• Journal of Soil and Groundwater Environment
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• v.26 no.6
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• pp.65-73
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• 2021

Since the amount of red mud, generated from aluminum smelting process as a by-product, has increased worldwide, the recycle and metal resource recovery from the red mud is becoming more important. In this study, in order to recycle the red mud as a soil stabilizer to remediate arsenic contaminated soils, neutralization of red mud was investigated. Red mud was neutralized by washing with distilled water and NaCl, CaCl₂, FeCl₃, and HCl solutions and heating at 200-800℃, and arsenic stabilization characteristics in soils were evaluated with the neutralized red mud. Although washing with distilled water was not effective in neutralizing red mud, the application of the washed red mud to soils lowered the soil pH compared to the application of untreated red mud. Among NaCl, CaCl₂, FeCl₃, and HCl solutions, washing with FeCl₃ showed the most effective in lowering pH of the red mud from pH 10.73 to pH 4.26. Application of the neutralized red mud in soils resulted in quite different arsenic stabilization efficiency depending on soil samples. In M1 soil, which showed relatively high arsenic stabilization efficiency by untreated red mud, the neutralization of red mud resulted in little effect on arsenic stabilization in soil. On the other hand, in M2 soil, which showed low arsenic stabilization efficiency by untreated red mud, the neutralization of red mud increased arsenic stabilization significantly. Soil characteristics such as clay minerals and pH buffering capacity seemed to affect reactions between red mud and soils, which resulted in different effects of the red mud application on soil pH and arsenic stabilization efficiencies.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.104-105
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• 2020

Red mud is a highly alkaline waste by-product of the aluminum industry. Although recycling of red mud is being actively researched, a feasible technological solution has not been found yet. In this study, we propose that neutralization of red mud alkalinity could assist in its use as a construction material. Neutralized red mud ( pH 6-8) was prepared by adding sulfuric acid to liquefied red mud (pH 10-12). After adding liquid and neutralized red mud to the cement paste, the heat of hydration was measured. As a result of the experiment, the calorific value of the cement paste with liquid red mud was lowered and delayed compared to the cement paste with neutralized red mud.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.39-47
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• 2011

The objective of this study is to investigate the removal characteristics of cadmium(Cd) and lead(Pb) by adsorption on red mud and to study the adsorption characteristics of Cd and Pb using red mud activated by acid treatment and calcination. The adsorption of Cd and Pb on red mud was significantly achieved within 1hour and equilibrated after 5 hours. The adsorption capacity of Cd and Pb on red mud increased with increasing pH. The neutralization of red mud by distilled water or acid and the activation of red mud by acid treatment or calcination decreased the adsorption capacity of Cd and Pb on red mud, suggesting that Cd and Pb could be effectively eliminated by adsorption on red mud without any pretreatment or modification. Both Langmuir and Freundlich models were successfully applied to describe the adsorption behavior of Cd and Pb on red mud. The $q_m$ of Langmuir adsorption model and $K_F$ of Freundlich adsorption model were 5.230mg/g and 1.118mg/g for Cd and 22.222mg/g and 7.241mg/g for Pb, respectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.91-92
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• 2016

Red mud is an inorganic by-product produced from the mineral processing of alumina from Bauxite ores. the development of alkali-activated slag-red mud cement can be a representative study aimed at recycling the strong alkali of the red mud as a construction material. This study is to investigate the pore characteristics of alkali-activated slag-red mud soil pavement according to the red mud content. The results showed that the porosity of alkali-activated slag-red mud soil pavement increased but the compressive strength of that decreased as the red mud content increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.27-28
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• 2020

In this study, as a measure to recycle red mud, which is a byproduct of the Bayer Process, red mud was manufactured as liquid and recycled without drying and grinding. Previous studies have shown that mechanical performance decreases when liquid red mud is applied to cement concrete. Therefore, in this study, liquid red mud was neutralized with nitric acid and applied to cement paste to examine the properties of cement paste according to the addition of red mud. As a result, the compressive strength of 10% liquid red mud decreased by 37.7% compared to Plain, and 10% liquid red mud indicates similar strength to Plain and restores the strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.123-124
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• 2022

In this paper, the characteristics of slag cement mortar added with neutralized liquid red mud with sulfuric acid and reduced pH were reviewed to improve the strength degradation of cement concrete added with liquid red mud. As a result, in the case of compressive strength up to 7 days, the strength of the cement mortar added with liquid red mud tends to increase compared to Plain. This shows that adding liquid red mud to cement mortar tends to increase the initial age strength, and the compressive strength on the 28th shows 74% of Plain when adding non-neutralized liquid red mud and 89% when adding sulfate neutralized red mud. Therefore, it is judged that the compression strength is improved by neutralizing the liquid red mud with sulfuric acid.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.165-166
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• 2022

In this paper, the characteristics of slag cement mortar added with neutralized liquid red mud with nitric acid to reduce pH by neutralizing liquid red mud with nitric acid were reviewed to improve strength degradation of cement concrete added with liquid red mud. As a result, the compressive strength of cement mortar added with liquid red mud was higher than that of Plain on 1 and 3 days, and the strength of red mud neutralized with nitric acid was lower than that of cement mortar added with liquid red mud on 7 days, but the strength was recovered on 28th. It was found that the addition of red mud has the effect of improving the strength in the early age.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.23-24
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• 2019

In this paper, the compressive strength characteristics of cement paste were compared with the addition of liquefied red mud with the addition of nitric acid in order to improve the strength of the deteriorated cement. The results showed that the compressive strength with between 7 days and 28 days was greater than that of liquefied red mud. The ratio of daily compressive strength of the liquefied red mud is higher than that of the Plain with a 1 percent addition rate, and the ratio of compressive strength is lower than that of the Plain on the 28 days. Therefore, the compressive strength of neutralization liquefied red mud compared to liquidated red mud was relatively high, and the compressive strength of the red mud was shown to be improved to a level almost similar to that of Plain.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.21-22
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• 2022

In order to improve the strength degradation of the cement-based material to which strong alkaline liquid red mud was added, the liquid red mud was neutralized with sulfuric acid and added to the cement paste to examine the mechanical properties according to the amount added. As a result of measuring the compressive strength, the strength was higher when the red mud was neutralized with sulfuric acid and added to the cement paste than the cement paste to which the liquid red mud was added. As a result of hydration heat measurement, when red mud was neutralized with sulfuric acid and added to the cement paste, an initial strength higher than that of liquid red mud was expressed.

• Clean Technology
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• v.15 no.1
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• pp.38-41
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• 2009

Red mud is generated as a waste byproduct during the production of aluminum hydroxide/alumina from bauxite ore in the Bayer process. In this study coagulants for wastewater treatment were prepared by leaching iron and aluminum from red mud with hydrochloric acid. The removal efficiency of heavy metal ions by the red mud coagulant increased with increasing the adjusted pH value of the synthetic wastewater. When the red mud coagulant was prepared, the leaching efficiency of Fe decreased with increasing the weight of red mud, while the pH value of the red mud coagulant increased. The solution of the red mud coagulant mixed with water was reacted again with red mud to produce the leached solution, which had higher concentrations of Fe and Al and a higher pH value than the red mud coagulant. Also, its pH value was comparable to that of other coagulants: $FeCl_3$ and $Fe_2(SO_4)_3$.