氧化剂对低浓度硫酸溶解钛铁矿的影响

采用加入氧化剂和降低硫酸浓度等方法对传统的钛白粉生产工艺进行改进,探讨了氧化剂加入量、硫酸浓度、搅拌速度、反应时间等条件对钛铁矿酸解率的影响.通过正交实验获得了氧化剂对低浓度硫酸溶解钛铁矿的最佳工艺条件:KMnO4的加入量为钛铁矿质量的0.5％,硫酸浓度为60％,在600 r/min的搅拌速度下,控制温度为150℃后连续反应60 min.按这些工艺条件,钛铁矿酸解率可达到96％.     

KOH/Al_2O_3固体碱催化酯交换合成生物柴油的研究

采用等体积浸渍法制备了KOH/Al_2O_3负载型固体碱催化剂,并将其用于菜籽油与甲醇酯交换法合成生物柴油的研究;分别考察了催化剂附载量、煅烧温度、醇油摩尔比、反应温度、反应时间等条件对生物柴油产率的影响;结果表明:用等体积浸渍法,在400℃煅烧5 h,制得负载量为20%(w)的KOH/Al_2O_3催化剂.当催化剂用量为5%(w),醇油摩尔比为12:1,在60℃下反应2 h后,生物柴油产率高达92.3%(w).运用X-射线衍射、比表面积测定等手段对催化剂结构进行了表征,结果表明催化剂的活性与其晶相和比表面积密切相关.     

Phase transformation and reduction kinetics during the hydrogen reduction of ilmenite concentrate

The reduction of ilmenite concentrate by hydrogen gas was investigated in the temperature range of 500 to 1200℃. The microstructure and phase transition of the reduction products were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical microscopy (OM). It was found that the weight loss and iron metallization rate increased with the increase of reduction temperature and reaction time. The iron metallization rate could reach 87.5% when the sample was reduced at 1150℃ for 80 min. The final phase constituents mainly consist of Fe, M₃O₅ solid solution phase (M=Mg, Ti, and Fe), and few titanium oxide. Microstructure analysis shows that the surfaces of the reduction products have many holes and cracks and the reactions take place from the exterior of the grain to its interior. The kinetics of reduction indicates that the rate-controlling step is diffusion process control with the activation energy of 89 kJ·mol-1.     

Preparation of titanium dioxide from titania-rich slag by molten NaOH method

Preparing titanium dioxide from titania-rich slag (TiO₂ 73wt%) by molten NaOH method has been developed. The effects of temperature and reaction time on the titanium conversion were investigated. The results showed that temperature had significant influence on the titanium conversion as well as the structure of the product. About 92% of titanium in the titania-rich slag could be converted after reacting with NaOH at 500℃ for 1 h. Metatitanic acid was formed through the steps of washing treatment, acid dissolution, and hydrolysis. Well-dispersed spherical titanium dioxide particles with an average size of 0.1-0.4 μm can be obtained by calcination of metatitanic acid. In addition, the content of titanium dioxide in the product is up to 98.6wt%, which can be used as pigments after further treatment of coating and crushing.     

Effect of modifying agents on the hydrophobicity and yield of zinc borate synthesized by zinc oxide

The aim of this study was to synthesize zinc borate using zinc oxide, reference boric acid, and reference zinc borate (reference ZB) as the seed, and to investigate the effects of modifying agents and reaction parameters on the hydrophobicity and yield, respectively. The reaction parameters include reaction time (1–5 h), reactant ratio (H₃BO₃/ZnO by mass: 2–5), seed ratio (seed crystal/(H₃BO₃+ZnO) by mass: 0–2wt%), reaction temperature (50–120℃), cooling temperature (10–80℃), and stirring rate (400–700 r/min); the modifying agents involve propylene glycol (PG, 0–6wt%), kerosene (1wt%–6wt%), and oleic acid (OA, 1wt%–6wt%) with solvents (isopropyl alcohol (IPA), ethanol, and methanol). The results of reaction yield obtained from either magnetically or mechanically stirred systems were compared. Zinc borate produced was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and contact angle tests to identify the hydrophobicity. In conclusion, zinc borate is synthesized successfully under the optimized reaction conditions, and the different modifying agents with various solvents affect the hydrophobicity of zinc borate.     

