Preparation of Ti-rich material from titanium slag by activation roasting followed by acid leaching

A method of activation roasting followed by acid leaching using titanium slag was introduced to prepare Ti-rich material. The effects of HaPO4 dosage, roasting temperature, and roasting time on TiO2 grade were investigated. A Ti-rich material containing 88.54% TiO2, 0.42% （CaO＋MgO） was obtained when finely ground titanium slag was roasted with 7.5% H3PO4 at 1000 ℃ for 2 h, followed by a two-stage leaching in boiling dilute sulfuric acid for 2 h. The XRD patterns show that the product is titanium dioxide with a rutile structure. Mechanism studies show that structures of anosovite solid solution and silicate minerals are destroyed in the roasting process. As a result, titanium components in titanium slag are transformed into TiO2 （futile） while impurities are transformed into acid-soluble phosphate and quartz.

Conversion of coal gangue into alumina, tobermorite and TiO_2-rich material

A large amount of coal gangue from coal mining and processing is regarded as waste and usually stockpiled directly. In order to recycle the valuable elements from the coal gangue, an integrated process is proposed. The process consists of three steps: 1concentrating alumina from the coal gangue via activation roasting followed by alkali leaching of Si O2 which produces alumina concentrate for alumina extraction by the Bayer process; 2) synthesizing tobermorite whiskers from the filtrated alkali liquo containing silicate via a hydrothermal method and reusing excess caustic liquor; and 3) enriching titanium component from the Baye process residue by sulfuric acid leaching. Alumina concentrate with 69.5% Al_2O_3 and mass ratio of alumina to silica(A/S) of 5.9pure 1.1 nm tobermorite whisker and TiO_2-rich material containing 33% TiO_2 are produced, respectively, with the optimal parameters Besides, the actual alumina digestion ratio of alumina concentrate reaches 80.4% at 270 oC for 40 min in the Bayer process.

基于正交实验对煤灰中锂提取率多因素分析

以广西上林万福矿区煤灰为对象,采用活化-焙烧-浸取等实验方法尝试提取其中的锂元素,结合正交试验与数理统计的方法分析该方法对锂提取率的主控因素。结果表明,影响煤灰中锂浸出的主控因素为烧结剂(试剂种类参数)、烧结剂比例(试剂用量参数)、活化温度(温度参数),其余参数(反应时间)对浸出率影响较小。探讨了活化焙烧法最佳试验条件,即活化剂为碳酸钙、烧结剂为硫酸铵、浸取剂为硫酸、活化剂比例为2∶1、烧结剂比例为1∶3、浸取剂浓度为1%、固液比为1∶5、活化时间为30 min、活化温度为800℃、烧结时间为30 min、烧结温度为400℃、浸取时间为60 min、浸取温度为60℃。在最优试验参数条件下,通过4组平行重复性实验验证了锂的浸取效果,平均浸取率达80.40%。广西上林万福矿区煤灰在锂含量上表现出极大潜力,另外Ga,Y,Er,Yb和Lu元素均高于世界平均水平,多种元素的协同提取有望实现效益最大化。

基于加压酸浸工艺的天然石墨低氟提纯方法

石墨经氢氟酸法提纯后环保成本高,且产品纯度不能满足现状。采用3种改进工艺对天然石墨提纯,研究改进工艺条件下不同石墨原料的浸出效果,得到最佳的石墨原料与工艺,并对相应样品进行X射线衍射和扫描电子显微镜表征。结果表明:在温度50℃、氩气压力3 MPa条件下,可将球形石墨尾料的纯度由97.69%提高至99.54%;改进的工艺中,以球形石墨尾料为原料的无氟酸浸-焙烧活化-加压酸浸法,不仅可得到99.979%的高纯石墨,而且可从源头减少环保成本。

Mineralogical characterization and leaching behavior of Nigerian ilmenite ore

The characterization and H2SO4 leaching behavior of a Nigerian ilmenite ore following mechanical activation and alkali roasting were investigated. The effects of NaOH/ore ratio, H2SO4 concentration, leaching and roasting temperature on the Ti recovery from the milled ore were examined. The results show that mechanical activation significantly enhances the dissolution of ilmenite ore. Under the leaching conditions of 90 °C, 60% （v/v） H2SO4 and 4 h, about 72% Ti extraction was obtained from a milled ore roasted at 850 °C with 60% NaOH. X-ray diffraction （XRD） phase analysis of the roasted mass, water treated residue and leach residue supports the reaction mechanism and experimental results.

