scholarly journals Effect of Corrosion Time on the Synergistic Corrosion of Q235 Steel in Sodium Aluminate Solutions

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 753
Author(s):  
Bianli Quan ◽  
Junqi Li ◽  
Chaoyi Chen
Keyword(s):  
Charge Transfer ◽  
Iron Sulfide ◽  
Sodium Aluminate ◽  
Corrosion Products ◽  
Alumina Production ◽  
Steel Electrode ◽  
Aluminate Solution ◽  
Q235 Steel ◽  
Sodium Aluminate Solution ◽  
Corrosion Time

During Bayer alumina production with high-sulfur bauxite, the sulfide ions in the sodium aluminate solution caused serious corrosion to Q235 steel, which is the material of the tank equipment. This study investigates the effect of corrosion time on Q235 steel synergistic corrosion in sodium aluminate solution using the weight-loss method and electrochemical measurements. The results indicate that the corrosion rate decreases sharply, the rate equation satisfies the mathematical model of power function at the initial stage of corrosion, and the transformation of unstable iron sulfide to stable iron oxide at the later stage results in the decrease in sulfur content in the corrosion products and surface pseudo-passivation. There are two main types of corrosion products, as follows: one is the octahedral crystal particle, which is composed of Fe2O3, Fe3O4, Al2O3 and NaFeO2, and the other is the interlayer corrosion between the surface layer and the matrix, which is composed of FeS, FeS2 and MnS2. At day 3, the dynamics of the Q235 steel electrode is controlled by charge transfer and ion diffusion. However, at other times the dynamics are mainly controlled by charge transfer.

scholarly journals Effect of process parameters on the morphology and adsorption properties of nanocrystalline boehmite

2014 ◽  
Vol 68 (3) ◽  
pp. 357-362
Author(s):  
Zoran Obrenovic ◽  
Ljubica Nikolic ◽  
Radislav Filipovic ◽  
Marija Milanovic ◽  
Ivan Stijepovic
Keyword(s):  
Ph Value ◽  
High Surface ◽  
High Surface Area ◽  
Average Crystallite Size ◽  
Sodium Aluminate ◽  
Adsorption Properties ◽  
Transition Alumina ◽  
Aluminate Solution ◽  
Bayer Liquor ◽  
Sodium Aluminate Solution

In the last decade, exploration of transition alumina phases with good adsorption properties has attracted a great research interest from both a fundamental and a practical point of view. The transition phases of alumina are metastable polymorphs of aluminum oxide formed through the thermal dehydration of aluminum trihydroxide and aluminum oxyhydroxide. Powder X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. In this work transition alumina powders were synthesized starting from sodium aluminate solution prepared from Bayer liquor. The neutralization of sodium aluminate solution was performed with the use of sulphuric acid, while glucose was added in the starting solution. In this way, the single phase nanocrystalline boehmite was obtained. As-synthesized boehmite powders have high surface area (above 360 m2/g) and the average crystallite size less than 5 nm. The results showed that the properties of the powders (structure, morphology) are strongly influenced by the initial pH value of sodium aluminate solution, as well as by the duration of neutralization step.

scholarly journals Obtaining of transition phases of alumina starting from sodium aluminate in Bayer process

2011 ◽  
Vol 65 (3) ◽  
pp. 271-277
Author(s):  
Zoran Obrenovic ◽  
Radislav Filipovic ◽  
Marija Milanovic ◽  
Ivan Stijepovic ◽  
Ljubica Nikolic
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Sodium Aluminate ◽  
High Specific Surface Area ◽  
Heterogeneous Structure ◽  
Aluminate Solution ◽  
Bayer Liquor ◽  
Sodium Aluminate Solution

Transition (active) phases of alumina were synthesized starting from sodium aluminate solution prepared out of Bayer liquor. The neutralisation of sodium aluminate solution was performed by sulphuric acid. Powder X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and low-temperature nitrogen absorption studies were employed to trace the formation of the transition phases of alumina. The results show that the properties of the powders (phase composition, morphology and specific surface area) are strongly influenced by the initial pH value of the system, as well as by the duration of neutralisation step. It is possible to obtain powders with heterogeneous structure with dominant phase of bayerite, gibbsite or boehmit by tuning the pH and concentration of the starting sodium aluminate solution. The transition (active) phases of alumina (?- and ?-alumina) with high specific surface area (264-373 m2/g) are formed through the thermal dehydratation of aluminium hydroxide (bayerite and gibbsite) and aluminium oxyhydroxide (boehmite or pseudoboehmite) at the temperature of 500?C. Namely, bayerite and pseudoboehmite transforms to ?-phase of alumina upon heating, while gibbsite transforms to ?-phase, maintaining the parent morphology.

Investigations on a Novel Process to Recycle Valuable Metals from Spent Al2O3-Based Catalyst

2013 ◽  
Vol 634-638 ◽  
pp. 3222-3226
Author(s):  
Yan Hai Shao ◽  
Ming Ming Li ◽  
Xiong Tong
Keyword(s):  
Sodium Aluminate ◽  
Leach Liquor ◽  
Spent Catalyst ◽  
Water Leaching ◽  
Calcination Process ◽  
Aluminate Solution ◽  
X Ray ◽  
Sodium Aluminate Solution ◽  
Valuable Metals ◽  
Leaching Residue

Based on X-ray phase analysis and exploratory experiments, a novel process was proposed to recycle multiple valuable metals like Al, V, Mo, Ni and Co from spent Al2O3-based catalyst. The spent catalyst was roasted by adding sodium carbonate with certain mol ratio, after water leaching, Al, V and Mo could be extracted into leach liquor, whereas Ni and Co were enriched in the leaching residue. V and Mo were precipitated in step from leach liquor by adding CaO and BaAl2O4, respectively. After removal of V and Mo, Al(OH)3 was prepared from sodium aluminate solution with carbonation decomposition process, and the purity of Al2O3 is 99.98%. With sodium bicarbonate leaching-purification-precipitation-calcination process, V2O5 could be prepared from V-bearing residue. Ni and Co were leached from water leaching residue with sulfuric acid. Recoveries of Al, V, Mo, Ni and Co from spent catalyst are 87.0%, 88.7%, 92.1%, 97.8% and 98.6%, respectively.

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