High‐efficiency
            preparation of
            Fe–Al
            based flocculants from red mud by microwave selective carbothermic reduction and magnetic separation

Red mud is a by-product of alumina production from bauxite ore by the Bayer method, which contains considerable amounts of valuable components such as iron, aluminum, titanium, and scandium. In this study, an approach was applied to extract iron, i.e., carbothermic reduction roasting of red mud with sodium and potassium carbonates followed by magnetic separation. The thermodynamic analysis of iron and iron-free components’ behavior during carbothermic reduction was carried out by HSC Chemistry 9.98 (Outotec, Pori, Finland) and FactSage 7.1 (Thermfact, Montreal, Canada; GTT-Technologies, Herzogenrath, Germany) software. The effects of the alkaline carbonates’ addition, as well as duration and temperature of roasting on the iron metallization degree, iron grains’ size, and magnetic separation process were investigated experimentally. The best conditions for the reduction roasting were found to be as follows: 22.01% of K2CO3 addition, 1250 °C, and 180 min of duration. As a generalization of the obtained data, the mechanism of alkaline carbonates’ influence on iron grain growth was proposed.

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Extraction of Iron from Russian Red Mud by a Carbothermic Reduction and Magnetic Separation Process

Materials Proceedings ◽

10.3390/iec2m-09247 ◽

2021 ◽

Vol 3 (1) ◽

pp. 23

Author(s):

Dmitry Zinoveev ◽

Alexander Petelin ◽

Pavel Grudinsky ◽

Andrey Zakunov ◽

Valery Dyubanov

Keyword(s):

Experimental Data ◽

Magnetic Separation ◽

Grain Growth ◽

Red Mud ◽

Carbothermic Reduction ◽

Iron Reduction ◽

Solid Phase ◽

Reduction Process ◽

Alumina Production ◽

Average Size

Red mud is a hazardous waste of alumina production. Currently, the total accumulated amount of red mud is over 4 billion tons. The promising method of red mud processing is a carbothermic reduction of iron at 1000–1400 °C into metallic form followed by magnetic separation. In this study, the mechanism of carbothermic solid-phase reduction of red mud was investigated. Based on the experimental data, the two-step mechanism of the first rapid stage of the process was proposed, which leads to almost full iron reduction. The estimated value of activation energy has indicated that solid-phase diffusion is a rate-controlling step for this stage. However, an almost full reduction is necessary, but insufficient factor for successful magnetic separation. The second crucial factor of the process is enlargement of iron grain size, which leads to gangue-grain release during grinding and increases efficiency of the magnetic separation. The prediction model of iron grain growth process during the carbothermic reduction process was suggested. The calculation of average size of iron grains formed during the reduction process that was performed according to the assumption of diffusion-controlled process showed their correlation with experimental data. Various methods were proposed to promote the process of iron grain growth during carbothermic reduction of red mud.

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Influence of Sodium Sulfate Addition on Iron Grain Growth during Carbothermic Roasting of Red Mud Samples with Different Basicity

Metals ◽

10.3390/met10121571 ◽

2020 ◽

Vol 10 (12) ◽

pp. 1571

Author(s):

Pavel Grudinsky ◽

Dmitry Zinoveev ◽

Denis Pankratov ◽

Artem Semenov ◽

Maria Panova ◽

...

Keyword(s):