Mineralogical and sink-float studies of Jajarm low-grade bauxite

Jajarm’s bauxite deposits are mainly diasporic, and they have a low mass ratio of Al₂O₃/SiO₂. It is necessary to increase the run-of-mine mass ratio before feeding the material to the Bayer process. Chemical analysis indicated that the low-grade bauxite sample from Jajarm contained 43.9wt% Al₂O₃ and 13.35wt% SiO₂, resulting in a mass ratio of 3.29. According to mineralogical studies, the presence of aluminosilicate minerals such as kaolinite, illite, and quartz was the main reason for the decrease of the mass ratio. Microscopic observations revealed that, with the size reduction from -1000+710 to -38 μm, the liberation degree of diaspore increased from 10% to 60%, and that of aluminosilicates increased from 20% to 85%. Heavy liquids with the densities of 2.8, 3.0, 3.2, and 3.4 g/cm3 were used to evaluate the heavy media separation in three sizes, i.e., -3350+710, -710+212, and -212+125 μm. Laboratory studies confirm that the density of 3.2 g/cm3 can produce the concentrates (in sunk fractions) with recoveries of 89.09%, 91.24%, and 84.68% with the Al₂O₃/SiO₂ mass ratios of 5.03, 5.16, and 5.15 for the -3350+710, -710+212, and -212+125 μm sizes, respectively.     

由钛铁矿制备高纯度盐酸钛液

报道了由钛铁矿制备高纯度盐酸钛液的工艺过程,研究了萃取纯化过程中TBP浓度、水相酸度、萃取平衡时间及钛液浓度等因素对实验结果的影响,考察了盐酸浸取钛铁矿的条件。结果表明,TBP萃取纯化盐酸钛液十分有效,控制适当条件可得到高纯度钛液。     

Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride

Many reactive metals are difficult to prepare in pure form without complicated and expensive procedures. Although titanium has many desirable properties (it is light, strong and corrosion-resistant), its use has been restricted because of its high processing cost. In the current pyrometallurgical process--the Kroll process--the titanium minerals rutile and ilmenite are carbochlorinated to remove oxygen, iron and other impurities, producing a TiCl4 vapour. This is then reduced to titanium metal by magnesium metal; the by-product MgCl2 is removed by vacuum distillation. The prediction that this process would be replaced by an electrochemical route has not been fulfilled; attempts involving the electro-deposition of titanium from ionic solutions have been hampered by difficulties in eliminating the redox cycling of multivalent titanium ions and in handling very reactive dendritic products. Here we report an electrochemical method for the direct reduction of solid TiO2, in which the oxygen is ionized, dissolved in a molten salt and discharged at the anode, leaving pure titanium at the cathode. The simplicity and rapidity of this process compared to conventional routes should result in reduced production costs and the approach should be applicable to a wide range of metal oxides.     

Al,K和Si对钼粉还原及烧结过程的影响

采用液固掺杂技术将不同含量的KOH,H₂SiO₃和Al（NO₃）₃·9H₂O溶液加入到MoO₂粉末中,并通过还原、压制和烧结工艺制备成钼棒。研究了掺杂钼粉的平均费氏粒度、松装密度与掺杂量的关系,采用扫描电子显微镜（SEM）对掺杂钼粉的表面形貌及烧结钼棒的断口形貌进行了分析。研究结果表明,随着K,Al和Si掺杂量的提高,钼粉的粒度及松装密度均呈先减小后增大的变化趋势,且钼棒晶粒中的气孔呈增多趋势。通过SEM分析发现,由于K,Al和Si的掺杂,烧结钼棒的断裂形貌由沿晶断裂逐渐向穿晶断裂转变。综合比较后认为,Mo-0.005Al-0.27K-0.098Si和Mo-0.005Al-0.36K-0.1305Si为最优配方。     

万寿菊中叶黄素的提取皂化工艺研究

该文以四氢呋喃和乙醇的二元混合溶剂为主要提取剂,对万寿菊颗粒中叶黄素的提取皂化工艺进行了研究。实验分别考察了加入四氢呋喃与乙醇的比例、反应时间、料液比、加水体积、加碱量、反应温度对叶黄素得率的影响。在单因素试验的基础上,选取影响较大的4个因素采用L9(34)正交试验考察对叶黄素得率的影响,以得率为指标,确定最佳工艺条件为A1B2C2D3,即料液比为1∶20,加碱质量1.6 g,反应时间4 h,THF∶乙醇=2∶8。由此可知:此条件下叶黄素得率为1.14%,所得浸膏中叶黄素的含量达到10.32%。     

A new process of extracting vanadium from stone coal

A new process of extracting vanadium from the stone coal vanadium ore in Fangshankou, Dunhuang area of Gansu Province, China was introduced. Various leaching experiments were carried out, and the results show that the vanadium ore in Fangshankou is difficult to process due to its high consumption of acid and the high leaching rate of impurities. However, the leaching rate can be up to 80% and the content of V₂O₅ in the residue can be between 0.22%–0.25% in the process of ore fine grinding→oxidation roasting→mixing and ripening→aqueous leaching→P₂O₄ solvent extraction→sulfuric acid stripping→oxidation and precipitation→decomposition by heat. Also, the quality of flaky V₂O₅ produced by this process can meet the requirements of GB3283–87. The total leaching rate of vanadium is 70%. Also, three types of wastes are easy to treat. The vanadium extraction process is better in relation to the aspect of environmental protection than the sodium method.     

