基于磁选预富集的湖北枣阳金红石矿石选矿试验

为高效率、低成本、小污染、高效益地开发利用湖北枣阳金红石矿石资源,根据主要脉石矿物有弱磁性,而金红石无磁性的特点,以高梯度中强磁选预富集工艺为基础进行了金红石选矿试验。结果表明：①在磨矿细度为-0.074 mm占88.60%的情况下,1粗1扫高梯度中强磁选抛尾产率可达29.16%,中强磁选精矿金红石含量为3.07%、回收率为89.50%;②高梯度中强磁选精矿经1粗3精3扫闭路浮选,可获得金红石含量64.53%、回收率为82.21%的金红石浮选精矿;③金红石浮选精矿采用高梯度强磁选-焙烧-酸浸工艺提纯,高梯度强磁选背景磁感应强度为1.2 T,焙烧温度为900 ℃、时间为45 min,盐酸浸出的酸浓度为10%、液固比为1∶5、温度为80 ℃、时间为30 min,最终获得金红石含量为87.88%、回收率为71.21%、TiO2品位为90.12%的金红石精矿。与传统的重选预富集工艺相比,采用磁选工艺可减少细粒金红石损失,提高金红石回收率,为国内金红石资源的高效开发利用提供了一种新思路。     

枣阳大阜山原生金红石矿脱泥试验研究

对枣阳大阜山原生金红石矿进行了选矿试验研究,为有效减少矿泥和脉石对浮选影响,分别采用了单一摇床重选、重磁联合、沉降和反浮选工艺进行脱泥抛尾,脱泥之后再进行金红石浮选。试验结果表明,在浮选前进行脱泥作业能够显著提高浮选指标,反浮选脱泥抛尾工艺效果更好,一次性抛弃尾矿产率为10.85%,金红石损失率为7.08%,反浮选脱泥后再进行正浮选,采用C5-9羟肟酸作为捕收剂,经过一次粗选,精矿品位达21.12%,回收率达75.08%。     

Rheological and volumetric properties of TiO2-ethylene glycol nanofluids

Homogeneous stable suspensions obtained by dispersing dry TiO₂ nanoparticles in pure ethylene glycol were prepared and studied. Two types of nanocrystalline structure were analyzed, namely anatase and rutile phases, which have been characterized by scanning electron microscopy. The rheological behavior was determined for both nanofluids at nanoparticle mass concentrations up to 25%, including flow curves and frequency-dependent storage and loss moduli, using a cone-plate rotational rheometer. The effect of temperature over these flow curve tests at the highest concentration was also analyzed from 283.15 to 323.15 K. Furthermore, the influence of temperature, pressure, nanocrystalline structure, and concentration on the volumetric properties, including densities and isobaric thermal expansivities, were also analyzed.     

湖北枣阳金红石矿选矿工艺研究

摘要:湖北枣阳金红石矿因其矿石性质复杂,嵌布粒度粗细不均,长期以来选矿回收率在50%左右,指标较低。通过对该金红石矿石性质的研究,采用脱泥—浮选-磁选原则流程,使用改性活化剂PX进行活化,联合使用选择性较好的捕收剂S.P.A和捕收能力强的脂肪醇O.C.T进行捕收,最终可获得含TTiO2为92.38%,金红石TiO2为89.38%的精矿产品,回收率达到70%以上,指标较好。根据物质组分的研究,矿石中还含有少量石榴子石,对其采用分级摇床工艺进行综合回收,可获得品位为93.3%石榴子石的精矿产品。      

The superior lithium storage capabilities of ultra-fine rutile TiO2 nanoparticles

The lithium storage capabilities of ultra-fine rutile TiO₂ nanoparticles have been studied. Ultra-fine rutile TiO₂ nanoparticles with only several nanometers in size have been prepared by a modified wet-chemical method with a high yield. Unexpectedly, the rutile TiO₂ nanoparticles with 3 nm in size exhibit superior lithium storage properties. Specifically, they show long term cycling stability upon extended cycling for at least 300 cycles with a capacity loss of only 0.17% per cycle, and good rate capability up to a 30 C rate. The excellent reversible lithium storage capabilities could be attributed to the ultra-fine size giving rise to a very short diffusion path, and the relatively large surface area which provides more sites for lithium insertion.     

What atomic resolution annular dark field imaging can tell us about gold nanoparticles on (1 1 0)

Annular dark field scanning transmission electron microscopy imaging was recently applied to a catalyst consisting of gold nanoparticles on TiO₂ (1 1 0), showing directly that the gold atoms in small nanoparticles preferentially attach to specific sites on the TiO₂ (1 1 0) surface. Here, through simulation, a parameter exploration of the imaging conditions which maximise the visibility of such nanoparticles is presented. Aberration correction, finite source size and profile imaging are all considered while trying to extracting the maximum amount of information from a given sample. Comment is made on the role of the thermal vibration of the atoms in the nanoparticle, the magnitude of which is generally not known a priori but which affects the visibility of the nanoparticles in this imaging mode.     

