Alumina Phase Transformation from Thermal Decomposition of Ammonium Alum Synthesized from Kankara Kaolin (original) (raw)
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Synthesis of gamma alumina from Kankara kaolin using a novel technique
Applied Clay Science, 2015
Synthesis of gamma alumina from Kankara kaolin using simple novel dealumination, precipitation and calcination steps and the product characterization have been presented. The raw clay was wet beneficiated, metakaolinized and dealuminated. Amorphous aluminum hydroxide was precipitated from the aluminum sulfate produced, using sodium hydroxide solution as the precipitating agent. Chemical, mineralogical, physiochemical, morphological and thermal analyses of the products were carried out using XRF, XRD, BET, FTIR, SEM, TEM and TGA/DTA. The aluminum hydroxide produced was subjected to thermal treatment at variable calcination temperatures in the range of 300 to 900°C, gradual phase transformation was observed, a fully formed gamma alumina phase was observed at 900°C. XRF analysis of the various materials at each stage of processing showed a progressive trend of increase in Al 2 O 3 content, at calcination of 900°C the Al 2 O 3 content was 91.02 wt.%. The XRD pattern of the alumina obtained at 900°C was similar to that of commercial gamma alumina. The BET surface area, pore volume and pore diameter of the as-synthesized gamma alumina were 102.6 m 2 /g, 0.0305 cm 3 /g and 11.89 Å respectively and the crystal size was 10 nm. This novel process is an industrially feasible alternative to the conventional Bayer process, and it offers a solution to the environmental hazards posed by the wastes generated by the Bayer process.
Phase Transformations of α-Alumina Made from Waste Aluminum via a Precipitation Technique
We report on a recycling project in which α-Al 2 O 3 was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H 2 SO 4 solution to form an Al 2 (SO 4 ) 3 solution. The Al 2 (SO 4 ) 3 salt was contained in a white semi-liquid solution with excess H 2 SO 4 ; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al 2 (SO 4 ) 3 ·18H 2 O. The Al 2 (SO 4 ) 3 ·18H 2 O was calcined in an electrical furnace for 3 h at temperatures of 400-1400 °C. The heating and cooling rates were 10 °C /min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al 2 (SO 4 ) 3 ·18H 2 O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al 2 O 3 at high temperatures. The X-ray diffraction results indicated that the α-Al 2 O 3 phase was realized when the calcination temperature was at 1200 °C or higher.
Phase transformation of α-alumina from aluminium waste
2011
α-Al 2 O 3 were produced from aluminium wastes (aluminium cans). Roasted aluminium cans were mixed with concentrated H 2 SO 4 to form Al 2 (SO 4 ) 3 solution. The solution was filtered out and mixed with ethanol to form white solid of Al 2 (SO 4 ) 3 .18H 2 O. The Al 2 (SO 4 ) 3 .18H 2 O was calcined for 3 hours at temperatures of 400 to 1400ºC. The phase change was investigated using XRD and FESEM. All transitional alumina produced at low temperatures converts to α-Al 2 O 3 at high temperature, since a series of alumina formation by dehydration and desulphonation of the Al 2 (SO 4 ) 3 .18H 2 O. X-ray diffraction show phase of α-Al 2 O 3 after calcined at temperature 1200 ºC.
Preparation of Nanogama Alumina from Iraqi Kaolin
2018
The work reports a procedure for the synthesis of γ-alumina from the Iraqi kaolin. Kaolin was transformed to metakaolin by calcination at 750 °C for 45 minute. γ-alumina powder was synthesized through extracting alumina from metakaolin via H2SO4 treatment and precipitation by ethanol, which produces aluminum sulfate of 99% purity. The precipitated aluminum sulfate was dried and calcined at 800, 850, 900 and 1000 °C to study the thermal decomposition of aluminum sulfate. The crystallinity and phase of the synthesized for the assignment of calcined samples was characterized by X-ray diffraction measurements, paving the temperature at which the aluminum sulfate is converted to γ-alumina nano particles. Pure alumina nanoparticle 98.81% was prepared by calcination of aluminum sulfate at 1000 °C for 2 hour. The specific surface area, pore volume and pore size for γ-alumina nano particles were determined by BET measurement i.e. 117 m 2 /gm, 1.1 cm 3 /g and 337.6 Å respectively. The size of...