从攀钢高炉渣中提取分离TiO_2制备高钛渣研究

研究利用TjO_2对酸碱的稳定性,采用低温下酸解、熔融状态下碱熔的方法除去高炉渣中除TiO_2以外的所有可溶性杂质,从而制备出高钛渣。其具体方法是:将粒度为80目～200目的高炉渣用5mol/L～7mol/L的盐酸在60℃～100℃的条件下反应4h～8h,除去钙、镁、铝、铁等元素的酸溶性杂质,酸分解后的产物经过滤、酸洗后,滤渣与1:1.6～1:1.8的NaOH在600℃～800℃共熔1小时左右后用pH=11～13的NaOH溶液洗涤,使SiO_2以NaSiO_3的方式除去,从而得到二氧化钛质量百分比为70%左右的高钛渣。     

Preparation and photocatalytic properties of ilmenite NiTiO<Subscript>3</Subscript> powders for degradation of humic acid in water

The powders of ilmenite structure NiTiO₃ were prepared by a modified Pechini process using tetrabutyl titanate and nickel acetate as raw materials, and using citric acid and ethanol as a chelating agent and a solvent respectively. The powder samples were characterized by thermogravimetric and differential thermal analysis (TG-DTA) and X-ray diffraction (XRD). The photocatalytic activity of NiTiO₃ under the irradiation of ultraviolet rays (UV) light was evaluated by degrading humic acid (HA) in water as a probe reaction. The possible photodegradation mechanism was studied by the examination of active species ·OH, ·O₂⁻, and holes (h⁺) through adding scavengers. The TG-DTA and XRD results indicated that the good crystal structure of ilmenite phase NiTiO₃ could be obtained when the Ni-Ti citrate complex was calcined at 600°C. The photocatalytic activity experiments indicated that NiTiO₃ had favourable photocatalytic activity under the irradiation of UV light, and the photocatalytic degradation rate of HA reached 95.3% after a 2.5 h reaction with the photocatalyst calcined at 600°C and a photocatalyst dosage of 0.4 g/L. The possible photocatalytic mechanism was deduced that holes (h⁺) and ·OH radicals are the major reactive active species in the photocatalytic reaction, and dissolved oxygen plays a weak role in the degradation of HA.     

Preparation of mesoporous MgO-templated carbons from phenolic resin and their applications for electric double-layer capacitors

Mesoporous carbons were synthesized using thermoplastic phenolic resin (PF) as carbonaceous precursor and magnesium citrate as template precursor. Pore structure was determined as ink-bottle-like geometry through TEM, N2 adsorption analysis combined with TG curves. The porous carbons prepared were then applied as electrode material for electric double-layer capacitors. The capacitor performance was examined in 30 wt% KOH aqueous solution by cyclic voltammetry and galvanostatic charge/discharge measurements. The carbon prepared with MgO/PF mass ratio of 8/2 had a BET surface area of 1920 m² g^?1 and exhibited a capacitance of 220 F g^?1 at a current density of 50 mA g^?1. Besides, the carbon with the ratio of 4/6 had the optimize proportion of mesopores, which ensures its good rate performance that up to 98.3%, expressed as the ratio of the capacitance measured at 1000 mA g^?1 against that at 50 mA g^?1.     

A novel hydrothermal method for zinc extraction and separation from zinc ferrite and electric arc furnace dust

A novel hydrothermal process was developed to extract zinc from pure zinc ferrite (ZnFe₂O₄) nanopowder and zinc-containing electric arc furnace (EAF) dust using hexahydrated ferric chloride (FeCl₃·6H₂O) as a decomposing agent. The effects of solid FeCl₃·6H₂O to ZnFe₂O₄ ratio by mass (R_F/Z), hydrothermal reaction temperature, and time on zinc extraction were systematically investigated. In the results, when the hydrothermal reaction is conducted at 150℃ for 2 h with R_F/Z of 15:20, the efficiency of zinc extraction from ZnFe₂O₄ reaches 97.2%, and the concentration of ferric ions (Fe3+) in the leaching solution is nearly zero, indicating a high selectivity for zinc. In addition, the zinc extraction efficiency from the EAF dust reaches 94.5% in the case of the hydrothermal reaction performed at 200℃ for 10 h with the solid FeCl₃·6H₂O to EAF dust ratio by mass (R_{F/EAF dust}) of 15:10. Zinc and iron separation is achieved by adjusting the pH value of the leaching solution according to the different precipitation pH values of metal hydroxides.     

