STUDY OF CONDITIONS OF TRANSITION OF SILICON INTO ALUMINATE SOLUTION DURING LEACHING OF RAW ALUNITE AND ITS REMOVAL FROM THIS SOLUTION

When extracting aluminum from the alunite ore of the Zaglik deposit by leaching, silicon, which is part of the alunite, passes into solution in the form of a silicate ion in a small amount. Silicon in solution not only degrades the quality of the produced alumina but also contributes to the clogging of pipes and equipment during its production. In this work, we investigated the dynamics of the distribution of silicon in the liquid phase upon leaching of raw alunite at room temperature and heating in an alkaline solution. A method of extracting silicon from an aluminate solution is proposed to obtain high-quality aluminum hydroxide. Desilication was carried out by recirculating the parent solution. The silicon dioxide sorption ability from the solution of the material, which was obtained as a result of acid activation of alunite mud, was investigated. It was found that alunite mud activated with sulfuric acid, in comparison with non-activated mud, has the ability to separate the silicate ion from the aluminate solution with a higher percentage of yield

Effect of Corrosion Time on the Synergistic Corrosion of Q235 Steel in Sodium Aluminate Solutions

During Bayer alumina production with high-sulfur bauxite, the sulfide ions in the sodium aluminate solution caused serious corrosion to Q235 steel, which is the material of the tank equipment. This study investigates the effect of corrosion time on Q235 steel synergistic corrosion in sodium aluminate solution using the weight-loss method and electrochemical measurements. The results indicate that the corrosion rate decreases sharply, the rate equation satisfies the mathematical model of power function at the initial stage of corrosion, and the transformation of unstable iron sulfide to stable iron oxide at the later stage results in the decrease in sulfur content in the corrosion products and surface pseudo-passivation. There are two main types of corrosion products, as follows: one is the octahedral crystal particle, which is composed of Fe2O3, Fe3O4, Al2O3 and NaFeO2, and the other is the interlayer corrosion between the surface layer and the matrix, which is composed of FeS, FeS2 and MnS2. At day 3, the dynamics of the Q235 steel electrode is controlled by charge transfer and ion diffusion. However, at other times the dynamics are mainly controlled by charge transfer.

Feasibility of Applying Alkaline-Earth Metal Carboaluminates for Bayer Process Aluminate Solution Purification from Organic Impurities

The article is devoted to the problems of aluminate solutions sorption purification from harmful organic impurities in the production of alumina from the Bayer experiment. The study of sorption of basic classes of organic impurities isolated from industrial aluminate solutions showed that magnesium and calcium hydrocarboaluminates have a high selectivity in relation to the most harmful classes of organic substances for the process. The results of the sorption process kinetics and thermodynamics studies are given, optimal technological parameters of sorption purification and conditions for the synthesis of active sorbents from alkaline aluminate solutions and activated magnesium and calcium raw materials are determined.

On the Mechanism of Silica Transition into Alumina Solutions in the Leaching of Nepheline Sinters

The article deals with the mechanism of transition of silicon to aluminate solutions in the process of leaching aluminum sinters in the production of alumina from nepheline. It was found that features of the transition in silica aluminate solutions by leaching cakes of various types relate to the structure of two-calcium silicate, and the dependence of reactions in the aluminate solution, its temperature and composition. A pattern has been established that determines the relationship between the SiO2/Al2O3 ratio in the list and the concentration of silica in aluminate solutions after leaching.