Enhanced removal of iron minerals from high-iron bauxite with advanced roasting technology for enrichment of aluminum

Mössbauer and X-ray Diffraction Spectroscopy of High-Iron Bauxites from Kazakhstan

The bauxite ores of Kazakhstan were analyzed using Mössbauer spectroscopy, X-ray diffraction and an X-ray fluorescence analysis. Experimental data on the structural-phase composition of bauxites were obtained, and the features of the iron-bearing minerals within them were revealed. The studied bauxites were high in iron. The magnetic part of bauxite was mainly represented by aluminohematite with a concentration of CAl = 3.34-5.73 at.%, alongside goethite in small amounts. The predominant phase in the bauxite samples was the alumina-bearing mineral gibbsite with a well-crystallized monoclinic lattice. The main siliceous mineral of bauxite is kaolinite, which showed distorted octahedral positions in a number of samples. Siderite amounts were found to vary in the range of 0-15 at.% in the present iron-bearing minerals. Ilmenite was also present in the bauxite of some deposits; anatase was found in all bauxites and was the final product of ilmenite decomposition in the weathering crust.

Biomass waste as a clean reductant for iron recovery of iron tailings by magnetization roasting

The magnetization roasting with coal as primary reductants adds cost and causes environmental pollution. Therefore, it is of great importance to investigate the biomass application as a reductant for magnetization roasting to recover iron from low-utilization iron tailings for emission mitigation and green utilization. This study systematically investigated the impact of biomass (pyrolysis gas from agricultural and forestry waste) as a reductant on the conversion of iron tailings to magnetite in magnetization roasting. Additionally, the thermal decomposition of biomass, phase transformation and microstructure evolution of iron tailings were analyzed by TG, XRD, BET, and other methods to elucidate the conversion mechanism for facilitating magnetized hematite in iron tailings with biomass-derived gas. The results showed that woody biomass was a more appropriate reductant for magnetization roasting; 650 °C was the optimal temperature for the complete transformation of hematite to magnetite by reduction roasting with biomass waste. Through magnetic separation, the concentrate with an iron grade of 62.04% and iron recovery of 95.29% was obtained, and the saturation magnetization was enhanced from 0.60 emu/g to 58.03 emu/g of iron tailings. During the magnetization roasting, CO and H₂ generated from biomass reduced the hematite in tailings particles from interior to exterior, forming a loose structure with rich microfissures, facilitating the subsequent separation operations. This study offers a novel reference for applying biomass to exploit hematite minerals and shows the potential of biomass for energy savings and emission reduction in the utilization of iron tailing resources.

Efficient iron recovery from iron tailings using advanced suspension reduction technology: A study of reaction kinetics, phase transformation, and structure evolution

Recycling iron tailings is significant for environmental security and resource recovery, as they contain iron-rich minerals. Given the complex composition of iron minerals and the low grade of iron present in the tailings, innovative suspension roasting-magnetic separation (SRMS) technology was proposed to treat iron tailings that would separate out the iron minerals for recovery. In this study, the reduction kinetics, phase transformation, and structure evolution of the iron tailings were investigated to explain the mechanism behind magnetite production from iron tailings. These studies were conducted using chemical analyses, X-ray diffraction, Brunauer-Emmett-Teller specific surface area, and scanning electron microscopy. The results showed that high temperatures during the suspension reduction process were conducive to improving the reduction rate of the iron tailings. The best kinetics model for this reduction reaction of iron tailings is the P1 model, which demonstrated a linear increase in the conversion degree with the extension of the reaction time. The corresponding mechanism function was f(α) = 1, the apparent activation energy (E_α) was 51.56 kJ/mol, and the kinetics equation was k = 3.14exp(- 51.56/RT). Using the SRMS technology, magnetite gradually formed from hematite, starting at the outer particle layers and moving inward toward the core. The microcracks and pores in the surface of the particles increased, which promoted CO penetration into the particles where it reacted with the hematite. Our results provide important insight into the efficient and clean recycling of iron tailings.

Solvent Extraction of Iron(III) from Al Chloride Solution of Bauxite HCl Leaching by Mixture of Aliphatic Alcohol and Ketone

Research into the solvent extraction of iron(III) from a chloride solution after bauxite HCl leaching by neutral oxygen-containing extractants and their mixtures were studied and the iron(III) extraction degree from chloride solutions using alcohols is presented. The effect of dilution of alcohol with a ketone by an extraction mixture in relation to its effectiveness was investigated. The iron(III) was efficiently extracted by the mixture of 1-octanol and 1-decanol (70%) with 2-undecanone (30%) from hydrochloric bauxite leach liquor at an O:A ratio = 2-4:1 at an iron(III) concentration of 7.4 g/L and 6 M HCl. For the removal of iron-containing organic phase from impurities (Al, Ca, Cr) that are co-extracted with iron(III), we used two step scrubbing at O:A = 5:1 by 7 M HCl as a scrub solution. The iron(III) stripping at the O:A ratio is shown. Using counter-current cascade of extractors, it was possible to obtain an FeCl3 solution with the iron(III) content of 90.5 g/L and total impurities less than 50 mg/L.