and can significantly contribute in decreasing environmental pollution caused by the dumping of bauxite tailings. The Cr(III) removal capacity highly depends on the initial p H value and concentration of Cr(III) in the solution. The maximum removal capacity of Cr(III) was evaluated to be 85.1 mg×g^(-1) for zeolite 4A, measured at an initial p H value of 4 and an initial Cr(III) concentration of 5 mg·L^(-1). This approach enables a higher removal capacity at lower concentrations of Cr(III), which is a clear advantage over the chemical precipitation method. The removal mechanism of Cr(III) by zeolite 4A was examined. The results suggest that both ion exchange and the surface adsorption-crystallization reaction are critical steps. These two steps collectively resulted in the high removal capacity of zeolite 4A to remove Cr(III).
Extraction and separation of nickel and cobalt from saprolite laterite ore were studied by using a method of microwave-assisted hydrothermal leaching and chemical deposition. The effects of leaching temperature and time on the extraction efficiencies of Ni2+ and Co2+ were investigated in detail under microwave conditions. It is shown that the extraction efficiencies of Ni2+ and Co2+ from the ore pre-roasted at 300 C for 5 h were 89.19% and 61.89% when the leaching temperature and time were about 70 C and 60 min, respectively. For the separation process of Ni and Co, the separation of main chemical components was performed by adjusting the pH values of sulfuric leaching solutions using a NaOH solution based on the different pH values of precipitation for metal hydroxides. The final separation efficiencies of Ni and Co were 77.29% and 65.87%, respectively. Furthermore, the separation efficiencies of Fe of 95.36% and Mg of 92.2% were also achieved at the same time.
Yan ZhaoJian-ming GaoYi YueBen PengZai-qing QueMin GuoMei Zhang
Nanostructured TiO2 with different morphologies and crystal phases was successfully synthesized from titanium-containing electric furnace molten slag by using a hydrothermal method followed by reflux process in acid solution. The effects of acid concentration, reflux time, and acid type on the formation of TiO2 were systematically investigated by scanning electron microscopy, X-ray diffraction(XRD), transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM),and X-ray fluorescence(XRF). It is indicated that TiO2 nanorod with rutile phase is achieved in nitric or hydrochloric acid, while anatase TiO2 nanodisk is formed in sulfuric acid.With the increase of the concentration of hydrochloric acid from 0.3 to 1.5 mol L-1, the dispersibility and crystallinity of the final product can be improved. With prolonging the reflux time from 6 to 14 h, the rutile TiO2 nanorod with uniform crystal size and high crystallinity is obtained. The growth mechanism of TiO2 nanorod and nanodisk prepared under different conditions was also discussed.
TiO_2 visible light catalysts with different crystalline phases and morphologies were synthesized from titanium-bearing electric arc furnace molten slag(Ti-bearing EAF slag)by using a simple acidolysis process.The effects of the p H of the HCl solution,liquid to solid ratio(RL/S,HCl solution to the residue ratio,m L/g) and acidolysis time on the micro-morphology and crystalline phase of as-prepared TiO_2 photocatalysts were systematically investigated.The results indicated that with decreasing p H in the HCl solution and increasing RL/S,the crystalline phase and micro-morphology of the obtained TiO_2 nanostructures tended to transform from anatase type TiO_2 with spherical nanoparticle structures to rutile type TiO_2 with needle-like nanorod structures.The acidolysis time had little influence on the crystalline phase but great impact on the size of the obtained TiO_2.The growth mechanism of TiO_2 from Ti-bearing EAF slag during the acidolysis process was also discussed.In addition,the influence of RL/Son the photocatalytic properties of the synthesized nanostructured TiO_2 was studied.The results showed that the photodegradation efficiency for Rhodamine B solution could reach 91.00% in 120 min when the RL/Swas controlled at 50:1.
