The influence of process parameters in the three-stage purification of aluminate solution from the Bayer process and aluminum hydroxide was considered in this paper. One of the ways of purification is treating the aluminate solution in order to reduce the concentrations in the starting raw material (solution) and then treating the aluminum hydroxide at a certain temperature and time in order to obtain an alumina precursor of adequate quality. The purification process itself is divided into three phases. The first phase involves the treatment of sodium aluminate with lime in order to primarily remove Ca²⁺ and (SiO₃)²⁻ impurities. Phase II aims to remove impurities of Zn²⁺, Fe²⁺, and Cu²⁺ by treatment with controlled precipitation using specially prepared crystallization centers. In Phase III, Na⁺ is removed by the process of hydrothermal washing of Al₂O₃ ∙ 3H₂O. In this work, parameters such as temperature (T), reaction time (t), and concentration of lime (c) were studied in order to remove the mentioned impurities and obtain the purest possible product that would be an adequate precursor for special types of alumina.

The synthesis of oxide nanopowders through ultrasonic spray pyrolysis (USP) represents a sustainable method for producing high-purity, spherical particles tailored for advanced material applications. Recent developments in USP synthesis leverage the continuous transport of aerosols from an ultrasonic generator to a high-temperature furnace, with nanopowders collected efficiently using an electrostatic precipitator. This study explored the use of USP for titanium oxysulfate and aluminum nitrate solutions derived from the aluminum industry, focusing on resource recovery and waste reduction. Titanium oxysulfate was synthesized by leaching slag, generated during the reduction of red mud, with sulfuric acid under oxidizing, high-pressure conditions. After purification, the titanium oxysulfate solution was processed using USP in a hydrogen reduction atmosphere to yield spherical titanium dioxide (TiO₂) nanopowders. The hydrogen atmosphere enabled precise control over the nanoparticles’ morphology and crystallinity, enhancing their suitability for use in applications such as photocatalysis, pigments, and advanced coatings. In parallel, both synthetic and laboratory solutions of aluminum nitrate [Al(NO₃)₃] were prepared. The laboratory solution was prepared by leaching aluminum hydroxide oxide (AlOOH) with hydrochloric acid to form aluminum chloride (AlCl₃), followed by a conversion to aluminum nitrate through the addition of nitric acid. The resulting aluminum nitrate solution was subjected to USP, producing highly uniform, spherical alumina (Al₂O₃) nanopowders with a narrow size distribution. The resulting nanopowders, characterized by their controlled properties and potential applicability, represent an advancement in oxide powder synthesis and resource-efficient manufacturing techniques.

Introduction/purpose: Bauxite residue as a waste product from the aluminium industry produced through the Bayer process is mainly composed of iron oxide, titanium oxide, silicon oxide and undissolved alumina together with a wide range of other oxides and a minor content of rare earth elements, gallium, vanadium and scandium, which vary according to the country of origin of the bauxite. The extraction of valuable elements from bauxite residues and the minimisation of bauxite residues during different treatments are an open research field. Methods: Different hydrometallurgical and pyrometallurgical methods were used for the treatment of bauxite residues. In this study, the results of the hydrometallurgical treatment of bauxite residue from Alumina Zvornik using sulfuric acid and hydrochloric acid will be shown in order to study the change of the mineralogical composition. Leaching efficiency will be calculated using the ICP OES analysis. The XRD-Analysis was used for the characterization of the initial material and solid residues studying the change of the mineralogical phases. Results: Leaching of bauxite residues with sulphuric and hydrochloric acid leads partially to the change of mineralogical structure and the transfer of elements into a liquid phase. Natural precipitation of iron is observed over time. Silica gel formation is confirmed during leaching of bauxite residues with hydrochloric acid. Conclusion: A new research strategy for treating bauxite residue is needed in order to ensure a complete change of the initial minearlogical structure and the most efficient transfer of metals into a liquid phase.

This study investigates the influence of specific surface area (SSA) and aluminum hydroxide particle size on sodium aluminate’s purification efficiency in the Bayer process. This research examines how variations in SSA affect the adsorption and incorporation of contaminants such as Cu, Fe, and Zn, as well as the optimal balance between effective purification and excessive Al₂O₃ loss. Different SSA values and purification durations are analyzed to optimize the purification process and determine conditions that maximize impurity removal while maintaining system stability. Additionally, solid residue characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) provides insights into impurity incorporation mechanisms, including isomorphic replacement, surface adsorption, and co-crystallization. This study highlights key process parameters that influence impurity behavior and crystallization dynamics, offering valuable guidance for refining industrial purification strategies and improving aluminum hydroxide quality.

Acidic wastewater generated during sulfuric acid leaching of reduced tionite within the EUROTITAN process was treated using three low-cost adsorbents: fly ash, bentonite, and red mud slag. Tionite is a solid residue originating from the sulfate route of TiO₂ production, whereas the investigated wastewater is a secondary acidic stream produced during hydrometallurgical treatment of reduced tionite. The initial wastewater was characterized by low pH and elevated concentrations of Fe, Al, Ti, B, Cu, Mn, Pb, Cr, and Li. Batch adsorption experiments were carried out by varying contact time from 4 to 24 h and adsorbent dosage from 5 to 15 g/L. The results showed distinct selectivity depending on adsorbent type and solution chemistry. Bentonite exhibited the most stable performance, achieving nearly complete removal of Pb, Cu, B, and Li, while Fe and Al were only partially removed and Ti removal remained limited. Fly ash showed high affinity toward Pb and Cu, but its performance was strongly affected by dosage and contact time. Red mud slag demonstrated excellent Pb removal, high Cu removal, and time- and dosage-dependent Ti removal, although partial dissolution of Fe- and Al-bearing phases occurred under strongly acidic conditions. Overall, the results confirm that industrial by-products and natural clay materials can contribute to partial purification of acidic metallurgical wastewater, while additional neutralization or polishing steps are required for complete treatment.

Titanium is classified as a critical element and its application is very important in many industrial sectors. The synthesis of titanium compounds in this paper includes the synthesis of titanium oxide, ruthenium oxide-titanium oxide, core (titanium oxide)/shell(gold) particles and TiAlV-alloy. The synthesis is carried out using ultrasonic pyrolysis and aluminothermic reduction. As starting material, titanium oxy sulphate and tetra-n butylorthotitanat were used. Ultrasonic spray pyrolysis(USP) is simple technique for synthesizing nanoparticles and thin films,via ultrasonic atomization to create fine aerosol droplets that undergo thermal decomposition. Aluminothermic reduction represents an exothermic reeaction using aluminium as the reducing agent. Although the preparation of pure titanium is difficult because of its reactivity and high tendency to form oxides, some innovative solutions will be considered such as molten salt electrolysis. The great affinity of titanium towards oxygen is the biggest problem of how to obtain titanium metal powder and prevent oxidation.