Effect of Carrier Processing Temperature on Its Properties for Adsorption of Active Metals

The influence of the carrier pseudo-boehmite （PB）, which was impregnated with a Ni-Mo-P solution under over- saturation conditions and treated at different temperatures, on its property for adsorption of active metals （Ni, Mo） was studied. The results showed that the amount for adsorption of active metal was decreased with an increasing treatment tem- perature of the carrier. After phase transition of the carrier PB to γ-Al2O3, its capacity for adsorption of active metals was significantly reduced. The difference in properties for adsorption of active metals （Ni, Mo） by PB dried at 120℃ and γ-Al2O3 calcined at 600℃ was studied in detail. The results suggested that the ability of the PB carrier to adsorb metals was higher than that of theγ-Al2O3 carrier. Especially, the ratio of chemically adsorbed metals on the PB support was much higher than 3＇-alumina. The chemical adsorption sites on the PB carrier were proved to be much more than those on the γ-Al2O3 carrier. Ni and Mo chemical adsorption sites differed a lot on the carrier possibly because of the difference in chemical adsorption sites.

Preparation of nano-TiO_2 photocatalysts and their decomposition activity in phenol-contaminated water

ZiO2 was prepared by the hydrolyzation method in （NH4）2SO4-modified TiCl4 solution, and TiO2 photocatalysts were obtained by accelerating the precipitation of TiO2 powder in a high-temperature water bath. The photocatalysts were characterized by Brunauer-Emmett-Teller （BET）, X-ray diffraction （XRD）, Raman spectrum and UV-Vis （Ultraviolet-Visible） spectrometry techniques, and the photocatalytic activity in phenol-contaminated water was investigated. The results showed that photocatalysts calcined at 400 ℃ had a specific surface area of 138.2 m^2/g and an average particle size of 9 nm, and a significant increase in thermal stability of anatase phase. At the calcination temperature of 700 ~C, the crystal form of TiO2 started to change into rutile （anatase： 97%, rutile： 3%）. The activity of TiO2 photocatalysts prepared with （NH4）2SO4-modified TIC14 solution was markedly stronger than that without （NH4）2SOg-modified TIC14 solution. Maximal photocatalytic activity was observed at the mole ratio of Ti：（NH4）2SO4= 1：2, the water-bath temperature of 90℃ and the calcination temperature of 700 ℃.

Photoactivity of titanium dioxide/carbon felt composites prepared with the assistance of supercritical carbon dioxide: Effects of calcination temperature and supercritical conditions

TiO2-coated carbon felt(TCF)composite catalysts have been prepared via a supercritical treatment of titanium tetraisopropoxide(TTIP)as the precursor.The physical properties of the catalysts were characterized by means of thermogravimetric and differential thermal analysis(TG–DTA),X-ray diffraction(XRD),fluorescence spectroscopy,scanning electron microscopy (SEM),and BET surface areas techniques.The photocatalytic activities of the materials were evaluated using the degradation of Congo red(CR)as a probe reaction.All the composites showed much higher photocatalytic activity than commercial P25 due to significant synergistic effects.Reused TCF retained high photocatalytic activity for degradation of CR.The photocatalytic efficiency in CR degradation was found to be strongly dependent on the TiO2-coating ratio and calcination temperature.A possible mechanism for the enhanced reactivity involves shuttling of electrons from TiO2 particles to the carbon felt(CF)as a result of an optimal arrangement in TCF that stabilizes charge separation and reduces charge recombination.In addition to the significant synergistic effects,the abundant spaces between adjacent carbon fibers allow UV light to penetrate into the felt-like photocatalyst to a considerable depth,so that a three-dimensional environment is available for the photocatalytic reaction.

Study on Al2O3 Extraction From Activated Coal Gangue under Different Calcination Atmospheres

Coal gangue was calcinated under air, nitrogen, carbon dioxide, air-hydrogen, and hydrogen atmospheres. The effects of different calcination temperatures and atmospheres on the mineral composition of activated coal gangue were investigated by X-ray diffraction. Moreover, the acid leaching kinetics of aluminum oxide from coal gangue was investigated with sulfuric acid. It showed that the air atmosphere promoted kaolinite decomposition during coal gangue calcination. The hydrogen atmosphere promoted the activation and decomposition of kaolinite at reaction temperatures exceeding 650℃. The carbon dioxide atmosphere eliminated the influence of residual carbon on coal gangue. When the ratio of acid/coal gangue was 1.5 and reaction temperature was 650℃, the sulfuric acid leaching rate under air, air-hydrogen, carbon dioxide, hydrogen and nitrogen atmospheres were 93.66%, 90.90%, 84.06%, 81.91% and 77.54% respectively. The acid leaching reaction process conformed to unreacted shrinking core model of particle unchanged, and was controlled by the interracial chemical reaction. The reaction kinetic equation for the leaching process was 1-（1-x）1/3=kt with an apparent activation energy of 48.97 kJ/mol.