Non-isothermal reduction kinetics of titanomagnetite by hydrogen

Reduction of titanomagnetite (TTM) powders by H2-Ar gas mixtures was investigated under a non-isothermal condition by using a thermogravimetric analysis system. It was found that non-isothermal reduction of TTM proceeded via a dual-reaction mechanism. The first reaction was reduction of TTM to wüstite and ilmenite, whereas the second one was reduction of wüstite and ilmenite to iron and titanium dioxide. By using a new model for the dual reactions, which was in an analytical form and incorporated different variables, such as time, temperature, particle size, and hydrogen partial pressure, rate-controlling steps for the dual reactions were obtained with the apparent activation energies calculated to be 90–98 and 115–132 kJ/mol for the first and second reactions, respectively.     

氧化铝熟料溶出二次反应过程SiO_2进入铝酸钠溶液的动力学机理

基于采用较高液固比(20∶1)的实验条件,避免了因硅酸钠与铝酸钠反应形成水合铝硅酸钠(钠硅渣),可将氧化铝熟料溶出二次反应动力学过程分为SiO_2进入铝酸钠溶液和Al_2O_3损失两个动力学过程,详细研究了SiO_2进入铝酸钠溶液过程的动力学行为. 通过选择合适的动力学模型对实验数据进行处理,获得了该过程的动力学方程. 方程表明,该过程的表观活化能较小,仅为24.86kJ·mol~(-1),说明其过程发生需要突破的活化能能垒较小,相应反应较易发生,其动力学机理与表面化学反应有关,也与扩散有关. 铝酸钠溶液中Al_2O_3质量浓度对过程的影响远远大于铝酸钠溶液中Na_2CO_3质量浓度和NaOH质量浓度的影响,因此认为熟料溶出过程中,导致SiO_2进入铝酸钠溶液的原因主要是熟料中的硅酸钙与NaAl(OH)_4相互作用.     

Development of high volume rice husk ash alumino silicate composites

The development of high volume rice husk ash (RHA) alumino silicate composites (ASC) was studied. RHA was used as the source of silica and aluminium in the ASC. The mass ratios of RHA:Al(OH)3 of 70:30 to 99:1 were tested. The results indicate that the obtained ASC mortars are not stable and disintegrate in water. Boric acid was introduced to the mixture to overcome this problem. Stable ASC mortars with high RHA:Al(OH)₃ mass ratios of 90:10 to 97.5:2.5 were obtained with the use of boric acid and 115℃ curing. The compressive strength of the mortar of 20 MPa was gained. The immersion test indicates that high volume RHA ASC mortars show good resistance in 3vol% H₂SO₄ solution, but is slightly less durable in 5wt% MgSO₄ solution.     

NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> reduction by coupling combustion with recycling flue gas in iron ore sintering process

A new process called ‘NO _x reduction by coupling combustion with recycling flue gas (RCCRF)’ was proposed to decrease NO _x emission during the iron ore sintering process. The simulation test of NO _x reduction was performed over sintered ore and in the process of coke combustion. Experimentally, NO _x reduction was also carried out by sintering pot test. For sintered ore, the amount of NO _x emission is reduced by 15wt%–25wt% at 400–550°C using 2.0vol% H₂ or 2.0vol% CO, or reduced by 10wt%–30wt% at 560–720°C using 0.15vol% NH₃. NO _x reduction is around 10wt% by coupling combustion of pyrolysis gas and coke, or around 16wt% by recycling flue gas into coke combustion. By RCCRF, the maximum NO _x reduction ratio is about 23wt% in coke combustion experiment and over 40wt% in sintering pot test.     

Synthesis of titanium oxycarbonitride by carbothermal reduction and nitridation of ilmenite with recycling of polyethylene terephthalate (PET)

An innovative and sustainable carbothermal reduction and nitridation (CTRN) process of ilmenite (FeTiO₃) using a mixture of polyethylene terephthalate (PET) and coal as the primary reductant under an H₂-N₂ atmosphere was proposed.The use of PET as an alternative source of carbon not only enhances the porosity of the pellets but also results in the separation of Fe from titanium oxycarbonitride (TiO_xC_yN_z) particles because of the differences in surface tension.The experiments were carried out at 1250℃ for 3 h using four different PET contents ranging from 25wt% to 100wt% in the reductant.X-ray diffraction (XRD),scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX),and LECO elemental analysis were used to study the phases and microstructures of the reduced samples.In the case of 75wt% PET,iron distinctly separated from the synthesized TiO_xC_yN_z phase.With increasing PET content in the sample,the reduction and nitridation rates substantially increased.The synthesis of an oxycarbonitride with stoichiometry of TiO_0.02C_0.13N_0.85 with minimal intermediate titanium sub-oxides was achieved.The results also showed that the iron particles formed from CTRN of FeTiO₃ exhibited a spherical morphology,which is conducive for Fe removal via the Becher process.