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Zhu X.-B.,Henan Polytechnic University | Zhu X.-B.,Henan Key Discipline Open Laboratory of Mining Engineering Materials | Li W.,Henan Polytechnic University | Guan X.-M.,Henan Polytechnic University
Yejin Fenxi/Metallurgical Analysis | Year: 2015

The red mud sample was heated and fused in muffle furnace with sodium hydroxide using its strong basicity and ablation property. The fusant was firstly leached in worm water followed by dissolution with 30 mL of hydrochloric acid. Then, the aluminum sheet was added for reduction in presence of sodium bicarbonate solution for protection. Finally, the content of titanium dioxide in red mud was determined by ammonium ferric sulfate titrimetry using ammonium thiocyanate solution as indicator. The effect of sample dosage, particle size, sodium hydroxide dosage, roasting condition, sample dissolution condition and protection solution on the determination was investigated. The results showed that the optimal experimental conditions were as follows: the dosage of sodium hydroxide dosage was 6 g, the roasting temperature was 650℃, the roasting time was 20 min, the reducing agent was 2.2 g of aluminum sheet, the protection solution was saturated sodium bicarbonate solution, and the placing time before titration was less than 15 min. The proposed method was applied to the determination of titanium dioxide in actual red mud sample, and the found results were consistent with those obtained by inductively coupled plasma atomic emission spectrometry. The relative standard deviation (RSD, n=5) was less than 0.2%. ©, 2015, Central Iron and Steel Research Institute. All right reserved.

Zhu X.,Henan Polytechnic University | Zhu X.,Henan Key Discipline Open Laboratory of Mining Engineering Materials | Li W.,Henan Polytechnic University | Li W.,Henan Key Discipline Open Laboratory of Mining Engineering Materials | And 2 more authors.
Journal of Hazardous Materials | Year: 2015

The research has focused on the dealkalization of red mud after active roasting and water leaching, which is obtained from bauxite during alumina production. The main factors such as roasting temperature, roasting time, water leaching stage, leaching temperature, leaching reaction time and liquid to solid ratio were investigated. The mechanism of dealkalization was in-depth studied by using ICP-AES, XRD, TG-DSC, SEM-EDS and leaching kinetic. The results show that the dealkalization rate reached 82% under the condition of roasting temperature of 700°C, roasting time of 30min, four stage water leaching, liquid to solid ratio of 7mL/g, leaching temperature of 90°C and reaction time of 60min. The diffraction peak of Na6CaAl6Si6(CO3)O24·2H2O in red mud was decreased during the active roasting process, whereas the mineral phases of NaOH·H2O and Na2Ca(CO3)2 were appeared. The content of alkali obviously decreased and the grade of other elements increased during the process of active roasting and water leaching, which was in favor of next application process of red mud. The water leaching was controlled by internal diffusion of SCM and the apparent activation energy was 22.63kJ/mol. © 2014 Elsevier B.V.

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