Exploitation of Kaolin as an Alternative Source in Alumina Production
International Conference on Raw Materials and Circular Economy, 2021
The extensive consumption of aluminum, combined with the shortage of the existing raw materials, and particularly bauxite, necessitates the exploitation of alternative raw materials for the production of alumina. The present paper focuses on the possible use of kaolin, as an abundant, cheap and high-aluminum content raw material, in alumina production, via the application of the Aranda-Mastin technology in the leaching step. From this point of view, leaching experiments were conducted on untreated kaolin and thermally treated, metakaolin, applying atmospheric pressure, temperature of 90 °C and with an aqueous solution of a low HCl concentration as the leaching agent. Leaching, in the aforementioned conditions, is an industrially applied process, characterized by highly efficient aluminum dissolution in the case of metakaolin with low silicon dissolution at a short retention time, but with respectively lower achieved results for untreated kaolin. In order to raise the aluminum dissol...
Utilization of Kalapsha Kaolin to Prepare High Purity Alumina
Egyptian Journal of Chemistry, 2019
K ALABSHA kaolin was calcined at 700 o C then treated with hydrochloric acid to produce aluminum chloride hexahydrate. The hexahydrate was obtained in crystalline form through injection of hydrogen chloride gas in saturated solution and purified on several steps to obtain alumina of high purity. Acid leaching conditions, namely, acid to kaolin stoichiometric ratio(S), reaction time (t) and reaction temperature (T) were optimized using surface response methodology. A maximum alumina recovery of 83.2% was predicted on using 1.4 stoichiometric acid to solid ratio, a reaction temperature of 104 o C and a reaction time of 3 hours. This result was then assessed experimentally. The hexahydrate crystals obtained were subsequently purified in a three stage process to increase their purity to 99.961%. Calcination of these crystals for 4 hours at 1100 o C produced highly crystalline alumina with purity 99.9%.
2014
In this work lime-sinter method was investigated to recover alumina from Iraqi colored kaolinitic claystone. The claystone was intimately mixed with limestone and the mixture was sintered. The annealed sintered material dusts to a fine powder which required no grinding. This material was leached with sodium carbonate solution, and an alumina extract (sodium aluminate solution) was obtained. By bubbling carbon dioxide gas into this extract solution, gibbsite [Al(OH) 3 ] precipitated and on calcinations at 1350 °C ,alumina in the form of alpha (α-Al 2 O 3) of high purity (98%) can be obtained. In the course of this investigation, the effect of sintering temperature and time, concentration of sodium carbonate solution, leaching time and sintered powder to sodium carbonate solution ratio were studied. About 85% of the alumina in the claystone was extracted at the optimum conditions. The alumina obtained in this method assaying 98% Al 2 O 3 , 1.45% SiO 2 , 0.04% Fe 2 O 3 , and 0.13% CaO ...
Extraction of γ-Alumina from Low-Cost Kaolin
Resources, 2018
A combined process is proposed for the utilization of local kaolin to produce alumina particles. The applied process is made in two stages: calcination at 700 • C with sodium chloride and leaching with sulfuric followed by hydrochloric acids. The optimal extraction efficiency can be obtained when the conditions are as follows: leaching temperature is at 140 • C, leaching time is 3 h 45 min and concentration of sulfuric acid is 40 wt.%. The results show that the purity of alumina reaches 79.28%, which is suitable for the production of aluminum metal. It is evident that this method of extraction of alumina from the kaolin ash is practical and feasible. The structural and morphological properties of the calcined microcrystalline powder was characterized by X-ray diffraction and scanning electron microscope (SEM).
Synthesis and characterization of nano-sized α-alumina powder from kaolin by acid leaching process
Applied Clay Science, 2017
αalumina powder with particle size < 100 nm and spherical shape was prepared from calcined kaolin by acid leaching method. Here hydrochloric acid was used as a leaching agent. The amorphous white powders formed after precipitation, washing and drying were characterised by the different technique like XRD, TG-DSC and FTIR. Particle size distribution, specific surface area and microstructural analysis of the 1200°C calcined powder were also carried out to ascertain the size, shape and distribution of the particles. The phase pure α-alumina with a size range < 100 nm, was formed at 1200°C. The presence of a surfactant during processing also exhibited a positive effect on modification of particle size.