Red Mud from Brazil: Thermal Behavior and Physical Properties

Abstract

The main constituents of red mud produced in Aluminio city (S.P., Brazil) are iron, aluminum, and silicon oxides. It has been determined that the average particle diameter for this red mud is between 0.05 and 0.002 mm. It is observed that a decrease in the percentage of smaller particles occurs at temperatures greater than 400 °C. This observation corresponds with the thermal analysis and X-ray diffraction (XRD) data, which illustrate the phase transition of goethite to hematite. A 10% mass loss is observed in the thermal analysis patterns due to the hydroxide–oxide phase transitions of iron (primary phase transition) and aluminum (to a lesser extent). The disappearance and appearance of the different phases of iron and aluminum confirms the decomposition reactions proposed by the thermal analysis data. This Brazilian red mud has been classified as mesoporous at all temperatures except between 400 and 500 °C where the classification changes to micro/mesoporous.

Thin films produced on 5052 aluminum alloy by plasma electrolytic oxydation with Red Mud-containing Electrolytes

“…The smaller and more rounded particles are recurrent when there are higher proportions of iron, and the larger and more irregular particles contain higher percentage of aluminum. These results are in good agreement with the literature about red mud 7 . The mineralogy of the red mud was analyzed by XRD and it complies with the literature 7,15 .…”

“…These results are in good agreement with the literature about red mud 7 . The mineralogy of the red mud was analyzed by XRD and it complies with the literature 7,15 . In the XRD patterns of red mud given in Figure 3, it can be observed peaks corresponding to sodalite (NaAlSi 4 Figure 4 shows the average current density, ρ i , as a function of treatment time.…”

“…The red mud (RM) is a residue from the clarifying Bayer process. It is a highly alkaline insoluble solid containing significant amount of elements such as iron, silicon, titanium and aluminum [7][8][9] . Such characteristics suggest the red mud to be considered as a promising material to be used in electrolyte solutions for coating of aluminum by PEO since the incorporation of such valuable elements in the coating may contribute to the improvement of wear and corrosion resistances of the substrates.…”

“…Such characteristics suggest the red mud to be considered as a promising material to be used in electrolyte solutions for coating of aluminum by PEO since the incorporation of such valuable elements in the coating may contribute to the improvement of wear and corrosion resistances of the substrates. The red mud has been studied for the construction industry, adsorbent metals and organic materials and CO 2 capture 7 . In recent years it has been studied as ceramic films for protecting metals [10][11][12][13] .…”

Preparation of Modified Red Mud-Supported Fe Catalysts for Hydrogen Production by Catalytic Methane Decomposition

“…The TG curves of the uncalcined 20Fe/MRM catalyst precursor showed three weight loss steps that were similar to those of RM, revealing that the continuous weight loss was approximately 26.89% of the total weight from room temperature to 800 ∘ C. The first weight loss of 12.51% from 25 to 139 ∘ C was ascribed to the physically adsorbed water; the second weight loss of 8.02% from 139 to 294 ∘ C may be due to gibbsite and Fe hydroxide (formed in the homogeneous precipitation process during catalyst preparation) decomposing into -Al 2 O 3 [46] and hematite, respectively; the third weight loss of 6.36% in the temperature range from 294 to 800 ∘ C was attributed to decomposition of the remaining hydroxides. The uncalcined 20Fe/MRM catalyst precursor exhibited a greater total weight loss than RM, which indicated a greater hydroxide content in the uncalcined 20Fe/MRM catalyst precursor than in RM due to the added Fe contents that directly increased the iron hydroxide formed during the precipitation process.…”