A Novel Approach for Comprehensive Utilization by Leaching Pyrite Cinder with Titanium Dioxide Waste Acid by Response Surface Methodology.

Comprehensive utilization of two industrial wastes by leaching pyrite cinder with titanium dioxide waste acid was proposed by using response surface methodology of the Box-Behnken design method. The effects of leaching conditions such as leaching temperature, leaching time, and waste acid/pyrite cinder ratio on the leaching yield were examined. The prediction model including the leaching variables with a good fitting result was established to predict the leaching yield or optimize the leaching variable values. The regression equation model was significant and reliable with an actual correlation coefficient R2 of 0.9856. The leaching conditions greatly affected the leaching rate, reaction equilibrium, solubility of the acid decomposed substances, and the common ion effects, influenced the leaching process, and finally improved the leaching yield. The variables such as leaching temperature and waste acid/pyrite cinder ratio had the greatest collaborative interactions, and the effects of the waste acid/pyrite cinder ratio were larger than the other two. The verification experiments confirmed that the leaching yield values could be achieved at 82.68 % under the optimal conditions.

Hydrolysis Kinetics of Low-Concentration Industrial TiOSO4 Solution and Structural Evolution of Metatitanic Acid.

Using the industrial low-concentration TiOSO4 solution as the raw material, the hydrolysis kinetics and structural evolution of metatitanic acid was investigated. The samples were characterized by TiO2 content, XRD analysis, particle size distribution, FT-IR spectroscopy, Raman analysis, and HRTEM. The curves of hydrolysis yield showed S type shape, and the hydrolysis process consisted of the induction period, rapid hydrolysis period, and mature period. The rapid hydrolysis period was the first-order reaction, and increasing of hydrolysis temperature would shorten the induction period and hydrolysis period while prolonging the mature period had an approximate linear positive correlation on the hydrolysis yield and hydrolysis rate. The actual hydrolysis yield at the graying point was consistent with the calculated hydrolysis yield. The calculated pre-exponential factor k0 was 1.40 × 1018 min-1 and activation energy Ea was of 147.6 kJ/mol. With the hydrolysis temperature increasing, the grain size increased, the lattice stress decreased, the average particle size of metatitanic acid decreased, and the sulfur content decreased, resulting from the growth and adjustment of crystals and colloidal particles. Also, the SO42- ions promoted the formation of anatase TiO2 crystals. The formation of the precipitated particles underwent processes such as gel, crystal growth, aggregation, and condensation.

Synthesis of dual-modified Fe-doped and carbon-coated Li4Ti5O12 anode based on industrial H2TiO3 for Li-ion batteries.

Spinel Li4Ti5O12 (LTO) is a promising candidate for lithium-ion battery anodes because of its exceptional stability and safety. However, its extensive application is limited by a high comprehensive cost, poor electronic conductivity, and other inherent defects. This work presents a novel synthesis procedure to synthesize carbon-coated Fe-doped LTO composites through carbon reduction, in the presence of Fe-containing industrial H2TiO3 as the titanium source, and glucose as the carbon source. The presence of the Fe-dopant is confirmed through XRD, with Rietveld refinement and EDS experiments. Results show that Fe2+ replaces a portion of Ti4+ after doping, leading to an increase in the LTO cell parameters and the corresponding cell volume. FLTO/C, presents a capacity of 153.79 mAh g-1 at 10 C, and the capacity decay per cycle is only 0.0074% after 1000 cycles at 5 C. Moreover, EIS experiments indicate that the incorporation of Fe and carbon lowers the charge transfer resistance and improves the diffusion and migration of Li+. Notably, since this preparation process requires no additional Fe source as a raw material, it is simple, cost-effective, and suitable for large-scale production and further application.

Structural evolution of metatitanic acid and iron removal during hydrolysis of industrial TiOSO4 solution.

The ferrous ion content of metatitanic acid affected the whiteness, purity and applications of TiO2, controlled by the hydrolysis conditions and metatitanic acid structure. The structural evolution of metatitanic acid and ferrous ion removal was investigated by hydrolyzing the industrial TiOSO4 solution. The hydrolysis degree was conformed to Boltzmann model with good fitting. TiO2 content of metatitanic acid gradually increased as hydrolysis proceeding due to its stronger compact structure and weaker colloidal property, caused by the aggregation and adjustment of the precipitated particles. At lower TiOSO4 concentration, the crystal size increased significantly, lattice strain decreased, and average particle size constantly adjusted and reduced. The micropores and mesopores were mainly formed by aggregating and stacking of primary agglomerate particles, bonded and filled with sulfate and hydroxyl. The ferrous ion content decreased linearly with the increase of TiO2 content, and reducing moisture content of metatitanic acid was an effective way to reduce Fe content. This would save more water and energy consumption, help to improve the clean production level of TiO2.

Substantially boosted photocatalytic detoxification activity of TiO2 benefited from Eu doping.