Magnetic Separation ◽

Grain Growth ◽

Red Mud ◽

Sodium Sulfate ◽

Phase Distribution ◽

Solid Phase ◽

Alumina Production ◽

Metallic Particles ◽

Iron Phase ◽

High Alkalinity

Red mud is an iron-containing waste of alumina production with high alkalinity. A promising approach for its recycling is solid-phase carbothermic roasting in the presence of special additives followed by magnetic separation. The crucial factor of the separation of the obtained iron metallic particles from gangue is sufficiently large iron grains. This study focuses on the influence of Na2SO4 addition on iron grain growth during carbothermic roasting of two red mud samples with different (CaO + MgO)/(SiO2 + Al2O3) ratio of 0.46 and 1.21, respectively. Iron phase distribution in the red mud and roasted samples were investigated in detail by Mössbauer spectroscopy method. Based on thermodynamic calculations and results of multifactorial experiments, the optimal conditions for the roasting of the red mud samples with (CaO + MgO)/(SiO2 + Al2O3) ratio of 0.46 and 1.21 were duration of 180 min with the addition of 13.65% Na2SO4 at 1150 °C and 1350 °C followed by magnetic separation that led to 97% and 83.91% of iron recovery, as well as 51.6% and 83.7% of iron grade, respectively. The mechanism of sodium sulfate effect on iron grain growth was proposed. The results pointed out that Na2SO4 addition is unfavorable for the red mud carbothermic roasting compared with other alkaline sulfur-free additives.

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Recovering metals from red mud by thermal treatment and magnetic separation

JOM ◽

10.1007/bf03221357 ◽

1996 ◽

Vol 48 (1) ◽

pp. 25-28 ◽

Cited By ~ 7

Author(s):

Paolo Plescia ◽

Dante Maccari

Keyword(s):

Thermal Treatment ◽

Magnetic Separation ◽

Red Mud

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Generation of titania-rich slag and iron from ilmenite concentrate by carbothermic reduction and magnetic separation in the presence of Na2CO3

Canadian Metallurgical Quarterly ◽

10.1080/00084433.2021.1910427 ◽

2021 ◽

pp. 1-12

Author(s):

Wei Lv ◽

Richard Elliott ◽

Xuewei Lv ◽

Junyi Xiang ◽

Fanmao Wang ◽

...

Keyword(s):

Magnetic Separation ◽

Carbothermic Reduction ◽

Ilmenite Concentrate

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Recovery of iron from high-iron red mud using suspension magnetization roasting and magnetic separation

Minerals Engineering ◽

10.1016/j.mineng.2022.107394 ◽

2022 ◽

Vol 178 ◽

pp. 107394

Author(s):

Jianwen Yu ◽

Yanfeng Li ◽

Yang Lv ◽

Yuexin Han ◽

Peng Gao

Keyword(s):

Magnetic Separation ◽

Red Mud ◽

High Iron

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Red Mud-Based Polyaluminum Ferric Chloride Flocculant: Preparation, Characterization and Flocculation Performance

10.21203/rs.3.rs-159842/v1 ◽

2021 ◽

Author(s):

Yong Cheng ◽

Longjun Xu ◽

Chenglun Liu ◽

Zao Jiang ◽

Qiyuan Zhang ◽

...

Keyword(s):

Red Mud ◽

High Efficiency ◽

Low Cost ◽

Oxygen Demand ◽

Industrial Applications ◽

Iron Chloride ◽

Raw Material ◽

Molar Ratio ◽

Polymerization Temperature ◽

Solution Ph

Abstract In this work, red mud was used as raw material to extract Al and Fe with hydrochloric acid. The high-efficiency polyaluminum iron chloride (PAFC) flocculant was prepared via adjusting the pH of the leaching solution, the molar ratio of aluminum and iron, and the polymerization temperature. The effect of synthesis and flocculation conditions on the flocculation performance of aged landfill leachate was investigated. The results confirmed that the PAFC prepared at the polymerization pH of 2.5, the Al/Fe molar ratio of 8, and the polymerization temperature of 70 °C had the optimum flocculation effect. The flocculation consequences of PAFC and commercial polyaluminum iron chloride flocculant (CPAFC) under different flocculation conditions were compared. The chemical oxygen demand (COD), UV254, chroma and settlement height of PAFC at flocculant concentration of 60 g/L and solution pH of 6 were 72.2%, 79.2%, 82.9% and 9.5 cm (within 90 min), respectively. PAFC has excellent flocculation performance and can be used as a simple, potentially low-cost wastewater treatment agent in industrial applications.

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