Theoretical analysis of light scattering properties of encapsulated rutile titanium dioxide pigments in dependent light scattering regime

Using numerical simulation, we study and compare the optical properties of model systems representing three types of scatterer: (a) standard TiO₂ pigments, (b) standard TiO₂ pigments encapsulated by a hard polymer shell and (c) standard TiO₂ pigments encapsulated by a layer of air and a polymer shell. Calculations are performed taking into account multiple and dependent light scattering regimes. Assuming an equivalent amount of TiO₂ in each system, results show that a standard TiO₂ pigment particle encapsulated by air could be a better opacifier than a standard un-encapsulated TiO₂ pigment because the presence of air could provide: (a) additional volume to the existing particle to scatter light; (b) better redistribution of the scattered field in the backward hemisphere; (c) a scattering cross-section less affected by crowding and (d) spacing effects due to the presence of the thin hard polymer shell which is required to encapsulate the air layer. Nonetheless, results also suggest that such benefits could probably not be exploited in real paint systems as encapsulated TiO₂ would only be more efficient than standard TiO₂ in a range of pigment volume filling fractions (PVC) that would not generate enough scattering efficiency to yield complete hiding as required by international standards.     

The synthesis of a porous-type of TiO2 with rutile structure

The synthesis of a porous-type of TiO₂ with rutile structure was studied. The focuses were on the thermal treatment temperature and time. AEROXIDE® TiO₂ P 25, as a fumed TiO₂, was thermally treated in a vertical-type tubular furnace by the natural dropping method. Even though the thermal treatment time was less than 1?s, a drastic increase of polymorphism from anatase structure to rutile structure was observed. The relationships between the rutile structure transformation ratio and surface area of obtained porous type of TiO₂ were investigated depending on the thermal treatment temperature. The porous-type of fumed TiO₂ showed high dispersibility in the sedimentation test although is showed large particle size.     

Comparative study of the dispersion of three oxide pigments with sodium polymethacrylate dispersants in alkaline medium

The adsorption of sodium polymethacrylate (NaPMA) dispersants onto three oxide powders (hematite, goethite and rutile) in alkaline medium has been investigated together with the resulting stabilization of the suspensions. Under basic conditions of waterborne coatings formulation, hematite and rutile are negatively charged whereas goethite is almost neutral. Adsorption isotherms, electrophoretic mobility, particle size, IR spectroscopy and rheological measurements were used to investigate the polymer–pigments interactions. It was found that adsorption of the anionic NaPMA polymer on the three pigments was still possible even at pH above the isoelectric point (IEP). Depending on the pH and the type of oxide, electrostatic interactions, chemical complexation at the surface or/and hydrogen bonding were suggested to be the predominant contributions to the adsorption process. The adsorption at high pH was enough for preventing particles aggregation and ensuring an efficient stabilization of the suspensions. The viscosity measurements performed at pH close to the IEP's also suggested that besides the electrostatic stabilization, the NaPMA polymers provided a steric stabilization. The steric effect was larger with the polymers of higher molar mass. The comparison of the three oxide showed that the affinity for the surface site came mainly from chemical interaction with acidic surface sites in the order rutile > goethite > hematite. The strong adsorption on rutile came from the aluminum treatment of its surface.     

Flame synthesis of titania particles from titanium tetraisopropoxide in premixed flames

An experimental investigation of flame synthesis of titania particles was conducted in premixed flames. The titanium precursor and silicon dopant used in this study were titanium tetraisopropoxide (TTIP) and hexamethyldisiloxane (HMDS), respectively. The objective of this study was to investigate the influence of flame condition, TTIP concentration, and HMDS on the phase composition and particle morphology of titania synthesized in flames. It was found that the anatase content of titania particles made in flames was appreciably increased by the increase of oxygen concentration in the oxidizer. The increase of flame temperature results in the decrease of anatase content. A significant increase in rutile content of titania particles was observed by increasing the particle residence time at high temperatures. The doping of HMDS in flames inhibits the transformation of anatase to rutile phase and, therefore, reduces the rutile content of product particles. Under the flame doped with low concentrations of HMDS, titania particles with SiO₂ particle agglomerates attached were produced. Further increase of the HMDS concentration up to the Si to Ti molar ratio equal to 0.375 results in the formation of a large amount of SiO₂ agglomerates in the product.