The wide energy band and high recombination rate of photogenerated carriers severely limit the photocatalytic activity of TiO2. It has been demonstrated that ion doping can induce lattice defects, change the energy band structure, optimize the separation efficiency of photogenerated carrier, thus promoting the photocatalytic activity of the catalyst. In this work, Eu-doped TiO2 was synthesized by a sol-gel method, and the composition and photogenerated carrier separation efficiency of the samples were analysed by various characterization methods. The results show that Eu-TiO2 was successfully prepared and Eu-TiO2 exhibits higher photogenerated carrier separation efficiency and generates more superoxide radicals compared to the bare TiO2. Photocatalytic activity of the samples was evaluated by the degradation of Rhodamine B (RhB), and the results show that Eu doping improves the photocatalytic activity of the samples, the sample with Eu/Ti molar ratio of 0.2% displays 2.3-fold increase in photocatalytic activity compared to the blank TiO2. The improved photocatalytic activity can be attributed to the fact that Eu doping facilitates the effective separation of photogenerated carriers.

Hydrothermal preparation of high purity TiO2 from industrial metatitanic acid by response surface methodology.

The response surface methodology of Box Behnken design was used to investigate the effects of hydrothermal conditions on the high purity TiO2 preparation from industrial metatitanic acid. The method had a good fitting result in the prediction model, and the effects could be calculated from a second-order polynomial equation. The hydrothermal conditions greatly affected the structure and purity for the metatitanic acid and rutile TiO2, influenced the process of nucleation and crystallization, grain growth, polymerization, agglomeration and aggregation, further improved the particle size distribution, structure and surface adsorption capacity of metatitanic acid, reduced the adsorption of impurity ions, and finally improved the purity of TiO2. The variables such as hydrothermal temperature, slurry concentration and hydrothermal time had synergistic effects, and the effects of hydrothermal time were larger than the other two. The verification experiments confirmed that the predicted values could be achieved at 99.99% under the optimal hydrothermal conditions.

Ag-Incorporated Polydopamine/Tannic Acid Coating on Titanium With Enhanced Cytocompatible and Antibacterial Properties.

Titanium (Ti) and its alloys are the most commonly used materials for bone implants. However, implant failure often happens due to bacterial infection. Developing antibacterial coatings on Ti implants is an effective strategy. Dopamine and tannic acid were cross-linked to form coating on Ti through Michael addition and Schiff base reaction. In addition, the Ag ions were grafted on the coating by the redox reaction of phenolic hydroxyl groups. Thus, an Ag-incorporated polydopamine/tannic acid coating was prepared on Ti substrate. SEM, EDS, water contact angle, FTIR, and XRD results demonstrated that the coating was formed on Ti successfully. The antibacterial activity of the coating against Gram-negative E. coli was examined, and the cytotoxicity of the coating was investigated by mouse fibroblast cells. The improvement of hydrophilicity, good cytocompatibility, and antibacterial effectiveness indicates that the coating has potential to surface modification of Ti implants.

Effects of Structural Factors of Hydrated TiO2 on Rutile TiO2 Pigment Preparation via Short Sulfate Process.

The structural factors such as crystal structure, particle size distribution and impurity content of hydrated TiO2 had great effects on the structures and pigment properties of the rutile TiO2. The rutile TiO2 white pigment was prepared via the Short Sulfate Process from low concentration industrial TiOSO4 solution. In order to produce rutile TiO2 pigment with good structures and excellent pigment properties, the crystal size of the hydrated TiO2 should be controlled less than 8.9 nm and as close as possible to 7.9 nm, which could effectively promote the phase transformation and crystal growth of the rutile TiO2. The appropriate particle size distribution of hydrated TiO2 had obvious effects on obtaining rutile TiO2 with narrower particle size distribution and near 0.20 µm. It was best to adjust the hydrolysis conditions to reduce the specific surface area of the hydrated TiO2 so as to reduce the iron ion impurity adsorption.

Effects of calcining temperature on photocatalytic activity of Fe-doped sulfated titania.

Using industrial titanyl sulfate as a raw material, Fe-doped sulfated titania (FST) photocatalysts were prepared by using the one-step thermal hydrolysis method and characterized using XRD, SEM, TGA-DSC, FTIR, UV-Vis DRS and N(2) adsorption-desorption techniques. The effects of calcining temperature on the structure of the titania were investigated. The photocatalytic activity of the FST was evaluated using the photodegradation of methylene blue and photooxidation of phenol in aqueous solutions under UV and visible light irradiation, respectively. The results evinced that Ti(4+) is substituted by Fe(3+) in titania lattice and forms impurity level within the band gap of titania, which consequently induces the visible light absorption and visible-light-driven photocatalytic activity. The synergistic effects of Fe-doping and sulfation are beneficial to the efficient separation of the photogenerated carriers and also improve the quantum efficiency of photocatalysis. In addition, Brönsted acidity arisen from the strong inductive effect of sulfate is also conducive to enhancing the photocatalytic performance of FST. However, when the calcining temperature is higher than 800°C, sulfur species and surface hydroxyl groups decompose and desorb from FST and the specific surface area decreases sharply. Moreover, severe sintering and rutile phase formation occur simultaneously. All these are detrimental to photocatalytic activity of FST.