Research on High-Pressure Hydrochloric Acid Leaching of Scandium, Aluminum and Other Valuable Components from the Non-Magnetic Tailings Obtained from Red Mud after Iron Removal

Red mud is a hazardous waste of the alumina industry that contains high amounts of iron, aluminum, titanium and rare-earth elements (REEs). One of the promising methods for the extraction of iron from red mud is carbothermic reduction with the addition of sodium salts. This research focuses on the process of hydrochloric high-pressure acid leaching using 10 to 20% HCl of two samples of non-magnetic tailings obtained by 60 min carbothermic roasting of red mud at 1300 °C and the mixture of 84.6 wt.% of red mud and 15.4 wt.% Na2SO4 at 1150 °C, respectively, with subsequent magnetic separation of metallic iron. The influence of temperature, leaching duration, solid-to-liquid-ratio and acid concentration on the dissolution behavior of Al, Ti, Mg, Ca, Si, Fe, Na, La, Ce, Pr, Nd, Sc, Zr was studied. Based on the investigation of the obtained residues, a mechanism for passing valuable elements into the solution was proposed. It has shown that 90% Al, 91% Sc and above 80% of other REEs can be dissolved under optimal conditions; Ti can be extracted into the solution or the residue depending on the leaching temperature and acid concentration. Based on the research results, novel flowsheets for red mud treatment were developed.

Template Synthesis of Well-Defined Rutile Nanoparticles by Solid-State Reaction at Room Temperature

Well-defined nanoparticles of rutile (with the size of 5 nm) were successfully prepared by the unusual solid-state transformation of an amorphous precursor in well-defined nanospace of a mesoporous silica template (SBA-15) at room temperature. An aqueous colloidal suspension of the rutile nanoparticles was successfully obtained by dissolution of SBA-15 and subsequent pH adjustment. The isolated rutile nanoparticles were used for H₂ evolution from an aqueous methanol solution by UV irradiation.

Study on the grain size control of metatitanic acid in a mixture acid system based on Arrhenius and Boltzmann fitting

Herein, to control the particle size of metatitanic acid produced via titanium thermal hydrolysis in sulfuric-chloric mixture acid (SCMA) solutions, the relationship between its grain size and hydrolysis parameters is discussed, and the corresponding mathematical model was established using the experimental data. Firstly, Ti(OH)(SO4)(Cl)(H2O)3 was selected as the most likely initial structure in the SCMA solution by comparing the experimental and corresponding simulated Raman spectra by density functional theory (DFT). Secondly, according to the predicted initial structure of TiO2+ and the experimental data for the hydrolysis process, with an increase in the concentration of TiO2+ and reaction temperature, the hydrolysis rate and grain size increased, while the agglomerate particle size decreased. Finally, a mathematic model was established and fitted by the Arrhenius equation and the Boltzmann distribution to describe the relationship between the grain size and hydrolysis parameters, as follows.

Improved photo-induced charge carriers separation through the addition of erbium on TiO2 nanoparticles and its effect on photocatalytic degradation of rhodamine B

Er_xTi_1-xO₂ nanocomposites was prepared by a simple sol-gel method with various proportion of erbium viz., x=0.02, x=0.04, x=0.06, x=0.08 and x=0.10. The prepared nanocomposites were studied using XRD, UV-Vis DRS, Raman spectra, HR-SEM, EDS, TEM, PL and impedance spectroscopy. XRD revealed that modified TiO₂ nanocomposites possessed only the anatase phase with crystallite sizes of about 8.1 to 12.7nm and which is well consistent with TEM analysis. It is seen that erbium ion exist in the nanocomposites based on the analysis of EDS. HR-SEM analysis revealed that the Er_xTi_1-xO₂ nanocomposites are spherical in shape with size between 10 and 20nm. The amount of erbium remarkably affects the structural, optical and electrical properties. Loading erbium could produce 4f energy levels between valence and conduction bands thus narrowing optical band gap and generates visible absorption peaks. It was found that erbium modified TiO₂ nanocomposites induced a shift in Raman. The enhancement of life time of charge carriers was observed on erbium inclusion.

Microwave-assisted seed preparation for producing easily phase-transformed anatase to rutile

Microwave heating seeds were used for dilute titanyl sulfate hydrolyzing. The uniform metatitanic acid particles could transform to rutile easily.